Class 12
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Chemistry
Amines
NCERT Solutions
NCERT Solutions
Amines
20 Solutions
Q1
Exercises
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
(i)
(
C
H
3
)
2
C
H
N
H
2
(\mathrm{CH}_{3})_{2} \mathrm{CHNH}_{2}
(
CH
3
)
2
CHNH
2
(ii)
C
H
3
(
C
H
2
)
2
N
H
2
\mathrm{CH}_{3}(\mathrm{CH}_{2})_{2} \mathrm{NH}_{2}
CH
3
(
CH
2
)
2
NH
2
(iii)
C
H
3
N
H
C
H
(
C
H
3
)
2
\mathrm{CH}_{3} \mathrm{NHCH}(\mathrm{CH}_{3})_{2}
CH
3
NHCH
(
CH
3
)
2
(iv)
(
C
H
3
)
3
C
N
H
2
(\mathrm{CH}_{3})_{3} \mathrm{CNH}_{2}
(
CH
3
)
3
CNH
2
(v)
C
6
H
5
N
H
C
H
3
\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHCH}_{3}
C
6
H
5
NHCH
3
(vi)
(
C
H
3
C
H
2
)
2
N
C
H
3
(\mathrm{CH}_{3} \mathrm{CH}_{2})_{2} \mathrm{NCH}_{3}
(
CH
3
CH
2
)
2
NCH
3
(vii)
m
−
B
r
C
6
H
4
N
H
2
m-\mathrm{BrC}_{6} \mathrm{H}_{4} \mathrm{NH}_{2}
m
−
BrC
6
H
4
NH
2
Q1
Exercises
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
(i)
(
CH
3
)
2
CHNH
2
(\text{CH}_3)_2\text{CHNH}_2
(
CH
3
)
2
CHNH
2
(ii)
CH
3
(
CH
2
)
2
NH
2
\text{CH}_3(\text{CH}_2)_2\text{NH}_2
CH
3
(
CH
2
)
2
NH
2
(iii)
CH
3
NHCH
(
CH
3
)
2
\text{CH}_3\text{NHCH}(\text{CH}_3)_2
CH
3
NHCH
(
CH
3
)
2
(iv)
(
CH
3
)
3
CNH
2
(\text{CH}_3)_3\text{CNH}_2
(
CH
3
)
3
CNH
2
(v)
C
6
H
5
NHCH
3
\text{C}_6\text{H}_5\text{NHCH}_3
C
6
H
5
NHCH
3
(vi)
(
CH
3
CH
2
)
2
NCH
3
(\text{CH}_3\text{CH}_2)_2\text{NCH}_3
(
CH
3
CH
2
)
2
NCH
3
(vii)
m
−
BrC
6
H
4
NH
2
m-\text{BrC}_6\text{H}_4\text{NH}_2
m
−
BrC
6
H
4
NH
2
Q2
Exercises
Give one chemical test to distinguish between the following pairs of compounds.
(i)
Methylamine and dimethylamine
(ii)
Secondary and tertiary amines
(iii)
Ethylamine and aniline
(iv)
Aniline and benzylamine
(v)
Aniline and N-methylaniline.
Q2
Exercises
Give one chemical test to distinguish between the following pairs of compounds.
(i)
Methylamine and dimethylamine
(ii)
Secondary and tertiary amines
(iii)
Ethylamine and aniline
(iv)
Aniline and benzylamine
(v)
Aniline and N-methylaniline.
Q3
Exercises
Account for the following:
(i)
p
K
b
\text{p}K_b
p
K
b
of aniline is more than that of methylamine.
(ii)
Ethylamine is soluble in water whereas aniline is not.
(iii)
Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv)
Although amino group is
o
o
o
- and
p
p
p
- directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of
m
m
m
-nitroaniline.
(v)
Aniline does not undergo Friedel-Crafts reaction.
(vi)
Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
(vii)
Gabriel phthalimide synthesis is preferred for synthesising primary amines.
Q3
Exercises
Account for the following:
(i)
p
K
b
\mathrm{p} K_{b}
p
K
b
of aniline is more than that of methylamine.
(ii)
Ethylamine is soluble in water whereas aniline is not.
(iii)
Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv)
Although amino group is o- and p- directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
(v)
Aniline does not undergo Friedel-Crafts reaction.
(vi)
Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
(vii)
Gabriel phthalimide synthesis is preferred for synthesising primary amines.
Q4
Exercises
Arrange the following:
(i)
In decreasing order of the
p
K
b
\text{p}K_b
p
K
b
values:
C
2
H
5
NH
2
,
C
6
H
5
NHCH
3
,
(
C
2
H
5
)
2
NH
\text{C}_2\text{H}_5\text{NH}_2, \text{C}_6\text{H}_5\text{NHCH}_3, (\text{C}_2\text{H}_5)_2\text{NH}
C
2
H
5
NH
2
,
C
6
H
5
NHCH
3
,
(
C
2
H
5
)
2
NH
and
C
6
H
5
NH
2
\text{C}_6\text{H}_5\text{NH}_2
C
6
H
5
NH
2
(ii)
In increasing order of basic strength:
C
6
H
5
NH
2
,
C
6
H
5
N
(
CH
3
)
2
,
(
C
2
H
5
)
2
NH
\text{C}_6\text{H}_5\text{NH}_2, \text{C}_6\text{H}_5\text{N}(\text{CH}_3)_2, (\text{C}_2\text{H}_5)_2\text{NH}
C
6
H
5
NH
2
,
C
6
H
5
N
(
CH
3
)
2
,
(
C
2
H
5
)
2
NH
and
CH
3
NH
2
\text{CH}_3\text{NH}_2
CH
3
NH
2
(iii)
In increasing order of basic strength:
(a)
Aniline,
p
p
p
-nitroaniline and
p
p
p
-toluidine
(b)
C
6
H
5
NH
2
,
C
6
H
5
NHCH
3
,
C
6
H
5
CH
2
NH
2
\text{C}_6\text{H}_5\text{NH}_2, \text{C}_6\text{H}_5\text{NHCH}_3, \text{C}_6\text{H}_5\text{CH}_2\text{NH}_2
C
6
H
5
NH
2
,
C
6
H
5
NHCH
3
,
C
6
H
5
CH
2
NH
2
.
(iv)
In decreasing order of basic strength in gas phase:
C
2
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
(
C
2
H
5
)
3
N
\text{C}_2\text{H}_5\text{NH}_2, (\text{C}_2\text{H}_5)_2\text{NH}, (\text{C}_2\text{H}_5)_3\text{N}
C
2
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
(
C
2
H
5
)
3
N
and
NH
3
\text{NH}_3
NH
3
(v)
In increasing order of boiling point:
C
2
H
5
OH
,
(
CH
3
)
2
NH
,
C
2
H
5
NH
2
\text{C}_2\text{H}_5\text{OH}, (\text{CH}_3)_2\text{NH}, \text{C}_2\text{H}_5\text{NH}_2
C
2
H
5
OH
,
(
CH
3
)
2
NH
,
C
2
H
5
NH
2
(vi)
In increasing order of solubility in water:
C
6
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
C
2
H
5
NH
2
\text{C}_6\text{H}_5\text{NH}_2, (\text{C}_2\text{H}_5)_2\text{NH}, \text{C}_2\text{H}_5\text{NH}_2
C
6
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
C
2
H
5
NH
2
.
Q4
Exercises
Arrange the following:
(i)
In decreasing order of the
p
K
b
\mathrm{p} K_{b}
p
K
b
values:
C
2
H
5
N
H
2
,
C
6
H
5
N
H
C
H
3
,
(
C
2
H
5
)
2
N
H
\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHCH}_{3}, (\mathrm{C}_{2} \mathrm{H}_{5})_{2} \mathrm{NH}
C
2
H
5
NH
2
,
C
6
H
5
NHCH
3
,
(
C
2
H
5
)
2
NH
and
C
6
H
5
N
H
2
\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}
C
6
H
5
NH
2
(ii)
In increasing order of basic strength:
C
6
H
5
N
H
2
,
C
6
H
5
N
(
C
H
3
)
2
,
(
C
2
H
5
)
2
N
H
\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{N}(\mathrm{CH}_{3})_{2}, (\mathrm{C}_{2} \mathrm{H}_{5})_{2} \mathrm{NH}
C
6
H
5
NH
2
,
C
6
H
5
N
(
CH
3
)
2
,
(
C
2
H
5
)
2
NH
and
C
H
3
N
H
2
\mathrm{CH}_{3} \mathrm{NH}_{2}
CH
3
NH
2
(iii)
In increasing order of basic strength:
(a)
Aniline, p-nitroaniline and p-toluidine
(b)
C
6
H
5
N
H
2
,
C
6
H
5
N
H
C
H
3
,
C
6
H
5
C
H
2
N
H
2
\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHCH}_{3}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}
C
6
H
5
NH
2
,
C
6
H
5
NHCH
3
,
C
6
H
5
CH
2
NH
2
.
(iv)
In decreasing order of basic strength in gas phase:
C
2
H
5
N
H
2
,
(
C
2
H
5
)
2
N
H
,
(
C
2
H
5
)
3
N
\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}, (\mathrm{C}_{2} \mathrm{H}_{5})_{2} \mathrm{NH}, (\mathrm{C}_{2} \mathrm{H}_{5})_{3} \mathrm{N}
C
2
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
(
C
2
H
5
)
3
N
and
N
H
3
\mathrm{NH}_{3}
NH
3
(v)
In increasing order of boiling point:
C
2
H
5
O
H
,
(
C
H
3
)
2
N
H
,
C
2
H
5
N
H
2
\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}, (\mathrm{CH}_{3})_{2} \mathrm{NH}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}
C
2
H
5
OH
,
(
CH
3
)
2
NH
,
C
2
H
5
NH
2
(vi)
In increasing order of solubility in water:
C
6
H
5
N
H
2
,
(
C
2
H
5
)
2
N
H
,
C
2
H
5
N
H
2
\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, (\mathrm{C}_{2} \mathrm{H}_{5})_{2} \mathrm{NH}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}
C
6
H
5
NH
2
,
(
C
2
H
5
)
2
NH
,
C
2
H
5
NH
2
.
Q5
Exercises
How will you convert:
(i)
Ethanoic acid into methanamine
(ii)
Hexanenitrile into 1-aminopentane
(iii)
Methanol to ethanoic acid
(iv)
Ethanamine into methanamine
(v)
Ethanoic acid into propanoic acid
(vi)
Methanamine into ethanamine
(vii)
Nitromethane into dimethylamine
(viii)
Propanoic acid into ethanoic acid?
Q5
Exercises
How will you convert:
(i)
Ethanoic acid into methanamine
(ii)
Hexanenitrile into 1-aminopentane
(iii)
Methanol to ethanoic acid
(iv)
Ethanamine into methanamine
(v)
Ethanoic acid into propanoic acid
(vi)
Methanamine into ethanamine
(vii)
Nitromethane into dimethylamine
(viii)
Propanoic acid into ethanoic acid?
Q6
Exercises
Describe a method for the identification of primary, secondary and tertiary amines. Also write chemical equations of the reactions involved.
Q6
Exercises
Describe a method for the identification of primary, secondary and tertiary amines. Also write chemical equations of the reactions involved.
Q7
Exercises
Write short notes on the following:
(i)
Carbylamine reaction
(ii)
Diazotisation
(iii)
Hofmann's bromamide reaction
(iv)
Coupling reaction
(v)
Ammonolysis
(vi)
Acetylation
(vii)
Gabriel phthalimide synthesis.
Q8
Exercises
Accomplish the following conversions:
(i)
Nitrobenzene to benzoic acid
(ii)
Benzene to
m
m
m
-bromophenol
(iii)
Benzoic acid to aniline
(iv)
Aniline to 2,4,6-tribromofluorobenzene
(v)
Benzyl chloride to 2-phenylethanamine
(vi)
Chlorobenzene to
p
p
p
-chloroaniline
(vii)
Aniline to
p
p
p
-bromoaniline
(viii)
Benzamide to toluene
(ix)
Aniline to benzyl alcohol.
Q9
Exercises
Give the structures of A, B and C in the following reactions:
(i)
CH
3
CH
2
I
→
NaCN
A
→
OH
−
/
Partial hydrolysis
B
→
NaOH
+
Br
2
C
\text{CH}_3\text{CH}_2\text{I} \xrightarrow{\text{NaCN}} \text{A} \xrightarrow{\text{OH}^-/\text{Partial hydrolysis}} \text{B} \xrightarrow{\text{NaOH}+\text{Br}_2} \text{C}
CH
3
CH
2
I
NaCN
A
OH
−
/
Partial hydrolysis
B
NaOH
+
Br
2
C
(ii)
C
6
H
5
N
2
Cl
→
CuCN
A
→
H
2
O
/
H
+
B
→
NH
3
,
Δ
C
\text{C}_6\text{H}_5\text{N}_2\text{Cl} \xrightarrow{\text{CuCN}} \text{A} \xrightarrow{\text{H}_2\text{O}/\text{H}^+} \text{B} \xrightarrow{\text{NH}_3, \Delta} \text{C}
C
6
H
5
N
2
Cl
CuCN
A
H
2
O
/
H
+
B
NH
3
,
Δ
C
(iii)
CH
3
CH
2
Br
→
KCN
A
→
LiAlH
4
B
→
0
∘
C
HNO
2
C
\text{CH}_3\text{CH}_2\text{Br} \xrightarrow{\text{KCN}} \text{A} \xrightarrow{\text{LiAlH}_4} \text{B} \xrightarrow{0^\circ\text{C}}{\text{HNO}_2} \text{C}
CH
3
CH
2
Br
KCN
A
LiAlH
4
B
0
∘
C
HNO
2
C
(iv)
C
6
H
5
NO
2
→
Fe/HCl
A
→
273
K
NaNO
2
+
HCl
B
→
Δ
H
2
O
/
H
+
C
\text{C}_6\text{H}_5\text{NO}_2 \xrightarrow{\text{Fe/HCl}} \text{A} \xrightarrow[273 \text{K}]{\text{NaNO}_2+\text{HCl}} \text{B} \xrightarrow[\Delta]{\text{H}_2\text{O}/\text{H}^+} \text{C}
C
6
H
5
NO
2
Fe/HCl
A
NaNO
2
+
HCl
273
K
B
H
2
O
/
H
+
Δ
C
(v)
CH
3
COOH
→
NH
3
,
Δ
A
→
NaOBr
B
→
NaNO
2
/
HCl
C
\text{CH}_3\text{COOH} \xrightarrow{\text{NH}_3, \Delta} \text{A} \xrightarrow{\text{NaOBr}} \text{B} \xrightarrow{\text{NaNO}_2/\text{HCl}} \text{C}
CH
3
COOH
NH
3
,
Δ
A
NaOBr
B
NaNO
2
/
HCl
C
(vi)
C
6
H
5
NO
2
→
Fe/HCl
A
→
273
K
HNO
2
B
→
C
6
H
5
OH
C
\text{C}_6\text{H}_5\text{NO}_2 \xrightarrow{\text{Fe/HCl}} \text{A} \xrightarrow[273 \text{K}]{\text{HNO}_2} \text{B} \xrightarrow{\text{C}_6\text{H}_5\text{OH}} \text{C}
C
6
H
5
NO
2
Fe/HCl
A
HNO
2
273
K
B
C
6
H
5
OH
C
Q10
Exercises
An aromatic compound 'A' on treatment with aqueous ammonia and heating forms compound 'B' which on heating with
Br
2
\text{Br}_2
Br
2
and KOH forms a compound 'C' of molecular formula
C
6
H
7
N
\text{C}_6\text{H}_7\text{N}
C
6
H
7
N
. Write the structures and IUPAC names of compounds A, B and C.
Q11
Exercises
Complete the following reactions:
(i)
C
6
H
5
NH
2
+
CHCl
3
+
alc. KOH
→
\text{C}_6\text{H}_5\text{NH}_2 + \text{CHCl}_3 + \text{alc. KOH} \rightarrow
C
6
H
5
NH
2
+
CHCl
3
+
alc. KOH
→
(ii)
C
6
H
5
N
2
Cl
+
H
3
PO
2
+
H
2
O
→
\text{C}_6\text{H}_5\text{N}_2\text{Cl} + \text{H}_3\text{PO}_2 + \text{H}_2\text{O} \rightarrow
C
6
H
5
N
2
Cl
+
H
3
PO
2
+
H
2
O
→
(iii)
C
6
H
5
NH
2
+
H
2
SO
4
(conc.)
→
\text{C}_6\text{H}_5\text{NH}_2 + \text{H}_2\text{SO}_4 \text{(conc.)} \rightarrow
C
6
H
5
NH
2
+
H
2
SO
4
(conc.)
→
(iv)
C
6
H
5
N
2
Cl
+
C
2
H
5
OH
→
\text{C}_6\text{H}_5\text{N}_2\text{Cl} + \text{C}_2\text{H}_5\text{OH} \rightarrow
C
6
H
5
N
2
Cl
+
C
2
H
5
OH
→
(v)
C
6
H
5
NH
2
+
Br
2
(
aq
)
→
\text{C}_6\text{H}_5\text{NH}_2 + \text{Br}_2(\text{aq}) \rightarrow
C
6
H
5
NH
2
+
Br
2
(
aq
)
→
(vi)
C
6
H
5
NH
2
+
(
CH
3
CO
)
2
O
→
\text{C}_6\text{H}_5\text{NH}_2 + (\text{CH}_3\text{CO})_2\text{O} \rightarrow
C
6
H
5
NH
2
+
(
CH
3
CO
)
2
O
→
(vii)
C
6
H
5
N
2
Cl
→
(i) HBF
4
→
(ii) NaNO
2
/
Cu
,
Δ
\text{C}_6\text{H}_5\text{N}_2\text{Cl} \xrightarrow{\text{(i) HBF}_4} \xrightarrow{\text{(ii) NaNO}_2/\text{Cu}, \Delta}
C
6
H
5
N
2
Cl
(i) HBF
4
(ii) NaNO
2
/
Cu
,
Δ
Q12
Exercises
Why cannot aromatic primary amines be prepared by Gabriel phthalimide synthesis?
Q13
Exercises
Write the reactions of (i) aromatic and (ii) aliphatic primary amines with nitrous acid.
Q14
Exercises
Give plausible explanation for each of the following:
(i)
Why are amines less acidic than alcohols of comparable molecular masses?
(ii)
Why do primary amines have higher boiling point than tertiary amines?
(iii)
Why are aliphatic amines stronger bases than aromatic amines?
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