Which of the following Grignard reagents can be prepared?

Explain the factors favouring $S_{N}2$ reaction.

When $3-$methylbutan$-2-$ol is treated with $HBr$,the following reaction takes place:
$CH_3-CH(CH_3)-CH(OH)-CH_3 \xrightarrow{HBr} CH_3-C(Br)(CH_3)-CH_2-CH_3$
Give a mechanism for this reaction.
(Hint : The secondary carbocation formed in step $II$ rearranges to a more stable tertiary carbocation by a hydride ion shift from $3^{rd}$ carbon atom.)

The reaction of $1$-bromohexane with aqueous $NaOH$ solution follows the order

What is the major product obtained when $tert-$butyl bromide is heated with silver fluoride?

An alkyl halide may be converted into an alcohol by