Download Amines

Dr Nahed Elsayed
1
Learning Objectives
Chapter ten discusses the following topics and by the end of this chapter the
students will:
 Know the structure and classification of amines
 Know the naming rules for amines & precedence order of functional groups in
compounds have more than one functional group.
 Know the physical properties of amines
 Know the effect of lone pair of electrons of N atom on basic properties of amines
Know the different methods used in synthesis of amines
 Know the reactions of amines; in addition to behaving as bases amines can be
nucleophiles.
Structure & Classification
Amines: is a class of organic compounds that contain the NH2 group
Amines are derivatives of ammonia that have one or more of the hydrogen replaced with alkyl
and/ or aryl group.
Amines are formed in many biological systems. So it used in drugs and medicines.
Classification Of Amines
H
R
H
R
N:
R
N:
R
R
N:
R
H
primary (1°) amines
secondary (2°) amines
tertiary (3°) amines
Common Nomenclature Of Amines
 The common names of amines are derived by listing the name (s) of the
group (s) surrounding the nitrogen (in alphabetical order) and adding the
suffix amine.(N.B. if two vowels come together ; the first must be omitted
e.g. ethanamine).
 Symmetrical 2° & 3° amines (i.e. the substituents surrounding the N atom
are identical) are named by adding the multiplication prefix (di or tri) to
the name of the alkyl group.
H
N
CH3
H3C N CH3
H3C NH2
Methylamine
Benzylmethyl amine
Trimethylamine
 Structures with higher priority groups, the NH2 group is called amino
COOH
H2N
4-Aminobenzoic acid
IUPAC Names Of Primary Amines
 If the compound does not contain a functional group except amino group,
then the compound is named by finding the longest alkane chain containing
the amino group and replacing the e in the IUPAC name by the suffix amine
 However if the compound contain other functional groups then the order
of precedence determines which group are named with prefix or suffix. (see the
precedence table on slide 6)
The highest precedence group takes the appropriate suffix with all other groups taking
the prefix (es), however = or Ξ bonds only take suffix form (ene, yne respectively).
5-Methyl-3-hexanamine
NH2
CH3 CH2 CH
2-Butanamine
CH3
5-Aminoheptanoic acid
NH
CH3
CH3 CH2 CH
CH3
N-methyl-2-butanamine
3-Amino-2-butanol
H2N CH2 CH2OH
2-Aminoethanol
Precedence Order of Functional Groups
(Descending Order)
Class
Functional group Prefix
suffix
Carboxylic acids
Cyclic alknes or alkenes
with COOH group
COOH
oic acid
carboxylic acid
Aldehydes
Cyclic alknes or alkenes
with CHO group
-CHO
Formyl
al
carbaldehyde
ketone
-C=O
oxo
one
Alcohols
-OH
hydroxy ol
Amines
-NH2
amino
amine
Ethers
-OR
alkoxy
-
Alkenes and aAlkynes
= & Ξ bonds
-
ene & yne
Naming Of Aromatic Amines
They have common names accepted by the IUPAC system, but if the benzene
ring contain groups of higher priorities (COOH > CHO > C=O > OH > NH2) in this
case the amino group is added as a prefix.
NH2
Aniline
NH2
NO2
o-Nitroaniline
NH2
NH2
CH3
OH
p-Toluidine
p-Aminophenol
Physical Properties of Amines
Solubility :
 All amines are capable of forming hydrogen bonds with water, alcohols
(solvents having OH group) thus they are soluble in water.
The lower molecular weight amines with up to six carbons show appreciable
solubility in water.
Boiling point :
 Because they possess a polar N-H bond, primary and secondary amines are
capable of forming hydrogen bonds among their molecules; therefore they have:
higher boiling points than alkanes but lower than alcohols (alcohols form stronger
h-bonds than amines).
Tertiary amines can not form H-bonds among their molecules and their
molecules are more branched thus they have the lowest boiling points among
amines.
Basicity Of Amines
Base strength :
Aromatic amines less basic than aliphatic amines
 Electron donating (releasing) groups on N atom increase the basicity
Electron withdrawing groups decrease the basicity
H3C
N
NH2
NH2
H
CH3
>
H3C
NH2
>
>
O2N
H3C
Most basic
NH2
NH2
>
>
NH2
NO2
Least basic
Preparation Of Amines
1) Alkylation of Ammonia:
RNH3X
NH3 + RX
OH
RNH2
2) Reduction of Nitro groups:
3) Reduction of Nitriles:
H2/Pt
R-CN
R-CH2NH2
4) Reduction of Amides:
O
R
145 Chem.
C
NH2
LiAlH4
R-CH2NH2
10
Reaction of Amines
• Salts Formation:
HCl
R-NH2
• Amides Formation:
R-NH3Cl
O
O
R
C
Cl
+
`
R-NH
2
R
R
C
`
NHR
`
NR
O
• Imines Formation:
C
H
+
`
R-NH
2
R
C
H
• Diazonium Salts Formation:
NH2
OH
N2 Cl
+
NaNO2
HCl
H3O+/ 
OoC
Diazonium salt
(benzene diazonium chloride)
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Questions
•
•
•
•
Write the structure of p-nitrobenzylamine?
How to prepare ethylamine from acetamide?
Why are aliphatic amines is more basic than
aromatic amines?
Select the stronger base from each pair of
compounds?
NH2
NH2
or
a)
NH2
NH2
or
b)
H3C
O2N
c)
or
N
H
N
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Questions?