胺Amine

胺的氮原子用孤对电子接受质子：RNH₂ + H₂O ⇌ RNH₃⁺ + OH⁻。烷基的推电子作用使氮上电子密度增大，所以甲胺（共轭酸 pKa 约 10.6）碱性强于氨（9.25）。苯胺中氮的孤对电子部分离域到苯环上，不易接受质子，碱性比氨弱得多（共轭酸 pKa 约 4.6）。胺与酸反应生成可溶于水的铵盐。

The nitrogen lone pair accepts a proton: RNH₂ + H₂O ⇌ RNH₃⁺ + OH⁻. Alkyl groups push electron density onto nitrogen, so methylamine (conjugate acid pKa about 10.6) is a stronger base than ammonia (9.25). In phenylamine the lone pair is partly delocalised into the ring and less available, so it is a much weaker base (conjugate acid pKa about 4.6). Amines react with acids to form water-soluble ammonium salts.

卤代烷与过量浓氨在乙醇中密封加热生成伯胺，但产物会继续反应生成仲胺、叔胺和季铵盐的混合物。腈用 LiAlH₄ 或 H₂/Ni 还原得到伯胺，且碳链比原卤代烷多一个碳。苯胺由硝基苯用锡和浓盐酸还原，再加 NaOH 释放出游离胺制得。

Haloalkanes heated with excess concentrated ammonia in ethanol in a sealed tube give primary amines, though further reaction gives a mixture with secondary and tertiary amines and quaternary ammonium salts. Reducing nitriles with LiAlH₄ or H₂/Ni gives primary amines with one more carbon than the original haloalkane. Phenylamine is made by reducing nitrobenzene with tin and concentrated hydrochloric acid, then adding NaOH to release the free amine.

胺作为亲核试剂与酰氯反应生成酰胺：CH₃NH₂ + CH₃COCl → CH₃CONHCH₃ + HCl。苯胺在 10 °C 以下与亚硝酸（NaNO₂ + HCl）反应生成重氮盐，重氮盐与苯酚等在碱性条件下偶联生成有色的偶氮化合物，这是偶氮染料的制法。苯胺与溴水反应立即生成 2,4,6-三溴苯胺白色沉淀。

As nucleophiles, amines react with acyl chlorides to form amides: CH₃NH₂ + CH₃COCl → CH₃CONHCH₃ + HCl. Phenylamine reacts with nitrous acid (NaNO₂ + HCl) below 10 °C to give a diazonium salt, which couples with phenol or similar compounds in alkali to form coloured azo compounds, the basis of azo dyes. With bromine water phenylamine at once gives a white precipitate of 2,4,6-tribromophenylamine.