Question

Write a chemical equation to convert the following:

Methanol to ethanol.

Answer 1

1. Conversion to Methyl Iodide: React methanol with Phosphorus and Iodine.

\[\ce{CH3OH + HI ->CH3I + H2O}\]

2. Chain Elongation (Adding Carbon): React with Ethanolic Potassium Cyanide (KCN).

\[\ce{CH3I + KCN(alc{.}) ->CH3CN + KI}\]

3. Reduction to Primary Amine: Reduce Methyl Cyanide using Sodium and Ethanol (Mendius reaction).

\[\ce{CH3CN + 4[H] ->[Na/C2H5OH][]CH3CH2NH2}\]

4. Conversion to Ethanol: React the amine with Nitrous Acid (NaNO₂ + HCl).

\[\ce{CH3CH2NH2 + HNO2 -> CH3CH2OH + N2↑ + H2O}\]

Alternative (Grignard Method): A faster laboratory way is to oxidise methanol to formaldehyde and then use a Grignard reagent:

\[\ce{CH3OH ->[{[O]}][]\underset{(Formaldehyde)}{HCHO}}\]

\[\ce{HCHO + CH3MgBr ->[H3O+][]\underset{(Ethanol)}{CH3CH2OH}}\]