Dictionary of Chemistry [6th Ed.]

amidol 28

a
C

O

NH 2

R amide group

Amides

ing the ammonium salt of the corre-

sponding carboxylic acid. Amides can

also be made by reaction of ammonia

(or an amine) with an acyl halide. See

also hofmann’s reaction. 2.Inor-

ganic compounds containing the ion

NH 2 – , e.g. KNH 2 and Cd(NH 2 ) 2. They

are formed by the reaction of ammo-

nia with electropositive metals.

A

• Information about IUPAC nomenclature

amidolSee aminophenol.

aminationA chemical reaction in

which an amino group (–NH 2 ) is in-

troduced into a molecule. Examples

of amination reaction include the re-

action of halogenated hydrocarbons

with ammonia (high pressure and

temperature) and the reduction of

nitro compounds and nitriles.

aminesOrganic compounds de-

rived by replacing one or more of the

hydrogen atoms in ammonia by or-

ganic groups (see illustration). Pri-

mary amines have one hydrogen

replaced, e.g. methylamine, CH 3 NH 2.

They contain the functional group

–NH 2 (the amino group). Secondary

amineshave two hydrogens replaced,

e.g. methylethylamine, CH 3 (C 2 H 5 )NH.

Tertiary amines have all three hydro-

gens replaced, e.g. trimethylamine,

(CH 3 ) 3 N. Amines are produced by the

decomposition of organic matter.

They can be made by reducing nitro

compounds or amides. See also imines.

A

• Information about IUPAC nomenclature
  of primary amines


• Information about IUPAC nomenclature
  of secondary and tertiary amines

amine saltsSalts similar to ammo-

nium salts in which the hydrogen

atoms attached to the nitrogen are

replaced by one or more organic

groups. Amines readily form salts by

reaction with acids, gaining a proton

to form a positive ammonium ion,

They are named as if they were sub-

stituted derivatives of ammonium

compounds; for example, dimethy-

lamine ((CH 3 ) 2 NH) will react with

hydrogen chloride to give dimethyl-

ammonium chloride, which is an

ionic compound [(CH 3 ) 2 NH 2 ]+Cl–.

When the amine has a common non-

systematic name the sufÜx -ium can

be used; for example, phenylamine

(aniline) would give [C 6 H 5 NH 3 ]+Cl–,

known as anilinium chloride. For-

merly, such compounds were some-

times called hydrochlorides, e.g.

aniline hydrochloride with the for-

mula C 6 H 5 NH 2 .HCl.

Salts formed by amines are crys-

talline substances that are readily

soluble in water. Many insoluble

*alkaloids (e.g. quinine and atropine)

are used medicinally in the form of

soluble salts (‘hydrochlorides’). If al-

kali (sodium hydroxide) is added to

solutions of such salts the free amine

is liberated.

If all four hydrogen atoms of an

ammonium salt are replaced by or-

ganic groups a quaternary ammo-

nium compound is formed. Such

compounds are made by reacting ter-

tiary amines with halogen com-

pounds; for example, trimethylamine

((CH 3 ) 3 N) with chloromethane

(CH 3 Cl) gives tetramethylammonium

chloride, (CH 3 ) 4 N+Cl–. Salts of this

type do not liberate the free amine

when alkali is added, and quaternary

hydroxides (such as (CH 3 ) 4 N+OH–) can

be isolated. Such compounds are

strong alkalis, comparable to sodium

hydroxide.

amino acidAny of a group of