Acetaldehyde is a reactive organic compound that can undergo various types of reactions. The nature of the reacting species determines the type of reaction that takes place. In this context, the statement "Acetaldehyde reacts with nucleophiles only" is correct, and the explanation for the same is as follows:

What are Nucleophiles and Electrophiles?

Nucleophiles are chemical species that have a tendency to donate a pair of electrons to an electron-deficient or positively charged species. They are usually anions or molecules with a lone pair of electrons. Electrophiles, on the other hand, are species that have a tendency to accept a pair of electrons from a nucleophile. They are usually cations or molecules with a positive charge or an electron-deficient center.

Why does Acetaldehyde React with Nucleophiles Only?

Acetaldehyde has a carbonyl group (-CHO) that contains a partially positive carbon atom and a partially negative oxygen atom. This makes the carbon atom an electrophilic center, which can react with nucleophiles. The lone pair of electrons on the nucleophile attack the carbonyl carbon, leading to the formation of a tetrahedral intermediate, which then collapses to form a new bond and expels the leaving group.

Acetaldehyde can undergo various nucleophilic reactions, such as:

1. Addition of Grignard reagents: Grignard reagents are strong nucleophiles that can add to the carbonyl group of acetaldehyde and form a new carbon-carbon bond.

2. Addition of cyanide ion: Cyanide ion is a strong nucleophile that can add to the carbonyl group of acetaldehyde and form a cyanohydrin.

3. Formation of imines: Acetaldehyde can react with primary amines to form imines, which are important intermediates in organic synthesis.

Conclusion

In conclusion, acetaldehyde reacts with nucleophiles because of the electrophilic nature of its carbonyl carbon. The lone pair of electrons on the nucleophile attacks the carbonyl carbon, leading to the formation of a tetrahedral intermediate, which then collapses to form a new bond and expels the leaving group. Therefore, option B, i.e., "Acetaldehyde reacts with nucleophiles only" is the correct answer.