2370 PI
CI-TEM Dr. S. A. Dantlekar November 16"', 2005
Exam 4 A (100 points)
.
Name:
Section A: 90 points: Select the best answer for ANY 18 of questions 1-23. You may answer extra questions, without penalty, for possible extra credit. ( 5 poiiits each
,-__
(
1
d
A)
1. (R)-3-Cbloro-1-butene reacts with HCI by Markovnikov addilion, and the products are separated by gas chroniatography. I-Iow marly total fractioils would be obtained and how many would be optically active? A) Two optically active fractions and one optically inactive I One optically active fraction and two optically illactive 3 C) One optically active fraction and one optically inactive D) One optically active fraction only E) Two optically active fractions I I
< \ \ I
,
L
I
I
2. Which of the following carbocatiolls would be likely to undergo rearrangement?
CH3
I
<,
',
CH31'H--C-CH3
t
+
I
C'H3
I
D) More than one of the above E) All of the above
3. How inany :H NMR sig~lals would tlie following compound give?
CI($CH~H
I
j
cl
I
I
CMEM 2370
Exam 4 A
Nov 16"', 2003 .,
4. Which statement(s) is (are) true of acid-catal yzed alcohol deliydrations?
A ) Rearrangelnents of less stable carbocations to more stable carbocations are common. B) Loss of a proton by the carbocation is a fast step.
I
C) Fol-niation of a carbocation from the protonated alcohol is a slow step. . D) Protonation of the alcohol is a fast step. E) All of the above
5. A compound C5kIloO gave the following spectral data: 'H NMR spectrum IR spectrum, doublet, 6 1.10 strong peak singlet, 6 2.10 near 1720 cm-' seplet. 6 2.50 structi~re the compound? for Which is a ~~easonable
CHEM 2370
Exam 4 A
Nov 16"', 2005
6. The addition of bromine to cyclohexene would produce the compound(s) represented by structure(s): I ,
r
/ , I
H
g
A)
k7
f-LZBt,
H
H
-1
,
B)
C) D)
(-3,
x -/
I I1 alone I11 alone 1 alone I and I1 I1 and 111
II
111
7. Which reaction would you expect to liberate the most heat? A) CH3
'1.
1
a
I
ill
I
CHEM 2370
Exam 4 A
Nov 161h, 200,
8. Which would be the major product of the following reaction? 1 / I L FlL, qrl,l#'l/:"t,
d
-111:
,/
D2
Nl
9. Which product(s) would be produced by acid-catalyzed dehydration of the following alcohol?
CH3
-IF,,
I
CH~CCHZCH~CH~
I
A)
OH CH3
HA, heat (-Hz01 CH3
I
1
CH3CHCH-CHCH3 and CH~CHCHZCH=CHZ CH3 CHCHzCH=CHz CH3
CH3
I
D)
CH3 CH3
I I I I I
CHZ=CCHZCHZCH~ and C H ~ C - C H C H Z C H ~
CH~CHZCHZC-C-CCHzCHzCH3 CH3 CH3
E)
CHZ
I
CHEM 2370
Exan 4 A
Nov 16"', 2005
10. Which reaction sequence woulcl con\:el-t &-2-bute e to trans-2-butene? A) H30', heat; then cold dilute K M ~ O J fie$ 4 % ~ d\Lenb Q ) HBr; then NaNH2; then H2, Pt f13 \ / I c))BI-~ICCI,; then 2 NaNH?; then Qlliq. NR? c=L 1 D) Br2/CC14; then 2 NaNH2; then H2/Ni313(P-2) / f4 tl E) None of these
r
-+
I
\
L1
. -
I product I.
What would result from the following reaction?
t:.A.AnO.
CH, LH
/H
o
cold, d;!ulz
7
12. PI-eclict t h e major product:
,
(Irons)
Eli3
I
II
Ill
A) No E2 reaction will occur. B) I11
C) 1 ' ~ I1j E) Equal arnou~lts I and I1 of
CHEM 2370
Exaln 4 A
13. A compound has the molecular formula of c6HI00. decolorizes bromine in carbon It tetrachloride. The IR s ectmm of ihe compound has a bmad peak at 3500 cn1-I and a . , , sharp peak at 3300 cm- . The ' H NMR spectrum consists of: triplet, 6 1.0 single[, 52.4 (11-1) singlet, 6 1.4 singlet, 63.4 (IH) quartet, 6 1.6 A likely structure for the co~npound which of these? is
P
,'\"I
('1
14. The C7 compound which gives 3 signals in the broadband proton-decoupled 4 spectrum could be:
I3c
(A)) 2.4-Die~ethylpenta~le R j Heptsne C) 2-Methylhexane D) 2,2,3-Trimethylbutane E) 3,3-Dimethylyentane
Pnei 6
bxam 4 A
IVov lb"', 2005
15. An alkene, X, with the formula C7HI0 adds one mole of hydrogen on catalytic hydrogenatio~i. On treatment with hot basic KMn04 followed by acidification, X yields
-
C7'" :
I
11
A1
Which is a possible structure for X?
A) I V
"i
Eli:" D) 11
E j None of these
16. The 'H NMR spectrum of which of these compounds would consist of a triplet, singlet and quartet &? A) C1
I
CH3CH2CHCH (CH3) 2
CHEM 2370
Exam 4 A
ti
17. Which of these is the lnost satisfactory method for the preparation of cis-2-pentene? A CH3CH2CHBrCH2CH3 CH3CH20Na/CH3CH20H + B CH3CrCCH2CH3+ H2,Ni2B (P-2)
[,8) The bl-oadbnnd proton-decoupled "C NMR spectrum of a hexyl chloride exhibits five -_ signals. Wllicli of these structures could be the correct one for the cornpoutid?
~
~
l.LA f u i /
~
~
~
I
'
1
J 1 0 \
11
,
i ' l
I
1
19. Which compound listecl below would you expect to be the major product of this reaction?
CHI
1
CH3CHzCBr
+
ethanol
KOH
?
I
t i ,
I
I
\
reflux
CH3
A) CHzJIHCHCH3 I
20. Reaction of trans-2-pentene with a solution of Br2in C C 4 produces:
Ill
&
;;I C) Both I and I1 D) 1 E) IV
Page 9
CHEM 2370
Exam 4 A
in 21. For the C-2 liyd~.ogens 1-propanol, the theoretical multiplicity in the 'H NMR spectrum. is which of these?
(3, t el
8 D) 5
E) 2
1
r'
1
\
(-; P,
22. Which of these is not fonned when cyclopentene reacts with an aqueous solution of bromine?
\
'
I
i (
23. An optically active compound, A, with the molecular formula C7H reacts with cold dilute K M n 0 4 and gives IR absorption at about/3300 bin-'. On catalytic hydrogenation, A - is converted to B (C7His)and B is also opticaly aclive. Whicli is a possible structure for A?
d
HEM 2370
Nov 16"', LUOS
SECTION B: 10 points
24. Complete ANY TWO of the following reactiol-is, giving regiochemical and/or stereochemical cletails as relevant.
(
i) BH3, THF Z-3-lmethyl-2-11exene .................... \=ii) H202,NaOH
z-
-
+'
?