Question

Which of the following is incorrect?

• A. Primary alcohols are very easily oxidised to aldehydes, which are oxidised to acids with the same number of C-atoms.
• B. Secondary alcohols are very easily oxidised to ketones, which are oxidised to acids with the same number of C-atoms.
• C. Secondary alcohols are easily oxidised to ketones, which are oxidised to acids with a lesser number of C-atoms.
• D. Secondary and tertiary alcohols on oxidation form acids with lesser number of C-atoms.

Hint:

Remember that primary alcohols are oxidised to aldehydes and then acids, while secondary alcohols typically form ketones that are not easily oxidised to acids.

Answer 1

The Correct Option is B

To solve the problem, we need to understand the oxidation process of alcohols, focusing on primary, secondary, and tertiary alcohols:

Primary Alcohols: These are oxidized to aldehydes, which can be further oxidized to carboxylic acids without altering the number of carbon atoms. This statement is true.

Secondary Alcohols: These are oxidized to ketones. However, for further oxidation to carboxylic acids, the carbon chain is typically broken, resulting in acids with a smaller number of carbon atoms. Thus, secondary alcohols do not form acids with the same number of C-atoms through oxidation. Based on this, the following point is incorrect:

Secondary alcohols are very easily oxidised to ketones, which are oxidised to acids with the same number of C-atoms.

Tertiary Alcohols: These are resistant to oxidation; under strong conditions, they might break into smaller fragments, resulting in carboxylic acids with fewer carbon atoms. This aligns with the true statement regarding secondary and tertiary alcohols forming acids with fewer C-atoms.

Thus, the incorrect statement among the provided options is:
Secondary alcohols are very easily oxidised to ketones, which are oxidised to acids with the same number of C-atoms.

Answer 2

Let's evaluate each statement:
1. Primary alcohols can indeed be oxidised to aldehydes, which can then be further oxidised to acids with the same number of carbon atoms. This statement is correct.
2. Secondary alcohols are oxidised to ketones, but ketones are generally resistant to oxidation under normal conditions. Furthermore, ketones are not oxidised to acids with the same number of carbon atoms, but rather to acids with fewer carbon atoms.
Thus, this statement is incorrect.
3. Secondary alcohols are easily oxidised to ketones, and ketones are oxidised to acids with a lesser number of carbon atoms. This is correct because ketones can be oxidised to carboxylic acids, which may have fewer carbon atoms.
4. Secondary and tertiary alcohols, on oxidation, may form acids with fewer carbon atoms, which is also correct. Tertiary alcohols are typically very resistant to oxidation.
Thus, the incorrect statement is (B).