Halkoarenes & Haloarenes MCQs for NEET — Chemistry Questions with Answers

(a) The S_N2 mechanism always involves 100% inversion since nucleophile attack from back side of leaving group.

$$\begin{gathered} \mathrm{R}-\mathrm{X}\stackrel{{\mathrm{OH}}^{-}}{\to }\mathrm{O}\stackrel{-}{\mathrm{H}}---\mathrm{R}---\mathrm{X} \\ \downarrow \\ \mathrm{OH}-\mathrm{R}+{\mathrm{X}}^{-}: \end{gathered}$$

(c) Steric hindrance in tertiary halides give rise to less reactivity for S_N2.

(b) In S_N1 reaction, there is slight more inversion product than retention product because S_N1 reaction also depends on shielding effect of the front side of the reacting carbon.

Dehydrohalogenation is the process of eliminating hydrogen and halogen atoms from an alkyl halide to form an alkene. The reagents commonly used for this process are alcoholic KOH, sodium amide (NaNH2), and sodium ethoxide (C2H5ONa). Therefore, the correct option is 'all of these'.

According to NCERT, vinylic halides are compounds in which the halogen atom is bonded to an $sp^2$-hybridised carbon atom of a carbon-carbon double bond (C=C).

The NCERT states: 'In the IUPAC system of nomenclature, alkyl halides are named as halosubstituted hydrocarbons.'

As per the NCERT text, 'Allylic halides: These are the compounds in which the halogen atom is bonded to an $sp^3$-hybridised carbon atom adjacent to carbon-carbon double bond (C=C) i.e. to an allylic carbon.'

The NCERT states: 'For dihalogen derivatives, the prefixes o-, m-, p- are used in common system but in IUPAC system, as you have learnt in Class XI, the numerals 1,2; 1,3 and 1,4 are used.'

According to the NCERT text, 'Haloalkanes contain halogen atom(s) attached to the $sp^3$ hybridised carbon atom of an alkyl group whereas haloarenes contain halogen atom(s) attached to $sp^2$ hybridised carbon atom(s) of an aryl group.'

Table 6.1 in the NCERT lists 'Vinyl chloride' as the common name for $CH_2=CHCl$, with 'Chloroethene' being its IUPAC name.