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Comprehensive Inorganic Chemistry

EDITORIA

L BOAR D J . C . BAILA R JR. , Urbana H . J . EMELÉUS , F.R.S. , Cambridge tSI R RONAL D NYHOLM , F.R.S. , London A . F . TROTMAN-DICKENSON , Cardiff {Executive Editor)

The Chemistry of

OXYGE N E . A. V. Ebsworth, J. A. Connor and J. J. Turner

Chapte

r 2 2 o f

Comprehensiv

e Inorgani c Chemistr y

PERGAMO

N PRES S OXFOR D . NE W YOR K . TORONT O SYDNE Y . PARI S . BRAUNSCHWEI G

Pergamon Press Offices:

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5

Librar

y o f Congres s Catalo g Car d No . 77-18973
6

Printed

in Great Britain by A, Wheaton & Co, Exeter ISB N 0 0 8 01885
8 3 (har d cover ) ISBN 0 08 018857 5 (Flexicover)

PREFACE

Th e excellen t receptio n tha t ha s bee n accorde d t o Compre- /tensive Inorganic Chemistry sinc e th e simultaneou s publicatio n o f th e five volume s o f th e complet e wor k ha s bee n accompanie d b y th e ple a tha t section s shoul d b e mad e availabl e i n a for m tha t woul d enabl e specialist s t o purchas e copie s fo r thei r ow n use . T o mee t thi s deman d th e publisher s hav e decide d t o issu e selecte d chapter s an d group s o f chapter s a s separat e editions . Thes e chapter s will , apar t fro m th e correction s o f misprint s an d th e additio n o f prefator y materia l an d individua l indices , appea r jus t a s the y di d i n th e mai n work . Extensiv e revisio n woul d dela y publicatio n an d greatl y rais e th e cost , s o limitin g th e circulatio n o f thes e definitiv e reviews . A . F . TROTMAN-DICKENSO N

Executive

Editor vi i

22. OXYGEN

E . A . V . EBSWORT H

University of Edinburgh

J . A . CONNO R The University of Manchester an d J . J . TURNE R

The University, Newcastle-upon-Tyne

1 . OXYGEN 1.1 . DISCOVER Y O F OXYGEN * B y th e middl e o f the seventeenth century it was appreciated that air containe d a compo nen t associate d wit h breathin g an d burning . I n th e first theory of burning to become widely accepted , thi s componen t wa s calle d phlogiston . Whe n somethin g burned , i t wa s believe d t o releas e phlogisto n t o th e ai r aroun d it . I f th e burnin g too k plac e i n a seale d system , i t stoppe d afte r a tim e becaus e th e ai r i n th e syste m becam e saturate d wit h phlogiston . Ther e wer e seriou s difficultie s abou t thi s interpretation . Fo r instance , metal s suc h a s ti n gai n i n weigh t whe n the y burn . However , th e theor y wa s widel y accepte d unti l th e en d o f th e eighteent h century . Bot h th e experimentalist s generall y credite d wit h th e discover y o f oxygen , Josep h

Priestl

y an d Car l Wilhel m Scheele , wer e believer s i n th e phlogisto n theory . Indeed , Scheel e calle d hi s experiment s ".. . proof s tha t Hea t o r Warmt h consist s o f Phlogisto n an d Fir e Air" . Scheel e obtaine d oxygen , whic h h e calle d fire air , b y heatin g nitrates , mercuri c oxide , o r manganes e dioxid e i n retort s t o th e end s o f whic h bladder s ha d bee n fixed; Priestl y heate d mercuri c oxid e wit h a magnifyin g glas s an d collecte d th e ga s ove r water . Bot h foun d tha t th e ga s the y ha d obtaine d woul d suppor t combustio n bette r tha n doe s commo n air ; an d afte r som e experiment s wit h mic e Priestl y venture d t o breat h som e o f i t himself , wit h ver y pleasan t results . Priestl y isolate d wha t h e calle d "dephlogisticate d air " o n 1 Augus t 1774; after further experiments he wrote about his results to Sir John Pringle, the President o f th e Roya l Society , i n Marc h 1775
, an d hi s lette r wa s rea d befor e th e Societ y o n 2 3 March , whil e a detaile d accoun t o f hi s experiment s wa s publishe d i n th e sam e yea r i n th e secon d volum e o f his book Experiments and Observations on Different Kinds of Air. Scheele worke d a t abou t th e sam e time , bu t h e ha d difficultie s wit h hi s publisher s (a s other s hav e 1 M . E . Weeks , The Discovery of the Elements, 6th edn., published by the Journal of Chemical Education, Ne w Yor k (1956) ; D . McKie

, Antoine Lavoisier, Gollancz, London (1935); J. G. Gillam, The Crucible, Robert Hale, London (1954); The

Collected Papers of C. W. Scheele (translated by L. Dobbin), Bell, Edinburgh (1931). 68
5

686 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

ha d sinc e then) , an d hi s book , Chemische Abhandlung von der Luft und dem Feuer, did not appea r unti l 1777
.

Neithe

r Priestl y no r Scheele , however , seem s full y t o hav e understoo d th e signifi canc e o f thei r discoveries . Whe n Priestl y wa s i n Pari s i n Octobe r 1774
, h e mentione d som e o f hi s result s t o th e distinguishe d Frenc h Academician , Antoin e Lavoisier , wh o wa s intereste d i n combustion . Lavoisie r wa s als o i n touc h wit h Scheele . H e repeate d an d extende d Priestly' s experiments , an d bega n t o conside r hi s result s i n th e ligh t o f th e deficiencie s o f th e phlogisto n theory . H e burne d ti n i n a seale d vessel , an d showe d tha t afte r combustio n th e weigh t o f th e vesse l wa s effectivel y unchange d a s lon g a s th e sea l wa s no t broke n ; thus the increase in weight of the tin on combustion could not be derived from outsid e th e vessel . I f th e ti n ha d los t phlogiston , the n th e phlogisto n mus t hav e negativ e mass . From these and other experiments he concluded that when the metal burned what reall y happene d wa s tha t i t combine d wit h somethin g i n th e air ; tha t "something " wa s th e ga s discovere d b y Priestl y an d Scheele , whic h Lavoisie r calle d "princip e oxygine" . Hi s vie w wa s no t absolutel y correct . H e though t h e wa s talkin g o f a principl e o f acidity , fo r "oxygine " come s fro m th e Gree k wor d oxus, meanin g sharp , an d henc e acid . Bu t i t wa s Lavoisier' s penetratio n o f mind , couple d wit h th e experiment s o f himself , of Priestly, an d o f Scheele , tha t le d t o th e collaps e o f th e phlogisto n theor y an d t o th e developmen t o f moder n chemistry . 1.2 . GENERA L Oxyge n i s th e eight h elemen t i n th e Periodi c Table . Th e electroni c structur e ca n b e represente d i n term s o f one-electro n wav e function s a s ls 2 2s 2 2p 4 ; th e groun d stat e an d som e o f th e lowe r excite d stat e term s ar e give n i n Tabl e 1 , wit h thei r energie s abov e th e groun d state , and some other important properties of oxygen are given in Table 2. Detailed calcula tion s o f th e wav e functio n fo r th e oxyge n ato m hav e bee n mad e usin g SC F an d othe r methods 2 . Oxyge n form s compound s wit h al l th e element s o f th e Periodi c Tabl e excep t fo r th e lightes t rar e gases . Thes e compound s coul d i n principl e b e forme d i f oxyge n wer e t o los e electron s (formin g cations) , t o gai n electron s (formin g anions ) o r t o shar e electron s (formin g bonds) . Th e first fou r ionizatio n potential s an d th e first tw o electro n affinitie s ar e give n i n Tabl e 2 . Thes e value s sho w tha t th e los s o f electron s fro m oxyge n i s a proces s requirin g muc h energy . Compound s ar e know n i n whic h oxyge n i s formall y cationic , suc h a s O/PtF^ , bu t i n al l know n case s th e cation s ar e polyatomic , an d i n genera l th e chemistr y o f oxyge n i s no t cationic . Th e doubl y charge d anio n O - 2 i s a commo n species , eve n thoug h it s formatio n fro m th e gaseou s ato m involve s substantia l absorptio n o f energ y ; i n ioni c oxide s th e lattic e energie s ar e ver y hig h an d mor e tha n compensat e fo r th e energ y o f formatio n o f O -2 . Thi s mus t als o explai n wh y th e singl y charge d 0 ~ i s onl y know n a s a n unstabl e specie s i n irradiate d solid s an d i n th e ga s phase ; i n oxide s i t i s unstabl e wit h respec t t o disproportionatio n t o O 2 an d O -2 . Th e coordinatio n number s o f 0~ 2 ions i n oxide s ar e se t ou t i n Tabl e 2 , an d ar e considere d i n mor e detai l i n sectio n 3.3 . Oxyge n ca n for m tw o additiona l bond s eithe r b y formin g tw o σ-bond s wit h othe r atom s o r groups , a s i n (ΟΗβ^Ο , o r b y formin g a σ-bon d an d a π-bon d wit h th e sam e othe r ato m 2 A . L . Mert s an d M . D . Torrey , / . Chem. Phys. 3 9 (1963 ) 694
; C . C . J . Roothaa n an d P . S . Kelly , Phys. Rev. 13 1 (1963 ) 1177
; E . Clementi , / . Chem. Phys. 4 0 (1964 ) 1944
.

GENERAL

TABL

E 1. ATOMIC ENERGY LEVELS OF OXYGEN

68
7

Electro

n configuratio n

2J22/>

4

2522/?3(450)35

2522/73(450)35

2522/73(450)3

^

2*22/73(450)3

^

2522/>3(450)4

y

2*22/73(450)4

5

2522/73(450)3ί

/

Ionization

:

2522/7

3 Stat e * "2/7 4 3 p 2/? 4 I D 2/7 4 1 5 3 5 55
0 3 5 35
0 3/ 7 5 p 3/ 7 3 p 4 5 55
0 4 5 35
0 3d 5£> 0 2/7 3 45
Ο / 2 1 0 2 0 2 1 1 2 3 2 1 0 2 1 4 3, 2 2,1, 0 3/

2 Energy above

groun d stat e (cm -1 ) 0. 0 158.
5 226.
5 1 5 867.
7 3 3 792.
4 7 3 767.8
1 7 6 794.6
9 8 6 625.3
5 8 6 627.3
7 8 6 631.0
4 8 8 630.8
4 8 8 630.3
0 8 8 631.0
0 9 5 476.4
3 9 6 225.
5 9 7 420.2
4 9 7 420.3
7 9 7 420.5
0 10 9 836.
7 Dat a fro m C . E . Moore , Atomic Energy Levels, NB S Circula r 46
7 (1949) . TABL

E 2. SOME PHYSICAL PROPERTIES OF THE OXYGEN ATOM

Ionizatio

n potentials a (eV )

Electro

n affinitie s (eV ) Atomi c weigh t (O 2 scale) d Atomi c radius e Ioni c radiu s d Va n de r Waal s radiu s r

Electronegativity

e 1st , 13.614 ; 2nd , 35.146
; 3rd , 54.934
; 4th , 77.39
4 1st , 1.478±0.00 2 b ; 2nd , (O , - > 0," 2 ) , -7.8±0. 3

15.999

4 0.7 3 A 1.3 9 ±0.00 4 A -1.5 0 A 3.4 6

Coordinatio

n number s a t oxygen: β (i ) I n ioni c o r near-ioni c compound s 2 (e.g . S1O2) , 3 (e.g . rutile) , 4 (e.g . ZnO) , 6 (e.g . MgO) , 8 (e.g . Na 2 0 ) (ii ) I n molecula r compound s 1 (e.g . CO) , 2 (e.g . H 2 0) , 3 (e.g . Me 2 OBF 3 ) , 4 (e.g . Be 4 OAc ) • C . E . Moore , Atomic Energy Levels, NB S Circula r 467
, 1949
. b R . S . Berry , J . C . Mackie , R . L . Taylo r an d R . Lynch , / . Chem. Phys. 4 3 (1965 ) 3067
. c Fro m thermochemica l cycles : M . F . C . Lad d an d W . H . Lee , Acta Cryst. 1 3 (1960 ) 959
. d A . E . Camero n an d E . Wickers , / . Am. Chem. Soc. 8 4 (1962 ) 4175
. e R . T . Sanderson , Chemical Periodicity, Reinhol d (1960) . ' A . Bondi , / . Phys. Chem. 6 8 (1964 ) 441
. Th e valu e i s abou t th e sam e fo r -O - an d fo r =0 . • Se e sectio n 3 . C.I.C . VOL II - Y

688 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

o r group , a s i n )C=0 . Specie s i n whic h oxyge n form s jus t on e σ-bon d wit h anothe r grou p (e.g . OH ) hav e bee n detecte d spectroscopically , bu t the y ar e fre e radical s an d ar e no t normall y stabl e unde r chemica l conditions . Fo r once , al l scale s o f electronegativit y agre e tha t oxyge n i s a ver y electronegativ e element . Th e electronegativit y depend s o n th e orbital s an d th e electro n configuration ; calculation s hav e bee n mad e o f th e parameter s associate d wit h th e valenc e stat e o f oxygen , base d o n spectroscopi c measurements 3 . A s expected , th e doubl e bond s ar e shorte r tha n th e singl e bonds , an d the y hav e highe r energie s an d stretchin g frequencies . Bond s o f intermediat e orde r ar e foun d i n man y compounds , includin g oxyanion s suc h a s RCO^ , COj 2 , NOj, or SO4 2 ; relationship s betwee n bon d length , bon d orde r an d stretchin g forc e constant s hav e bee n describe d fo r B O 4 , C O 5 , N O <* , SiO 7 , P O 7 , S O 8 an d CI O 7 bonds . Lik e fluorine, oxyge n i s a ligan d whic h tend s t o promot e oxidatio n o f othe r element s t o whic h i t i s boun d (cf . Os VIII 04) . Bond s fro m 2-coordinate d oxyge n ar e usuall y considere d a s forme d fro m (roughly ) sp* hybrid orbitals, leading to bond angles at oxygen near the tetrahedral value. This leave s tw o lon e pairs , whic h ar e als o regarde d a s bein g i n roughl y sp*-orbita\s. Thu s i n eac h o f th e compounds H2O, Μβ2θ and F 2 0 , th e angle s ar e nea r 109
° (Tabl e 3) . However , oxyge n ca n als o us e it s lon e pair s t o for m eithe r intermolecula r σ-bond s o r intramolecula r

π-bond

s additiona l t o th e norma l σ-bonds .

Additional

σ-bonds. Despit e it s hig h electronegativity , oxyge n i s a lon e pai r donor .

Compound

s lik e Μβ 2 0 for m complexe s wit h acceptor s suc h a s BF3 , an d value s fo r th e energie s o f som e donor-accepto r bond s involvin g oxyge n ar e give n i n Tabl e 4 , wit h som e value s fo r othe r element s fo r comparison . Wate r i s a well-know n dono r ligan d i n transitio n meta l chemistry ; oxyge n i s als o a hydroge n bon d acceptor , a s i n carboxyli c aci d dimer s an d i n ice . Al l thes e interaction s involv e th e lon e pairs . I n ic e an d i n basi c berylliu m acetate , th e angle s a t th e 4-coordinate d oxyge n atom s ar e roughl y tetrahedral , whic h als o implie s tha t th e lon e pair s ar e i n approximatel y spi-orbitals; similarly , i n HaO + , whic h i s isoelec - troni c wit h NH3 , th e angl e i s nea r 109°
. I n compounds , wher e i t form s tw o σ-bond s (e.g . Me20) , oxyge n i s a har d (clas s A ) base , thoug h i n compound s lik e Me2C= 0 i t ha s som e "soft " character . Wate r come s nea r th e "smal l Δ " en d o f th e spectrochemica l series ; wate r an d OH ~ hav e smal l trans-eïïects, an d i n th e nephelauxiti c serie s wate r an d OH ~ com e clos e t o F ~ a s ligand s wit h th e smalles t effect . Internal π-bonding. If an attached atom or group Q has empty orbitals of π-symmetry relativ e t o th e Q- 0 σ-bond , thes e wil l overla p th e lon e pai r orbital s a t oxygen , an d th e overla p ma y lea d t o th e formatio n o f a dono r π-bond . Thu s i n carbo n monoxid e th e C O bon d i s o f highe r orde r tha n 2 , an d th e strengt h o f th e bon d ca n b e attribute d a t leas t partl y t o a n interactio n o f th e for m (0 + = C - ) . I n compound s i n whic h oxyge n i s formin g tw o o r mor e σ-bonds , dono r π-bondin g lik e thi s wil l affec t bon d angle s a t oxygen . Th e dono r π-overla p wil l b e greates t whe n th e lon e pair s ar e i n pur e /?-orbitals . If one lone pair i s i n a pur e /^-orbital , th e tw o σ-bond s an d th e othe r lon e pai r mus t b e buil t fro m on e s~ and two /7-orbitals. This would lead (if all three σ-orbitals are equivalent) to an angle of

120°

. If both lone pairs are in pure /7-orbitals, the σ-bonds must be built from 5/7-orbitals, 3 G . Pilcher and H. A. Skinner, /. Inorg. Nucl. Chem. 24 (1962) 937. 4 J . Krogh-Moe , Acta Chem. Scand. 17 (1963) 843. 5 J . P . Fackle r and D. Coucouvanis, Inorg. Chem. 7 (1968) 181. * Yu . Ya . Kharitonov , Izv. Akad. Nauk SSSR, Otdel Khim. Nauk 1962, 1953. 7 E . A . Robinson , Can. J. Chem. 41 (1963) 3021. * P . Haake , W. B. Miller and D. A. Tyssee, /. Am. Chem. Soc. 86 (1964) 3577.

GENERAL

TABL E 3 . ANGLE S A T OXYGE N I n specie s QO

Z Angle

1 . Neither Z nor Q π-acceptors: H 2 0 F 2 0 (CH 3 ) 2 0 CH3O H RbO H 2 . Q, π-acceptor; Z, not:

S1H3OCH

3 3 . Q and Z both π-acceptors : C1 2 0 CI2O 7 SiH 3 OC 6 H 5 (SiH 3 ) 2 0 SiOS i i n silicate s (GeH 3 ) 2 0 [0 3 POP0 3 ]- 4 [0 3 SOS0 3 ]- 2 [0 3

CrOCr0

3 ]" 2 [CI5MOMCI5]- 4 ( M = Ru , Re ) 4 . Q 3 0+ : H 3 0 + (ClHg) 3 0 +

104.52

° 103.
1 ±0.05 °

111.5±1.5

° 109
° ±3 ° 180
° 120.
6 ±0.9 °

110.8±1

°

118.6±0.7

° 12

1 ±1°

144.
1 ±0.9 °

140-180

° 126.
5 ±0.3 ° 133.5
° 124
° 115
° 180
° 112
° 120

° How

measure d vib . ? wav e E D E D ? wav e E D E D E D E D E D X-ra y E D X-ra y X-ra y X-ra y X-ra y X-ra y X-ra y Phase vap . vap . vap . vap . vap . vap . vap . vap . vap . vap . soli d vap . soli d soli d soli d soli d soli d soli d Reference a b c c d e f g h i j k 1 m n 0 P q a W . S . Benedict , N . Gaila r an d E . K . Plyler , / . Chem. Phys. 2 4 (1956 ) 1139
. b Y . Morin o an d S . Saito , / . Mol. Spectrosc. 1 9 (1966 ) 435
. c K . Kimur a an d M . Kubo , / . Chem. Phys. 3 0 (1959 ) 151
. d C . Matsum a an d D . R . Lide , / . Chem. Phys. 5 0 (1969 ) 71
. e C . Glidewell , D . W . H . Rankin , A . G . Robiett e an d G . M . Sheldric k (t o b e published) . f J . D . Dunit z an d K . Hedberg , / . Am. Chem. Soc. 7 2 (1950 ) 3108
. 8 B . Beagley , Trans. Faraday Soc. 6 1 (1965 ) 1821
. h C . Glidewell , D . W . H . Rankin , A . G . Robiette , G . M . Sheldrick , B . Beagle y an d J . M . Freeman , Trans. Faraday Soc. 6 5 (1969 ) 2621
. 1 A . Almenningen , O . Bastiansen , V . Ewing , K . Hedber g an d M . Traetteberg , Acta Chem. Scand. 17 (1963) 2455. J D . W . J . Cruickshank , / . Chem. Soc. 1961
, 5486
; D . W . J . Cruickshank , H . Lynto n an d G . A . Barclay , Acta Cryst. 1 5 (1962 ) 493
. k C . Glidewell , D . W . H . Rankin , A . G . Robiette , G . M . Sheldrick , B . Beagle y an d S . Cradock , / . Chem. Soc. (A) , 1970
, 315
. 1 D . M . Macarthu r an d C . A . Beevers , Acta Cryst. 1 0 (1957 ) 428
. m H . Lynto n an d M . R . Truter , / . Chem. Soc. 1960
, 5112
. n C . A . Brystro m an d K . A . Wilhelmi , Acta Chem. Scand. 5 (1951) 1003. 0 A . M . Mathieson , D . P . Mello r an d N . C . Stephenson , Acta Cryst. 5 (1952 ) 185
; J . C . Morrow , Acta Cryst. 1 5 (1962 ) 851
. p C . E . Nordman , Acta Cryst. 1 5 (1962 ) 18 . q S . Séavniëa r an d D . Grdenié , Acta Cryst. 8 (1955 ) 275
.

690 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

TABL

E 4. GAS-PHASE DISSOCIATION ENTHALPIES FOR SOME

MOLECULA

R COMPLEXES (kcal mol

-1 )

Comple

x Me 2 OBF 3 Et 2 OBF 3 THFBF 3 Me 2 OBMe 3 Me 2 OAlMe 3 Me 2 OGaMe 3 Me 2 OBH 3 AH 13. 3 10. 9 13. 4 a b 9. 5 a Complex Me 2 SGaMe 3 Me 2 SBH 3 Me 3 NBF 3 Me 3 NAlMe 3 Me 3 NGaMe 3 Me 3 PBF 3 AH ~ 8 5. 2 b b 2 1 18. 9 Dat a from F. G. A. Stone, Chem. Rev. 58 (1958) 101. a To o unstable to study. b To o stable to determine. c Fo r dissociation into Me 2

S and B

2 HÔ . an d th e angl e at oxygen will be 180°. These possibilities, which are represented below in valence-bon d terms , ar e extreme s : intermediate angles might be expected, deriving from a balanc e betwee n π-bondin g (widenin g th e angle , an d removin g electron s fro m oxygen ) an d charg e distributio n (whic h wil l ten d t o kee p electron s o n th e oxyge n atom ) :

Interna

l π-bondin g wil l lea d t o shorte r an d stronge r bonds , an d shoul d weake n th e dono r propertie s o f the oxygen atom; the shortness and strength of bonds between oxygen and borono , silicon ™ o r transitio n elements 1 1 hav e bee n accounte d fo r i n term s o f thi s typ e of interaction . Severa l compound s are known in which oxygen is bound to one or two

π-acceptor

s an d in which the angle at oxygen is unusually wide (see Table 3). A similar argumen t coul d b e use d t o explain why angles in ChO + migh t b e neare r 120
° tha n 109°
;

π-interaction

s betwee n silico n an d Q woul d b e greates t i f the lone pair at Q were in a pure /7-orbital . However , thi s argumen t shoul d b e use d wit h som e caution ; th e angl e a t oxyge n i n RbO H i s 180°, yet there is unlikely to be significant π-bonding between rubidium and oxygen . Oxyge n i s known in a variety of formal oxidation states, from +2 to - 2. Of these, th e positiv e state s ar e (b y definition ) onl y foun d whe n oxyge n i s bound to a more electro negativ e element - whic h mus t b e fluorine - or forms part of a cation such as 0}. In other oxidatio n state s greate r tha n - 2 the oxygen atom concerned must either be bound to at leas t on e othe r oxyge n ato m o r for m par t o f a catio n o r fre e radical . A potential diagram fo r th e redo x chemistr y o f oxyge n i n aqueou s solutio n i s give n i n Tabl e 5 . » C. A. Coulson and T. W. Dingle, Acta Cryst. B24 (1968) 153. ! 0 D . W. J. Cruickshank, /. Chem. Soc. 1961, 5486. 1 1 F . A . Cotton and R. M. Wing, Inorg. Chem. 4 (1965) 867.

ISOTOPES OF OXYGEN

TABL E 5 . REDUCTIO N POTENTIAL S O F OXYGE N 69
1 (a)E ° I L , + 06 7 ^-HO2- +1-

5 +1-77

1 1 +Π·72 . ττ π πτ τ \ vt π +2-82 1 9

H Π

_ J +1-22 9 (b ) Ε · ο 2 -°' 5 6 o r +· 0 ' 4 1 ΗΟ

Γ =^- 0H+OH--ÌM20H-

-00 8 +0-8 7 Dat a fro m W . L . Latimer , The Oxidation States of the

Elements

and their Potentials in Aqueous Solution, 2n d edn. , Prentice-Hal l (1952) . 1.3 . ISOTOPE S O F OXYGE N

Unstabl

e Isotope s Th e know n radioactiv e isotope s o f oxyge n ar e al l artificial ; the y ar e liste d i n Tabl e 6 wit h representativ e nuclea r reaction s b y whic h they hav e bee n made . Th e half-live s ar e al l s o shor t tha t th e isotope s ar e unsatisfactor y fo r trace r work , thoug h som e trace r studies 1 2 hav e bee n mad e wit h O 15 . TABL E 6 . RADIOACTIV E ISOTOPE S O F OXYGE N

Isotop

e 01 3 O H OI S Öl * O2

0 Formation

Oi*(He3

, He*)Oi3

Ci2(He3

, /i)0"

Oi*(He3

, a)Oi5

Oi8(/i

, γ)0™ Oi8(/ , />)O2

0 ti, sec

7 3 12 2 29.
4 1

4 Decay

ß +

ß+

ß~ ß~

Referenc

e a b b b b • G . W . Butler , U S Atomi c Energ y Comm . UCRL-17783 , CFSTI , 1967.
CA 6 8 (1968) 64756η
. b R . L . Heath , i n Handbook of Chemistry and Physics, Chemica l Rubbe r Co. , Ne w Yor k (1967) . Stabl e Isotope s B y fa r th e mos t abundan t isotop e o f oxyge n i s O 16 , bu t natura l oxyge n (bot h elemen t an d compounds ) contain s smal l amount s o f O 1 7 an d O 1 8 (Tabl e 7) . Th e proportion s o f 1 2 C . T . Doller y an d J . B . West , Nature 18 7 (1960 ) 1121
.

692 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

thes e isotope s depen d t o a significan t exten t upo n th e sourc e o f oxygen . Natura l processe s suc h a s th e evaporatio n o f wate r lea d t o som e fractionatio n becaus e o f th e influenc e o f molecula r weigh t upo n physica l properties ; ther e ar e smal l difference s i n th e proportio n o f O 1 8 i n wate r fro m differen t natura l sources , an d indee d th e proportio n o f O 1 8 i n ocea n wate r varie s wit h th e depth 13 . Ther e i s als o som e isotopi e fractionatio n i n chemica l cycle s i n natur e tha t involv e oxygen . Th e variation s i n apparen t atomi c weigh t o f natura l oxyge n ma y b e a s great 1 4 a s ±0.0003 . TABL E 7 . STABL E ISOTOPE S O F OXYGE N

Isotop

e 01 6 OH " 01 8 Mass " (Ci 2 = 12.00 0 00 0 0 ) 15.99 4 91
5 16.99 9 13 4 17.99 9 16

0 Natural abundance

a

99.758

7 0.037 4 0.203 9 a W . H . Johnso n an d A . O . Nier , Handbook of Physics, McGraw - Hill , 2n d edn. , 1967
, pp . 9-63 . b Nuclea r spi n = 5/2 ; nuclea r magneti c momen t = 1.8930 nuclear magnetons ; nuclea r quadrupol e momen t = - 4ex 10~ 27
cm 2 . (Fro m J . A . Pople , W . G . Schneide r an d H . J . Bernstein , Nuclear Magnetic

Resonance,

McGraw-Hill , 1959.
) Man y differen t processe s hav e bee n describe d fo r producin g molecula r oxyge n o r oxyge n compound s enriche d i n O 1 7 o r O 18 ; som e mak e us e o f th e slightl y differen t equilibriu m constant s fo r compound s o f O 1 6 an d O 1 7 o r O 18 , bu t mos t depen d o n som e physica l propert y o f O 2 o r oxyge n compound s suc h a s H2 O o r N2O . I n practic e th e mos t importan t processe s ar e th e fractiona l distillatio n o f wate r an d (fo r hig h enrichments ) th e therma l diffusio n o f oxyge n gas ; th e ga s fe d int o th e colum n fo r separatio n b y therma l diffusio n ma y b e obtaine d b y th e electrolysi s o f wate r tha t ha s alread y bee n enriche d i n O 1 8 b y fractiona l distillation . Heav y wate r o f enrichmen t u p t o 9 8 atom- % O 1 8 an d 2 0 atom- % O 1 7 i s commerciall y available, a s i s oxyge n ga s 99
% i n O 1 8 o r 90-95
% i n O 17 . Thes e ar e th e mos t commonl y use d startin g material s ; of course it is possible to produce enriched O2 b y th e electrolysi s o f enriche d water . Sample s o f oxyge n an d it s compound s ar e usuall y analyse d fo r isotopi e compositio n b y mas s spectrometr y ; if compounds are involatile, thei r oxyge n mus t b e converte d int o som e volatil e specie s first. O 18 . Oxygen-1 8 ha s bee n extensivel y use d t o stud y mechanism s o f reactions , an d i n particula r o f hydrolysis . Th e exchang e rate s o f man y commo n oxyacid s an d oxyanion s hav e bee n studie d quantitativel y o r semi-quantitatively 15 ; th e structure s o f simpl e molecule s containin g oxyge n hav e bee n determine d b y microwav e spectroscopy 1 6 wit h th e hel p o f sample s enriche d i n O 18 , an d vibration s involvin g th e movemen t o f oxyge n atom s hav e bee n identifie d b y th e exten t t o whic h the y shif t i n sample s enriche d i n O 18 . I n th e infrare d 1 3 M . Dole , J. Gen. Physiol. 4 9 (1965 ) 5 . 1 " A . E . Camero n an d E . Wickers , / . Am. Chem. Soc. 8 4 (1962 ) 4175
. 1 5 D . Samuel , i n Oxygenases (ed . O . Hayashi) , Academi c Press , Ne w Yor k (1962) . 1 6 M . C . L . Gerry , J . C . Thompso n an d T . M . Sugden , Nature 21
1 (1966 ) 846
.

ISOTOPES OF OXYGEN 693

spectr a o f adduct s o f molecula r oxyge n wit h compound s o f transitio n metals , there is a band nea r 800-90
0 cm" 1 tha t i s assigne d t o th e (O-O ) stretchin g mode . I n (tbuNC) 2 Ni(0 2 ) an d (tbuNC)2Pd(02 ) thi s ban d split s int o thre e whe n th e comple x i s prepare d fro m 0 2 con tainin g 2 5 atom- % O 18 : th e thre e component s ar e du e t o stretchin g mode s i n L 2 M(02 6 ) , L 2 M(0 16 0 18 ) an d L 2 M(02 8 ) ; th e relativ e intensitie s an d th e difference s i n frequenc y betwee n th e band s confir m thi s assignment 17 . A simila r approac h ha s le d t o th e identifica tio n i n matrice s a t lo w temperature s o f activ e specie s containin g mor e tha n on e oxyge n atom . Th e preparatio n o f O 1 8 i n naturall y occurrin g system s ha s bee n muc h studie d i n con nectio n wit h climatolog y an d palaeoclimatology . Th e variatio n i n O 1 8 conten t o f arcti c sno w ove r th e yea r help s t o establis h th e origi n o f th e wate r fro m whic h th e sno w wa s formed 18 . I n palaeoclimatolog y i t i s th e oxyge n isotopi e compositio n o f carbonat e i n fossil s tha t i s measured 19 » 20 . Th e variatio n wit h temperatur e o f th e equilibriu m constan t fo r th e reactio n H 2

Oi8+l/3(C0

16 )~ 2 ^H 2

Oi6+l/3(COj

8 )- 2 ha s bee n determine d accurately . Certai n fossi l shell-fis h contai n carbonat e rock . Th e temperatur e a t whic h thi s carbonat e wa s precipitate d ca n b e determine d fro m th e isotopi e distributio n o f th e carbonat e i n th e shell , usin g th e equatio n / = 16.5-4.3^+0.14<5 2 wher e t i s th e temperatur e i n ° C an d δ i s a measur e o f th e differenc e betwee n th e O 1 8 conten t o f th e sampl e an d o f th e standar d workin g gas . Thi s us e o f th e O 1 8 conten t o f carbonat e i s sometime s referre d t o a s th e carbonat e thermometer . I n practice , matter s ar e no t s o simple 19 . Fo r th e informatio n obtaine d t o hav e an y meaning , certai n condition s mus t b e fulfilled . Th e carbonat e mus t hav e bee n precipitate d i n isotopi e equilibriu m wit h th e surroundin g water ; th e isotopi e compositio n oftha t wate r mus t b e known ; an d ther e mus t hav e bee n n o subsequen t exchange . Thoug h som e shell fish (e.g . coral ) precipitat e carbonat e tha t i s no t i n equilibriu m wit h th e surroundin g water , i n mollusc s th e equilibriu m i s maintained . Fo r shell s fro m ope n ocean s i t i s usuall y assume d tha t th e O 1 8 conten t o f th e surroundin g wate r wa s no t ver y differen t fro m tha t o f ocea n wate r nowadays ; fo r isolate d ocean s thi s ma y wel l no t b e s o becaus e o f suc h thing s a s evaporation , an d allowanc e mus t b e mad e fo r thi s (perhap s b y usin g th e O 1 8 conten t o f th e phosphat e o f th e shell) . Bu t i t i s wit h th e thir d conditio n tha t th e mos t seriou s diffi cultie s arise . I t i s har d enoug h t o mak e sur e tha t th e oxyge n fro m th e carbonat e i n th e shel l i s extracte d an d analyse d withou t exchange ; i t i s eve n harde r t o mak e sur e tha t nothin g untowar d ha s happene d t o th e sampl e betwee n fossilizatio n an d analysis . Fortunatel y ther e ar e som e interna l test s tha t ca n b e applied . Fo r example , i n most , bu t no t all , fossi l shell s studie d th e rati o o f (0 18 :0 16 ) t o Sr+ 2 i s th e sam e a s i t i s i n ocean s a t present ; therefor e shell s i n whic h thi s rati o i s ver y differen t ma y b e suppose d t o hav e undergon e "diagehetic " change s (i n othe r word s the y ar e useles s fo r isotopi e analysis) . However , ther e i s alway s th e naggin g possibilit y tha t a particula r sampl e ma y b e atypical - som e molluscs , fo r instance , d o no t deposi t carbonat e uniforml y throughou t th e year - an d i t i s rar e tha t 1 7 K . Hirota , M . Yamamoto , S . Otsuka , A . Nakamur a an d Y . Tatsuno , Chem. Communs. 1968
, 533
. i s L . Alda z an d S . Deutsch , Earth Planet Sci. Letters 3 (1967 ) 267
. w H . A . Lowenstam , i n Problems in Palaeoclimatology (ed . A . E . M . Nairn) , Wile y (1964) , p . 227
. 2 0 R . Bowen , Palaeotemperature Analysis, Elsevier , Amsterda m (1966) .

694 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

enoug h goo d sample s fro m a particula r are a ar e availabl e fo r a prope r statistica l analysis . Som e claim s abou t palaeotemperatur e ma y hav e bee n base d o n ver y slende r evidenc e derive d fro m th e carbonat e thermometer ; bu t whe n al l i s sai d an d don e th e remarkabl e thin g i s tha t suc h a n extrapolatio n t o th e temperature s o f pas t age s i s eve n possible . O 17 . Th e isotop e O 1 7 i s importan t despit e it s smal l natura l abundanc e becaus e i t i s th e onl y stabl e isotop e o f oxyge n wit h nuclea r spin , an d s o i s th e onl y on e tha t ca n b e use d t o stud y oxyge n n.m.r . o r oxyge n hyperfin e interaction s i n electro n resonanc e spectroscopy 21
.

Unfortunately

, however , th e spi n o f 5/ 2 i s associate d wit h a larg e quadrupol e moment , leadin g t o broa d n.m.r . line s becaus e o f th e relativel y rapi d relaxatio n o f th e oxyge n nuclei .

Chemica

l shift s ar e difficul t t o determine , an d couplin g i s ofte n no t observe d a t all . How ever , broadenin g du e t o quadrupola r relaxatio n ha s itsel f bee n use d t o giv e informatio n abou t th e field gradien t a t th e oxyge n nucleus ; line s ar e sharpe r whe n oxyge n i s boun d t o a n electropositiv e element , eve n i n a hig h oxidatio n state , becaus e the n th e oxyge n ato m approximate s t o th e io n O^ 2 i n whic h th e field gradien t a t th e nucleu s i s zero . Som e value s fo r O 1 7 chemica l shift s ar e give n i n Tabl e 8 ; the y wer e measure d relativ e t o H2O 1 7 (usuall y a s externa l standard) , an d som e o f th e uncertaintie s ar e substantial . I t i s clea r fro m thes e an d othe r value s tha t oxyge n formin g tw o σ-bond s give s resonanc e i n th e rang e -25 0 t o 0 pp m fro m H 2 0 1 7 ( +ve to high field), but that oxygen forming a double bon d give s resonanc e i n th e rang e - 140
0 t o - 25

0 ppm. The dichromate ion

22
, fo r instance , give s tw o resonances , th e on e (stronge r an d sharper ) a t - 112 9 pp m du e t o th e terminal , an d th e othe r (weake r an d broader ) a t - 34 5 pp m du e t o th e bridgin g "oxyge n atoms .

Similarly

23
, aqueou s aceton e give s a singl e O 1 7 resonanc e i n th e )C= 0 region , a t - 52

3 ppm, indicating that the molecule dissolves unchanged ; formaldehyde gives a

resonanc e a t - 5 1 ppm , i n th e "single-bond " region , s o i t i s conclude d tha t th e specie s presen t i s th e hydrate d for m H 2 C(OH) 2 . Acetaldehyd e give s tw o peaks , th e on e a t - 55

0 ppm associated with the unchanged molecule CH3CHO, and the other at -67 ppm

associate d wit h th e hydrate d for m CH3CH(OH) 2 . Exchang e betwee n thes e tw o specie s an d th e solven t i s slo w o n th e n.m.r . timescale . Fo r doubly-boun d oxyge n ther e i s a correlatio n betwee n th e chemica l shif t an d th e frequenc y o f th e first ultraviolet/visibl e absorptio n band 24
. Furthermore , a correlatio n ha s bee n reporte d betwee n bon d length , bon d orde r an d O 1 7 chemica l shift s i n som e Cr(VI)- 0 species 2 ^ . Th e ful l rang e o f validit y o f th e latte r correlatio n ha s stil l t o b e established . Io n hydratio n ha s bee n extensivel y studie d b y O 1 7 n.m.r . spectroscopy . Fo r certai n paramagneti c ion s ther e ar e "contac t shifts " whic h wit h C0+ 2 an d Ni + 2 lea d t o th e observa tio n o f separat e resonance s du e t o wate r i n th e hydratio n shel l o f th e catio n an d t o th e solven t itself . For certain diamagnetic ions which exchange their hydration water slowly wit h th e solvent , separat e O 1 7 resonance s fo r solven t an d fo r solvatin g wate r hav e bee n observe d (Tabl e 9) . Ther e ar e othe r case s wher e exchang e o n othe r ground s i s know n t o b e slow , bu t where , non e th e less , th e onl y O 1 7 resonanc e observe d i s tha t du e t o th e solvent . Th e additio n o f Co+ 2 o r Dy+ 3 ion s t o th e solutio n cause s th e solven t resonanc e t o shif t t o lo w field throug h th e "contac t shift " mechanism , an d s o ca n expos e th e resonanc e du e t o th e hydrate d diamagneti c cation ; thi s devic e ha s als o bee n use d t o separat e th e 2 1 B . L . Silver and Z. Luz, Quart. Rev. 21 (1967) 458. 2 2 B . N . Figgis , R . G . Kid d and R. S. Nyholm, Can. J. Chem. 43 (1965) 145. 2 3 P . Greenzaid , Z . Lu z an d D . Samuel , J. Am. Chem. Soc. 89 (1967) 749. 2 4 B . N . Figgis , R . G . Kid d and R. S. Nyholm, Proc. Roy. Soc. A, 269 (1962) 469. 2 5 R . G . Kidd , Can. J. Chem. 4 5 (1967 ) 605.

TABLE 8. CHEMICAL SHIFTS FOR O

17 , RELATIV E T O H 2 0 1 7 (ppm )

Transitio

n elemen t system s Na 3 V0 4 ' Na 2 Cr0 4 a

K2M0O4

a Na 2 W0 4 a NaMn0 4 a NaTc0 4 a NaRe0 4 a Ru0 4a Os0 4a Cr0 2 Cl 2 (1 ) d Na 2 Cr 2 0 7 d UO J aq. r

Fe(CO)

5e (

D Ni(CO)

4e (l ) -571±4 -83 5 + 5 -540± 2 -420± 2 -1219+ 8 -749± 7 -569± 4 -1119+1 0 -796± 3 -146 0 ± 8 -112 9 (term. ) -34 5 (br. ) -1115± 2 -38 8 + 8 -362±

8 Main group systems

H2O 2 (30 % aq. ) K2CO 3 ( 7 M b ) HNO 3 (100% ) POCI 3 (1 ) H3PO 4 (1 ) SOCI 2 (1 ) SO2CI 2 (1 ) H2SO 4 (cone. ) Na 2 Se0 4 (3 M b ) H 6 Te0 6 (aq. ) NaC10 3 (2. 4 M b ) HClO 4 (60%aq. )

NaC104

(2. 4 M b ) NaBr0 3 (2. 4 M b ) XeOF 4

Xe(OH)

2 h (aq. ) a a a a c a a c a g a c a a h i -187±5 -192± 4 -414± 3 -216± 2 -8 0 -292± 2 -304± 3 -14 0 -204±1 2 -12 0 -28 7 + 3 -28 8 -288± 5 -297± 5 -31 3 + 2 -27 8 + 2 Carbon-oxygen systems c MeO H EtO H tBuO H Fura n CH3CH O Aceti c aci d

CH3COOCH

3 (CH 3 CO) 2 0 di-tBu 2 0 2 MeONH 2 tBuON

O + 37

- 6 -7 0 -24 1 -59 5 -25 4 f-355(C=0 ) \-137(OMe ) f-393(C=0 ) < I- 259
CO ) -26 9 -3 5 -83 8 (N=0 ) -51 3 CO ) a Dat a fo r aqueou s solutions , unles s otherwis e stated , fro m B . N . Figgis , R . G . Kid d an d R . S . Nyholm , Proc. Roy. Soc. A , 26
9 (1962 ) 469
. b 0. 1 N aqueou s alkali . c Dat a fo r pur e liquid s fro m H . A . Christ , P . Diehl , H . R . Schneide r an d H . Dahn , Helv. Chim. Acta 4 4 (1961) 865
. d B . N . Figgis , R . G . Kid d an d R . S . Nyholm , Canad. J. Chem. 4 3 (1965 ) 145
. e R . Bramley , B . N . Figgi s an d R . S . Nyholm , Trans. Faraday Soc. 5 8 (1962) 1893
; R . G . Kidd , Canad. J. Chem. 4 5 (1967) , 605
. f S . W . Rabideau , / . Phys. Chem. 7 1 (1967 ) 2747
. " Z . Lu z an d I . Pecht , / . Am. Chem. Soc, 8 8 (1966) , 1152
. h J . Shamir , H . Selig , D . Samue l an d J . Reubin , / . Am. Chem. Soc. 8 7 (1965) 2359
. 1 J . Reuben , D . Samuel , H . Seli g an d J . Shamir , Proc. Chem. Soc. 1963
, 270
. i*h

696 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

resonance s o f wate r an d o f phosphori c acid 26
. Th e hydratio n o f ion s o r complexe s o f Be+ 2 , Al+3 , Ga+3, VO+2, Tl+3, Co+ 2 , Ni+ 2 an d Cu+ 2 ha s bee n studie d usin g thes e an d simila r techniques . Finally , O 1 7 n.m.r . afford s informatio n abou t H bondin g an d th e structur e o f aqueou s solutions ; O 1 7 resonances , lik e proto n resonances , ar e shifte d t o lo w field b y hydroge n bonding 27
. Th e e.s.r . spectr a o f organi c compound s containin g O 1 7 hav e bee n importan t i n relatio n t o calculation s o f th e electroni c structure s o f thes e compounds , an d particularl y o f heterocycli c compounds . Th e hyperfin e interactio n constant s i n 0 17 -labelle d Mn(acac) 3 ha s bee n used 2 8 a s th e basi s fo r a n estimat e o f th e covalen t characte r o f th e metal-oxyge n bonds . Th e e.s.r . spectru m o f a sampl e o f CF3OOCF 3 tha t ha d bee n photolyse d i n th e TABL E 9 . COUPLIN G CONSTANT S)

Specie

s CIO 4 XeOF 4 H2 O (MeO) 3P CI3P O M11O 4 Me

2CO Coupling nuclei

C135-01

7

Xei29_o

n Hl-01 7

P31-01

7

Ρ31-Ο

Π

Mn55-Oi

7

C13-01

7

Couplin

g constant s

85.5±0.

5 69
2 ±1 0

79±

2 16 0 22
5 3 0 2

2 Reference

a b c d d e e 1 M . Alei , / . Chem. Phys. 4 3 (1965 ) 2904
. b J . Shamir , H . Selig , D . Samue l an d J . Reuben , / . Am. Chem. Soc. 8 7 (1967 ) 2359
. c A . E . Flori n an d M . Alei , / . Chem. Phys. 4 7 (1967 ) 4268
. d H . A . Christ , P . Diehl , H . R . Schneide r an d H . Dahn , Helv. Chim. Acta 4 4 (1961 ) 865
. e M . Broz e an d Z . Luz , / . Phys. Chem. 7 3 (1969 ) 1600
. presenc e o f smal l amount s o f 0 2 enriche d (~30% ) i n O 1 7 showe d tha t a fre e radica l ha d bee n forme d wit h thre e differen t set s o f O 1 7 hyperfin e splittin g constants , an d i t wa s con cluded 2 9 tha t th e radica l wa s th e trioxid e specie s CF3COOO . Hyperfin e structur e i n th e e.s.r . spectru m o f [(H 3 N) 5

Co(02)Co(NH3)5]

+ 5 du e t o O 1 7 i n th e peroxy-bridg e provide d th e first direc t evidenc e tha t th e unpaire d electro n i s associate d wit h th e bridg e a s wel l a s wit h th e cobal t nuclei 30
. 1.4 . OCCURRENC E AN D EXTRACTIO N Oxyge n i s th e mos t abundan t elemental . I n combine d for m i t make s u p 46.60
% b y weigh t o f th e rock s o f th e earth' s crust , an d (a s th e element ) 20.94

6 + 0.002% by volume of

2 6 J . A . Jackso n an d H . Taube , / . Phys. Chem. 6 9 (1965 ) 1844
. 2 7 Z . Lu z an d G . Yagil , / . Phys. Chem. 7 0 (1966 ) 554
. 2 8 Z . Luz , B . L . Silve r an d D . Fiat , / . Chem. Phys. 4 6 (1967 ) 469
. 2 9 R . W . Fessenden , / . Chem. Phys. 4 8 (1968 ) 3725
. 3 0 J . A . Wei l an d J . K . Kinnaird , / . Phys. Chem., 7 1 (1967 ) 3341
. 3 1 The Production of Oxygen, Nitrogen and the Inert Gases, Britis h Oxyge n Co . (1967) .

OCCURRENCE AND EXTRACTION 697

dr y ai r a t se a level . Nowaday s th e atmospher e i s th e primar y sourc e o f oxyge n fo r large - scal e commercia l productio n o f th e ga s o r liquid , bu t chemica l processe s hav e bee n devise d an d extensivel y use d i n th e past . Mos t ar e base d o n substance s whic h combin e wit h oxyge n a t on e temperatur e an d releas e i t o n heating . Th e ol d Bri n proces s mad e us e o f th e reaction betwee n bariu m oxid e an d oxyge n a t 600°
: hig h pressur e

BaO+O.5O2

, Ba0 2 lo w pressur e Th e bariu m oxid e i s heate d wit h ai r tha t ha s bee n free d o f CO2 , wate r vapour , organi c matte r an d dust ; th e pressur e i s lowered , an d pur e oxyge n i s evolved . A modificatio n o f th e proces s ha s recentl y bee n devised ^ i n whic h us e i s mad e o f th e fac t tha t th e meltin g poin t o f BaC> 2 (450° ) i s muc h lowe r tha n tha t o f Ba O (1923°) . Severa l simila r processe s hav e bee n propose d fo r makin g pur e oxygen , whic h ha s als o bee n mad e electrolytically , bu t almos t al l oxyge n i s no w produce d b y th e liquefactio n an d fractiona l distillatio n o f air .

Method

s fo r doin g thi s diffe r i n detail . Th e Lind e doubl e colum n consist s o f on e fractionat in g colum n operatin g a t abou t atmospheri c pressure , an d anothe r operatin g a t 5- 6 atm . A t th e highe r pressur e nitroge n boil s a t - 170° , an d s o ma y b e condense d usin g liqui d oxyge n fro m th e colum n a t lowe r pressur e a s refrigerant . Afte r initia l compressio n an d coolin g b y water , th e ai r i s furthe r coole d b y hea t exchang e wit h gase s leavin g th e columns ; th e coolin g b y expansio n tha t follow s ma y tak e plac e unde r Joule-Thompso n conditions , b y doin g externa l work , o r b y a combinatio n o f th e two . I n th e productio n o f oxyge n gas , th e us e o f hea t exchanger s calle d regenerator s i s o f considerabl e importance 33
.

Alternativ

e source s o f oxyge n fo r enclose d system s hav e becom e o f increasin g im portanc e i n th e pas t fe w year s wit h th e developmen t o f spac e craf t an d nuclea r submarines .

Scheme

s hav e bee n devise d fo r producin g oxyge n fro m CO

2 by means of algae, or by catalytic

hydrogénatio n followe d b y electrolysi s o f th e wate r formed 34
. Oxyge n "candles " hav e bee n propose d fo r carryin g oxygen ; thes e consis t o f salt s o f oxy-anion s whic h ar e bot h thermall y unstabl e an d ric h i n oxygen , suc h a s L1CIO4 , NaC10 3 o r KO2 . A lithiu m perchlorat e candl e ha s bee n describe d consistin g o f 84.82
% b y weigh t o f L1CIO4 , 10.94 % M n an d 4.24 % o f LÌ2O2 ; th e soli d i s compresse d t o a densit y o f 2.3 2 g/cc , an d th e oxyge n availabl e o n heatin g i s equivalent , volum e fo r volume , t o tha t fro m liqui d oxygen 3 ^ . I n th e laboratory 36
, oxyge n ma y b e mad e b y heatin g potassiu m permanganat e o r othe r salt s thermall y unstabl e an d ric h i n oxygen , bu t commercia l oxyge n ca n b e purifie d b y successiv e treatmen t wit h ΚΜηθ4 , wit h KOH , an d wit h concentrate d H2SO4 . Th e bes t metho d o f makin g pur e oxyge n i n th e laborator y i s t o catalys e th e decompositio n o f 30
% H2O 2 wit h thi n nicke l shee t suspende d b y a platinu m wire ; electrolysi s ma y als o b e used . 3

2 S. A. Guerrieri, US pat. 3,310,381, 1966 (Chem. Abstr. 66 (1967) 106659z).

3 3 R . L . Shower and L. C. Matsch, Adv. PetroKlhem. Refining 9 (1964) 1. 3

4 p. J. Hannan, R. L. Shuler and C. Patouillet, NASA Ace. No. N63-14930, 1962 (Chem. Abstr. 62

(1965 ) 2006a)
; NAS A Ace . No. N64-10551,1963 (Report No. AD 420927) (Chem. Abstr. 61 (1964) 16488d). 3 5 C . S . Coe , Chem. Engng. Progress, Symp. Ser. 60 (1964) 161. 3

6 G. Brauer (ed.), Handbook of Preparative inorganic Chemistry, 2nd edn., Academic Press, New York

(1963) , p. 334.

698 OXYGEN : E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

1.5 . STRUCTURA L PROPERTIE S

Electroni

c Structur e Th e electroni c structur e o f th e oxygen molecule can be represented very simply as 0=0 . This representation indicates that the O-O bond should be short and strong (as it is - se e Tabl e 10) but offers no explanation for the paramagnetism of the molecule. To accoun t for this property in terms of simple valence-bond theory, it is necessary to invoke TABL E 10. SOME MOLECULAR PROPERTIES OF O2 IN ITS GROUND STATE Bon d dissociatio n energ y Bon d lengt h Bon d stretching-forc e constan t

Ionizatio

n potentia l (adiabatic )

Electro

n affinities : 1s t 'Double '

Polarizabilit

y : Spin-orbi t couplin g constan t λ Z) = 5.114±0.002eV = 1.20 7 39
8 Â (fro m u.v . spectrum ) = 1.20 7 4 1 ±0.00 0 0 2 A (fro m th e e.s.r . spectrum ) k = 11.40 9 x 10- 5 dyn e cm~ i = 12.07 5 ±0.0 1 e V = 0.4 3 ± 0.0 1 e V = -6.7±0.6e V (fo r 0

2(g)->02-2(g)

= 1.2x10-2 4 = 2.4x10-2 4 = 1.6x10-2 4 = 1.985cm- i Reference a b c b d e f g h β P . Brix and G. Herzberg, Can. J. Phys. 32 (1954) 110. b G . Herzberg, Spectra of Diatomic Molecules, 2nd edn., van Nostrand (1950). c M . Tinkham and M. W. P. Strandberg, Phys. Rev. 97 (1955) 951. d K . Watanabe, J. Chem. Phys. 26 (1957) 542. e J . L . Pack and A. V. Phelps, /. Chem. Phys. 44 (1966) 1870. f L . A . D'Orazio and R. H. Wood, /. Chem Phys. 69 (1965) 2558. 8 Landolt-Börnstein , Zahlenwerte und Functionen aus Physik-Chemie-Astronomie-Geophysik und Technik,

Sechst

e Auflage , 1 Band, 3 Teil, p. 510. h K . Kayama and J. L. Baird, /. Chem. Phys. 46 (1967) 2604. three-electro n bonds 3 7 o r t o us e th e "double quartet" approach 3 » . In simple molecular orbita l terms , th e paramagnetism is explained by the two unpaired electrons in the anti- bondin g π^-orbital 39
. The configuration is

(σίΐ5)2(συ1ί)2(σί25)2(σΜ25)2(σ,2ρ)2(πΜ2ρ)4(πί2/7)2.

Althoug

h in B 2 , C

2 and N2 the (a

g 2p) leve l is above the (n u 2p) leve l becaus e of interaction wit h (a g 2s) 9 i n O2 the order is as shown. More detailed calculations using the LCAO SCF metho d wit h configurationa l interaction 4 0 give s goo d agreemen t wit h the observed value fo r th e total energy, but the agreement between the observed and the calculated values for th e dissociatio n energ y is less satisfactory. Th e photo-electro n spectru m o f molecula r oxyge n excite d usin g He l radiatio n (21.2 3 eV ) give s a t least four and possibly five bands, all with vibrational progressions. The adiabatic ionizatio n potential s an d observed vibration frequencies are given in Table 11 A. 3 7 L . Pauling, The Nature of the Chemical Bond, 3rd edn., Cornell University Press, Ithaca, NY. 3 8 J . W . Linnett, The Electronic Structure of Molecules, Methuen, London (1964). 3

9 J. N. Murrell, S. F. A. Kettle and J. M. Tedder, Valence Theory, Wiley, New York (1965).

4 0 K . Ohno, in Middle U.V.: Its Science and Technology (ed. A. E. S. Green), Wiley, New York (1966).

STRUCTURAL PROPERTIES 699

Th e ban d a t lowes t I.P . correspond s t o remova l o f a n anti-bondin g n g electron producin g O J i n it s electroni c ground-stat e 2 U g ; a s woul d hav e bee n expected , th e vibratio n frequenc y i s greate r tha n i n O2 . Th e nex t band , wit h a lon g vibrationa l progression , correspond s t o remova l o f a π-bondin g electron givin g 0+( 4 Iï w ) ; peak s associate d wit h th e productio n o f 0+( 2 Π Μ ) ma y als o occu r i n thi s region . Th e nex t ban d correspond s t o remova l o f a σ-bondin g electron givin g 0+( 4 Σ 9 ), an d th e fifth ban d ma y correspon d t o th e formatio n o f 0 2H ( 4 Σ J o r 0+( 2

Σ;")

. In each case the electron removed is bonding, as shown by the drop in vibration frequenc y o n ionization 4 ° a . TABL E 1 1 A . PARAMETER S FRO M TH E PHOTO-ELECTRO N SPECTRU M O F 02

Adiabati

c I.P. , e V 12.0 7 16.1 2 a 18. 7 20.2

9 Vibration frequency

excite d (0-1) , cm T l 178
0 101
0 288
7 109
0 113

0 State of O2 formed

2 n , 4 n u 2 n u 4 Σ , 4 Σ Μ o r 2Σ 7 a Th e (0-0 ) transitio n o f thi s serie s was no t identified . Dat a fro m D . W . Turne r et ah, Molecular Spectroscopy, Wiley , Ne w York , 1970
.

Molecula

r an d Crysta l Structur e Th e O- O distanc e i n gaseou s 0 2 ha s bee n determine d ver y accuratel y b y analysi s o f th e

Schumann-Rung

e band s i n th e u.v . an d als o b y microwav e spectroscop y (se e Tabl e 10) . Th e O- O distance s i n liqui d an d soli d oxyge n hav e no t bee n accuratel y determined , bu t th e diffractio n measurement s fo r th e thre e soli d form s ar e consisten t wit h (O-O ) bonde d distance s clos e t o thos e fo r fre e O2 , a s i s th e smal l chang e i n (O-O ) stretchin g frequenc y wit h chang e i n phase . TABL E 11B . SOLI D (^-STRUCTURE S For m a ß y Clas s

Monoclini

c

Rhombohedra

l Cubi c Space group

C2lm(Cl")

RlmW h )

PmMOl) Unit cell

dimension s a = 5.40 3 ±0.00 5 b = 3.42 9 ±0.00 3 c = 5.08 6 ±0.00 5 a = 4.21 0 ±0.0 7 a = 46
° 16'±9 ' a = 6.8 3 ±0.0

5 Molecules in

uni t cel l 2 3

8 Reference

a b c a C . S . Barrett , L . Meye r an d J . Wassermann , / . Chem. Phys. 4 7 (1967 ) 592
. b R . A . Alikhanov , Soviet Physics JETP 18 (1964 ) 556
; E . M . Hörl , Acta Cryst. 1 5 (1962 ) 845
. c T . A . Jordan , W . E . Streib , H . W . Smit h an d W . N . Lipscomb , Acta Cryst. 1 7 (1964 ) 777
. 4<> a D . W . Turner , C . Baker , A . D . Bake r an d C . R . Brundle , Molecular Spectroscopy, Wiley , Ne w York , 1970
.

700 OXYGEN: E. A. V. EBSWORTH, J. A. CONNOR AND J. J. TURNER

Th e structur e o f crystallin e y-oxyge n (th e highes t temperatur e form) 4 1 i s ver y lik e tha t o f a-F 2 . Ther e ar e eigh t molecule s i n th e uni t cel l : two are roughly spherically disordered, o n m3(T h ) sites , an d si x ar e cylindricall y disordere d o n 42m(D
2d ) sites , wit h th e 4 (5 4 ) axi s perpendicula r t o th e molecula r axis . Thi s phas e i s sof t an d transparent , an d les s dens e tha n th e others ; it s structur e i s regarde d a s mor e lik e tha t o f liqui d oxyge n tha n lik e tha t o f th e 3-74 8 FIG . 1. The structure of a-oxygen; monoclinic C2/m. Atom centres and intermolecular distances ar e indicate d ; molecules are centred at 000 and Ü0, with O-O bonds approximately normal to the (O-O ) plane . (Reproduce d wit h permissio n fro m C . S . Barrett , L . Meye r an d J . Wasserman , / . Chem. Phys. 4 7 (1967 ) 592.
) E (volts ) (6loX ) 2 0 (72 3 (76 3 (100 0 1 0 - r? r lonizatio n limits OE •M M < 2 > i Jil l 'ι' Ι I-U r Mi ! ly-U f i=l-279 X re=l 409X °2*> Eg Γ

β=Ι·38ΪΧΟ$Α

2 Π" " Fourth -Thir d oVri u Secon d _,.e=H227 X - + Γ~^Γ ~ rirst 1 ο;χ·π , r. = l-604X (4 ) (5 ) (6 ) (7 ) (10)(8)(9 ) J 02B ? 2U (3 ) r c- I-207X

02Χ

3

Σς

FIG . 2. Energy level diagram of the O2 molecule. (Reproduced with permission from G. L.

Weissle

r an d P o Lee , / . Opt. Soc. Am. 4 2 (1952 ) 200.
) 4 1 T . A . Jordan , W . E . Streib , H . W . Smit h an d W . N . Lipscomb , Acta Cryst. 1 7 (1964 ) 777
.

SPECTROSCOPIC PROPERTIES 701

/?-form . Thi s i s consisten t wit h th e relativel y smal l hea t an d volum e change s o n meltin g (smalle r tha n th e correspondin g change s associate d wit h th e transitio n o f ß t o a - se e Tabl e 15c) 42
» 43
, an d wit h th e closel y simila r vibrationa l spectr a o f γ-Οζ an d liqui d O2 .

The/?-for

m i s rhombohedral 42
· 4 3 an d th e a-for m i s monoclini c (Tabl e 11B) . Th e structur e o f th e α-for m i s give n i n Fig . 1 ; the O2 molecules lie parallel to one another, and with their molecula r axe s perpendicula r t o th e O- O planes 43
. FIG

. 3. Potential energy as a function of internuclear distance for states of the O2 molecule. The dotted lines show results of different calculations for the %" state. (Reproduced

wit h permission from D. H. Volman, Advances in Photochemistry 1 (1963) 46.) 1.6 . SPECTROSCOPI C PROPERTIE S

Electroni

c Spectr a The spectrum of isolated 0 2 . Th e groun d state 4 4 o f 0 2 i s 3 Zj . Th e state s i A g an d ι

Σ+

ar e derive d fro m th e sam e electro n configuration ; transition s t o eac h o f thes e state s fro m th e groun d stat e ar e formall y forbidden , bu t ar e observe d a s ver y wea k band s i n th e absorp tio n o f O 2 a t -800 0 cm- i 0Δ , < - Vj) an d ~ 13,20 0 cm- i pl + * - 3 Ij) . Transition s t o th e nex t state s involv e excitatio n o f a π^-electro n t o a π^-orbital . Fragment s o f a ver y wea k ban d serie s du e t o th e transitio n 3 Δ ω < - 3 Σ ^ wer e detecte d b y Herzberg 4 * clos e t o th e wea k ban d serie s fo r th e transitio n 3 Σ + < - 3 Σ " nea r 36,00
0 cm~ i (th e Herzber g bands ) an d th e eve n weake r series 4 6 associate d wit h th e transitio n *Σ ~ < - 3 Σ ^ nea r 37,00
0 cm -1 . Al l thre e o f thes e transition s ar e forbidden . Th e stron g Schumann-Rung e band s nea r 50,00
0 cm - 1 ar e 4

2 R. A. Alikhanov, Soviet Physics JETP 18 (1964) 556.

4

3 C. S. Barrett, L. Meyer and J. Wassermann, /. Chem. Phys. 47 (1967) 592.

4

4 G. Herzberg, The Spectra of Diatomic Molecules, 2nd edn., Van Nostrand, New York (1950).

4 5 G . Herzberg, Can. J. Phys. 31 (1953) 657. 4

6 p. Brix and G. Herzberg, Can. J. Phys. 32 (1954) 110.

TABLE 12. PARAMETERS FROM THE ELECTRONIC SPECTRA OF O2. STATES ARE FOR O2 UNLESS OTHERWISE STATED

Electroni

c stat e 2

Π,(0$

) 3 Σ " 'Σ ; 'Σΐ 'Δ, 'Σ? /^-electro n configuratio n σ2 Α π Ι

σ]π\π) °

2

Α*\

σ\π\π\ °

2

Α*\

° 2 Α* 2

°\<Α

Te (Â ) 1.122

7 Ι.6Ο4

1.59 7 [1.42 ] 1.22 7 65

ο 1.2155 1/207 39

8 T e (cm-i ) 4 9 357.
6 3 6 678.9
ι 3 6 09 6 1 3 195.222
ι 7918.
1 0 COe (cm-i ) 1876.
4 700.3

6 650.4

9 819.
0

1432.687

4 1509.
3

1580.361

3 CO e Xe (cm-i ) 16.5 3 8.OO2 3 17.03 6 22.5
ο

13.9500

8 12. 9

12.073

0 (o e y e (cm-i ) -0.3753 s 0.105 e -0.0107 5

0.0546 Reference

a , b c a a a a r e = equilibriu m internuclea r distance ; T e = electroni c energ y abov e th e groun d state ; co e = harmoni c fundamenta l vibrationa l frequency ; co e x e = vibrationa l constan t fo r second-orde r anharmoni c term ; oe e y e = vibrationa l constan t fo r third-orde r anharmoni c term . • G . Herzberg , The Spectra of Diatomic Molecules 2n d edn. , va n Nostrand , Ne w Yor k (1950) . b P . Bri x an d G . Herzberg , Canoa*. J. Phys. 3 2 (1954 ) 110
. c G . Herzberg , Canad. J. Phys. 3 1 (1953 ) 657
.

O X o X o o z z > •z Ό

H G PI

SPECTROSCOPIC PROPERTIES 703

derive d fro m th e allowed transition 3 Σ " < - 3

Σ~;

they converg e to a limit at 57,128 cm - 1 an d a continuum to about 70,000 cm -1 . At higher energies the spectrum becomes complex, an d fragment s o f several Rydberg series have been detected 4 7 (Fig . 2). Ban d system s associate d wit h al l thes e transition s excep t 3 Δ Μ < - 3 Σ ^ hav e bee n analysed , an d th e derived molecular constants are given in Table 12; promotion of an electron fro m n u t o n g lead s to a lengthening of the O-O bond and a decrease in the vibration frequency , a s simpl e theor y predicts . O n th e othe r hand , ionizatio n strengthen s th e bon d b y removin g a n antibonding electron. In the spectrum of solid a-oxygen at 4°K, the structure o f th e band s indicat e tha t th e molecula r constant s fo r the gas and for 0C-O2 are very similar bu t no t exactly the same 48
. In y-02 and ß-Q>2 the bands are broader than in the liquid or i n 0Î-O 2 49
. Ther e are further splittings of the vibrational bands in the spectrum of the crystal 4 " » 4 * .

Potentia

l energ y curve s hav e bee n calculate d for all the bound states, and for some of th e repulsiv e one s (Fig . 3). Th e lowe r state s dissociat e to two 3

P oxygen atoms, but the

3 Σ ~ stat e give s on e 3 P an d on e l D atom. There is clear evidence for predissociation in the Schumann-Runge systemSO; th e relevan t repulsiv e state s seem s t o b e 3 Tl g9 bu t the details of the process are not clear. Bands involving intermolecular interactions. I n th e spectra of condensed or compressed oxyge n ther e ar e bands that are not due to transitions of isolated O2 molecules 51
; som e of thes e feature s lie under the banded spectra of the O2 transitions 52
. The y are attributed to transition s in molecular complexes (perhaps short-lived collision complexes), but there mus t b e more than one type of intermolecular process involved, for in compressed oxygen th e intensitie s o f different bands vary in different ways as the pressure is changed or as foreig n gase s are added. The band near 15,800 cm - 1 i s attributed to the (0-0) transition associate d wit h simultaneou s excitatio n o f two 3 Σ ^ oxygen molecules to the 1 A g state 53
.

System

s o f x A g molecule s sho w emissio

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