Complete the following reactions:
$(1)$ Isopropyl bromide $\xrightarrow[{KOH, \Delta}]{{\text{alcoholic}}} X$ $\xrightarrow[{peroxide}]{{HBr}} Y$
$(2)$ $n$-propyl alcohol $\xrightarrow[{443 \ K}]{{\text{Conc. } H_2SO_4}} X$ $\xrightarrow{{HBr}} Y$

Which of the following is $NOT$ obtained when a mixture of chloroethane and $1-$chloropropane is treated with sodium metal in dry ether?

The structure of the major product formed in the following reaction is

Chlorination of substance $A$ gives substance $B$. Substance $B$ reacts with alcoholic $KOH$ to give substance $C$,which decolorizes Baeyer's reagent. Ozonolysis of substance $C$ gives $HCHO$. What is substance $A$?

Correct statements regarding alkyl halides ($R-X$) among the following are: A. Alcohol being less polar solvent as compared to water, alcoholic $KOH$ favours elimination reaction with $R-X$. B. Order of reactivity towards $S_N1$ mechanism is $C_6H_5-CH_2-Cl > C_6H_5-CHCl-C_6H_5$. C. Non substituted aryl halides exhibit properties similar to alkyl halides. D. Vinyl chloride is an example of haloalkene and allyl chloride is an example of haloalkyne. E. $R-Cl$ can be prepared by reacting $R-OH$ with $SOCl_2$ but $Ar-Cl$ cannot be prepared by reacting $Ar-OH$ with $SOCl_2$. Choose the correct answer from the options given below:

Given below are four compounds:
$(a)$ $n$-propyl chloride,
$(b)$ $iso$-propyl chloride,
$(c)$ $sec$-butyl chloride,
$(d)$ $neo$-pentyl chloride.
Percentage of carbon in the one which exhibits optical isomerism is: