benzene pdf

Benzene is known to be a human carcinogen based on suficient evi-dence of carcinogenicity from studies in humans

71-43-2 Hazard Summary Benzene is found in the air from emissions from burning coal and oil gasoline service stations and motor vehicle exhaust Acute (short-term) inhalation exposure of humans to benzene may cause drowsiness dizziness headaches as well as eye skin and respiratory tract irritation and at high levels unconsciousness

Benzene is a planar hexagonal cyclic hydrocarbon The C–C–C bond angles are 120° = sp2 hybridized Each carbon possesses an unhybridized p-orbital which makes up the conjugated π-system The six π-electrons are delocalized through the π-system

• The Stability of Benzene • Benzene is much more stable than the cyclohexatriene – A reasonable prediction for the heat of hydrogenation of hypothetical cyclohexatriene is -360 kJ mol-1 (3 x cyclohexene -120 kJ mol-1) – The heat of hydrogenation for benzene is -280 mol-1 152 kJ mol-1 more stable than hypothetical cyclohexatriene

Chapter 22 1 Reactions of Benzene The most characteristic reaction of aromatic compounds is substitution at a ring carbon: Halogenation: H + Cl2 FeCl3 Cl + HCl Chlorobenzene Nitration: H2 SO4 H + HNO3 NO2 + H2 O Nitrobenzene Reactions of Benzene Sulfonation: SO3 H2 SO4 SO3 H Benzenesulfonic acid Alkylation: H + RX A lX3 R + HX An alkylbenzene

Benzene is a hexagonal and planar molecule with the formula C6H6 In benzene each carbon atom undergoes sp2 hybridisation to give three hybrid orbitals and an unchanged p orbital which is perpendicular to the plane containing the three hybrid orbitals Two of the hybrid orbitals overlap with two other hybrid orbitals of carbon