Which of the following reactions involve...

Which of the following reactions involve a decrease in the length of the carbon chain:-

Schmidt reaction

Hofmann's bromamide reaction

Hell-Volhard-Zelinski reaction

All of these

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The correct Answer is:

To determine which reactions involve a decrease in the length of the carbon chain, we need to analyze each reaction provided in the question. ### Step-by-Step Solution: 1. **Understanding the Reactions**: - We need to identify reactions that lead to a reduction in the number of carbon atoms in the reactants compared to the products. 2. **Smith Reaction**: - The Smith reaction involves the conversion of a carbonyl compound (like benzoic acid) to an amine (like aniline). - Example: Benzoic acid (C7H6O2) reacts with hydrozoic acid (HN3) in an acidic medium to form aniline (C6H5NH2). - Here, we start with 7 carbon atoms in benzoic acid and end up with 6 carbon atoms in aniline. - **Conclusion**: This reaction results in a decrease in the carbon chain length. 3. **Hoffman Bromamide Reaction**: - This reaction involves the degradation of amides to primary amines using a strong base and bromine (Br2). - Example: An amide (RCONH2) reacts to yield a primary amine (RNH2) with one less carbon atom. - **Conclusion**: This reaction also results in a decrease in the carbon chain length. 4. **Hell-Volhard-Zelinsky (HVZ) Reaction**: - This reaction involves the halogenation of the alpha carbon of a carboxylic acid. - Example: A carboxylic acid (RCOOH) reacts with bromine (Br2) in the presence of red phosphorus, resulting in the alpha-bromo carboxylic acid. - In this case, the number of carbon atoms remains unchanged as we are substituting a hydrogen atom with a bromine atom. - **Conclusion**: This reaction does not decrease the carbon chain length. 5. **Final Answer**: - The reactions that involve a decrease in the length of the carbon chain are: - **Smith Reaction** - **Hoffman Bromamide Reaction** ### Summary: The answer to the question is that the Smith Reaction and the Hoffman Bromamide Reaction involve a decrease in the length of the carbon chain.