$(CH_3)_2CHBr$ $\xrightarrow[(2) CuI]{(1) Li} (A)$ $\xrightarrow{(CH_3)_2CHCH_2Br} B$.
$'B'$ is

$RMgI$ when treated with ice-cold water liberated a gas which occupied $1.4 \text{ dm}^3/\text{g}$ at $STP$. The gas produced is further reacted with iodine in the presence of $HIO_3$ to give compound $(X)$. Compound $(X)$ in the presence of $Na$ and dry ether produced compound $(Y)$. The molar mass of compound $(Y)$ is . . . . . . $\text{g mol}^{-1}$. (Nearest integer)

$CH_3-CH_2-CH_2-CH_3 \xrightarrow{Br_2/hv}$
Major product in the above reaction is

$A$ racemic mixture is obtained due to the halogenation of:

The reaction of lithium di-$3-$pentylcuprate with ethyl bromide yields an alkane with the molecular formula $C_7H_{16}$. What is the structure of the alkane?

Identify the straight-chain hydrocarbon that is an isomer of $3-$ethyl$-2-$methylhexane.