The general formula of alkanones is

Analysis of the Question

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 must look at the functional group characteristic of this homologous series.

Explanation of the Concept

• Alkanones (Ketones): 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 (which can be the same or different).
• Let's evaluate the options provided: • A. RCHO: This is the general formula for alkanals (aldehydes). The carbonyl group is at the end of the carbon chain. • B. RCOR': This represents a carbonyl group bonded to two alkyl groups ($R$ and $R'$). This is the defining structure of ketones (alkanones). • 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 functional group of alkanones: The carbonyl group ($C=O$) must be attached to two carbon atoms.
2. Represent the alkyl groups attached to the carbonyl carbon as $R$ and $R'$.
3. Combine these to form the general representation: $R-CO-R'$ or $RCOR'$.
4. Compare this with the given options. Option B matches this structure perfectly.

Conclusion

The general formula for alkanones (ketones) is $RCOR'$.

Exam Tip

To avoid confusion in the exam hall, remember these "functional group suffixes":

• -al (Aldehyde) ends in -CHO.
• -one (Ketone) has the -CO- group in the middle.
• -oic acid (Carboxylic acid) ends in -COOH.
• -oate (Ester) contains the -COO- linkage.