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NOMENCLATURE OF AMINES

Q. Write a structural formula for each of the following compounds:

Ans.

(a) N,N-diethylanminocyclopentane
The principal or parent chain is cyclopentane

N,N - diethylamino refers to a 3⁰ amine which are named as N-alkyl -N-alkylaminoalkane or N,N- dialkylaminoalkane in case two substituent alkyl groups are the same.
thus, the chain is

the structural formula of N, N - diethylamino cyclopentane is

(b) ethylpropylamine

Secondary amines are named either as alkylalkylamine (common name) or as N-alrylalranamine.
Thus it is a secondary amine having structure-
CH₃ CH₂ -NH-CH₂ CH₂ CH₃

(c) tetramethylammonium hydroxide
The given compound is a quaternary ammonium compound. These are regarded as derivatives of ammonium salts in which all the four H-atoms of ammonium ion (NH₄⁺) are replaced by alkyl or aryl groups. Here alkyl group is methyl (-CH₃) Thus, replacing all four hydrogens of NH₄⁺ OH by -CH₃ we get the structure of tetramethyl ammonium hydroxide.
[(CH₃)₄N]⁺OH^-

(d) 1,3-diaminobutane
Here the parent chain is butane with amino (-NH₂) group at position 1 and 3.

Q. Write a correct name for each of the following compounds:

Ans.

(a) H₂N(CH₂)₃ NH_{2 =} H₂N-CH₂ -CH₂ -CH₂- NH₂
Aliphatic amines are called aminoalkanes. The complete name is given as follows:

(i) Parent alkane corresponding to straigtht chain is -CH₂ -CH₂ -CH₂- then the name propane.

(ii) The position of amino groups are indicated by arabic numerals with carbon atom bearing the amino group getting the lowest possible number.


therefore- the name is 1,3 -diaminopropane

(b)
This is a quaternary ammonium salt which is named as tetraalkylammonium followed by name of the ion. The alkyle group here is butyl, thus the name is tetrabutylammonium hydroxide.

(c) - NHCH₂ CH₃
This is an aromatic secondary amine. In this the parent name is benzenamine for
and since ethyl group is attached to N, it is named as 'N-ethyl'.
therefore- the complete name would be N - ethylbenzenamine

(d) It is a 3⁰ amine which are named as N-alkyl -alkylaminoalkane
The largest alkyl group forms a part of amino alkane while smaller alkyl groups are considered substituents.
The larger alkyl group here is cyclohexane and smallest alkyl groups are dialkyl (dimethyl)
therefore- name is N.N-dimethylaminocyclohexane.

Q. Draw the structures for and name and classify as primary, secondary, or tertiary all the isomeric amines with the molecular formula C₅H₁₃N.

Ans.

Amines show 4 types of isomerism:
(a) Chain Isomerism - Using this we get following three structures for C₅H₁₃N.

pentan - 1- amine (1⁰ amine)
- 3- methylbutan-1-amine (1⁰ amine)

2, 2 -dimethylropan-1- amine (1⁰ amine)

(b) Position Isomerism: - This is due to difference in position of the amino group.

pentan - 2- amine (1⁰ amine)

pentan - 3- amine (1⁰ amine)

3- methyl butan-2-amine (1⁰ amine)

(c) Metamerism - Which have same molecular formula but different alkyl groups in either side of the nitrogen atom.

H₃C - CH₂-NH-CH₂ CH₂ CH₃ N-ethylpropanamine (2⁰ amine)
H₃C -NH-CH₂ CH₂ CH₂ CH₃ N-methyl butonamine (2⁰ amine)
2-methyl-1-(N-methylamino) propane (2⁰ amine)

2- metyl -2-(N-methylamino) propane (2⁰ amine)

(d) Functional isomerism - 1⁰ 2⁰ 3⁰ amines having same molecular formula show functional isomerism among themselves. The 1⁰ and 2⁰ amines have already been covered albove, so the possible 3⁰ amines with molecular formula C₅H₁₃N are -

N- methyl-N,N-diethyamine (3⁰ amine)

N,N-dimethylaminopropane (3⁰ -amine)

Q. Write the formula for each of the following in its dipolar ion form.

Ans

(a) Leucine


(b) Threonine


(c) Methionine


(d) tyrosine