1. What are amines?
Amines are regarded as derivatives of ammonia in which one, two or all three hydrogen atoms are replaced by alkyl or aryl group.
2. Amines are derivatives of ammonia .
3. What are quaternary ammonium compounds?
These are compounds which are regarded as derivatives of ammonium salts in which all the four H-atoms are replaced by alkyl or aryl groups.
4. What are the various classifications of amines?
In one classification, Amines are classified into two categories: Aliphatic amines and aromatic amines.
1. Aliphatic amines: Amines in which the nitrogen atom is directly bonded to one or more alkyl groups.
2. Aromatic amines: Amines which have aromatic groups in the compounds. They are further classified as aryl amines and arylalkyl amines or side chain substituted amines.
a. Aryl amines: In these amines, the nitrogen atom is directly bonded to one or more aromatic rings or aryl groups.
b. Arylalkyl amines: In these amines, the nitrogen atom is bonded to the side chain of the aromatic ring.
In second type of classification, amines are classified as simple and mixed amines. This classification is applicable to secondary and tertiary amines which have two or three alkyl or aryl groups.
If the two or three alkyl or aryl groups are the same, it is a simple amine. If the alkyl groups are different, it is a mixed amine.
5. What is the common system of nomenclature of aliphatic amines?
In the common system, amines are called alkylamines. The suffix amines is added to the name of the corresponding alkyl group.
Ex: Methylamine, Ethylamine, Propylamine
Second common system
In the second system of the common system, primary amines are named as the amino derivatives of the corresponding hydrocarbons and are names as aminoalkanes. The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Secondary and tertiary amines are named as nitrogen substituted primary amine.
Primary amine is aminoethane and N-Methyl is added to it. N- indicates that the methyl group is attached to the nitrogen atom.
6. What is the IUPAC system of nomenclature of aliphatic amines?
The aliphatic amines are called alkamines. The letter ‘e’ in the alkane is replaced by suffix amine.
Ex: methanamine, ethanamine
The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Ex: 1-propanamine, 2-propanamine
7. What is the common system of nomenclature of aromatic amines?
Aromatic amines are called aryl amines. Suffix amine is added to the aryl group.
8. What is the IUPAC system of nomenclature of aromatic amines?
The simplest aromatic amine C6H5NH2 is called benzanamine.
Other aromatic amines are named as derivatives of benzenamine and positions of other groups are indicated by numbers
N-Methylbenzenamine, N,N-Dimethylbenzenamine, 2-Methylbenzenamine, 3-Methylbenzenamine
In IUPAC system, benzenamine may also be written as amino benzene.
9. Explain chain isomerism in amines.
Aliphatic amines containing four or more carbon atoms show chain isomerism as branched and straight chain alkyl groups can be attached to the nitrogen atom.
Example: Butan-1-amine, 2-Methylpropan-1-amine, and 2 Methylpropan-2-amine are chain isomers.
10. Explain metamerism in amines.
In amines metamerism, a type of isomerism in which different alkyl groups are attached to the Nitrogen atom of the amino group exists(molecular formula for isomers is same).
Example: Diethylamine, Methyl-n-propylamine, and Isopropylmethylamine are metamers.
11. Explain position isomerism in amines.
The amino group can be bonded to different carbon atoms of the alkyl group.
12. Explain functional isomerism in amines.
Primary, secondary and tertiary amines having the same molecular formula are isomers. This isomerism is functional isomerism because different alkyl groups (functional groups) are present in the molecules and give rise to isomerism
13. Explain various methods of preparing amines.
1. From alkyl halides –
By ammonolysis (Hoffmann’s method): When an aqueous or alcoholic solution of ammonia is heated with an alkyl halide at 373 K in a sealed tube, a mixture of three amines (primary, secondary and tertiary) is obtained. It is very difficult to separate the mixture.
By Gabriel’s phthalimide synthesis
In this synthesis, phthalimide is treated with alcoholic KOH to give potassium phthalimide.
Potassium phthalimide is treated with alky halide to form N-alkyl phthalimide.
The hydrolysis of N-alkyl phthalimide with 20% HCl under pressure or refluxing with NaOH gives primary amine.
This method can be used for preparing only primary amines.
2. Reduction of nitro compounds – by hydrogen, by active metals, and by LiAlH4
3. Reduction of nitriles (cyanides) and isonitriles (isocyanides)
Nitriles can be reduced to corresponding amines using H2/Raney Li or Pt, LiAlH4 or Na, C2H5OH
When sodium and alcohol are used, the reaction is called Mendius reaction
Isonitriles can be reduced to secondary amines using H2/Raney Li or Pt, LiAlH4 or Na, C2H5OH
4. From Amides – by reduction of amides, by Hofmann degradation method
Amides on treatment with Br2 and KOH give primary amines. The amine formed contains one carbon atom less than the parent amide.
5. From Oximes – by reduction
Oximes are obtained from aldehydes and ketones by reaction with hydroxylamine. The oximes of aldehydes or ketones can be reduced to primary amines with either Na/CH2H5OH or LiAlH4.
6. Reductive amination of aldehydes and ketones
Reaction between aldehydes or ketones and ammonia results in the formation of imines. Imines are reduced to primary amines with H2, Ni.
7. From alcohols – Sabatier and Mailhe method
8. Preparation of aniline from nitrobenzene