Amines and Ammonium Salts

Alcohols and alkyl halides are divided into subclasses according to the substitution pattern at the carbon bearing the functionality. In contrast, amines, which are considered as organic derivatives of ammonia, are divided into classes according to the number of carbon groups attached to the nitrogen.

NH₃

Ammonia

RNH₂

Primary

amine

R₂NH

Secondary

amine

R₃N

Tertiary

amine

The compound CH₃CH₂NHCH₃ is classified as a ___________ amine.

The compound CH₃CH₂NHCH₃ is classified

as a secondary amine.

The following compound is classified as a ___________amine.

tertiary amine

3. The compounds (CH₃)₃COH is classified as a ____________ alcohol; the compound (CH₃)₃CNH₂ is a ____________ amine.

The compounds (CH₃)₃COH is classified as a

tertiary alcohol; the compound (CH₃)₃CNH₂ is

a primary amine.

Common names of amines are formed by specifying the groups attached to nitrogen as prefixes to the word amine. The name is written as one continuous word.

CH₃NH₂

Methylamine

(CH₃CH₂)₂NH

Diethylamine

4. The compound (CH₃CH₂CH₂CH₂)₃N has the common name __________________.

The compound (CH₃CH₂CH₂CH₂)₃N has the

common name tributylamine or tri-n-butylamine.

If various alkyl groups are attached to the nitrogen, the name of the amine may be formed by citing the alkyl groups in alphabetical order (ignoring any multiplying prefixes for alphabetization) .

Ethylmethylpropylamine

Ethyldiisopropylamine

5. What is the common name of the following amine:

Cyclohexylethylmethylamine

In the IUPAC system, the suffix "—amine" is used to denote the amine functional in much the same way as "—ol" is used for alcohols. The "e" at the end of the alkane name for the longest continuous carbon chain in the amine is replaced with "amine" and a locant number is used to designate the position of the amine on the carbon chain. The chain is numbered such that the position bearing the amine functional group gets the lowest possible number.

2- Butanamine

Cyclopropanamine

6. Name the following compounds:

(a) 2-Methyl-3-pentanamine

(b) 1,3-Propanediamine

The name of any other alkyl groups attached to nitrogen are added as prefixes to the parent amine name and designated with the locant N (italic N) which indicates that the substituent is attached to nitrogen rather than carbon. Multiple groups are listed in the name according to the usual alphabetizing rules.

N,4-Dimethyl-2-hexanamine

N-Ethyl-N-methylcyclohexanamine

7. Name the following compound:

N-Methyl-N-(3-Methylheptyl)nonanamine

8. Give the IUPAC name for tributylamine.

N,N-Dibutylbutanamine

(In general, simple amines such as this are usually

referred to by their common names.)

Yet another way to names amines is to designate the -NH₂ group as a substituent by the prefix "amino". This method is reserved for use only with polyfunctional compounds. More will be said about polyfunctional compounds in a later chapter.

2-Aminoethanol

2-(Dimethylamino)-1-propanol

9. Name the following compound as a derivative of an alcohol.

2-Amino-1-cyclohexanol

(Since all of the positions on a cyclohexyl ring are equivalent

often the use of the locant "1" is omitted as in

2-aminocyclohexanol.)

A number of amines, especially those containing the nitrogen within a ring have special common names that are often used. Compounds with atoms other than carbon in a ring are referred to as heterocycles. An example is the six-membered cyclic amine shown below.

Piperidine

10. Name the following compound:

N-Ethylpiperidine

Salts of amines formed by protonation of nitrogen are best named by adding the suffix "ium" to the name of the amine (with elision of a final "e" when present). The anion is cited as a second, separate word.


1-Propanamine	1-Propanaminium chloride

Common names of salts of amines are formed by adding the word hydrochloride, hydrobromide, etc. to the common name of the amine. For the above example:


Propylamine	Propylamine hydrochloride

11. Give the common and systematic name for Et₃NH⁺ Br^-.

Common: Triethylamine hydrobromide

IUPAC: N,N-Diethylethanaminium bromide

Amine salts of the type R₄N⁺ X^- are know as quaternary ammonium salts and are named as derivatives of the ammonium (NH₄⁺) ion.

Et₄N⁺ BF₄^-

Tetraethylammonium Tetrafluoroborate

CH₃(CH₂)₁₇N⁺(CH₃)₃ Br^-

Trimethyloctadecylammonium bromide

Name the following compound:

Cyclohexyltrimethylammonium hydroxide

Ammonium ions derived from amines with special names are usually named by adding the ending "ium" to the name of the amine (dropping and "e" if present).

13. The name of the simple three-membered ring compound containing a nitrogen in the ring is aziridine. Name the following compounds.

(a) N-Methylaziridine

(b) N,N-Dimethylaziridinium bromide

Go to the Chapter on

Alkenes