(S)-1-Phenylethanol, C6H5-CH(OH)-CH3, is converted into 1-chloro-1-phenylethane by (i) SOCl2 in pyridine and (ii) SOCl2 alone (no base, non-nucleophilic solvent, with chloride delivered from the chlorosulfite by an SNi path). The major products are, respectively,

(i) (R), inversion; (ii) (S), retention

(i) (S), retention; (ii) (S), retention

(i) (R), inversion; (ii) (S), retention

(i) (R), inversion; (ii) (R), inversion

(i) (S), retention; (ii) (R), inversion

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JEE Main levelSingle correct optionDifficulty 2 of 3o3126

(S)-1-Phenylethanol, $C X_{6} H X_{5} - CH (OH) - CH X_{3}$ , is converted into 1-chloro-1-phenylethane by (i) $SOCl X_{2}$ in pyridine and (ii) $SOCl X_{2}$ alone (no base, non-nucleophilic solvent, with chloride delivered from the chlorosulfite by an SNi path). The major products are, respectively,

A(i) (S), retention; (ii) (S), retention
B(i) (R), inversion; (ii) (S), retention
C(i) (R), inversion; (ii) (R), inversion
D(i) (S), retention; (ii) (R), inversion

Answer: B

With pyridine, free chloride attacks the chlorosulfite from the back (SN2) and gives inversion. Without base, the chlorosulfite collapses to a tight ion pair and chloride is delivered from the same face (SNi), giving retention. Priorities (

Cl / O > C X_{6} H X_{5} > CH X_{3} > H

) are the same in alcohol and chloride, so inversion gives R and retention gives S.

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(S)-1-Phenylethanol, CX6​HX5​−CH(OH)−CHX3​, is converted into 1-chloro-1-phenylethane by (i) SOClX2​ in pyridine and (ii) SOClX2​ alone (no base, non-nucleophilic solvent, with chloride delivered from the chlorosulfite by an SNi path). The major products are, respectively,

Answer: B

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