Is Acetamide base or acid? | Preparation | Properties | Uses

Preparation of Acetamide

Laboratory Method

Ammonia acetate is heated in the presence of glacial acetic acid to make Acetamide in the laboratory.

CH3COONH4 CH3CONH2 + H2O

Glacial acetic acid is used to prevent side reaction.

CH3COONH4 CH3COOH + NH3

In the presence of glacial acetic acid, the forward reaction is not effective due to the high velocity of the opposite reaction and the main product is acetamide produce when ammonium acetate is heated.

Chemistry Notes

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Method: Approximately equal amounts of dry ammonium acetate and glacial acetic acid are taken in a round-bottomed flask. A long and direct air condenser is attached to the flask. Put the flask on a wire mesh and heat it for about 4 hours.

Partial dehydration of ammonium acetate occurs and the water formed in the reaction exits the air condenser. After this, the flask mixture is poured into a distillation flask.

A thermometer and air candenser are placed in the distillation flask. Attaches the air condenser to the receiver. Heats the flask and collects the distilled fluid in the receiver.

Above in 200°C temperature they collect the distilled fluid in another receiver. It contains acetamide. When cooled it converts into a solid form. Pure acetamide is obtained after its ether or alcohol is crystallized.

Methyl Cyanide

Acetic acid is obtained from complete water decomposition of methyl cyanide and acetamide is obtained from partial water decomposition of methyl cyanide. Partial water decomposition of methyl cyanide is done in two ways.

  • Alkaline hydrogen peroxide
  • Dissolved in concentrated sulfuric acid and poured into cold water

CH3-CN + H2O CH3CONH2

Acetamide can also be made by the reaction of ammonia solution concentrated on acetyl chloride, acetic anhydride or ethyl acetate.

CH3COCl + 2NH3 CH3CONH2 + NH4Cl

(CH3CO)2O + 2NH3 CH3CONH2 + CH3COONH4

CH3COOC2H5 + NH3 CH3CONH2 + C2H5OH

Acetamide Physical Properties

It is colorless, needle-shaped and crystalline solids. It is soluble in water, alcohol and ether. In pure state it is odorless but in impure state it smells like rat. Its melting point is 82°C and the boiling point is 222°C.

Acetamide Chemical Properties

Water decomposition: It is slowly decomposed by water and quickly by dilute acids.

CH3CONH2 + H2O CH3COOH + NH3

It is more rapidly decomposed by dilute bases. Sodium acetate and ammonia are formed in this reaction. This reaction is used to test amide group.

CH3CONH2 + NaOH CH3COONa + NH3

Amphoteric Properties: It reacts with intense acids to form temporary salts which exhibit its alkaline properties.

CH3CONH2 + HCl(Base) CH3CONH2.HCl(acetamide hydrochloride)

It reacts with sodium metal to form a salt called sodium acetamide which exhibits its acidic properties.

2CH3CONH2 + 2Na 2CH3CONH.Na(sodium acetamide) + H2

It is Amphoteric due to exhibiting both acidic and alkaline properties.

Reduction: This H2/Ni. Sodium ethanol is reduced by LiAlH4 or NaBH4 to form ethyl amine.

CH3CONH2 + LiAlH4 CH3CH2NH2 + H2O

Action of nitrous acid: It reacts with nitrous acid to make acetic acid and nitrogen gas is free.

NaNO2 + HCl NaCl + NHO2

CH3CONH2 + NHO2 CH3COOH + H2O + N2

Dehydration: On heating acetamide with phosphorus pentoxide, one molecule of water is released from one of its segments and forms methyl cyanide.

CH3CONH2 + P2O5 CH3CN + H2O

Hoffmann bromamide Reaction: Methyl amine is obtained when acetamide is heated with bromine and caustic potash solution. Here are the reactions:

CH3CONH2 + Br2 CH3CONHBr + HBr

KOH + HBr KBr + H2O

CH3CONHBr + KOH CH3NCO + KBr + H2O

CH3NCO + 2KOH CH3NH2 + K2CO3

The complete reaction can be represented by the following equation.

CH3CONH2 + Br2 + 4KOH CH3NH2 + 2KBr + K2CO3 + 2H2O

With the help of this reaction amide group (-CONH2) can be converted into amino group (-NH2). This reaction is very important and is used to obtain a lower member from a higher member of a homogeneous category.

What is acetamide used for?

  • Being hygienic, it is used in softening the fabrics etc.
  • Used in making methyl amine.
  • It is used in making diethyl bromo bromoacetamide. Which is used as a sleeping medicine called neuronal.

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