The dehydrobromination of $2-bromobutane$ gives $CH_3-CH=CH-CH_3$. The product is

Two bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ have lost their original labels. They are labeled as $A$ and $B$ for testing. $A$ and $B$ are taken separately in test tubes and boiled with $NaOH$ solution. The final solution of each test tube is acidified with dilute $HNO_3$ and a little $AgNO_3$ is added. Solution $B$ gives a yellow precipitate. Which of the following statements is correct?

Which of the following Grignard reagents can be prepared?

Arrange the following halides in the decreasing order of their reactivity towards $S_{N^1}$ reaction.
$(I) \ CH_3CH_2CH_2Cl$ $(II) \ CH_2 = CH - CH(Cl)CH_3$
$(III) \ CH_3CH_2CH(Cl)CH_3$

Which one of the following is more reactive towards $S_{N}2$ reaction?

Identify the alkyl halide that undergoes $SN^2$ reaction most rapidly.