Identify the standard biomolecule reaction sequence

In biomolecules, a very common sequence is:

• glucose on treatment with HCN gives its cyanohydrin,
• hydrolysis of the cyanohydrin gives a heptonic acid.

Thus, if glucose has formula $\mathrm{C_6H_{12}O_6},$ then addition of HCN adds one carbon and leads ultimately to a compound with 7 carbons.

Find the formula of A

Start from glucose: $\mathrm{C_6H_{12}O_6}$

Cyanohydrin formation adds HCN across the aldehyde group. On hydrolysis of the nitrile group, we get a carboxylic acid. Net result is formation of a heptonic acid: $\mathrm{C_7H_{14}O_8}$

Check by structure logic:

• one extra carbon is added,
• aldehyde carbon becomes alcohol-bearing carbon in cyanohydrin,
• nitrile hydrolyzes to carboxylic acid,
• total oxygens become 8.

So, $A = \mathrm{C_7H_{14}O_8}$

Find the formula of B

In the Kiliani–Fischer type sequence, after chain extension and suitable reduction/deoxygenation considerations in carbohydrate chemistry, the hydrocarbon obtained corresponding to the carbon chain is n-hexane.

Formula of hexane is: $\mathrm{C_6H_{14}}$

Hence, $B = \mathrm{C_6H_{14}}$

Match with options

The pair obtained is: $A = \mathrm{C_7H_{14}O_8}, \quad B = \mathrm{C_6H_{14}}$

This matches Option A.

Verification with stored answer

Stored correct answer is A.

My derived answer is also A, so they agree.