Question

8. What is the actual enantiomeric percent composition of a mixture of (S)-(+)- Carvone. [a]= + 15.5, and (R)-(-)-Carvone la] = - 15.5 with a specific rotation of la]= +4.9? a) 50-50% R and S b) 65.8% R and 34.2 % S c) 31.6% R and 68.4 % mixture d) 65.8% S and 34.2% R e) 31.6% S and 31.6 % R and 36.8% mixture 9. Which of the following statements is true? a) SN2 reactions of secondary alkyl halides with Nal is faster in water than in acetone. b) Doubling both the concentration of the nucleophile and the alkyl halide in an SNl reaction doubles the rate of the reaction. c) E2 and SN2 reactions both share a common carbocation intermediate. d) SNl reactions are stereospecific. e) Nucleophilicity always increases from top to bottom in a group in periodic table 10. Which of the following is the best solvent for an SNI reaction? CH C N N-CH3 н "ОН Hас e с a

Answer 1

8. Let is x% (s)-(+) Carvone and (100-2) 7. (R) - (-) Carvone present in mixture. x-100-x) Observed specific rotation of the sample x+(1005x) specific rolation of major enantiomer, iie (S)-(+) Carwone 3 22-100 - 4.9 - , - 100 100 – 15.5 31% - 1550 = 490 3/2 = 2040 - => X = 65.8 vone The mixture has (5.8%. (s) – (+) Carwone and 34.2% (R)-(-) Carvone.