Chemistry - STEREO ISOMERISM Question with Solution | TestHub

In these cross structures the horizontal bonds project towards you and the vertical bonds point away.

(a) Priorities : CH₂Br (1) $>$ CH(CH₃)₂ (2) $>$ CH₂CH₃ (3) $>$ CH₃ (4). The lowest priority group (CH₃) is on a vertical bond (away). 1 $\to$ 2 $\to$ 3 runs counterclockwise : S.

(b) Priorities : HO (1) $>$ CH₂OH (2) $>$ CH(CH₃)CH₂CH₃ (3) $>$ H (4). H is on a horizontal bond (towards), so the result is inverted. 1 $\to$ 2 $\to$ 3 runs counterclockwise, inverted : R.

(c) Priorities : Br (1) $>$ CH₂CH₃ (2) $>$ CH₃ (3) $>$ H (4). H is horizontal (towards). 1 $\to$ 2 $\to$ 3 runs clockwise, inverted : S.

(d) Priorities : CH₂CH₂CH₂CH₃ (1) $>$ CH₂CH₂CH₃ (2) $>$ CH₂CH₃ (3) $>$ CH₃ (4) (first point of difference at the third carbon). CH₃ is horizontal (towards). 1 $\to$ 2 $\to$ 3 runs clockwise, inverted : S.

Ans. (a) S (b) R (c) S (d) S