Question

1. an unknown organic compound p has the molecular formula \\(c_2h_6o\\). some information about the compound is shown.

• p can be made by fermentation process.
• p can be oxidised to form q.
• p reacts with q to form r and water.

which of the following combinations gives the correct homologous series for p, q and r?

\

$$\begin{array}{|c|c|c|c|} \\hline & p & q & r \\\\ \\hline a & \\text{alcohol} & \\text{carboxylic acid} & \\text{ester} \\\\ b & \\text{alkene} & \\text{alcohol} & \\text{carboxylic acid} \\\\ c & \\text{alkane} & \\text{alkene} & \\text{alcohol} \\\\ d & \\text{carboxylic acid} & \\text{ester} & \\text{alkane} \\\\ \\hline \\end{array}$$

Explanation:

Identify compound P

Using the Fermentation of Glucose knowledge point

$$
LATEXBLOCK0
$$

Identify compound Q

Using the Alcohol Oxidation knowledge point

$$
LATEXBLOCK1
$$

Identify compound R

The reaction between an alcohol and a carboxylic acid in the presence of an acid catalyst produces an ester and water.

$$ \text{CH}_3\text{CH}_2\text{OH} + \text{CH}_3\text{COOH} ightleftharpoons \text{CH}_3\text{COOCH}_2\text{CH}_3 + \text{H}_2\text{O} $$

Therefore, compound R is ethyl ethanoate, which belongs to the ester homologous series.

Match with options

Comparing our identified homologous series for P, Q, and R with the table:

• P: alcohol
• Q: carboxylic acid
• R: ester

This matches row A.

Answer:

• (A) P: alcohol, Q: carboxylic acid, R: ester (Correct answer)
• (B) P: alkene, Q: alcohol, R: carboxylic acid
• (C) P: alkane, Q: alkene, R: alcohol
• (D) P: carboxylic acid, Q: ester, R: alkane