The general formula of alkanones is

Analysis

The question asks for the general formula of alkanones. In organic chemistry, alkanones are more commonly known as ketones. To identify the correct formula, we need to look at the functional group characteristic of ketones.

Concept Explanation

• Ketones (Alkanones): These are organic compounds characterized by a carbonyl group ($C=O$) bonded to two carbon atoms. The general structure is $R-C(=O)-R'$, where $R$ and $R'$ are alkyl groups.
• Functional Group: The carbonyl group ($C=O$) is located within the carbon chain, not at the end.
• General Formula: Since a ketone requires the carbonyl carbon to be attached to two other carbon-containing groups (alkyl groups), the simplest representation is $R_2CO$.

Let's evaluate the other options provided:

• A. RCHO: This is the general formula for alkanals (aldehydes), where the carbonyl group is at the end of the chain.
• C. RCOOH: This is the general formula for alkanoic acids (carboxylic acids).
• D. RCOOR: This is the general formula for alkanoates (esters).

Step-by-Step Solution

1. Identify the homologous series: Alkanones = Ketones.
2. Recall the structure of a ketone: $R-C(=O)-R$.
3. Combine the components: Two $R$ groups attached to a $CO$ (carbonyl) unit.
4. This matches the expression $R_2CO$.

Conclusion

The general formula for alkanones is $R_2CO$.

Exam Tip: To avoid confusion in the exam hall, remember the "position" of the functional group:

• Aldehydes (Alkanals): The 'H' is at the end ($R-CH=O$).
• Ketones (Alkanones): The 'O' is sandwiched between two 'R' groups ($R-C=O-R$).
• Acids (Alkanoic acids): They have an extra 'OH' ($R-COOH$).