[PDF] [PDF] Chem263_Nov 25_notes_2010

[PDF] Carboxylic acid Derivatives

Reactivity of Acid Derivatives The carboxylic acid derivatives vary greatly in their reactivities with nucleophiles For example acid chlorides hydrolyze in moist air, whereas amides hydrolyze slowly even in boiling alkaline water

[PDF] Functional Derivatives of Carboxylic Acids

boxyl group: acid halides, acid anhydrides, esters, and amides Under the general 14 2 What Are the Characteristic Reactions of Carboxylic Acid Derivatives?

CARBOXYLIC ACIDS AND THEIR DERIVATIVES 1 Carboxylic

also give no reaction Amino acids react after addition of formaldehyde (which blocks the basic amino group) Positive reactions are also obtained with weak 

[PDF] carboxylic acids and their derivatives - Caltech Authors

group, are similar to and different from alcohols, which have the OH group, Most of the reactions of carboxylic acids belong to one of four principal classes,

[PDF] Carboxylic Acids and Their Derivatives: Nucleophilic Addition

The carboxyl group consists of two parts, the acyl group and the attached hydroxyl Nitriles can also be prepared by nucleophilic substitution reactions of 1 o

[PDF] Chem263_Nov 25_notes_2010

25 nov 2010 · Acid chlorides are prepared from carboxylic acids by reaction with that makes the carbonyl group of the carboxylic acid derivative more easily 

[PDF] CARBOXYLIC ACIDS AND THEIR DERIVATIVES Prof RN Goyal

Acidity of Carboxylic Acids Preparation of Carboxylic Acids Two Individual members Formic Acid and Acetic Acid Reactions due to aldehyde group

[PDF] Reactivity of Carboxylic Acid and Ester Groups in the Functionalized

functional groups depend on structure in ways having no analogy in reactions in solution influenced by the carboxylic acid group if it was within 1 nm of the

[PDF] 17 Carbonyl Compounds I

For a carboxylic acid derivative to undergo a nucleophilic acyl substitution reaction, the incoming nucleophile must not be a much weaker base than the group 

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Chem 263 Nov 25, 2010 Preparation of Acid Chlorides Acid chlorides a re prepared from carboxylic acids by reacti on with thionyl chloride (SOCl2) by a mechanism we will not discuss now. ROH

O SOCl 2 RCl O SO 2 HCl

Hydrolysis of Acid Chlorides Acid chlorides react under acidic or basic conditions to yi eld car boxylic acids. This hydrolysis reaction is a typical nucleophilic acyl substitution. Acid halides, anhydrides, esters and amides react in a similar fashion under these hydrolysis conditions. Under basic conditions, the hydroxide anion attacks the carbonyl group of the acid chloride to yield a tetrahedral intermediate reversibly, which then displaces the chloride irreversibly to yield the carboxylic a cid. Since we are under basic conditi ons, the base will deprotonate the acid to yield the carboxylate salt. The displacement step of the reaction is irreversible because the chloride is a far better atom to stabilize a negative charge than the oxygen. RCl

O RCl O OH ROH O OH NaOH RO O Na NaOH Cl

Under acidic conditions, the protonated carbonyl group of the acid chloride is attacked by water to yield the tet rahedral intermediate , which is then deprotonated to become a neutral species. The intermediate then displaces the chloride anion to yield the carboxylic acid. Once again the displacement step of the reaction is irreversible due to the reasons given above. RCl

O RCl O OH H HOH H H RCl O OH H ROH O H HCl

Reactivity of Carboxylic acid Derivatives Nucleophilic acyl substitution reactions usually take place in two steps: addition of the nucleophile and elimination of a leaving group. Although both steps can affect the overall rate of the reaction, it is generally the first step that is rate-limiting. Therefore any factor that makes the carbonyl group of the carboxylic acid derivative more easily attacked will favor the reaction. Electronically, polarized acid derivatives are attacked more readily than less polar ones. Thus, acid chlorides are more reactive than anhydrides, which are more reactive than esters, which are more reactive than amides. This is due to the electronegative group, such as chlor ine, polarizi ng the carbonyl group more strongly than an alkoxy group (ester) or an amino group (amide). RNR'

2 O ROR' O RO O R Cl O R' O

Less ReactiveMore Reactive

An important factor of the observed reactivity order is that it is possible to transform a more reactive acid derivative into a less reactive one. Acid chlorides for example can be converted into anhydrides, ester and amides but amides cannot readily be converted into esters, anhydrides or acid chlorides directly. The chart below will help you re member the r eactivity order and t he possible transformations. The reactivity of a carboxylic a cid is approximately between an anhydride and an ester. The carboxylate salt is the least reactive but is easily converted to the carboxylic acid with acidic treatment. Using the chart, the carboxylic acid can easily be converted to the acid chloride by treatment with thionyl chloride (SOCl2). The acid chloride can then be converted to a less reactive derivative such as an anhydride, ester or amide. As seen from the chart, an anhydride can be directly converted to an ester or an amide. An ester can be directly converted to an amide. Each of these derivatives can be converted back to the carboxyl ic acid or carboxyla te salt by either acid or base hydrolysis. Using the chart, an amide cannot be directly converted to an acid chloride. First the amide must be hydrolyzed to the carboxylic acid by acid or base, then reacted with thionyl chloride to yield the acid chloride.

R NR' 2 O ROR' O RO O R Cl O R' O

Less Reactive

More Reactive

ROH O RO M O HCl NaOH H SOCl 2

An exampl e is the conversion of a cetyl chlori de to acet ic anhydride. Since an a cid chloride is more reactive than an anhydride, treatment of acetyl chloride with carboxylate salt of acetic acid (sodium acetate) will give acetic anhydride and sodium chloride. O

Cl Na-O O O OO NaCl

acetyl chloride acetic anhydride Another example is the conversion of acetyl chloride to methyl acetate. An acid chloride is more reactive than an ester, therefore treatment of acetyl chloride with methanol will yield methyl acetate and HCl. O

Cl HO CH 3 O O CH 3 HCl

acetyl chloride methanol methyl acetate Another example is the conversion of acetyl chloride to acetamide. An acid chloride is more reactive than an amide, therefore treatment of acetyl chloride with ammonia will yield acetamide. O

Cl NH 3 NH 2 O HCl

acetyl chloride ammonia acetamide The above acetamide can be prepared from ester as well, since esters are more reactive than amides. O

O NH 3 NH 2 O OH In each of the above examples, the reverse reaction will NOT proceed OCH 3 OCH 3 O O H 2 NNH 2 NH NH O O 2 CH 3 OH NH OCH 3 O O NH 2 CH 3 OH hydrazine NH NH O O [ O ] NH 2 N N O O NH 2 Light O O NaOH Na Na

Alkaloids Nitrogen-containing compounds from plant sources are referred to as alkaloids. The study of alkaloids provided much of the growth of organic chemistry in the nineteenth century and still remains a growing area of research. One particular group of alkaloids are the morphine alkaloids. O

HO HO N H

Morphine Morphine was the first alkaloid isolated in pure form from the poppy. Morphine has addictive properties and is also an analgesic (pain kill er). There fore deri vatives of morphine were synthesized to try to separate the addictive properties from the analgesic properties. One of the first such derivatives involved the treatment of morphine with acetyl chloride to yield an acetylated derivative of morphine. This compound was found to be 1000x better of an analgesic and was referred to as the "hero" compound. This Forming 6-membered ring is favorable

compound was also found to be 1000x more addictive than morphine and is commonly known as heroin. O

HO HO N H O Cl O O O N H O O

Morphine Heroin However, the above reaction does not really work(very slow) with and it does not with Example: N

NH O HN CH 3 H N O N O O OH H H

This structurally complicated molecule is called ergotamine. It is a mycotoxin produced by fungi Claviceps paspalii and it causes constriction of blood vessels. It is the cause for the disease St. Anthony's Fire in the middle ages through contamination on rye. When ergotamine is treated with acid/water, what is the bond that will react with the left side of the structure? O

O O or use Oquotesdbs_dbs20.pdfusesText_26