Question

assign the following as r or s.
i
a. r
b. r
c. s
d. s
ii
a. r
b. s
c. r
d. s

Explanation:

Step1: Determine priorities for compound I

For the chiral - center in compound I, the priorities of the groups attached to the chiral carbon are determined by atomic number. The order of priorities is: $-OH$ (highest, atomic number of O = 8) > $-COOH$ (next, due to the double - bonded O) > $-CH_3$ > $-H$ (lowest). When the lowest - priority group ($-H$) is pointed away from the observer, the direction of the remaining groups from high to low priority is clockwise, so it is $R$.

Step2: Determine priorities for compound II

For the chiral - center in compound II, the priorities of the groups attached to the chiral carbon are: $-Cl$ (highest, atomic number of Cl = 17) > $-CH(CH_3)_2$ > $-CH_2CH_3$ > $-H$ (lowest). When the lowest - priority group ($-H$) is pointed away from the observer, the direction of the remaining groups from high to low priority is counter - clockwise, so it is $S$.

Answer:

B. R, S