Reaction of Sodium with Organic Compounds

Let's take a look at this question:

Reaction of sodium with organic compounds question

To determine the moles of hydrogen evolved we need to know the 3 functional groups that will react with sodium metal.

Reaction of sodium with organic compounds functional groups that react with sodium

1. Alcohols to form alkoxide

ROH + Na → RO-Na+ + 1/2 H2(g)

2. Phenols to form phenoxide

PhOH + Na → PhO-Na+ + 1/2 H2(g)

3. Carboxylic acids to form carboxylate

RCOOH + Na → RCOO-Na+ + 1/2 H2(g)

All these functional groups undergo deprotonation or donate their proton.

Hence the reaction with sodium is considered as acid-base or neutralisation with respect to organic compound.

Here's my video lesson on how to compare acidity of these organic compounds.

Finally we can now look back at citric acid.

Reaction of sodium with organic compounds deducing mole of h2 per mole of citric acid

Citric acid contains 3 carboxylic acid groups and 1 alcohol group.

For each of these functional groups, one mol of functional group will form 0.5 mol of H2 gas.

Hence 1 mol citric acid will produce 2 mol H2(g). [Answer = B]

Topic: Carboxylic Acid, Organic Chemistry, A Level Chemistry, Singapore

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