Question

Decreasing order of reactivity of hydrogen halide acids in the conversion of $ROH\to RX$ is

• A. $HCl>HBr>HI>HF$
• B. $HI>HBr>HCl>HF$
• C. $HF>HCl>HBr>HI$
• D. $HF>HBr>HI>HCl$

Answer 1

Answer: (B)

Since the conversion of an alcohol to alkyl halide is an nucleophilic substitution reaction and the nucleophilicity (ie, tendency to donate an electron pair to the carbon atom) of the halide ions decreases in the order, $I^{-}>B{r}^{-}>C{l}^{-}>F^{-}$ , Thus, the order of reactivity of halogen acids decreases in order : $HI>HBr>HCl>HF$ .