Chemistry 261 Quiz 3 Practice Fall 2013 The following quiz contains 32 questions valued at 1 point/question Name: ________________________________________________________ 1. Cis-trans isomers isomers are a. b. c. d. e.
Diastereomers Enantiomers Stereoisomers Constitutional isomers More than one of the above
E 2. Which of the following molecules is achiral? H
Br
Br
H
Br
Cl
H
Cl
H
H
Br
Cl
Br
Br
Cl
Cl
H
H
I
II
III
a. b. c. d. e. C
I II III More than one of the above None of the above
3. Which of the following is true of any (R) -enantiomer?
a. b. c. d. e.
It is dextrorotatory It is levorotatory It is an equal mixture of + & - rotations It is the mirror image of the (S)-enantiomer More than one of the above
D 4. Which of the following represents (S)-1-Chloro-1-fluoroethane?
Cl
CH3
F
F H
H
Cl
H
Cl
CH3
CH3
F
I
II
III
a. b. c. d. e.
I II III More than one of the above None of the above
D 5. Which of the following compounds would show optical activity? a. b. c. d. e. D
cis -1,4- Dimethylcyclohexane trans -1,4- Dimethylcyclohexane cis -1,4- Dimethylcycloheptane trans -1,4- Dimethylcycloheptane
More than one of the above
6. Of the compounds corresponding to the general name dichlorocyclobutane , how many are optically active? a. b. c. d. e.
0 1 2 3 4
C 7. If an optically active compound has a measured rotation of +5 o in a 1 dm tube at a concentration of 10.0 g/50.0 mL, what is the specific rotation? a. b. c. d. e.
+50o +25o +10o +1o +0.5o
B 8. What is the % composition of a mixture of (S)-(+)-2-butanol, [a] = +13.52 o, and (R)-(-)-2-butanol if the specific rotation of the mixture = -4.51 o? a. b. c. d. e. D
75% (R), 25% (S) 25% (R), 75% (S) 50% (R), 50% (S) 67% (R), 33% (S) 33% (R), 67% (S)
9. Which of the following is a meso compound? CH3
a. b. c. d. e.
H
H
Br
H3C
H
Br
H
H OH CH3
H3C
F
H
F
CH3
OH
CH3
I
II
III
I II III More than one of the above None of the above
D
10. Please name the following compound using IUPAC nomenclature rules 2 (C,C,H)
1 3 (C,H,H)
Name: (S) -3-chloro-2-methylhexane 11. Please completely name the following compound according to IUPAC rules I
I
Name: (3R,4R) -3,4-diiodoheptane
12. How are the following structures related? H
CH3
CH3 CH3
a. b. c. d. e.
H
H
H
CH3
Same compound Enantiomers Meso forms Diastereomers Conformational isomers
A 13. How are the following structures related?
a. b. c. d. e. A
H
CH3
F
F
Constitutional isomers Enantiomers Identical Diastereomers Not isomeric
14. I & II are: H
Br H
Br I
a. b. c. d. e.
II
Constitutional isomers Enantiomers Identical Diastereomers Not isomeric
C 15. How are the following compounds related? CH3 Cl
H
Cl
CH3
H
Cl
Cl
H
CH3
a. b. c. d. e. B
H
CH3
Constitutional isomers Enantiomers Different conformations of the same molecule Diastereomers Not isomeric
16. I & II are: Cl
Cl I
a. b. c. d. e.
II
Constitutional isomers Enantiomers Identical Diastereomers Not isomeric
B 17. I & II are: HO
OH
I
a. b. c. d. e. D
Constitutional isomers Enantiomers Identical Diastereomers Not isomeric
II
18. Please select the rate law for the following reaction CH3CH2CH2CHBrCH3 + OH-
CH3CH2CH2CHOHCH3 + Br-
( RBr )
a. b. c. d. e.
Rate = k [RBr] k [RBr] [OH-] k [RBr]2 [OH-] k [RBr] [OH-]2 Rate = k [RBr]2 [OH-]2
B 19. In an SN1 reaction, why doesn’t increasing the concentration of the nucleophile increase the rate of reaction? Dissociation into a carbocation and leaving group is the rate determining step 20.Consider the reaction of 2-chloro-2-methylpentane with sodium iodide. What would be the effect on the rate of reaction if one were to simultaneously double both the 2-chloro-2-methylpentane and the sodium iodide? a. b. c. d. e. B
There would be no effect on rate Rate would increase 2x Rate would increase 4x Rate would increase 6x Rate would increase 8x
21. Which of the following reactions proceeds with inversion of configuration at the carbon bearing the leaving group? a. b. c. d. e.
SN2 SN1 E2 E1 All of the above
A 22.What product(s) would you predict in the following reaction? H
H
CH3ONa ?
CH3
Br
CH3OH
H
H
H
OCH3
CH3
OCH3
CH3
H
I
a. b. c. d. e. B
I II III An equimolar mixture of I & II None of the above
II
CH3O
H
Br
H III
23.By analyzing starting materials and products for the following reaction, which type of mechanism is occurring?
+
Br
a. b. c. d. e.
N3
N3
SN1 SN2 E1 E2 More than one of the above
A 24.Which of the following alkyl chlorides is essentially unreactive in an S N2 reaction? a. Cl
b. Cl
c. Cl
d. Cl
e. Cl
E
25.Which of the following is the strongest nucleophile in aqueous solution? a. b. c. d. e.
FClBrIAll are equally strong
D
26.Why is the reaction between sodium isopropoxide and isopropyl amine to generate diisopropyl ether not feasible? a. Because elimination would be favored by an E2 mechanism b. Because elimination would be favored by an E1 mechanism c. Because a mixture of substitution and elimination products would be formed d. Because there is no good leaving group available e. In fact, the reaction would proceed and give excellent yields D 27.Which of the following is not a good leaving group? a. b. c. d. e. A
C2H5OClICH3CO2All of the above are good leaving groups
28.Which would be the principal product(s) of the following reaction? O O
CH3SNa
S
CH3SH
O
SCH3
I
a. b. c. d. e.
II
SCH3
III
IV
I II III IV More than one of the above
C 29.The principal product(s) of the following reaction would be dictated by which mechanism?
NaCN DMF
Cl
a. b. c. d. e. B
SN1 SN2 E1 E2 None of the above
30.Which would be the principal product(s) of the following reaction? HO Br 80 oC
(CH3)2CHCH2O
I
a. b. c. d. e.
II
III
IV
I II III IV More than one of the above
E 31. Which would be the principal product(s) of the following reaction? Li Br
I
a. b. c. d. e. A
II
I II III IV More than one of the above
THF
III
IV
32.Please synthesize 2,2,3,3-tetrabromohexane from propyne and n-propyl chloride (1) (2) (3)
Deprotonate propyne with NaNH2 or NaH Add propyl chloride Isolate and add 2 eq. Br 2 in CCl4
Hint: when you are developing a synthesis, learn to count carbons to see where your pieces are coming from. Work backwards – this is known as the retrosynthetic approach. In this case 3 C from propyne and 3 C from n-propyl chloride, which, when coupled tog ether places the alkyne bonds between C2 and C3 – perfect for subsequent addition of 2 eq Br 2
