$R',R''$ = $H$ or alkyle(N- substituted amide)
- The hydrogen bonds between amide molecules explain their high melting and boiling temperatures:
Methanamide is liquid, while ethanamide is already solid at normal temperature.
- The hydrogen bonds between amide molecules and water molecules explain the solubility of amides in water:
From heptanamide, however, the hydrophobic character of the hydrocarbon chain wins out and the solubility becomes weak and then nil.
1) Reaction with ammonium carbonate to form ammonium carboxylate: $ 2 R-COOH + (NH_4)_2CO_3 \rightarrow 2 R-COO^-NH_4^+ + 2CO_2 + 2 H_2O $ then heating to form the amide by dehydration: 2) $ 2 R-COO^-NH_4^+ \rightarrow 2 R-CO(NH_2) + 2H_2O $
Violent reaction with ammonia to form amide and ammonium chloride:
$ 2 R-COCl + 2NH_3 \rightarrow R-CO(NH_2) + NH_4^+Cl^- $
The mechanism proceeds by nucleophilic attack of ammonia on the carbon of the acid chloride function:
Amides (b) are intermediate between nitriles (a) and ammonium carboxylates (c) - (1) Dehydration by $ P_2O_5 $ - (2) Hydration with diluted $ HCl$ - (3) Hot dehydration - (4) Hydrolysis -with dilute $ HCl$ gives the ammonium carboxylate (c) which is then converted (5) to carboxylic acid (d) - with dilute $ NaOH $ gives the ammonium carboxylate (c) which is then converted (6) into carboxylate ion (e)
The mesomerism:
produces a positive partial charge on the nitrogen. This charge retains the doublet of nitrogen, which greatly reduces the basicity of the amides.
Name the final substances obtained from the reagents: - Propanoyl chloride and dimethylamine →
- Methanamide and dilute hydrochloric acid →
- N -propyl- N -methylethanamide and dilute sodium hydroxide →