AMINES AND AMIDES

AMINES

It has a functional group of NH₂.

GENERAL MOLECULAR FORMULAR/STRUCTURE

It has a general molecular formula of RNH₂ or structure of              R – N – H

H

PREPARATION:

They are derivatives of ammonia where one or more hydrogen atoms have been replaced by alkyl or aryl groups e.g. RNH_z, R₂NH.

 

CLASSIFICATION:

Amines can be classified according to alkyl group.

 

1. Primary amine with one alkyl group e.g. RNH₂ or

R                      or                     CH₃

H          N          H                      H          N          H

2. Secondary amine with 2 alkyl groups e.g. R₂NH or

R                      CH₃

R          N    or     CH₃      N        H

H

3. Tertiary amine with 3 alkyl groups e.g. R₃N or

R                                             CH₃

R¹      N        R¹¹    or             CH₃          N      CH₃

Trimethyl amine

PHYSICAL PROPERTIES

1. They can dissolve in water.
2. They are gases and liquid.
3. They have fishy odour.

 

CHEMICAL PROPERTIES

1. As bases they neutralize acids.
2. They dissociate/ionize in water e.g. CH₃NH₂ + H₂O CH₃NH₃⁺+ OH^–

 

USES

1. Used in making nylon
2. They can also be used in making polyamide.

 

EVALUATION

1. State two (2) physical properties and two (2) chemical properties of amine.
2. Give the classes of amine according to the number of their alkyl groups.

 

AMIDES

O

It has functional group of –C    which is known as carbonamide group.

NH₂

STRUCTURE

O                 H        O

CH₃     C        or     H     C     C

NH₂                H    N    H

H

 

PREPARATION

–           Amide e.g. ethanmide can be derived from ethanoic acid in the presence of ammonia.

O                OOO

CH₃       C       +    NH₃   C     +   H₂O    CH3 – C      + NH₃           CH₃  C          +H₂O

OH                                   NH₂

OH                    NH₂

– Amide is commonly prepared by reacting esters with concentrated aqueous ammonia.                                               E.gCH₃COOC₂H₅  + NH₃             Ethanamide CH₃CONH₂ + C₂H₅OH

-They can also be prepared by removing a molecule of water from ammonium salt of carboxylic x acids.

e.g. CH₃COONH₄                CH₃CONH₂ + H₂O

 

PHYSICAL PROPERTIES

1. Only methanamide is a liquid while others are solid.
2. They have high melting point and high boiling point.

 

CHEMICAL PROPERTIES

1. Amide can be hydrolysed in the presence of alkali and mineral acid e.g.

CH₃CONH₂  +  H₂O          CH₃COOH + NH₃

2. In the presence of sodium hydroxide and bromine, amides produce amines with elimination of one     carbonyl group.

e.g.CH₃CONH₂  +  Br₂ + 4NaOH            CH₃NH₂ + 2NaBr + Na₂CO₃ + 2H₂O

USES

1. Used in the preparation of amines.
2. Used in making synthetic resins and plastics.
3. It can also be used in making fertilizer.

 

CARBAMIDE/UREA

This is an amide of hydrogen trioxo carbonate (IV) acid.  It is produced by compressing CO₂ and NH₃ at high pressure at 200⁰C.

H₂CO₃               CO(NH₂)₂

 

OH                               NH_z

 

O      C                              O      C

 

OH                           NH_z

Carbonamide/urea

 

N.B.:     Urea is produced in our body and excreted in the urine.

 

EVALUATION

1. Write the structural formula of amide.
2. Give one different between amine and amide.

 

WEEKEND ASSIGNMENT

1.Tertiary amine is represented as follow

1. R₂NH₂    B.  (CH₃)₂NH       C.R₂NH₃    D.  R₂N

2.Which of the following has fishy odour

1. alkanoic acid B.  alkanol    C.  amide     D.  amine

3.Amide can be regarded as derivatives of …………

1. alkanol  B.  policarboxylic acid   C.  monocarboxylic acid  D.  carbonxamide group

4.During the hydrolysis of amides, one of the following is produced.

1. monocarboxylic acids B.  water    C.  H₂SO₄    D.NaOH
2. Carbamide is an example of
3. amine    B.  alkane   C.  alkyl    D.  amide

 

THEORY

1(a).     State two (2) physical properties of amide.

(b).     How would you prepare ethanamide from an ester.

2(a).     State two (2) chemical properties of amide.

(b).     How would you identify an example of amine in the laboratory

 

See also

CARBOHYDRATES

NATURAL AND SYNTHETIC POLYMERS

Fats and Oils As Higher Esters

ALKANOIC ACIDS

ALKANOLS