Retro (Past 13 Year) JEE Main (Alkyl Halides) - Class 12 MCQ

Alkyl fluorides can be prepared by action of mercurous fluoride or antimony trifluorides (inorganic fluorides) on corresponding alkyl halide.
But, when action of Nal/acetone takes place on alkyl chloride bromide, alkyl iodide forms. This reaction is called 'Finkelstein reaction'

Free radical fluorination is highly explosive reaction. So not preferred for the preparation of fluoride.

Com pound A gives a precip itate w ith alcoholic AgNO₃ (here white is misprinting because the colour of ppt is light yellow), so it must contain Br in side chain.
On oxidation, it gives C₈H₆O₄, which shows the presence of two alkyl chains attached directly with the benzene nucleus.
Since compound B gives anhydride on heating, the two alkyl substituent must occupy adjacent (1,2) position.
Thus, A must b

and the reactions are as follows

The given compound, (-1)- chloro-1-phenylethane in the presence of SbCI5 forms a carbocation.

Since, the carbocation is a planar species, therefore it can be attacked by SbCl₆^- either from the front or back side of the carbocation with equal ease. As a result, 50:50 mixture of two enantiomers of 1 -chloro-1 -phenylethane undergoes racemisation due to the formation of a carbocation intermediate.

2 -methylbutane on monochlorination gives 4 isomers, among which I and III are chirai in nature.


Hence, 2 chiral compounds are formed in the above reaction.

Iodoform reaction is given by alcohols and ketones containing    group, respectively. Thus, among the given compounds, isobuty alcohol does not contain
Hence, it does not give iodoform reaction on treatment with I₂ / NaOH.

Hence, compounds (a), (b) and (c) will give iodoform while compound (d) (isobutyl alcohol) does not give any iodoform reaction

The reactivity of S_N1 reaction depends upon the stability of the intermediate, carbocation formed during these reactions. The stabililty order of the carbocation formed from the given species is

Hence, the reactivity order of the given bromide towardsS_N1 reaction is

Nucleophilic substitution bimolecular (S_N2) prefers less sterically hindered site to attack. Lesser the steric hindrance faster the S_N2 reaction. So ease of reaction is 1° > 2° > 3°.

S_N2 involves inversion of configuration stereo, chemically. Since, 1° alkyl halides are prone to S_N2 reactions, therefore CH₃CI undergoes complete strerochemical inversion.

Nucleophilicity order is

Stability of (I) > (II), hence (I) is predominant.

Addition is through the formation of allylic carbocation.

Under mild conditions (temperature = - 80°C) kinetic product is the 1, 2-addition product and under vigorous conditions, (temp. = 4°C) thermodynamic product is the 1 , 4-addition product.
Thus, 1-bromo-2-butene is the major product under given condition.