Download Document

Ch.36 notes – P.1
Ch.36 – Nitrogen compounds
A. Introduction
 Nitrogen compounds in organic chemistry can be divided into two basic groups:
_______________ and _______________.
 1o amines:
R
..
N
e.g.
H
CH3
CH3NH2
CH3CH2CHCHCH3
H
NH2
2o amines:
R
..
N
e.g.
H
CH3CH2-N-CH3
CH3CHCH3
H N CH3
H
R
3o amines:
R
e.g.
..
N
CH2CH2CH2CH3
R
CH3
R
N CH2CH2CH3
Quaternary ammonium ions:
R
+
+
e.g.
CH3
CH3
R N R
N CH3
CH3
R
Aromatic amines:
NH2
H
N
H
CH3
N
Ch.36 notes – P.2
 Lower members of amines are _____________ with a smell of ___________;
while the higher ones are liquids with a distinctive ____________ smell.
 Amines have ___________ boiling points than less polar compounds due to its
______________ bonding; but they have __________ boiling points than
alcohols and carboxylic acids because their hydrogen bonding are weaker.
 Lower members of amines are _____________ with water due to the hydrogen
bonding formation with water.
Ex.: Match the boiling points, 65℃, -6℃ and -88℃ with the corresponding
compounds CH3CH3, CH3NH2 and CH3OH.
B. Preparations of amines
1. Reduction of nitriles
e.g.
CH3CH2CN
2. From amides
 Reduction
O
CH3C NH2
 Hofmann degradation
O
CH3C NH2
Ch.36 notes – P.3
3. Alkalyation of aliphatic haloalkanes
R-X + NH3
R-X + RNH2
R-X + R2NH
R-X + R3N
A mixture of amines may be separated by ______________________________.
4. Phenylamine from reduction of nitrobenzene
By treating nitrobenzene with _______ and _____________ followed by excess
____________.
NO2
C. Base properties of amines
 Amines are similar to ammonia.
e.g.
..
H N H
+ H2O
H
..
R N R
+ H2O
R
NH2 + H2O
Hence, amines can react with acids to form salts.
Ch.36 notes – P.4
 Comparison of the basic strength:
pKb at 25℃
1o amine
CH3CH2NH2
3.27
CH3NH2
3.36
Ammonia
NH3
4.75
Phenyl amine
C6H5-NH2
9.38
Generally speaking, for basic strength:
R-NH2
NH3
C6H5-NH2
Because the basic strength depends on the availability of the lone-pair electrons
on the N atom, the present of alkyl group has a ________________________
and increases the basic strength.
For phenyl amine, _______________ effect occurs ( or __________________
of electrons occurs) and the lone pair electrons are less available for donation:
Ex.: Arrange the following compounds in the descending order of basicity:
NH3
CH3CONH2
A
B
(CH3CH2)2NH
C
CH3CH2NH2
D
 Since amines are basic, they react with acids to from stable crystalline salts.
RNH2
+ HCl
The amines can be regenerated by treating the salt with _________________.
Ch.36 notes – P.5
D. Reactions of amines
1. Reaction with acyl chlorides
O
CH3
C
CH3
Cl
N CH3
+ H
NH2
O
CH3
C
Cl
+
 Only ________ and ________ have the above reactions.
 The amides produced are ________________________________ with
______________
melting
points.
They
are
therefore
useful
for
__________________ unknown amines.
2. Reaction with benzyol chloride
The reactions are similar to acyl chloride except carried out in ________________.
e.g.
COCl
H
+
COCl
CH3CH2-N-H
NH2
+
Ch.36 notes – P.6
3. Diazonium salt formation
Primary amines react with ____________________________.
RH2
NH2
 The aliphatic diazonium salts are unstable and are decomposed once they are
formed into ___________________ and ___________________.
The carbonium ion is reactive and able to react with different nucleophiles.
H2O
Cl-
R+
NO2-
 The aromatic diazonium ion ( _________________________ ) is stable in
cold (
). Hence it can be isolated as crystalline salt.
a) The benzenediazonium ion is decomposed at higher temperature to give
phenol.
+
N
N
+ H2O
b) Produce halobenzene
+
N
N
Ch.36 notes – P.7
c) Produce cyanobenzene
+
N
N
d) Coupling reaction
Diazonium salts can couple with phenols or phenylamines to yield
________ compounds
+
N
G
N
+
e.g.
+
N
OH
N
+
+
N
N(CH3)2
N
+
SO3H
N
N
OH
+
Ch.36 notes – P.8
E. Uses of amines and their derivatives
1. Azo-compounds as highly coloured, they are used as _______ in dyeing industries.
2. Amines derivatives as ____________.
Ch.36 notes – P.9
F. Amino acids
Amino acids are compounds containing both the ________ and the ___________
groups, they are called __________________ compounds.
Amino acids:
H
R
C
H
e.g.
COOH
H
C
H
COOH
CH3
NH2
NH2
C
COOH
NH2
 Except when R = H, there are chiral centres in the molecules, i.e. they are
____________________________.
 α-amino acids show many properties inconsistent with the general structure,
e.g.: amino acids
1. are ________________________________ solids.
2. are ______________ in polar solvents but not in non-polar solvents.
3. the acidic strengths and basic strengths are _________ than expected.
 Amino acids exist as __________________, which are ________________.
H
H2N
C
R
COOH
Ch.36 notes – P.10
 Two amino acids can condense together to form a ___________, i.e. a
_________________.
H
H
O
C
N
H
H
H
O
C
OH
R
C
N
H
C
OH
R
 If more than three amino acid molecules join together, the polymer formed is
called a ___________________.
H
H
O
N
H
C
R
H
H
O
N
C
OH
 _______________ are polypeptides.
H
C
R
C
OH
Ch.36 notes – P.11
 Proteins can be _____________ to reform amino acids by boiling with
aqueous acid. Amino acids in a mixture can be separated by __________
__________________. The positions of the colourless amino acids are
revealed by spraying the paper with ________________, which gives a
______________ colour with amino acids.
Ex.:
Ch.36 notes – P.12