MULTIPLE CHOICE QUESTIONS
1. What is the correct IUPAC name of H2N-(CH2)5-NH2?
a. Pentan-1,5-diamine
b. 1,5-Diaminopentane
c. Pentamethylenediamine
d. Pentane-1,5-diamine
2. Which of the following does not react with Hinsberg reagent?
a. C2H5NH2
b. (CH3)2NH
c. (CH3)3N
d. CH3 CH(NH2)CH3
3. Which of the following amines are insoluble in water?
a. Methanamine
b. Ethanamine
c. Propanamine
d. Benzenamine
4. Which of the following is formed when an alkyl primary amine reacts with nitrous acid?
a. Alkyl nitrite
b. Secondary amine
c. Nitroalkane
d. Alcohol
5. Arrange the following compounds in increasing order of basicity: CH3NH2, (CH3)2 NH, NH3,
C6H5NH2 in aqueousmedium
a. C6H5NH2 < NH3 < (CH3)2NH < CH3NH2
b. CH3NH2 < (CH3)2NH < NH3 < C6H5NH2
c. C6H5NH2 <NH3 < CH3NH2<(CH3)2NH
d. (CH3)2NH < NH3 < C6H5NH2 < CH3NH2
2 MARKS QUESTION
1. Give reasons for the following:
(i) Aniline does not undergo Friedel-Crafts reaction.
(ii) (CH3)2NH is more basic than (CH3)3N in an aqueous solution
2.How do you convert the following:
a. C6H5CONH2 to C6H5NH2
b. Aniline to phenol
3 MARK QUESTIONS
1.Write the structures of main products when aniline reacts with the following
Reagents:
a)Br2 water
b)HCl
c)(CH3CO)2O/pyridine
2. Give one chemical test to distinguish between the following pairs of compounds
(1) Methylamine and Dimethylamine
(2)Aniline and benzylamine
A. (1) Methylamine on reaction with chloroform and alcoholic KOH gives foul smelling methyl
isocynide while dimethylamine does not.
(2) Aniline on treatment with nitrous acid forms Benzene diazonium chloride which on coupling
with phenol forms orange dye while benzylamine does not.
CASE BASED QUESTIONS
The basicity of amines of different classes do not follow a simple pattern because the number
of groups bonded to nitrogen affects the electron density at the nitrogen atom. And, the
stability of the conjugate acid in the solvent has a major effect on basicity. Thus, the basicity
of amines can be explained only for amines with similar structures at the nitrogen atoms.
The basicity of an amine is increased by electron-donating groups and decreased by electronwithdrawing groups. Aryl amines are less basic than alkyl-substituted amines because some
electron density provided by the nitrogen atom is distributed throughout the aromatic ring.
Basicity is expressed using Kb values measured from the reaction of the amine with water.
An alternate indicator of basicity is pKb, which is −log Kb. A strong base has a large Kb and
a small pKb. The basicity of amines is also expressed by the acidity of their conjugate acids.
A strong base has a weak conjugate acid, as given by a small value of Ka and a large pKa.
[Robert J. Ouellette, J. David Rawn, in Organic Chemistry Study Guide, 2015]
a) pKb values for NH3 , CH3NH2,(CH3)2NH and (CH3)3N has 4.75,3.38,3.27 and 4.22
respectively.
Write them in the decreasing order of basic strength. Usually the order of basicity of
amines will be different from the expected order.
b) Which are the three main factors affecting basicity of amines?
c) Write the decreasing order of basicity for CH3CH2NH2,(CH3CH2)2NH and
(CH3CH2)3N
d) Compare the basicity of m-toluidine and Aniline.
Answer
a) (CH3)2NH> CH3NH2>(CH3)3N>NH3
b) +I effect ,extent of hydrogen bonding with water molecules and steric effects of the
alkyl group
c) (CH3CH2)2NH>(CH3CH2)3N> CH3CH2NH2>NH3
d) m-Toluidine is more basic than aniline due to +I effect from meta position