Question

Which of the following compounds will give the Hell-Volhard-Zelinsky reaction?

• A. R-CH$_2$-COOH
• B. R$_3$C-CHO
• C. R$_2$CO
• D. H-COOH

Answer 1

The Correct Option is A

The Hell-Volhard-Zelinsky reaction is a halogenation reaction specific to carboxylic acids with at least one α-hydrogen atom. This reaction requires the presence of α-hydrogen adjacent to the carboxylic acid group (-COOH) for the halogenation process to occur.

Let's analyze each option: 

• R-CH₂-COOH: This compound is a carboxylic acid and has an α-hydrogen (the hydrogen attached to the carbon adjacent to the carbonyl carbon). Therefore, it can undergo the Hell-Volhard-Zelinsky reaction.
• R₃C-CHO: This is an aldehyde and not a carboxylic acid. It lacks the α-hydrogen that is adjacent to a carboxylic acid group, making it unsuitable for this reaction.
• R₂CO: This is a ketone, which similarly does not contain the necessary α-hydrogen next to a carboxylic acid functionality.
• H-COOH: Formic acid does not have any α-hydrogen atom adjacent to its carboxyl group; hence, it cannot participate in the Hell-Volhard-Zelinsky reaction.

Therefore, the correct answer is R-CH₂-COOH as it fulfills the criteria necessary for the Hell-Volhard-Zelinsky reaction.

Answer 2

As explained in the previous response, the Hell-Volhard-Zelinsky (HVZ) reaction is specific to carboxylic acids that have α-hydrogen atoms.

Let's reiterate the analysis:

• Option 1: R-CH₂-COOH: This is a carboxylic acid with α-hydrogen atoms (the hydrogens on the CH₂ group). Therefore, it will undergo the HVZ reaction.
• Option 2: R₃C-CHO: This is an aldehyde, not a carboxylic acid. The HVZ reaction does not apply to aldehydes.
• Option 3: R₂CO: This is a ketone, not a carboxylic acid. The HVZ reaction does not apply to ketones.
• Option 4: H-COOH: This is formic acid. While it is a carboxylic acid, it lacks α-hydrogen atoms. Therefore, it will not undergo the HVZ reaction.

Therefore, the compound that will give the Hell-Volhard-Zelinsky reaction is R-CH₂-COOH.

The correct answer is option A: R-CH₂-COOH