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Chemistry 20
Chapter 8
Amines
Amines
Amines:
• Are derivatives of ammonia NH3.
• Contain N attached to one or more alkyl (Aliphatic amine) or
aromatic groups (Aromatic amine).
-NH2 amino group
NH
CH22 CH3
CH3-NH2
CH3-NH-CH3
Eth ylb enzene
Amines
Amines are classified into three groups:
depending on the number of carbon groups bonded to nitrogen.
CH3—NH2
CH3

CH3—NH
Primary 1°
Secondary 2°
CH3

CH3—N—CH3
Tertiary 3°
Naming Amines
IUPAC name – 1° amines
The same method as we did for alcohols.
- Drop the final “-e” of the parent alkane and replace it by “-amine”.
- Use a number to locate the amino group (-NH2) on the parent chain.
NH2
NH2
NH2
CH3-CH-CH3 NH2 CH3-CH-CH-CH3
2
4
3
1 CH3 CHCH31
2
Cl
3
2-Propanamine
Cyclohexanamine
2-propanamine
3-chloro-2-butanamine
H2 N
6
5
4
3
2
1
NH2
1,6-Hexan ediamine
1,6-hexanediamine
Naming Amines
Common name
Names of alkyl groups (In alphabetical order) + “amine”
CH3—CH2—NH2
ethylamine
CH3—NH —CH3
dimethylamine
CH3
|
CH3—N—CH2—CH3
ethyldimethylamine
Aniline (common name)
NH
CH22 CH3
CH3
CH=CH
Aniline
Eth ylb enzene
NH
CH22 CH3
2
1
3
4
Eth ylb
NOenzene
CH3
NH
CH22 CH3
2
1
Toluen e
CH=CH2
Styrene
CH3 NH
CH22 CH3 CH=CH
1
2
3
3
CH3
4
CH3
Eth ylb enzene
Toluen
Etheylb
enzene
Styren
Cl
Toluen e
Styrene
2
4-Nitroaniline
3-Methylaniline
4-Chloro-3-methylaniline
Naming Amines
IUPAC name – 2° and 3° amines
– Take the largest group bonded to nitrogen as the parent amine.
– Name the smaller group(s) bonded to nitrogen, and show their locations
on nitrogen by using the prefix “N”.
NHCH3
N-Methylanilin e
CH3
CH
NHCH
N
N
3
CH3
C
N,N-Dimethyl-aniline
N,N-Dimeth
N-Methylanilin
e
cyclopentan amine
cyclopentan a
CH3
CH3-N-CH2-CH3
N,N-Dimethylethanamine
Heterocyclic amines
When N is one of the atoms of a ring.
N
H
Pyrrolidine
CH3
H
Pyridine
Nicotine
Physical properties of Amines
1. They have unpleasant odors (rotting fish like ammonia).
2. They are polar compounds.
Difference in electronegativity between N - H (3.0 – 2.1 = 0.9)
3. 1° and 2° amines have hydrogen bonds (N-H).
Weaker than alcohols (O-H).
3° amines do not form hydrogen bonds (no H atom).
4. Boiling points: Hydrocarbons< Amines < Alcohols
5. Almost soluble in water (hydrogen bonding).
Chemical properties of Amines
They are weak bases (like ammonia): react with acids.
(to form water-soluble salts)
H
CH3
N..
H
+
..
H – ..
O–H
H
CH3
N
+
H
-...
. ..O – H
H
Some amines present in our blood and make it approximately basic (pH = 7.4).
Chemical properties of Amines
Aliphatic amines are weak bases by comparison with inorganic bases
such as NaOH, they are strong bases among organic compounds.
Aliphatic amines are stronger bases than aromatic amines.
(slightly stronger than NH3)
Clas s
pKb
Example
N ame
Aliph atic
Ammonia
3.0 - 4.0 CH3 CH2 NH2
4.74
Ethan amin e Stron ger bas e
Aromatic
8.5 - 9.5 C6 H5 NH2
Anilin e
Weaker base
Examples
Complete each acid-base reaction and name the salt formed.
(a) ( CH3 CH2 ) 2 NH + HCl
+ CH3 COOH
(b )
N
Examples
Complete each acid-base reaction and name the salt formed.
Solutions:
(a) (CH3 CH2 ) 2 NH + HCl
(CH3 CH2 ) 2 NH2 + ClD ieth ylammoniu m
chloride
CH3 COO-
+ CH3 COOH
(b)
N
N+
H
Pyridinium acetate