Question

Classify the following statements as true (T), or false (F). If you classify statement as false, correct it, or explain why it is false.

            (a) If given stereoisomer rotates the plane of polarized light clockwise, its enantiomer rotates counter‐clockwise by exactly the same magnitude

(b) If compound has one stereogenic center with S configuration, it always rotates the plane of polarized light counter-clockwise.

(c) Molecule possessing stereogenic centers is always chiral.

(d) Mixture of equal amounts of both enantiomers of given compounds does not rotate the plane of polarized light.

(e) Racemic mixture has the same melting point as both corresponding enantiomer.

Answer 1

(a) If given stereoisomer rotates the plane of polarized light clockwise, its enantiomer rotates counter‐clockwise by exactly the same magnitude (TRUE )

(b) If compound has one stereogenic center with S configuration, it always rotates the plane of polarized light counter-clockwise. (FALSE )

reason : R and S configurations are purely based on just priority of the groups . it is qualitative measurements . but rotation is experimental . S compound may rotate clockwise or counter clockwise

(c) Molecule possessing stereogenic centers is always chiral. (FALSE)

reason: some molecules may contain stereogenic centers but they are not chirals it is due to plane of symmetry. suppose meso tartaric acid has two stereogenic centers but is its optical activity is zero that means it is achiral

(d) Mixture of equal amounts of both enantiomers of given compounds does not rotate the plane of polarized light.(TRUE)

reason : it is racemic mixture due to external compensation the total rotation is zero

(e) Racemic mixture has the same melting point as both corresponding enantiomer. (TRUE)