Question

In the reaction ..... the electrophile involved is

• A. dichlorocarbene $({:}CCl_2)$
• B. dichloromethyl cation $(\overset{\oplus}{C} HCl_2)$
• C. dichloromethyl anion $(\overset{\ominus}{C}HCl_2)$
• D. formyl cation $(\overset{\oplus}{C} HO)$

Answer 1

The Correct Option is A

To identify the electrophile involved in the reaction, we need to understand the nature of electrophiles and what they represent in chemical reactions. An electrophile is a chemical species that accepts an electron pair in order to form a bond. Electrophiles are generally atoms or molecules with a positive charge or a positive partial charge, which makes them electron-deficient and in need of electrons.

In the given options, we need to determine which species is most likely to act as an electrophile. Here are the options:

1. dichlorocarbene \big({:}CCl_2\big): This is a neutral species that has a divalent carbon atom with two non-bonding electrons. Although it is a neutral species, the carbon atom in dichlorocarbene is electron-deficient due to only having six electrons in its valence shell (rather than the usual eight). This makes it highly reactive and capable of accepting electron pairs, acting as an electrophile.
2. dichloromethyl cation \big(\overset{\oplus}{C} HCl_2\big): This species is positively charged, indicative of a strong electrophile. The presence of a positive charge typically indicates an electron vacancy, making it likely to accept electrons.
3. dichloromethyl anion \big(\overset{\ominus}{C}HCl_2\big): Anions are typically nucleophiles, as they possess a negative charge and an excess of electrons. Therefore, it's unlikely to act as an electrophile.
4. formyl cation \big(\overset{\oplus}{C} HO\big): This is a positively charged species, signifying that it also could act as an electrophile due to its electron deficiency.

Now, let's consider the most probable electrophile under typical reaction conditions:

• {:}CCl_2 (dichlorocarbene) is a carbene, which are known for their simultaneous electron-deficient carbon and high reactivity, making them effective electrophiles in reactions such as cyclopropanation.
• The presence of lone pairs and two chlorines adds to the stability of the carbene, enhancing its reactivity.

Consequently, the correct answer is dichlorocarbene ({:}CCl_2) as it is the species that effectively behaves as an electrophile in the context of the reaction described.