Amine

A general term _{for RNH2} (primary amine), _R2NH (secondary amine), and _R3N (tertiary amine), in which the hydrogen atoms of ammonia _NH3 have been replaced with one to three hydrocarbon groups or similar groups. They are named by adding amine to the name of the group R or the name of the parent compound _RH , or by adding _the prefix amino to the parent compound. For example, _C2H5NH2 is called ethylamine, ethanamine, or aminoethane. Common methods for synthesizing amines include the following:

(1) Reaction of alkyl halide with ammonia.

This method produces primary, secondary, and tertiary amines and quaternary ammonium salts (quaternary ammonium compounds) R ₄ N ⁺ X ^- , which must be separated.

(2) Reduction of nitriles, oximes, nitro compounds, acid amides, etc.

(3) Reductive amination of carbonyl compounds.

(4) Hofmann reaction of acid amides (Hofmann rearrangement).

(5) Hydrolysis of carbamic acid esters produced by the Curtius reaction (Curtius rearrangement) of acid azides.

(6) Hydrolysis of the product produced by the reaction of potassium phthalimide with an alkyl halide (Gabriel synthesis).

Lower amines with few carbon atoms are gases that are easily soluble in water and have an ammonia odor, medium-level amines are liquids that have a fishy odor, and higher amines are solids that are poorly soluble in water and are almost odorless. Amines are generally weak bases and react with acids to form ammonium salts. Primary and secondary amines react with acid chlorides or acid anhydrides to produce acid amides, but tertiary amines do not change.

RNH ₂ + R′COCl → RNHCOR′ + HCl

Aliphatic primary amines react with nitrous acid to generate nitrogen and produce alcohols, alkenes, etc., while aromatic primary amines react to form diazonium salts.

Secondary amines give N -nitroso compounds.

Aromatic tertiary amines generally undergo nuclear substitution to give C -nitroso compounds.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

アンモニアNH₃の水素原子を1～3個の炭化水素基またはこれに準じる基で置換したRNH₂(第一級アミン)，R₂NH(第二級アミン)，およびR₃N(第三級アミン)の総称．基Rの名称または母体化合物RHの名称にアミンをつけて命名するか，母体化合物に接頭辞アミノをつけて命名する．たとえば，C₂H₅NH₂はエチルアミン，エタンアミン，またはアミノエタンという．アミンの一般的合成法には，次のようなものがある．

(1)ハロゲン化アルキルとアンモニアとの反応．

この方法では，第一級，第二級，第三級アミンおよび第四級アンモニウム塩(第四級アンモニウム化合物)R₄N^＋ X^－を生じるので，それぞれを分離しなくてはならない．

(2)ニトリル，オキシム，ニトロ化合物，酸アミドなどの還元．

(3)カルボニル化合物の還元アミノ化．

(4)酸アミドのホフマン反応(ホフマン転位)．

(5)酸アジドのクルチウス反応(クルチウス転位)によって生じるカルバミン酸エステルの加水分解．

(6)フタルイミドカリウムとハロゲン化アルキルとの反応によって生じる生成物の加水分解(ガブリエル合成)．

炭素原子数の少ない低級のアミンは，アンモニア臭をもつ水に易溶な気体，中級のアミンは魚臭をもつ液体，高級のアミンは水に難溶の固体で，ほとんど無臭である．アミンは，一般に弱塩基で，酸と反応してアンモニウム塩をつくる．第一級，第二級アミンは，酸塩化物または酸無水物と反応して酸アミドを生じるが，第三級アミンは変化しない．

RNH₂ ＋ R′COCl → RNHCOR′ ＋ HCl

脂肪族第一級アミンは亜硝酸と反応して窒素を発生し，アルコールやアルケンなどを生じるが，芳香族第一級アミンはジアゾニウム塩になる．

第二級アミンはN-ニトロソ化合物を与える．

芳香族第三級アミンは一般に核置換によってC-ニトロソ化合物になる．

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