FINAL EXAMINATION Chemistry 3B Name: SID #: Laboratory GSI ...
Transcript of FINAL EXAMINATION Chemistry 3B Name: SID #: Laboratory GSI ...
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FINAL EXAMINATION Chemistry 3B
Name:__________________________ SID #:______________________ Print first name before second! Use capital letters!
Laboratory GSI (if applicable): Peter Vollhardt ______________________ December 15, 2006 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 25 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Grades will be posted on Wednesday, December 20, by 5 pm, outside 320 Latimer Hall. Good Luck! DO NOT WRITE IN THIS SPACE
I. ______ (60)
II. ______ (175)
III. ______ (60)
IV. ______ (40)
V. ______ (60)
VI. ______ (60)
VII. ______ (45)
Total:
(500)
2
I. [60 Points] Provide the IUPAC name or draw the structure, as appropriate, of the following
molecules. Remember the priority of functional groups in choosing names, indicate the correct stereochemistry (e.g., R, S, and E, Z), and do not forget about the alphabetical ordering of substituents!
(a)
(2S)-Amino-6-heptynoic acid
(b)
ClCl
Br
(c)
(R)-2, 3-Dihydroxypropanal
3
(d)
OCH2CH3
OO
(e)
N-(2-Methylpropyl)ethanamide
(f)
O
4
II. [175 Points; (a) - (j) 10 points each, (k) - (o) 15 points each] Add the missing components (starting materials, reagents, or products) of the following reactions in the boxes provided. Aqueous work-up (when required) is assumed to be part of a step. It is not part of any answer.
(a)
OS
CH3
OO
Na+-OCH3, CH3OH
(b) 1.
2.
NH2
O
OCH3
CH3 CH3O
OCH3
H
H(c)
5
(d)
P2S5
O
O
1H NMR: =2.35 (s, 6H), 2.01 (s, 6H) ppm (e)
N
CH3
HNO3, H+
(f)
O
H
HO
H
HO
HO
H
HHOH
OH
CH3OH, H+
(g)
O
CH3NH2, Na+ NCBH3�–
6
(h) +
CN
(i) 13C NMR = 220.2, 38.3, 23.3 ppm (j) Na+�–OCH3, HCH3OH
1H NMR spectrum:
CH3COOH
O
O
O
OCH3
O O
7
(k) 1.
NH
O 2. 3.
+N N
(l) 1. 2. 3COCH3
O
CH3CHCH2COCH3
OH O
CH
(m) 1. CH3OH, H+
2. 2 CH3MgBr
H+, CH3OH
OH
O
8
(n) 1. NaCN
2. CH3CH2CH2MgBr 3. CH2=P(C6H5)3
CH3I Mass spectrum of product: (o)
OCH3
O O
+
NH
OCH3CH3O
H3C CH3
O O +
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III. [60 Points] In an attempt to effect electrophilic methoxylation, benzene carbaldehyde A was treated with methyl hydroperoxide B in the presence of acid. The mass, IR, and NMR spectra of this product are shown in the following pages. From the complex mixture of products, traces of unknown C were obtained. H+
C (Unknown) + CH3OOH
H
O
A B
(a) After consideration of the spectral data, write the structure of the product in the box below. Structure of unknown
b. Interpret the spectral data as requested in the spaces provided, starting on the following page.
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1. 1H NMR Spectrum (for expanded section, see bottom spectrum).
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b. Draw again your suggestion for the unknown in the box and label the hydrogens A, B, C, and D giving rise to the corresponding signals in the spectrum. Use the Table below, if necessary. 2. 13C NMR Spectrum.
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Draw again your suggestion for the unknown in the box below and label the types of carbon atoms A�–E giving rise to the corresponding signals in the spectrum. 3. Mass spectrum.
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a. Clearly mark on the spectrum the molecular ion as �“M+�”. b. In the boxes above the respective fragment ions, indicate the molecular piece that has fragmented from M+, e.g. �“Cl�”, or �“CH3O�”, or �“CH3CH2�”, or ? 4. IR Spectrum.
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Confirm or rule out the presence or absence (circle one) of the following bonds. Enter an approximate expected stretching frequency in the box. ~ (Csp
2�–H) is: present absent at cm�–1
~ (Csp
3�–H) is: present absent at cm�–1
~ (O�–H) is: present absent at cm�–1
~ (C=O) is: present absent at
cm�–1
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IV. [40 Points] You are asked to assign the structures of the two pentoses D-ribose and D-lyxose. Ruff degradation of the former gives D-erythrose, that of the latter D-threose. Kiliani-Fischer extension of D-ribose furnishes D-allose and D-altrose, that of D-lyxose results in D-galactose and D-talose ribose. CHO CHO
HO H
CH2OH
H OH
H OH
CH2OH
H OH
D-(-)-Erythrose D-(-)-Threose D-Ribose D-Lyxose CHO
OHH
OHH
OHH
OHH
CH2OH
CHO
HHO
OHH
OHH
OHH
CH2OH
CHO
OHH
HHO
HHO
OHH
CH2OH
CHO
HHO
HHO
HHO
OHH
CH2OH
D-Allose D-Altrose D-Galactose D-Talose 1. Draw your assignments in the respective boxes, using Fischer projections.
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2. Specify the conditions of (a) the Ruff degradation
1. 2.
(b) the Kiliani-Fischer extension
1. 2.
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V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is much more space than you will need. (a)
NaOH,
OH
OH
O
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(b) 1. LiAlD4 2. H+, H2O (work up)
O
ON
CH3
N
O
OH
CH3
CH2D
Work from left to right in the following spaces. There is much more space than you will
need.
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(c) NaBH3CN, CH3OH 2N
H
O
NH
H
Work from left to right in the following spaces. There is much more space than you will need.
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VI. [60 Points] Provide a reasonable synthetic route from starting materials to product. Note: Several steps are required, and there may be more than one solution to the problem. You may use any additional organic or organometallic reagents to effect your conversions. Do not write mechanisms!
(a)
N O
O
H
Work from left to right in the following spaces. There is much more space than you will need.
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(b) H2N CNH
O
COOH
H2N COOH
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(c) The only organic starting materials:
OCH3
O O OCH3
N NO
O
O
Work from left to right in the following spaces. There is much more space than you will need.
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VII. [45 Points] Place an X mark in the box next to the most accurate statement.
(a) The longest wavelength band in the UV spectra of the hydrocarbons below moves to lower energy in the order
1 2 3 1, 2, 3
3, 2, 1
2, 1, 3
3, 1, 2
(b) Circle the compounds which are aromatic
O2N H
+N
N
O
N
NH
O
O
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(c) In the collection below, circle the most abundant fragments formed during the mass spectral ionization of 2-pentanone.
O
70 eV H+ C O CH3+ CH3CH
2
+ CH 2
+3CH2CH C3H6O+ C2H4
+
(d) The rates of electrophilic aromatic nitration of the following compounds increases in the order
Cl
Cl
N NCH3
1 2 3
1, 2, 3
2, 1, 3,
3, 2, 1
2, 3, 1
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(e) Give the products and their molar amounts per mole of starting material of the complete periodic acid oxidation of D-erythrose and D-erythrulose.
CHO
OHH
OHH
CH2OH
HIO4 D-Erythrose
CH2OH
O
OHH
CH2OH
D-Erythrulose
The End
Merry Christmas!
1
FINAL EXAMINATION Chemistry 3B
Name:__________________________ SID #:______________________ Print first name before second! Use capital letters!
Laboratory GSI (if applicable): Peter Vollhardt ______________________ December 17, 2008 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 25 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Good Luck! DO NOT WRITE IN THIS SPACE
I. ______ (60)
II. ______ (175)
III. ______ (60)
IV. ______ (40)
V. ______ (60)
VI. ______ (60)
VII. ______ (45)
Total:
(500)
2
I. [60 Points] Provide the IUPAC name or draw the structure, as appropriate, of the following
molecules. Remember the priority of functional groups in choosing names and indicate the correct stereochemistry (cis, trans, E, Z, R, and S, as appropriate)!
(a) Trans-3-oxo-4-hexenal
(b) 1-Bromo-4-(2,2-dichloropropyl)benzene
(c) (R)-2,3-Dihydroxypropanenitrile
1
2
3
(Fischer projection)
The numbers refer to the main chain
3
(d)
OCH2CH3
OH2N H
(e) N-Chloro-N-methyl-3-pentanamine
(f)
O
4
II. [175 Points; (a) - (j) 10 points each, (k) - (o) 15 points each] Add the missing components (starting materials, reagents, or products) of the following reactions in the boxes provided. Aqueous work-up (when required) is assumed to be part of a step. It is not part of any answer.
(a)
OS
CH3
OO
+CH3OH
O
O
O
O
Na+
(b) 1.
2.
NH2
H3CO
OCH3
H3CO
CH3O
OCH3
H3CO I
(c)
H
H
5
(d)
O
O
NH3, H+
13C NMR spectrum:
(e)
H3CN
HNO3, H+
NH2 (f)
O
H
H3CO
H
H3CO
H3CO
H
HHOCH3
OCH3
H2O, H+
mildly acidic O
6
(g) Two reagents
NH CH3
O
(h)
+
CN
H3CO
CN
(i) + NaOH
H2N ONH2
7
(j) OH
H3CO
1. LiAlH4 2. H+, H2O
IR spectrum of starting material:
13C NMR spectrum of starting material:
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(k) 1. 2.
H3C OH O (l) 1. 2. 3.
OH
NH2
NH2
Br
(m) HIO4
2 HCOOH + 1 CH2=O An aldose
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(n) 2.
CH3
1. N Br
O
O
Mass spectrum of product: 1H NMR spectrum of product:
ppm (o) 1. MnO2 2. NH3 + 3.
COOH
NH2
OH
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III. [60 Points] Diethyl malonate A was treated with bromine to give a product B. The mass, IR, and NMR spectra of B are shown in the following pages in the sequence :
1. 1H NMR , 2. 13C NMR , 3. Mass , 4. IR. B
Br2
OO
OO
A
(a) After consideration of the spectral data, write the structure of B in the box below. Structure of B
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1. 1H NMR spectrum (for expanded sections, see bottom spectra).
ppm
A
B
C
C (B
A
J = 8 Hz) (J = 8 Hz)
ppm ppm
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b. Draw again your suggestion for B in the box and label the hydrogens A, B, and C giving rise to the corresponding signals in the 1H NMR spectrum. Use the Table below, if necessary.
13
2. 13C NMR spectrum.
A
B
C
D
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Draw again your suggestion for B in the box below and label the types of carbon atoms A�–D giving rise to the corresponding signals in the spectrum. 3. Mass spectrum. Hint: Atomic weights: C = 12; H = 1; O = 16; Br exists in nature as a 1:1 mixture of Br = 79 and Br = 81.
a. Clearly mark on the spectrum the molecular ion(s) �“M+�”. b. In the boxes below, indicate the structure of the fragment ions with the m/z value given under the box. m/z = 193/195 29
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4. IR Spectrum.
Confirm the presence or absence (circle one) of the following bonds. Enter an approximate expected stretching frequency in the box. ~ (Csp
2�–H) is: present absent at cm�–1
~ (Csp
3�–H) is: present absent at cm�–1
~ (O�–H) is: present absent at
cm�–1
~ (C=O) is: present absent at
cm�–1
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IV. [40 Points] (a) D-Ribulose is a non-reducing pentose. Treatment with NaBH4 gives two alditols. One of them is identical to the product of NaBH4 reduction of D-ribose, the other is identical to the product of NaBH4 reduction of D-arabinose. Fill in the blanks below and provide a structure for D-ribulose. NaBH4
An alditol An alditol D-Ribulose NaBH4 NaBH4 CHO
HHO
OHH
OHH
CH2OHD-Arabinose
OHH
OHH
OHH
CH2OH
CHO
D-Ribose
(b) D-Erythrose was treated with aqueous bromine to give the aldonic acid A, which was
subsequently thermally dehydrated to B, and then treated with acidic acetone to give the final product C. Provide structures for A and B. CHO
H OH
CH2OH
H OH
Br2, H2O
H2O
H2O
OH
OH
C
CH2
O
OCH3
CH3Note: These"corners" are not atoms.
D-Erythrose A B
C
H+, H3C CH3
O
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V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is much more space than you will need. (a)
CH3
O
NaOH, H2O,
H3C
O
+
O
CH3
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(b)
NO2
O2N
O
2 NaOH, H2O NO2
O2N
Br
O
O
Work from left to right in the following spaces. There is much more space than you will need.
19
(c)
OH
CH3
CH3
H+, H2O
O
H3C CH3 Work from left to right in the following spaces. There is much more space than you will
need.
20
VI. [60 Points] Provide a reasonable synthetic route from starting material to product. Note: Several steps are required, and there may be more than one solution to the problem. Do not write mechanisms! Write out each step separately, including reagents and products. You need to apply retrosynthesis! You may use any additional organic or organometallic reagents to effect your conversions.
(a)
NH2
Note:
HCCl,
O
HCCl,
NH
H2NCCl,
O
and ClCH2NH2 do not exist and are not allowed as reagents.
Work from left to right in the following spaces. There is much more space than you will need.
21
(b)
H2N
O
COOH
NHNH2
COOH
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(c) For this problem, use the materials given below as the only organic compounds:
IO
O I
O
Starting material
Additional organic reagents
Work from left to right in the following spaces. There is much more space than you will need.
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VII. [45 Points] Place an X mark in the box next to the most accurate statement. (a) The acidity of 1�–4 increases in the order
H3NCH2COH
O CH3NH3 CH3C N H
1 2 3 4
1, 2, 3, 4
4, 3, 2, 1
4, 1, 2, 3
3, 2, 1, 4
(b) In the 1H NMR spectrum of the compund below circle the hydrogens that you expect to show peaks in the �“left half�” of the spectrum (that is > 5 ppm).
N
NO
OH
H
O
O
H
Cl
H H
H
H
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(c) The following Diels-Alder reaction follows the endo rule. True or false? Circle the correct answer below
CH3
CO2CH3
CO2CH3
+CO2CH3
CO2CH3
CH3
H
H
True False (d) The mass spectrum of N,N-dipropylpropanamine (see below) shows only a relatively small molecular ion peak at m/z = 143. The base (100%) peak is a fragment at m/z = 114. In the box below the spectrum, draw the structure of this fragment (including charges).
N N,N-dipropylpropanamine
25
(e) Aromatic heterocycles are frequently constructed in one step by a combination of aldol and imine condensations. With this statement in mind provide the most suitable retrosynthetic disconnection of A into two starting materials (boxes).
N CH3
CH3
CH3
O
A
+
The End
Merry Christmas!
1
FINAL EXAMINATION Chemistry 3B
Name:__________________________ SID #:______________________ Print first name before second! Use capital letters!
GSI (if you are taking Chem 3BL): ______________________
Peter Vollhardt December 16, 2009 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 19 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Good Luck! DO NOT WRITE IN THIS SPACE
I. ______
(60)
II. ______
(175)
III. ______
(60)
IV. ______
(40)
V. ______
(60)
VI. ______
(60)
VII. ______
(45)
Total:
(500)
2
I. [60 Points] Name or draw, as appropriate, the following molecules according to the
IUPAC rules. Indicate stereochemistry where necessary (cis, trans, E, Z, R, or S). (a) (R)-4-bromo-N-ethyl-N-methyl-pentanamide
(b) 1-Bromo-4-(2,2-dichloropropyl)benzene
(c) (R)-2,3-Dihydroxypropanal
(Fischer projection)
The numbers refer to the main chain
3
(d)
(e) Methyl 3-oxo-butanoate
(f)
4
II. [175 Points; (a) - (j) 10 points each, (k) - (o) 15 points each] Add the missing components (starting materials, reagents, or products) of the following reactions in the boxes provided. Aqueous work-up (when required) is assumed to be part of a step. It is not part of any answer.
(a)
H2, Pd�–C
C6H8O (b) 1.
2.
NH2
H3CO
OCH3
H3CO
(c)
H
H
5
(d)
(e)
(f)
(g) H CH3 NaBH3CN, CH3OH H2C=O +
N
6
(h)
OCH3
Complete the stencil above (i)
H3C
O
O
(j)
OH
H3CO
7
(k) 1. 2. (l) 1. 2. 3. (m) HIO4
2 HCOOH + 1 CH2=O An aldose
8
(n) (o) 1. MnO2 2. NH4CN 3. H+, H2O,
OH
9
III. [60 Points] The wavy lines in the following structure indicate four possible retrosynthetic disconnections of four bonds (numbered 1-4). O
1 2 3 4
Show the respective four reactions that would lead to the generation of each of these strategic bonds in the four boxes below. Note: It is fine to use a protected or otherwise modified fragment to make the desired connection, as long as it can be elaborated later into the target structure. However, do not show such elaboration. Each box should contain only the reagents that you would use to make the bond in question. Bond 1: Bond 2: Bond 3: Bond 4:
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IV. [40 Points] (a) D-Ribulose is a pentaketose. Treatment with NaBH4 gives two alditols. One of them is identical to the product of NaBH4 reduction of D-ribose, the other is identical to the product of NaBH4 reduction of D-arabinose. Fill in the blanks below and provide a structure for D-ribulose. NaBH4
D-Ribulose An alditol An alditol NaBH4 NaBH4
CHO
HHO
OHH
OHH
CH2OHD-Arabinose
OHH
OHH
OHH
CH2OH
CHO
D-Ribose
(b) D-Erythrose was treated with nitric acid to give the aldaric acid A, which was treated
with acidic acetone to give B. On heating, B dehydrated to the final product C. Provide structures for A and B.
11
V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is more space than you will need. (a)
H+, H2O, THF
12
(b) H+, H2O
Work from left to right in the following spaces. There is much more space than you will need.
13
(c) H+, H2O,
Work from left to right in the following spaces. There is much more space than you will need.
14
VI. [60 Points] Provide a reasonable synthetic route from starting material to product. Note: Several steps are required, and there may be more than one solution to the problem. Do not write mechanisms! Write out each step separately, including reagents and products. You need to apply retrosynthesis! You may use any additional organic or organometallic reagents to effect your conversions.
(a)
Work from left to right in the following spaces. There is much more space than you will need.
15
(b)
O
NH
S
NH2
S
HOOC
Work from left to right in the following spaces. There is much more space than you will need.
16
(c)
Work from left to right in the following spaces. There is much more space than you will need.
17
VII. [45 Points] Place an X mark in the box next to the most accurate statement. (a) The acidity of 1�–4 increases in the order:
H3NCH2COH
O CH3NH3 CH3C N H
1 2 3 4
1, 2, 3, 4
4, 3, 2, 1
1, 4, 2, 3
3, 2, 1, 4
(b) The following two sugars are:
CHO
OHH
HHO
OHH
OHH
CH2OH CHO
HO H
H OH
HO H
HO H
CH2OH
Identical
Enantiomers
Diastereomers
Anomers
18
(c) The following heterocycle will undergo electrophilic bromination at position:
N
N S
1
23
4
1
2
3
4 (d) The following reaction will give
O
O
Na+ OCH2CH3, CH3CH2OH
O
OO
OH
O
O
OO
19
(e) Which of the following molecules are reduced by LiAlH4? Check all the boxes that apply.
OH
O
N
Cl
The End
Merry Christmas!