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CHEM 3361-02 Exam III Fall 2022 108 Pts Total Name ____________________________________
Record the following number on your Scantron bubble-sheet by your name __________
Part I. Multiple Choice (90pts, 4.5pts/ea)
For Problems 1&2, consider the following reaction.
- Which of the following is the leaving group?
- What is the best description of the attachment of the leaving group? A. methyl B. 1° C. 2° D. 3°
- What is the order, most to least, of nucleophilicity of the following in a protic solvent?
I. CH 3 SH II. CH 3 S -^ III. CH 3 OH
a. I>II>III b. II>III>I c. II>I>III d. III>I>II e. III>II>I
- What is the order, most to least, of nucleophilicity of the following in an aprotic solvent?
I. OH-^ II. I -^ III. Cl - a. I>II>III b. I>III>II c. II>III>I d. III>I>II e. III>II>I
For Problems 5&6, consider the following structures.
Br
Br
Br
A. (^) B.^ Br C. D.^
E.
Br
- Which of the above gives the fastest S (^) N 2 reaction?
A. B. C. D. E.
- Which of the above gives no E2 reaction, even with a strong base?
A. B. C. D. E.
CH 3 CH 2 SNa ClCH 2 C CH 3
CH 3
CH 3
CH 3 CH 2 SCH 2 C CH 3
CH 3
CH 3
NaCl
CH 3 CH 2 -^ CH 3 CH 2 S -
CH 3
A. B. (^) C. (^) CH 3 D. Cl-^ E. Na+
- Which of the following gives the fastest substitution reaction?
HBr
NaBr
HCl
OH
A. B. NaCl
C. D.
OH
OH OH
For Problems 8&9, consider the following structures.
I. II.^ III.
- Rank the carbocations above from most to least stable.
A. I >II>III B. II>I>III C. III>I>II D. III>II>I
- Which of the above would be expected to undergo a hydride shift to form a more stable cation?
A. I B. II C. III D. I or II E. II or III
- Consider the following reaction. Which of the following would increase the rate of reaction? CH 3 CHCH 2 CH 2 I
CH 3
- (^) CH 3 S CH 3 CHCH 2 CH 2 SCH 3 + I
CH (^3)
DMF
I. Increase the concentration of CH 3 S -. II. Increase the concentration of the alkyl iodide. III. Change the solvent from DMF (shown at right) to methanol, CH 3 OH. A. I and II only B. I and III only C. II and III only D. all of the above
- Which of the following are product(s) of the following Sn2 reaction? H 3 C H
Br^ H
Nu:
H 3 C H
Nu^ H
H 3 C H
H^ Nu
H CH^3
Nu^ H
H CH^3
I. II. III.^ IV. H^ Nu
A. I B. II C. III D. IV E. More than one of the above are formed
C
O
H N(CH^ 3)^2
DMF
- Which of the following represents Product III in the following reaction sequence?
OH
HBr CH 3 OH Product II
NaNH (^2) Product I Product I Product II Product III
O CH (^3)
N H
CH (^3)
OH Br
A. B.^ C.^ D.
Br KOC(CH 3 ) 3
HOC(CH 3 ) 3 O (^) O
A. B. C. D. E.
CH 2 CH (^3)
I CH 3 CH 2 OH
CH 2 CH (^3)
OCH 2 CH (^3)
CH 2 CH (^3)
OH
CH 2 CH (^3) CHCH (^3)
A. (^) B. C. D.
I NaOCH (^3)
HOCH (^3)
H 3 CO
OCH (^3)
A. (^) OCH (^3) B. C. D.^ E.
OH H 2 SO 4 (conc) heat
OSO 3 H OSO 3 H
A. (^) B. C. (^) D.
Part II. Short Answer/Essay:
- Show the curly-arrow mechanism of the compound in the Sn2 substitution-reaction of the following compound with NaOCH 3 in HOCH 3. (5pts)
Ph
H
Br
H 3 C
H
NaOCH 3
CH 3 OH
- Show the curly-arrow mechanism of the following E2 elimination-reaction to the major product. You need NOT show stereochemistry. Briefly explain your answer. (5pts)
Cl KOCH^3
HOCH 3
Transition state
alkene. methoxide abstract the proton from more substituted site as base is small and more stable, more
In E2 elimination, the proton is abstracted and the leaving group leaves in a single step to synthesize
substituted alkene is generated.
