Problem 45 - Chemistry: The Central Science

Question

Draw the condensed structure of the compounds formed by condensation reactions between (a) benzoic acid and ethanol, (b) ethanoic acid and methylamine, (c) acetic acid and phenol. Name the compound in each case.

Step-by-Step Solution

Answer

The condensed structures of the compounds formed by condensation reactions are: (a) Benzoic acid and ethanol react to form ethyl benzoate with the structure \[C_6H_5COOCH_2CH_3\]. (b) Ethanoic acid and methylamine react to form N-Methyl ethanamide with the structure \[CH_3CONHCH_3\]. (c) Acetic acid and phenol react to form phenyl acetate with the structure \[CH_3COOC_6H_5\].

Step 1: (a) Benzoic acid and ethanol

The reacting functional groups in these compounds are the carboxyl group (COOH) in benzoic acid and the hydroxyl group (OH) in ethanol. In a condensation reaction, these groups combine, with the elimination of a water molecule. Benzoic acid: \[C_6H_5COOH\] Ethanol: \[CH_3CH_2OH\] On combining, the product formed is an ester with the structure \[C_6H_5COOCH_2CH_3\]. This ester will be named by localizing the alkyl group on the alcohol first and then the carboxyl group on the acid. Hence, the name of the compound: Ethyl benzoate.

Step 2: (b) Ethanoic acid and methylamine

The reacting functional groups in these compounds are the carboxyl group (COOH) in ethanoic acid and the amine group (NH2) in methylamine. Again, during the condensation reaction, these groups combine and a water molecule is eliminated. Ethanoic acid: \[CH_3COOH\] Methylamine: \[CH_3NH_2\] On combining, the product formed is an amide with the structure \[CH_3CONHCH_3\]. The amide will be named by replacing the "oic acid" of the acid with "amide" and putting the alkyl group of the amine in front. Hence, the name of the compound: N-Methyl ethanamide.

Step 3: (c) Acetic acid and phenol

The reacting functional groups are the carboxyl group (COOH) in acetic acid and the hydroxyl group (OH) in phenol. They combine in a condensation reaction, eliminating a water molecule. Acetic acid: \[CH_3COOH\] Phenol: \[C_6H_5OH\] On combining, the product formed is an ester with the structure \[CH_3COOC_6H_5\]. This ester will be named by localizing the alkyl group on the alcohol first, and then the carboxyl group on the acid. Hence, the name of the compound: Phenyl acetate.