Chapter 8 EXAM 20 PTS(2) PDF

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Chapter 8 practice problems....

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1 CHE 223 SECOND EXAMINATION (Chap. 8)

FALL 2020 PROF. J.I. RIZZO

Answer all questions in SEQUENTIAL ORDER. Read each question carefully before attempting to answer it. Your answers must be legible to be considered for grading. The points possible for each question are indicated, for a total of 20 points for the entire examination. Good luck  1. (2 pts) Determine the (R,S)-configuration designation for each of the stereogenic centers in the compound below. You must report it in the following format with the carbon number followed by notation, for example: ( 1S,2S, 3S etc). What is the number of stereoisomers for the compound below?

ANSWER ____________________

2. (3 pts) Explain in words and illustrate schematically how you would separate the following compounds. Draw the structure of each compound using bond-line formula: (2S,4S)-4-bromo-2-hexanol and (2R,4R)-4-bromo-2-hexanol

2

3. (2 pts) Designate R or S for each of the following compounds. ANSWER 3a) _____ ANSWER 3b) _____ Br OMe

Cl

a)

b) C

C H

HO

OH

H

4. (3 pts – NO PARTIAL CREDIT) Give the configuration at each stereogenic site for compounds a through i.

WRITE “R” or “S” below for each compound. If there is more than one stereogenic site designate 1S,2R etc a)

b)

c)

d)

e)

f)

3 5. (5 pts) Starting with (S)-2-pentanol, provide three different methods to prepare the corresponding alkyl halide. You must include proper reagents and solvents for full credit and show the product generated in each reaction. Chose 2 of the 3 methods you provided and give the complete mechanism for each using curved arrow formalism. Name each product.

4 MULTIPLE CHOICE SECTION (1 PT EACH) GIVE LETTERED ANSWERS ONLY 6. What is the relationship between these two structures?

A. B. C. D.

ANSWER _______

Stereoisomers Constitutional isomers Identical No relationship can be defined

7. Which of these tartaric acid isomers will have the same melting point?ANSWER ______ (A) (B) (C) (D)

(+)-tartaric acid and (-)-tartaric acid only (+)-tartaric acid and (-)-tartaric acid and racemic (+/-)-tartaric acid only (+)-tartaric acid and (-)-tartaric acid and meso-tartaric acid only meso-tartaric acid and racemic (+/-)-tartaric acid only

8. Which statement about these Fischer projections is correct? CH3

CH3 HO

H

HO

HO

H

H

ANSWER _______

CH3

CH3 H

H

OH

H

OH

H

OH

HO

OH H

CH3

CH3

CH3

CH3

I

II

III

IV

(A) I & III are enantiomers (B) II & IV are identical (C) II is a meso isomer (D) I & II are diastereomers

5 9. Enantiomers are:

ANSWER _______

(A) Any molecule that has a mirror image (B) Molecules that have one chiral center (C) Any non-superimposable molecules (D) Non-superimposable constitutional isomers (E) Non-superimposable molecules that are mirror images of each other

10. Which of the following are meso compounds? I. 2,4-dichloropentane II. 1,3-dimethylcyclopentane III. 2,3-dichloropentane

(A) I and II (B) I only (C) II only (D) I and III (E) II and III

ANSWER _______...