Question

ESSAY. Write your answer in the space provided or on a separate sheet of paper 131 Canone predict whether a compound with a single et carbon dextro the RS assignment at this asymmetricarbon? Explain briefly levorettory based on MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answer the question 14 A mixture of two enantiomers with a composition of 650, R has an observed rotation of -253 14 in a 100 cm polarimeter tube. If the mixture has a concentration 2.098 at 25°C what is the predicted lab ot an optically pure sample of the Senantiomer? A) 53.5 B) +124 +01.3" D) -25,3 E)-53.59 Use the following three where to the hors below снион CH,OH нон он нон нон CH, OH снон 15) The relationship between I and II is: A) enantiomers C) constitutional isomers B) same compound Di diastereomers ESSAY. Write your answer in the space provided or on a separate sheet of paper. 16) Explain the stereochemical relationship, if any, among the following two structures and describe whether or not they could be theoretically isolated from each other. (Note: Some H atoms are omitted for clarity 7 CHS H CH, MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question 17) What term describes the structural relationship between (20,38,4S)-2,3,4-trichloroheptane and 17) (2R 3R 4R)-2,3,4-trichloroheptane? A) conformers B) diastereomers C) constitutional isomers D) not isomers E) enantiomers ESSAY. Write your answer in the space provided or on a separate sheet of paper. 18) Which of the following terms best describes the pair of compounds shown: enantiomers, diastereomets, or the same compound?

Answer 1

13) The optical activity of a compound depends on two things; It should have chiral carbon( all the groups attached to the carbon atom should be different) and it should have tendency to rotate plane of polarised light.

The tendency to rotate the plane of polarised light clockwise is known as dextrorotatory and if the plane of polarised light is rotated anticlockwise then it is known as levorotatory. R and S assignment is done based upon the preferences given to the group. If preferences done is clockwise then it is R conformation whereas if it is anti-clockwise then it is assigned as S conformation.

14) The optical activity of pure sample of S conformer is found using formula

optical activity = optical rotation(degree)/ (mass concentration* path length)

option B) +12.4 degree is correct answer

15) The compound in I and II are same but they differ in its representation. The I is a fischer diagram and II is a Newman projection.They are not mirror images and non-superimposable. So, option D) diastereomers is correct answer.

16) The given structures differ in the positioning of the bulky groups like Br and CH₃ . The 1,3- di bromo subsitued compound has two Br groups on both the structures are on either axial axial (aa) or on equatorial equatorial(ee) positions. So both are Cis stereoisomers. But if we take substitution of methyl group on two structures, one is on equatorial postiona( left ) and other one is on axial position( right hand side). Since they differ in substitutions, the two images are not superimposable and can be separated from each other.

17) The two compounds are stereoisomers that are not mirror images of one another and are non-superimposable on one another. So, option B) diastereomers are correct answer.