Download - Exam Answers Quiz Keys
CHEM 238B, Winter 2010 QUIZ KEYS
Name _________________
Section ________________
CHEM 238B Quiz 1
Version A
1. Give an IUPAC name for each of the following structures
a. b. c.
2. Draw an arrow-pushing mechanism for the following problem and show the major product that
will result from the reaction.
Br
Br
(1Z, 3E, 5Z)-1,6-
dibromohexa-1,3,5-triene
o-fluorophenol
4-methyl-1-phenyl
cylcohexan-1-ol
CHEM 238B, Winter 2010 QUIZ KEYS
3. Classify the following heterocyclic molecules as aromatic, anti-aromatic, or not aromatic,
according to Huckel’s rule.
a. b.
antiaromatic aromatic
(not aromatic okay)
4. Give the major product for each reaction shown here:
5. Write the major product of this reaction.
O
HN
HB
NH
BH
NH
HB
1 mol. HCl
-80oC
1 mol. HCl
50oC
1 mol. Br2
-80oC
1 mol. Br2
50oC
2 mol. Br2
25oC
Cl
Br
BrBr
Br
Cl
Br
Br
Br
Br
H
H
1,2-addition @ cold temperature is kinetic control
1,4-addition observed w/ heat is thermodynamic control
1 2 3 4
12
34
Br2
H2O
Br
OH
hydration of bromonium intermediate occurs at
benzylic position, not tertiary
CHEM 238B, Winter 2010 QUIZ KEYS
Name _________________
Section ________________
CHEM 238B Quiz 1
Version B
1. Give an IUPAC name for each of the following structures
a. b. c.
2. Write the major product of this reaction.
3. Classify the following heterocyclic molecules as aromatic, anti-aromatic, or not aromatic,
according to Huckel’s rule.
a. b.
Aromatic Aromatic
Br
Br OH
NO2
NH HN
HB
NH
BH
NH
HB
(1Z, 3Z)-1,4-dibromohexa-
1,3,5-triene
p-nitrophenol 4-ethyl-1-phenyl
cylcohexan-1-ol
Br2
H2O
Br
OH
hydration of bromonium intermediate occurs at
benzylic position, not tertiary
CHEM 238B, Winter 2010 QUIZ KEYS
4. Draw an arrow-pushing mechanism for the following problem and show the major product that
will result from the reaction.
5. Give the major product for each reaction shown here:
1 mol. HCl
-80oC
1 mol. HCl
50oC
1 mol. Br2
-80oC
1 mol. Br2
50oC
2 mol. Br2
25oC
Cl
Br
BrBr
Br
Cl
Br
Br
Br
Br
H
H
1,2-addition @ cold temperature is kinetic control
1,4-addition observed w/ heat is thermodynamic control
1 2 3 4
12
34
CHEM 238B, Winter 2010 QUIZ KEYS
Name _________________
Section ________________
CHEM 238B Quiz 1
Version C
1. Give an IUPAC name for each of the following structures
a. b. c.
2. Give the major product for each reaction shown here:
Br Br
(1Z, 3Z)-1,3-dibromohexa-
1,3,5-triene
m-nitrotoluene
4-t-butyl-1-phenyl-
cylcohexan-1-ol
1 mol. HCl
-80oC
1 mol. HCl
50oC
1 mol. Br2
-80oC
1 mol. Br2
50oC
2 mol. Br2
25oC
Cl
Br
BrBr
Br
Cl
Br
Br
Br
Br
H
H
1,2-addition @ cold temperature is kinetic control
1,4-addition observed w/ heat is thermodynamic control
1 2 3 4
12
34
CHEM 238B, Winter 2010 QUIZ KEYS
3. Draw an arrow-pushing mechanism for the following problem and show the major product that
will result from the reaction.
4. Write the major product of this reaction.
5. Classify the following heterocyclic molecules as aromatic, anti-aromatic, or not aromatic,
according to Huckel’s rule.
a. b.
antiaromatic aromatic
(credit for not aromatic, can be if O’s are sp3)
O
O
HN
HB
NH
BH
NH
HB
CHEM 238B, Winter 2010 QUIZ KEYS
Name _____________________
Section ____________________
CHEM 238 B Quiz 2
Version A
1) Draw the missing intermediate and product in the reaction below; where E+ is an electrophile.
2) Circle the choice which best describes the relative rates of intermediate and product formation in
the reaction above.
a) Same
b) Slow, Fast
c) Fast, Slow
3) For the pair of compounds given below choose which one will react faster with the indicated
reagent and write a chemical equation for the faster reaction.
Fluorobenzene or (trifluoromethyl)benzene with benzyl chloride and aluminum chloride
CHEM 238B, Winter 2010 QUIZ KEYS
4) Write a structural formula for the compound:
(Z)-2-Phenyl-2-butene
5) Provide the reagents required at each step of the provided reaction.
1) AlCl3
2) NBS
3) strong base, NaOEt KOtBu etc
4) Zn0 (Hg) and aqueous acid
6) Propose a synthesis of 4-acetyl-2-nitrotoluene starting with toluene.
CHEM 238B, Winter 2010 QUIZ KEYS
Name _____________________
Section ____________________
CHEM 238 B Quiz 2
Version B
7) Propose a synthesis of 2-bromo-4-tert-Butyltoluene starting with toluene. If an ortho, para mixture
is formed in any step of the reaction, assume that you can separate the two isomers.
8) Provide the reagents required at each step of the following reaction.
1) AlCl3
2) NBS
3) strong base, NaOEt KOtBu etc
4) Zn0 (Hg) and aqueous acid
CHEM 238B, Winter 2010 QUIZ KEYS
9) Draw the missing intermediate and product in the reaction below; where E+ is an electrophile.
10) Circle the choice which best describes the relative rates of intermediate and product formation in
the reaction above.
d) Same
e) Slow, Fast
f) Fast, Slow
11) For the pair of compounds given choose which one will react faster with the indicated reagent and
write a chemical equation for the faster reaction.
Methyl benzoate or phenyl acetate with bromine/FeBr3 in an inert solvent.
12) Draw the structure of allylbenzene:
CHEM 238B, Winter 2010 QUIZ KEYS
Name _____________________
Section ____________________
CHEM 238 B Quiz 2
Version C
1) For the pair of compounds given choose which one will react faster with the indicated reagent and
write a chemical equation for the faster reaction.
Toluene or chlorobenzene with a mixture of nitric acid and sulfuric acid
2) Draw the missing intermediate and product in the reaction below.
3) Circle the choice which best describes the relative rates of intermediate and product formation in
the reaction above.
g) Same
h) Slow, Fast
i) Fast, Slow
CHEM 238B, Winter 2010 QUIZ KEYS
Propose a synthesis of pure 2-bromotoluene starting with toluene. If an ortho, para mixture is
formed in any step of the reaction, this would not be a ‘pure’ product as required.
4) The following structure may be represented by at least one alternative resonance structure in which
all six-membered rings correspond to Kekulé forms of benzene. Write such a resonance structure
for:
5) Provide the reagents required at each step of the following reaction.
O
O
O O
Br
1 2
3 4
Cl
1) AlCl3
2) NBS
3) strong base, NaOEt KOtBu etc
4) Zn0 (Hg) and aqueous acid
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #3.1 (Ch. 13-14) Name__________________________ Sec_______
(03) I. Provide unambiguous systematic names for the following organometallic compounds:
(07) II. For the compound shown below, predict the
1H and
13C NMR spectra, including peak multiplicities.
(03) III. J-coupling by alcohol protons (the OH) is observed when the 1H NMR spectrum is obtained using a polar aprotic
solvent (e.g., DMSO-d6) because intermolecular proton exchange is hindered by hydrogen bonding with the solvent.
Please explain: (a) How to distinguish primary and secondary alcohols from one another using this concept.
(b) The effect of treatment with excess D2O upon the alcohol proton resonances.
(02) IV. Circle the compound that contains a more polar metal carbon bond, and briefly explain why:
CHEM 238B, Winter 2010 QUIZ KEYS
(12) V. Consider the following reaction used in the total synthesis of the natural product Asteltoxin. Intermediate (B)
illustrates an example of what is known as a [2,3] sigmatropic rearrangement, which you have not seen yet, though as a
budding intellectual you find utterly fascinating(!). Note reactions (1) and (2) are two distinct additions that are performed
in the same reaction flask (also recall that Ph = phenyl):
(a) Propose a synthesis of the starting material (A) from a vinyl halide and electrophile of your choice.
(b) Draw the principal organic products formed between (A) and n-butyl lithium in step (1) of the reaction.
(c) How many 13
C resonances would be observed in (A)? How about (C)? A:____3_____ C:____9______
(Compound (A) is symmetrical, (C) has symmetry only in the phenyl substituent) (2 pts each; 1 pt if 6 or 7 assigned to (C))
(d) Ignoring the phenylsulfoxide unit, how does the UV λmax change from (A)���� (C)? ___________________________
Acceptable responses: “redshift;” “increases from conjugation;” “goes above 231 nm;” suggests longer λmax (2 pts)
Also: C appears at lower energy (longer λmax ) due to greater conjugation OR <200 becomes 220 -235 nm
(03) VI. Perform a retrosynthetic analysis on the following target molecule (TGT), working back to the ketone shown; you
do not need to provide reagents, just the synthetic intermediates and a brief descriptor of the transform (i.e. “bromination”,
“formation of Grignard reagent”, “dehydrobromination”, “protonation of anionic product”, etc.):
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #3.2 (Ch. 13-14) Name__________________________ Sec_______
(03) I. Provide unambiguous systematic names for the following organometallic compounds:
(07) II. For the compound shown below, predict the 1H and
13C NMR spectra, including peak multiplicities.
methyl propionate
1H NMR 13C NMR
O
O(a) 4.0 ppm (3H, singlet)
(b) 2.2 ppm (2H, quartet)
(c) 1.0 ppm (3H, triplet)
(1 pt each; -1 for switching
signals; -1 for wrong mult.)
200-220 ppm (C=O)
60-90 ppm (OCH3)
20-50 ppm (CH3C=O)
0-40 ppm (CH2CH3)
(1 pt each; -1 if any multiplicities)
(a)
(b)
(c)
(03) III. J-coupling by alcohol protons (the OH) is observed when the 1H NMR spectrum is obtained using a polar aprotic
solvent (e.g., DMSO-d6) because intermolecular proton exchange is hindered by hydrogen bonding with the solvent.
Please explain: (a) How to distinguish primary and secondary alcohols from one another using this concept.
(b) The effect of treatment with excess D2O upon the alcohol proton resonances.
(SEE ABOVE)
(02) IV. Circle the compound that contains a more polar metal carbon bond, and briefly explain why:
CHEM 238B, Winter 2010 QUIZ KEYS
(12) V. Consider the following reaction used in the total synthesis of the natural product Asteltoxin. Intermediate (B)
illustrates an example of what is known as a [2,3] sigmatropic rearrangement, which you have not seen yet, though as a
budding intellectual you find utterly fascinating(!). Note reactions (1) and (2) are two distinct additions that are performed in
the same reaction flask (recall that Ph = phenyl):
(a) Propose a synthesis of the starting material (A) from a vinyl halide and electrophile of your choice.
(SEE ABOVE)
(b) Draw the principal organic products formed between (A) and n-butyl lithium in step (1) of the reaction.
(SEE ABOVE)
(c) How many 13
C resonances would be observed in (A)? How about (C)? A:_________ C:__________
(d) Ignoring the phenylsulfoxide unit, how does the UV λmax change from (A)���� (C)? ___________________________
(03) VI. Perform a retrosynthetic analysis on the following target molecule (TGT), working back to the ketone shown; you
do not need to provide reagents, just the synthetic intermediates and a brief descriptor of the transform (i.e. “bromination”,
“formation of Grignard reagent”, “dehydrobromination”, “protonation of anionic product”, etc):
(SEE ABOVE)
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #3.3 (Ch. 13-14) Name__________________________ Sec_______
(03) I. Provide unambiguous systematic names for the following organometallic compounds:
(07) II. For the compound shown below, predict the 1H and
13C NMR spectra, including peak multiplicities.
(03) III. J-coupling by alcohol protons (the OH) is observed when the 1H NMR spectrum is obtained using a polar aprotic
solvent (e.g., DMSO-d6) because intermolecular proton exchange is hindered by hydrogen bonding with the solvent.
Please explain: (a) How to distinguish primary and secondary alcohols from one another using this concept.
(b) The effect of treatment with excess D2O upon the –CH2O– resonance of alcohol (CH3)2CHCH2OH.
(A) SEE ABOVE
(B) The observed doublet of doublets would become a doublet, since the O-H proton exchanges with 2D (NMR silent!)
(02) IV. Circle the compound that contains a more polar metal carbon bond, and briefly explain why:
CHEM 238B, Winter 2010 QUIZ KEYS
(12) V. Consider the following reaction used in the total synthesis of the natural product Asteltoxin. Intermediate (B)
illustrates an example of what is known as a [2,3] sigmatropic rearrangement, which you have not seen yet, though as a
budding intellectual you find utterly fascinating(!). Note reactions (1) and (2) are two distinct additions that are performed in
the same reaction flask (recall that Ph = phenyl):
(a) Propose a synthesis of the starting material (A) from a vinyl halide and electrophile of your choice.
(SEE ABOVE)
(b) Draw the principal organic products formed between (A) and n-butyl lithium in step (1) of the reaction.
(SEE ABOVE)
(c) How many 13
C resonances would be observed in (A)? How about (C)? A:_________ C:__________
(d) Ignoring the phenylsulfoxide unit, how does the UV λmax change from (A)���� (C)? ___________________________
(03) VI. Perform a retrosynthetic analysis on the following target molecule (TGT), working back to the ketone shown; you
do not need to provide reagents, just the synthetic intermediates and a brief descriptor of the transform (i.e. “bromination”,
“formation of Grignard reagent”, “dehydrobromination”, “protonation of anionic product”, etc):
(SEE ABOVE)
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #4.1 (Ch. 15-16) Name_________________________ Sect_______
(05) I. Suggest appropriate starting materials for the series of reactions below, all of which lead to the alcohol shown.
(05) II. Predict the major organic product, including stereochemistry as needed, in the following reactions. Also provide
an unambiguous systematic name for the products.
(06) III. Outline a practical synthesis of isobutylbenzene (PhCH2CH(CH3)2) starting from benzene, isobutyl alcohol
(HOCH2CH(CH3)2) and any necessary organic and inorganic reagents.
CHEM 238B, Winter 2010 QUIZ KEYS
(04) IV. Draw the principal organic product and an arrow-pushing mechanism for the reaction below.
(06) V. The following epoxidation strategy has been reported in the chemical literature.
(a) Propose a reasonable arrow-pushing mechanism. Note the numbered carbons in the substrate and product.
(b) Briefly comment on why this reaction was chosen to prepare this particular epoxide instead of using the
epoxidation reactions you have learned so far (e.g., mCPBA, or Br2/H2O then intramolecular SN2).
(04) VI. In the presence of thiophenol (PhSH) under strongly basic conditions, the 2,3-epoxy-1-ol below is converted in
high yield and regioselectivity to the 2,3-dihydroxy thioether product depicted. The mechanism of this hydroxyl transfer
reaction is known as the Payne Rearrangement. Show an arrow-pushing mechanism for this reaction (HINT: Start off by
deprotonating the alcohol in the starting material. ALSO: Use the product stereochemistry as a guide!!!!!!).
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #4.2 (Ch. 15-16) Name_________________________ Sect_______
(06) I. The following epoxidation strategy has been reported in the chemical literature.
(a) Propose a reasonable arrow-pushing mechanism. Note the numbered carbons in the substrate and product.
(b) Briefly comment on why this reaction was chosen to prepare this particular epoxide instead of using the
epoxidation reactions you have learned so far (e.g., mCPBA, or Br2/H2O then intramolecular SN2).
(SEE ABOVE)
(05) II. Suggest appropriate starting materials for the series of reactions below, all of which lead to the alcohol shown.
(05) III. Predict the major organic product, including stereochemistry as needed, in the following reactions. Also provide
an unambiguous systematic name for the products.
CHEM 238B, Winter 2010 QUIZ KEYS
(06) IV. Outline a practical synthesis of isobutylbenzene (PhCH2CH(CH3)2) starting from benzene, isobutyl alcohol
(HOCH2CH(CH3)2) and any necessary organic and inorganic reagents.
(04) V. Draw the principal organic product and an arrow-pushing mechanism for the reaction below. Note the reactant is
a single enantiomer, so stereochemistry should be included in the product.
(04) VI. In the presence of thiophenol (PhSH) under strongly basic conditions, the 2,3-epoxy-1-ol below is converted in
high yield and regioselectivity to the 2,3-dihydroxy thioether product depicted. The mechanism of this hydroxyl transfer
reaction is known as the Payne Rearrangement. Show an arrow-pushing mechanism for this reaction (HINT: Start off by
deprotonating the alcohol in the starting material. ALSO: Use the product stereochemistry as a guide!!!!!!).
(SEE ABOVE)
CHEM 238B, Winter 2010 QUIZ KEYS
QUIZ #4.3 (Ch. 15-16) Name_________________________ Sect_______
(05) I. Suggest appropriate starting materials for the series of reactions below, all of which lead to the alcohol shown.
(05) II. Predict the major organic product, including stereochemistry as needed, in the following reactions. Also provide
an unambiguous systematic name for the products.
(06) III. The following epoxidation strategy has been reported in the chemical literature.
(a) Propose a reasonable arrow-pushing mechanism. Note the numbered carbons in the substrate and product.
(b) Briefly comment on why this reaction was chosen to prepare this particular epoxide instead of using the
epoxidation reactions you have learned so far (e.g., mCPBA, or Br2/H2O then intramolecular SN2).
(SEE ABOVE)
CHEM 238B, Winter 2010 QUIZ KEYS
(06) IV. Outline a practical synthesis of isobutylbenzene (PhCH2CH(CH3)2) starting from benzene, isobutyl alcohol
(HOCH2CH(CH3)2) and any necessary organic and inorganic reagents.
(04) V. Draw the principal organic product and an arrow-pushing mechanism for the reaction below.
(04) VI. In the presence of thiophenol (PhSH) under strongly basic conditions, the 2,3-epoxy-1-ol below is converted in
high yield and regioselectivity to the 2,3-dihydroxy thioether product depicted. The mechanism of this hydroxyl transfer
reaction is known as the Payne Rearrangement. Show an arrow-pushing mechanism for this reaction (HINT: Start off by
deprotonating the alcohol in the starting material. ALSO: Use the product stereochemistry as a guide!!!!!!).
(SEE ABOVE)