When formaldehyde (methanal) is heated with potassium hydroxide (KOH), which of the following organic products is formed as a result of the Cannizzaro reaction?

Introduction / Context:
The reaction of aldehydes without alpha hydrogen, such as formaldehyde, with a strong base like potassium hydroxide is a classic example of the Cannizzaro reaction in organic chemistry. In this disproportionation reaction, one molecule of the aldehyde is oxidised to a carboxylate salt and another is reduced to an alcohol. This question asks you to identify the main organic product obtained when formaldehyde is heated with potassium hydroxide, which is a common textbook example.

Given Data / Assumptions:
- The aldehyde used is formaldehyde (also called methanal, HCHO). - The base used is potassium hydroxide (KOH). - Heating is involved, suggesting a base-catalysed reaction. - Options include methyl alcohol, acetylene, methane, and ethyl formate. - We assume the standard Cannizzaro reaction mechanism for aldehydes lacking alpha hydrogen.

Concept / Approach:
In the Cannizzaro reaction, two molecules of an aldehyde without alpha hydrogen react in the presence of a concentrated base. One aldehyde molecule is reduced to an alcohol, while the other is oxidised to a carboxylate salt. For formaldehyde, this means that one molecule is reduced to methanol (methyl alcohol), and another is oxidised to potassium formate. The correct approach is to recognise formaldehyde as a Cannizzaro-active aldehyde and identify methanol as one of the principal organic products.

Step-by-Step Solution:
Step 1: Write a simplified equation for the Cannizzaro reaction of formaldehyde: 2 HCHO + 2 KOH → CH3OH + HCOOK. Step 2: In this equation, CH3OH is methyl alcohol (methanol), and HCOOK is potassium formate, the salt of formic acid. Step 3: Among the options, only option a explicitly mentions methyl alcohol formed along with a salt of formic acid, which matches the known reaction. Step 4: Option b, acetylene, is an alkyne and is not produced in this base-induced disproportionation. Step 5: Option c, methane, would require a different type of reduction and is not the product of the Cannizzaro reaction of formaldehyde. Step 6: Option d, ethyl formate, is an ester and does not arise from simply heating formaldehyde with KOH. Step 7: Therefore, the correct answer is methyl alcohol along with a salt of formic acid (potassium formate).

Verification / Alternative check:
Organic chemistry textbooks consistently list formaldehyde as a key example of an aldehyde that undergoes the Cannizzaro reaction when treated with concentrated alkali. The reaction products are always described as methanol and a formate salt. This pattern also fits the general rule that in Cannizzaro reactions, the aldehyde is simultaneously oxidised and reduced: one molecule gives an acid salt, and another gives an alcohol, with no unsaturated hydrocarbons or esters directly produced under these simple conditions.

Why Other Options Are Wrong:
Acetylene (option b) is produced by quite different reactions, such as the hydrolysis of calcium carbide, and is not a product of base-catalysed disproportionation of aldehydes. Methane (option c) would require hydrogenation or decarboxylation mechanisms that are not relevant here. Ethyl formate (option d) is an ester of formic acid and ethanol and is formed by esterification, not by the Cannizzaro reaction of formaldehyde. Hence, these options do not match the known reaction pathway and products.

Common Pitfalls:
Students sometimes confuse the Cannizzaro reaction with other organic reactions and may guess any common organic molecule. Another typical error is to forget that aldehydes without alpha hydrogen, such as formaldehyde and benzaldehyde, undergo disproportionation rather than aldol condensation. Remembering the simple balanced equation and the pattern aldehyde → alcohol + salt of acid will help you quickly identify methyl alcohol as the main organic product here.

Final Answer:
When formaldehyde is heated with KOH, the main organic product is methyl alcohol (methanol), formed along with a salt of formic acid via the Cannizzaro reaction.