Fundamentals of Organic ChemistryChemistryCarboxylic Acid Derivatives
The Hell-Volhard-Zelinsky (HVZ) reaction involves the use of phosphorus and a halogen. For example: CH ₃ CH ₂ COOH P , Cl ₂ CH ₃ CHClCOOH The primary function of phosphorus in this reaction is:
Options
- Anone of these
- Bto form PCl ₃ , which directly carries out halogenation at the -carbon atom
- Cto form PCl ₃ , which converts the - COOH group into a - COCl group
- Dto act as a catalyst
Correct answer
C. to form PCl ₃ , which converts the - COOH group into a - COCl group
Step-by-step solution
In the Hell-Volhard-Zelinsky (HVZ) reaction, the -halogenation of carboxylic acids takes place. In the first step of the reaction, red phosphorus reacts with the halogen (e.g., Cl ₂ ) to form phosphorus trihalide ( PCl ₃ ). The PCl ₃ then reacts with the carboxylic acid to convert the - COOH group into an acid chloride ( - COCl ) group. Acid chlorides undergo enolization much more readily than carboxylic acids. The enol form then reacts with the halogen to undergo -halogenation, forming an -halo acid chloride, whic