Name of the alkene which will yield/chloro 1-methylcyclohexane by its reaction with HCl . Write the reactions involved.
Two alkenes are possible
Addition takes place in accordance with Markownikoff's rule i.e., negative part of the adding molecule will get attached to that carbon which has lesser number of hydrogen atom.
Which of the following haloalkanes reacts with aqueous KOH most easily? Explain giving reason.
(i) 1-bromobutane
(ii) 2-bromobutane
(iii) 2-bromo-2-methylpropane
(iv) 2-chlorobutane
2-bromo-2-methylpropane (iii), is a tertiary alkyl halide and it will form a stable carbocation on ionisation.
1-bromobutane is primary alkyl halide whereas 2-bromobutane and 2-chlorobutane is secondary alkyl halide.
Why can aryl halides not be prepared by reaction of phenol with HCl in the presence of $\mathrm{ZnCl}_2$ ?
Due to resonance in phenol, $\mathrm{C}-\mathrm{O}$ bond of phenol has some partial double bond character. Partial double bond character strengthen the bond. So, It is difficult to break this $\mathrm{C}-\mathrm{O}$ bond of phenol while the $\mathrm{C}-\mathrm{O}$ bond of alcohol is purely single bond and comparatively weaker bond.
So alkyl halides can be prepared by the reaction of alcohols with HCl in the presence of $\mathrm{ZnCl}_2$ while aryl halides can not be prepared by reaction of phenol with HCl in the presence of $\mathrm{ZnCl}_2$.
Which of the following compounds would undergo $S_N 1$ reaction faster and why?
Compound (B) will give $S_N 1$ reaction faster than compound $(A)$ because $S_N 1$ reaction depends upon the stability of carbocation. Benzyl chloride on ionisation gives $\mathrm{C}_6 \mathrm{H}_5 \stackrel{+}{\mathrm{C}} \mathrm{H}_2$ carbocation which is resonance srabilised while the carbocation obtained from compound $(A)$ is not stabilised by resonance.
Allyl chloride is hydrolysed more readily than n-propyl chloride. Why?
As we know that $\mathrm{S}_{\mathrm{N}} 1$ mechanism depends upon the stability of carbocation. Allyl chloride on hydrolysis gives resonance stabilised carbocation while no resonance is observed in the carbocation formed by $n$-propyl chloride.
Hence, allyl chloride undergoes hydrolysis much faster than $n$-propyl chloride.