α -H atom. For example, nitro compounds having the molecular formula C H NO exhibit the following isomerisms. Isomerism Structural formula of isomers Chain isomerism : They differ in the length of carbon chain. CH CH CH CH NO - nitrobutane and CH CHCH NO - methyl - -nitropropane Position isomerism: They differ in the position of nitro group.
CH CH CH CH NO - nitrobutane CH CHCH CH NO and - nitrobutane Functional isomerism: Nitroalkanes exhibit functional isomerism with alkylnitrites CH CH CH CH NO - nitrobutane and CH CH CH CH N = O butyl nitrite Tautomerism: Primary and secondary nitroalkanes, having α -H , also show an equilibrium mixture of two tautomers namely nitro – and aci – form Tautomerises (Nitro form) Nitromethane CH =N (Aci form) Tertiary nitro alkanes donot exhibit tautomerism due to absence of α -H atom. S.No. Nitro form Aci – form . Less acidic More acidic .
Dissolves in NaOH slowly Dissolves in NaOH instantly . Decolourises FeCl solution With FeCl gives reddish brown colour . Electrical conductivity is low Electrical conductivity is high XII U13-Organic Nitrogen XII U13-Organic Nitrogen - - - - . .
Acidic nature of nitro alkanes The α -H atom of & nitroalkanes show acidic character because of the electron with drawing effect of NO group. These are more acidic than aldehydes, ketones, ester and cyanides. Nitroalkanes dissolve in NaOH solution to form a salt. Aci – nitro derivatives are more acidic than nitro form.
When the number of alkyl group attached to α carbon increases, acidity decreases. due to +I effect of alkyl groups. NO > CH CH NO NO > CH Evaluate yourself Write all possible isomers for the following compounds. i) C H -NO ii) C H -NO .
. Preparation of nitroalkanes ) From