Amines and nitro compounds Vladimíra Kvasnicová

Amines = organic derivatives of ammonia in which one or more of the hydrogen atoms is replaced by an alkyl or by aromatic group (R) ammoniaNH 3 primary amineR 1 -NH 2 secondary amineR 1 -NH-R 2 tertiary amineR 1 -N(R 2 )-R 3 quarternary ammonium cationN(R) 4 + (choline, acetylcholine)

Properties of amines C 1 -C 5 amines are soluble in water (H-bonds) low MW: gases, sharp penetrating odour similar to ammonia amines with increasing MW: liquids and solids, they smell like decaying fish diamines are responsible for the odour of decaying animal tissue:  H 2 N-(CH 2 ) 4 -NH 2 = putrescine  H 2 N-(CH 2 ) 5 -NH 2 = cadaverine

Amines classification of amines  classification of alcohols! t-butylamine = primary amine t-butylalcohol = tertiary alcohol N-containing heterocyclic compounds, e.g.  piperidine = secondary alicyclic amine  indole = secondary aromatic amine suffix: -amine (alkyl amine or hydrocarbon amine) prefix: amino- or alkylamino hydrocarbon 3-(N-methylamino)pentane

Exercise CH 3 -CH 2 -NH 2 CH 3 -CH(NH 2 )-CH 3 CH 3 -CH 2 -N(CH 3 )-C 6 H 5 CH 3 -CH(NH 2 )-CH 2 -CH 3 CH 3 -CH(NH 2 )-CH 2 -OH H 2 N-(CH 2 ) 3 -NH 2 CH 3 -CH 2 -CH 2 -CH(CH 3 )-N(CH 3 ) 2 CH 3 -CH 2 -CH(NH 2 )-COOH

Exercise C 6 H 5 -NH 2 = aniline ! C 6 H 5 -NH-CH 3 C 6 H 5 -N(CH 3 ) 2 (CH 3 ) 2 NH CH 3 -CH 2 -CH 2 -N(CH 3 )-CH 2 -CH 3 C 6 H 11 -NH 2 H 2 N-C 6 H 4 -COOH C 6 H 5 -CH 2 -NH 2

Reactions of amines many chem. properties reflect the reactivity of the unshared pair of electrons on „N“ (= base)  CH 3 NH 2 + H 2 O → CH 3 NH OH - methylammonium ion amines are completely protonated in the reaction with a strong acid → ammonium salts (mor soluble in water)  CH 3 NH 2 + HCl → CH 3 NH Cl -  drugs containing –NH 2 are often given in the form of salts to improve their solubility in body fluids some detergents contain quarternary ammonium salts, they are used as germicides (for med. istruments)

Reactions of amines alkyl substituted amines are stronger bases than ammonia:  NH 3 + H 2 O → NH OH - K b = 1,8 x  CH 3 -NH 2 K b = 4,6 x  (CH 3 ) 2 -NH K b = 4,7 x aromatic amines are weaker bases:  C 6 H 11 -NH 2 K b = 4,6 x  C 6 H 5 -NH 2 K b = 4,3 x

Reaction of amines with HNO 2 it is used in cassifying unknown amines:  primary amines → diazonium salts (unstable) R-NH 2 + HNO 2 → R-N=N + → N 2 + alcohol  secondary amines → N-nitrosoamines (yellow oily comp.) R 1 -NH-R 2 + HNO 2 → R 1 R 2 N-N=O + water  tertiary amines + HNO 2 → no reaction aromatic primary amines react with HNO 2 in a reaction called DIAZOTATION  diazonium salts stabilized by the aromatic ring C 6 H 5 -NH 2 + NaNO 2 + 2HCl → C 6 H 5 -N=N + Cl - + NaCl + 2H 2 O benzenediazonium chloride

Reactions of amines diazonium salts are used for preparation of AZO DYES by the reaction with a phenol or an aromatic amine (= coupling reaction) example of azo dyes: methylorange azo compounds: -N=N- examples:  C 6 H 5 -N=N-C 6 H 5 azobenzene  C 6 H 5 -N=N-C 6 H 5 -CH 3 toluene-4-azobenzene

Exercise CH 3 -CH 2 -CH 2 -NH 2 C 6 H 5 -NH-C 6 H 5 N(CH 3 ) 3 CH 3 (CH 2 ) 2 -N(CH 3 )-CH 2 CH 3 C 6 H 5 -N(CH 3 ) 2 H 2 N-C 6 H 4 -COOH CH 3 -NH-CH 2 -CH 2 -CH 3 H 2 N-CH 2 -CH 2 -OH propylamine diphenylamine trimethylamine ethyl methyl propylamine dimethyl phenyl amine (N, N-dimethylaniline) 4-aminobenzoic acid methyl propyl amine 2-aminoethanol

Nitro compounds functional group: -NO 2 (= nitro group) only prefix: nitro-(there is no suffix used) preparation: by nitration (nitration mix = HNO 3 + H 2 SO 4 ) examples:  CH 3 -NO 2 nitromethane  O 2 N-CH 2 -CH 2 -NO 2 1,2-dinitroethane  CH 3 -CH(NO 2 )-CH 3 2-nitropropane  O 2 N-C(CH 3 ) 3 2-nitro-2-methylpropane  C 6 H 5 -NO 2 nitrobenzene (yellow liquid)  H 3 C-C 6 H 5 -NO 2 p-nitrotoluene

Properties of nitro compounds low MW: liquids of a sweet odour some nitroarenes are solid crystalline substances high b.p., water insoluble, often highly explosive the most important reaction: reduction C 6 H 5 -NO 2 nitrobenzene C 6 H 5 -N=Onitrozobenzene C 6 H 5 -NH-OHN-phenylhydroxylamine C 6 H 5 -N=N-C 6 H 5 azobenzene C 6 H 5 -NH-NH-C 6 H 5 hydrazobenzene C 6 H 5 -NH 2 aniline

Exercise - repetition toluene m-cresol o-xylene naphtalene benzyl phenyl anthracene benzoic acid p-benzoquinone cyclohexanol acetaldehyde phenol acetone diethylether formaldehyde vinylchloride methanethiol hydroquinone