Alcohols — practice questions

1. The molecular formula $C_4H_{10}O$ corresponds to butanol isomers (butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, 2-methylpropan-2-ol).
2. The alcohol is oxidised, so it must be a primary or secondary alcohol. This eliminates 2-methylpropan-2-ol (a tertiary alcohol).
3. The product B does not react with Fehling's solution. Fehling's solution is a test for aldehydes. This means B is not an aldehyde, so it must be a ketone.
4. Only secondary alcohols oxidise to form ketones. Therefore, alcohol A must be a secondary alcohol.
5. The only secondary alcohol with the formula $C_4H_{10}O$ is butan-2-ol, $CH_3CH(OH)CH_2CH_3$.
6. Oxidation of butan-2-ol gives the ketone butanone (also known as butan-2-one), $CH_3COCH_2CH_3$.

Answer: A is butan-2-ol. B is butanone.

1. Identify Reactants: The reaction is between an alcohol (propan-1-ol, $CH_3CH_2CH_2OH$) and a carboxylic acid (ethanoic acid, $CH_3COOH$). This is an esterification reaction.
2. Name the Ester: The name of the ester is derived from the alcohol and the carboxylic acid. The alcohol part is named first, changing the '-ol' suffix to '-yl'. So, 'propan-1-ol' becomes 'propyl'. The acid part is named second, changing the '-oic acid' suffix to '-oate'. So, 'ethanoic acid' becomes 'ethanoate'.
3. Combine Names: The product is propyl ethanoate.
4. Draw the Structure: The ester functional group is -COO-. The part from the carboxylic acid ($CH_3CO-$) bonds to the oxygen from the alcohol, which is attached to its alkyl group ($-CH_2CH_2CH_3$).

Answer: Name: Propyl ethanoate Displayed Formula:

      H   H   O    H   H   H
      |   |  //    |   |   |
H--C--C--C--O--C--C--C--H
      |   |        |   |   |
      H   H        H   H   H

(Structure is $CH_3COOCH_2CH_2CH_3$)