Consider the following reaction ,
`{:(I. RCOOH +PCl_(5) to R COOCl+ POCl_(3)+CHl),(II. 3RCOOH+PCl_(5) to 3R COCl+H_(3)PO_(3)),(III. RCOOH+SOCl_(2) to RCOCl+SO_(2)+HCl):}`
Which of the abvoe reaction (s) is/are preferred for the synthesis of RCOCl ?

Options

A. only I
B. Only II
C. Only III
D. All of these

Answer

C

Explanation

`{:(RCOOH +PCl_(5) to RCOCl+ POCl_(3)+HCl),(3RCOOH+PCl_(5) to 3RCOOCl+H_(3)PO_(3)),(RCOOH+SOCl_(2) to RCOCl+SO_(2)+HCl):}`
Thionly chloride is preferred because the other two products are gasesous and escape from the reaction mixture making the purification of the products easier.