1

NAME _______________________

ID # _______________________

ORGANIC CHEMISTRY I (2301)

9:30 – 10:45 am, August 2, 2012

Final Exam There will be two ways that you can pick up your graded Final Exam:

You can pick up your graded exam from Andy at office hours that he will hold on Monday, August 6th (9:30-10:30 am) at Coffman Union Starbucks.

Alternately, you will be able to pick up your graded exam from Chemistry department staff in 115 Smith beginning Monday, August 6th at noon. Exams that are not picked up within two weeks will be disposed of.

A periodic table, a chart of reaction conditions, and a table of typical NMR chemical shifts are attached to the back of this exam as aids. Otherwise, you are not permitted to use any other materials (including notes, books, or electronic devices of any kind). Right now, write your name and student ID number at the top of this page. When the exam begins, please write your name at the top of the next page. You may use pen or pencil. However, re-grades will be considered only for exams completed in pen. Please write your answers in the boxes/spaces provided. If your answer is not in the appropriate space (say, for example, it’s on the back of the page), draw us an arrow and/or note telling us where to look.

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NAME _______________________

Scoring: 1. _________ / 14 6. _________ / 25 2. _________ / 15 7. _________ / 16 3. _________ / 12 8. _________ / 16 4. _________ / 15 9. _________ / 29 5. _________ / 8 Total Score: _________ / 150

1. (14 pts) For each of the pairs of acids (or bases) below, Draw the conjugate base (or acid). Circle whether you think the first acid (or base) is more or less acidic (or basic) than the

second. Acid Conjugate Base Base Conjugate Acid

is

MORE ACIDIC

LESS ACIDIC

than

is

MORE BASIC

LESS BASIC

than

N

H

H

H

H

HO

H

H

O

H3C CH3

OH

H3C CH3

3

2. (15 pts) For the anion drawn at right, in the boxes provided:

Draw all significant resonance structures. In each structure, draw all atoms, bonds, lone pairs of electrons, and formal charges. Then, circle which resonance structure you think is the most significant, and which is the least. Circle only one MOST and one LEAST.

Draw a Lewis wedge/dashed-bond structure that illustrates the most stable three-dimensional conformation of the molecule. Draw all atoms, bonds, and charges, but omit lone pairs.

In the boxes provided, write the hybridization state on any atom heavier than hydrogen.

3. (12 pts) Each of the reactions below and on the next page is drawn with two possible

products. If one of the two products predominates, circle that preferred product. If the two products are produced equally, circle “BOTH”. If neither product would result from the reaction, circle “NEITHER”. Circle one answer only.

C CH

H

H

C

HO

C

H

H

H

3-dimensional representation

CN H

H

H

C

O H

C

H

H

H

O

atom hybridizations:

MOST or LEAST significant?

C CC C

resonance structure

MOST or LEAST significant?

BOTH (equally)

NEITHER

EtOH

Br

CH3

CH3

CH3

CH3

CH3

CH3

4

4. (15 pts) For each of the reactions below, fill in the empty box corresponding to the major

product. Wherever appropriate, illustrate stereochemistry in your drawings (using wedge and dashed bonds). If multiple enantiomers or diastereomers are produced, indicate this in the answer box (e.g., by writing “+ enantiomer”, etc.)

Br2

BOTH (equally)

NEITHER

(1 equiv) C C CH3H3C

H3C

CH3

Br

Br

H3CCH3

Br Br

Br Br

BOTH (equally)

NEITHER

mCPBA

H

CH3

H3C

HO

H3C H

H CH3

O

H CH3

H3C H

H2SO4

H2O

N

O

O

Br

(NBS)

AIBN

CH3

5

5. (8 pts) Each of the reactions below is drawn with two possible reaction conditions. If only

one of the two reaction conditions would generate the given molecule as the major product, circle those conditions. If both sets of conditions would accomplish the reaction, circle “BOTH”. If neither set of reaction conditions would succeed, circle “NEITHER”. Circle one answer only.

BOTH would work

NEITHER would work

Na2Cr2O7 H2SO4

1. (COCl)2, DMSO -60 °C 2. Et3N (Swern oxidation)

BOTH would work

NEITHER would work

Na, NH3

Pd, BaSO4 quinoline, H2 (g)

(Lindlar’s catalyst)

OH O

O

H

Br

CH3O Na

6

6. (25 pts) When the epoxide-alcohol starting material below is deprotonated with NaH, the resulting alkoxide reacts with itself to open the epoxide. That reaction, followed by acidic workup, can produce two different products; the difference between the products is dictated by which epoxide carbon is attacked by the alkoxide.

In this problem, we will name the products A and B, which are formed by protonation of intermediates A and B. (a) Using “electron pushing”, draw a mechanism that illustrates the formation of

intermediates A and B from the alkoxide. I’ve drawn the starting material for you—just add curved arrows to my structure. Then, draw the structures of intermediate A and intermediate B. Wherever appropriate, illustrate stereochemistry.

(b) Is intermediate A intermediate B?

O

H

H CH3

OH

1. NaH

(-H2)

O

H

H CH3

O Na

intermediate A

intermediate B

product A

product B

2. H3O+

2. H3O+

intermediate B

O

H

H CH3

O

O

H

H CH3

O

push electrons

here

intermediate A

MORE STABLE

than

the SAME

ENERGY as

LESS STABLE

than(Circle one.)

7

(c) On the potential energy diagram below, draw two curves that represent the two reactions you drew in part (a). The starting material (alkoxide) energy has already been drawn for you—you need to connect this starting point to energies of the reaction transition states, intermediate A, and intermediate B.

(d) How would the rate of the two reactions be affected if the starting material were a thiol instead of an alcohol? Assume that the thiolate on the right has the same energy as the alkoxide above, and that the sulfur-containing intermediates AS and BS are also the same energy as intermediates A and B. Would the thiolate react

the alkoxide? (Circle one.)

E

reaction coordinate

starting alkoxide intermediates A/B

O

H

H CH3

O

O

H

H CH3

S

FASTER than

the SAME RATE

as SLOWER

than

8

7. (16 pts) Draw a mechanism (using “electron pushing”) for each of the reactions shown on the next page. Draw each mechanistic step explicitly; don’t cheat by combining multiple processes in a single step. Use only the molecules shown in the problem; don’t invoke generic species. (E.g., don’t use “H-A” as a generic acid.)

Mechanism:

H2SO4 OH

9

8. (16 pts) For each set of starting materials and products shown below, propose a multistep synthesis. In addition to the molecules shown, you can use any reagents and reactions we’ve learned about in class. You might discover multiple answers to this problem; draw only your best (one) synthetic route. Feel free to draw an incomplete route—we will give you partial credit where we can.

Multistep synthesis:

C C HH

OH

H3C

OBr

Br

10

9. (29 pts) Acrylonitrile, the starting material on the right, can be polymerized into polyacrylonitrile (a component of plastic consumer goods) by heating it in solvent, but heating acrylonitrile in a mixture of ethanol and water generates a small molecule product instead. This product was isolated and characterized by NMR and IR spectroscopy and mass spectrometry; the spectra of this product are shown on the next two pages. High-resolution mass spectrometry determined an exact mass of 99.06840 amu for the highest-mass (parent, M+) peak in the MS spectrum, which corresponds to a molecular formula of C5H9NO.

(a) Based on the features in the IR spectrum below, what functional groups would you

expect the unknown molecule to have? Circle all answers that apply.

IR Spectrum:

(b) What is the structure of the product? In the box on the next page, draw the molecule’s

structure, including all hydrogens. Then, considering the 1H NMR spectrum,

C(sp2)

H

C C

C(sp)

H

C O

CN C5H9NO

H2O CH3CH2OH

100

50

0

4000 3000 2000 1500 1000

Tra

nsm

ittan

ce (

%)

(wavenumbers, cm-1)

2256

2982

O

H

C(sp3)

H

N

H

C N C C C N

11

Circle each group of equivalent H’s; Assign a 1H chemical shift () to each circled group, within 0.05 ppm; Connect any pair of coupled, inequivalent groups of H’s with a double-headed arrow,

and then label that arrow with the corresponding coupling constant (J).

1H NMR Spectrum:

the product (C5H9NO)

Format for answer to (c):

Cl Cl

H H

H H

H H

= 2.2 ppm

= 3.8 ppm

J = 7.0 Hz

12

(c) In an electron-ionization (EI) mass spectrometry experiment, parent ions often fragment into daughter ions that give information about the parent’s molecular structure. In the EI mass spectrum below, the parent mass peak at m/z = 99 corresponds to a radical cation (M•+) that fragments into ions with mass 84 and 59. In the boxes below, draw the structures of these ions. You do not need to do electron pushing to answer this question—just draw the cations. On all ion structures, make sure to specifically illustrate where the formal charge lies.

Mass Spectrum:

100

0

Rel

ativ

e In

tens

it y

m/z

20 40 60 80 100

99

84

59

54

M•+ (C5H9NO+, m/z = 99)

fragment ion with m/z = 59 fragment ion with m/z = 84

Final Exam Chart of Reaction Conditions

 

Cl2 or Br2, h

H2SO4 H2O

1. BH3•THF 2. H2O2, OH-

Cl

O

OO

H

(mCPBA)

 

mCPBA H2O

KMnO4 (cold, dilute)

H2O, OH- 

1. O3 2. (CH3)2S

Pt/H2(g)

NaNH2

Na NH3

HgSO4 H2SO4 1. KMnO4

KOH, 2. H3O

+

Pd, BaSO4 H2(g)

(quinoline)

N

(NBS)

h or AIBN

 

N

O

O

Br

Na2Cr2O7 H2SO4 1. (COCl)2

DMSO -60 °C 2. Et3N

(Swern oxidation)

TsCl pyridine

SOCl2 pyridine

PBr3

1. O3 2. H2O

KMnO4 H2O, pH 7

Per

iodi

c Ta

ble

of th

e E

lem

ents

C

hem

istr

y R

efer

ence

She

et

Cal

iforn

ia S

tand

ards

Tes

t

Sod

ium

22.9

9

Na

11

Ato

mic

num

ber

Ele

men

t sym

bol

Ave

rage

ato

mic

mas

s*

Ele

men

t nam

e

Hyd

roge

n1.

01H1

Lith

ium

6.94Li3

Sod

ium

22.9

9

Na

11

Pot

assi

um39

.10

19 K

Nic

kel

58.6

9

Ni

28

Rub

idiu

m85

.47

Rb

37

Rut

herfo

rdiu

m

(261

)

Rf

104

Mol

ybde

num

95.9

4

Mo

42

Ger

man

ium

72.6

1

Ge

32

1 1A

2 2A

1 2 3 4

7 7B

11 1B

12 2B

13 3A

16 6AK

ey 8

5 6 7

9 8B

10

14 4A

15 5A

17 7A

18 8A

3 3B 4 4B

5 5B

6 6B

Cop

per

63.5

5

Cu

29

Cob

alt

58.9

3

Co

27

Hel

ium

4.00

He2

Bor

on10

.81

B5

Car

bon

12.0

1

C6

Nitr

ogen

14.0

1

N7

Oxy

gen

16.0

0

O8

Flu

orin

e19

.00

F9

Neo

n20

.18

Ne

10

Alu

min

um26

.98

Al

13

Sili

con

28.0

9

Si

14

Pho

spho

rus

30.9

7

P15

Sul

fur

32.0

7

S16

Chl

orin

e35

.45

Cl

17

Arg

on39

.95

Ar

18

Cal

cium

40.0

8

Ca

20

Sca

ndiu

m44

.96

Sc

21

Tita

nium

47.8

7

Ti

22

Chr

omiu

m52

.00

Cr

24

Iron

55.8

5

Fe

26

Zin

c65

.39

Zn30

Gal

lium

69.7

2

Ga

31

Ars

enic

74.9

2

As

33

Sel

eniu

m78

.96

Se

34

Bro

min

e79

.90

Br

35

Kry

pton

83.8

0

Kr

36

Str

ontiu

m87

.62

Sr

38

Yttr

ium

88.9

1

Y39

Zirc

oniu

m91

.22

Zr

40

Nio

bium

92.9

1

Nb

41

Tech

netiu

m(9

8)Tc

43

Rut

heni

um10

1.07

Ru

44

Rho

dium

102.

91

Rh

45

Pal

ladi

um10

6.42

46

Silv

er10

7.87

Ag

47

Cad

miu

m11

2.41

Cd

48

Indi

um11

4.82

In49

Tin

118.

71

Sn

50

Ant

imon

y12

1.76

Sb

51

Tellu

rium

127.

60

Te52

Iodi

ne12

6.90I53

Xen

on13

1.29

Xe

54

Ces

ium

132.

91

Cs

55

Bar

ium

137.

33

Ba

56

Lant

hanu

m13

8.91

La

57

Haf

nium

178.

49

Hf

72

Tant

alum

180.

95

Ta73

Tung

sten

183.

84

W74

Rhe

nium

186.

21

Re

75

Osm

ium

190.

23

Os

76

Irid

ium

192.

22Ir77

Pla

tinum

195.

08

Pt

78

Gol

d19

6.97

Au

79

Mer

cury

200.

59

Hg

80

Tha

llium

204.

38

Tl

81

Lead

207.

2

Pb

82

Bis

mut

h20

8.98

Bi

83

Pol

oniu

m(2

09)

Po84

Ast

atin

e(2

10)

At

85

Pd

Rad

on(2

22)

Rn

86

Fran

cium

(223

)

Fr

87

Rad

ium

(226

)

Ra

88

Act

iniu

m(2

27)

Ac

89

Dub

nium

(262

)

Db

105

Sea

borg

ium

(266

)

Sg

106

Boh

rium

(264

)

Bh

107

Has

sium

(269

)

Hs

108

Mei

tner

ium

(268

)

Mt

109

Mag

nesi

um24

.31

Mg

12

Ber

ylliu

m9.

01Be4

Van

adiu

m50

.94

V23

Man

gane

se54

.94

Mn

25

* If

this

num

ber

is in

par

enth

eses

, the

n

it r

efer

s to

the

atom

ic m

ass

of th

e

mos

t sta

ble

isot

ope.

Pra

seod

ymiu

m

140.

91

Pr

59

Men

dele

vium

(258

)

Md

101

Cer

ium

140.

12

Ce

58

Neo

dym

ium

144.

24

Nd

60

Pro

met

hium

(145

)

Pm61

Sam

ariu

m15

0.36

Sm62

Eur

opiu

m15

1.96

Eu

63

Gad

olin

ium

157.

25

Gd

64

Terb

ium

158.

93

Tb65

Dys

pros

ium

162.

50

Dy

66

Hol

miu

m16

4.93

Ho

67

Erb

ium

167.

26

Er

68

Thu

lium

168.

93

Tm69

Ytte

rbiu

m17

3.04

Yb

70

Lute

tium

174.

97

Lu71

Tho

rium

232.

04

Th90

Pro

tact

iniu

m23

1.04

Pa

91

Ura

nium

238.

03

U92

Nep

tuni

um(2

37)

Np

93

Plu

toni

um(2

44)

Pu

94

Am

eric

ium

(243

)

Am95

Cur

ium

(247

)

Cm96

Ber

keliu

m(2

47)

Bk

97

Cal

iforn

ium

(251

)

Cf

98

Ein

stei

nium

(252

)

Es

99

Fer

miu

m(2

57)

Fm

100

Nob

eliu

m(2

59)

No

102

Law

renc

ium

(262

)

Lr

103

Co

pyr

igh

t ©

200

8 C

alifo

rnia

Dep

artm

ent

of

Ed

uca

tio

n