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Organic Problems
These problems are keyed to the exams. For example, problem 3.5 is the fifth homework
problem for Exam 3 and not the fifth problem for Chapter 3. Resist the temptation to only do a
few parts of the multiple part problems. The multiple parts are present because people need the
additional practice to understand the material. Ideally, you should finish the questions for a
particular exam 48 hours before the exam.
EXAM 1
1.1 Draw Lewis structures for each of the following:
(b) H2O
(c) CO2
(d) HCN
(a) C2H6
(g) Br2
(h) H2O2
(i) N2
(j) SO42(m) HNO2
(n) KNO3
(o) CH4O
(p) H2CO3
(s) NaHCO3 (t) CaCO3
(u) BH3
(e) C2H4
(k) NCl3
(q) C2H5OH
(f) C2H2
(l) CH2O
(r) HC2H3O2
1.2 Draw the Lewis structure for each of the following and determine the formal charge for each
atom.
(a) OH(b) H2O
(c) H3O+
(d) BH4(e) BF4(f) HCO3(g) CH3
(h) CH3(i) CH3+
(j) CH2
(k) NH2(l) NH4+
1.3 (a) Predict the shape of a carbon dioxide molecule, and show why it is nonpolar. (b) Sulfur
dioxide has a dipole moment of 1.63 D. What does this tell us about the shape of a sulfur
dioxide molecule? (c) The shape of nitrogen trifluoride is similar to that of ammonia. However,
the dipole moment is very small (0.24 D). Why is the dipole moment so low? (d) Explain why
BF3 is nonpolar.
1.4 Draw the Lewis structure and indicate all non-zero formal charges for each of the following.
(a) CH3ONO2 (b) CH3NCO (c) CH2CO
(d) CH2N2
(e) CH3NCS
(f) CH3CNO (g) KNH2
(d) NaN3
(i) CH2O
(j) HCO2H
1.5 Draw the three-dimensional structure for each of the following. Indicate which are nonpolar.
If the molecule is polar, indicate the direction of the dipole with an arrow.
(a) CH3Cl
(b) CCl4
(c) BeI2
(d) CH2O
(e) CH2Cl2
(f) CH2FCl
(i) BF3
(j) CH3OH
(g) CH3OCH3 (h) CHCl3
1.6 Draw the resonance structures for the nitrite ion. Determine the formal charge for each atom
in each structure. How do these structures account for the fact that the two N-O bonds are of
equal length?
1.7 Use molecular orbital energy level diagram to show why He2 does not exist, but He2+ does
exist.
1.8 What type of orbital is the lone pair on the nitrogen atom in ammonia expected to occupy?
What type of orbitals do the lone pairs in a water molecule occupy?
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1.9 Determine the formal charge for each atom in each of the following. (What is the overall
charge of each species?)
1.10 Boron trifluoride react with ammonia to produce BF3NH3. (a) Use Lewis structures to
diagram this reaction. (b) What factor promotes this reaction? (c) Determine the formal charge
on each atom in the product. (d) Predict the hybridization of boron in the reactant and in the
product. (e) Predict the hybridization of nitrogen in the reactant and in the product. (f) Indicate
all expected bond angles.
1.11 Draw the Lewis structure for the methyl cation (CH3+). Predict the shape of this ion.
Predict the hybridization and bond angle of the carbon atom. Indicate which of orbitals on the
carbon are unoccupied.
1.12 Draw structural formulas for all the isomers of C4H8.
1.13 Examination each of the following pairs of structures. Determine if the two structures
represent different views of the same compound, represent isomers of each other, or represent
different compounds that are not isomers.
a. CH2ClCHClCH3
and CH3CHClCH2Cl
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1.14 Draw the structural formulas for the nine isomers of C7H16, and give IUPAC name for each.
1.15 Draw all alcohols with the formula C5H12O, and give the IUPAC name for each.
1.16 Name each of the following
f. Draw and name a bicyclic compound that is an isomer of bicyclo [2.2.1] heptane.
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1.17 Give IUPAC names for each of the following.
1.18 What are the IUPAC names for each of the following compounds?
1.19 Draw structural formulas for each of the following compounds.
(a) 4-bromo-1-octene
(e) 4-ethylcyclohexene
(h)1,5-dichlorocyclohexene
(b) trans-3-hexene
(f) cis-2-pentene
(i) 1,3-dibromocyclopentene
(c) 3-methylcyclopentene
(g) 1,2-diethylcyclohexene (j) 4,4-dichloro-1-hexene
(d) vinylcyclohexane
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1.20 Draw the resonance structures for the cyanate ion, OCN- and the fulminate ion, CNO-. Use
formal charges to predict with of the resonance structures for each of these ions are the most
important.
1.21 (a) Draw the structural formula of each different product formed by the monochlorination of
1,1-dichloroethane. (b) Draw the structural formula of each different product formed by the
monochlorination of 1,2-dichloroethane. (c) Are the products structural isomers? (d) Draw the
structural formulas of all possible tetrachloroethanes that could form from your answers to parts
(a) and (b). (e) How many pentachloro products are possible?
1.22 Draw the different resonance structures for each of the following.
(b) CH3-S-CH2+
(c) CH2=CH-Cl
(a) CH3-NO2
+
(d) CH2=CH-C H-CH=CH2
(e) CH3CH=CH-CH=O+H
1.23 (a) Draw the most stable (lowest energy) conformer of cis-1,3-diethylcyclohexane. What is
the distribution of hydrogen atoms in axial and equatorial positions? (b) Draw the most stable
(lowest energy) conformer of 1,4-di-t-butyl-1,4-dimethylcyclohexane.
1.24 Determine the Index of Hydrogen Deficiency (Degree of Unsaturation) for each compound
in problem 1.19
1.25 List the following compounds in order of increasing boiling point; then supply a reason for
this order. (a) Dipropyl ether (b) 3-hexanol (c) n-octane (d) isooctane (2,2,4-trimethylpentane)
EXAM 2
2.1 Write a Lewis structure for each of the following species and indicate why each may serve as
a nucleophile. Which may also serve as an acid, and which may serve as a base.
(e) cyanide ion, CN(i) methylamine,CH3NH2
(a) ammonia, NH3
(b) ethyl alcohol, C2H5OH (f) ethoxide ion, C2H5O
(j) azide ion, N3(c) acetic acid, CH3COOH (g) acetate ion, CH3COO(k) ethanthiol, C2H5SH
(d) ethanthiolate ion, C2H5S (h) formic acid, HCOOH
(l) formate ion, HCOO2.2 Beginning with propyl bromide, and any other appropriate compounds, illustrate how a
nucleophilic substitution reaction may be used to synthesize each of the following.
c. CH3CH2CH2CN
a. CH3CH2CH2OH b. CH3CH2OCH2CH2CH3
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2.3 Choose which alkyl halide in each of the following pairs will react more rapidly via an SN2
mechanism. Explain your choice in each case.
a. CH3CH2CH2-Br or CH3CH2CH2-Cl
b. CH3CH2Cl or CH2=CHCl
c. CH3CH2CHBrCH3 or CH3CH2CH2CH2Br
2.4 Explain which member of each pair would react most rapidly via an SN2 reaction. (That is,
which is the best nucleophile (Nu)?)
(a) CH3CH2I + OH- Æ CH3CH2OH + I- or CH3CH2I + SH- Æ CH3CH2SH + I(b) CH3CH2I + CH3S-(1.0 M) Æ CH3CH2SH + I- or CH3CH2I + CH3S-(2.0 M)Æ CH3CH2SH + I(c) CH3CH2CH2Br + CH3OH Æ CH3CH2CH2OCH3 + HBr or
CH3CH2CH2Br + CH3O- Æ CH3CH2CH2OCH3 + Br(d) CH3Br + CH3SH Æ CH3SCH3 + HBr or CH3Br + CH3OH Æ CH3OCH3 + HBr
2.5 Explain which member of each pair would react most rapidly via an SN1 reaction. (Hint,
which has a faster rate of solvolysis?)
(a) (CH3)3CBr + H2O Æ (CH3)3COH + HBr or (CH3)3CBr + CH3OH Æ (CH3)3COCH3 + HBr
(b) (CH3)3CCl + CH3O-(0.001 M) Æ (CH3)3COCH3 + Cl- or
(CH3)3CCl + CH3O-(0.01 M) Æ (CH3)3COCH3 + Cl(c) (CH3)3CI + CH3OH Æ (CH3)3COCH3 + HI or (CH3)3CCl + CH3OH Æ (CH3)3COCH3 + HCl
(d) (CH3)2C=CHCl + H2OÆ (CH3)2C=CHOH + HCl or (CH3)3CCl + H2O Æ (CH3)3COH + HCl
2.6 Beginning with either methane, ethane, and/or cyclopentane outline a synthetic route for each
of the following. You may add any necessary solvents or inorganic reagents.
(a) CH3CH2OH (b) CH3CH2SH
(c) CH3CN
(d) CH3OCH2CH3
(e) cyclopentene
2.7 You have two compounds, CH3CHBrCH3 and CH3CH2CH2Br. Explain which you would
choose as a starting material to prepare an alkene with the maximum yield.
2.8 Explain why each of the following reaction will NOT occur.
(a) OH- + CH3CH3 Æ CH3CH2OH + H:(b) NH3 + CH3CH2OH2+ Æ CH3CH2NH3+ + H2O
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(c) CH3CH=CHBr + CH3S- Æ CH3CH=CHSCH3 + Br(d) (CH3)3CBr + CN- Æ (CH3)3C-CN + Br(e) cyclopentane + H2O Æ CH3CH2CH2CH2CH2OH
2.9 Which of the following reactions would give the higher yield of isopropyl methyl ether?
Explain your choice.
(a) (CH3)2CHONa + CH3I Æ CH3OCH(CH3)2 (b) CH3ONa + (CH3)2CHI Æ CH3OCH(CH3)2
2.10 Predict the product(s) for each of the following reactions. Determine if the mechanism is
E1, E2, SN1, SN2, or a combination. If more than one product is expected, which will be the
major product?
a. (CH3)3CI + CH3Ob. (CH3)3CO- + CH3I
°/CH OH
°/ CH
c. CH3CH2CH2CH2Br + CH3O-
COH
°/CH OH
d. CH3CH2CH2CH2Br + (CH3)3COe. C2H5O- + CH3CH2CHBrCH2CH3
f. CH3CHBrCH3 + (CH3)3COg.
°/ CH
°/ CH
COH
°/CH CH OH
COH
h.
2.11 Which of the reactants in each of the following pairs would behave as a stronger
nucleophile in a protic solvent?
(a) CH3COO- or OH- (b) CH3OH or CH3SH (c) H2S or HS- (d) CH3O- or CH3COO2.12 Derive a mechanism for each of the following reactions.
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2.13 Sodium or potassium iodide is commonly used as catalysts in many SN2 reactions of alkyl
chlorides and bromides. As an example, methyl bromide undergoes hydrolysis more rapidly in
the presence of potassium iodide. Explain this observation. Would acetone be a good solvent
for this reaction?
2.14 Hydrolysis of t-butyl chloride with sodium hydroxide yields t-butyl alcohol. In this
reaction, an increase in the hydroxide ion concentration does not cause a significant increase in
the rate of alcohol formation, but it does cause a significant increase in the rate of disappearance
of t-butyl chloride. Explain these observations.
2.15 Bicyclic compounds, similar to the ones pictures below, are very unreactive via a SN2
mechanism.
(a) Suggest an explanation for this observation. (b) This type of compound is also less reactive
via a SN1 mechanism. Explain this observation. (Hint: consider the general sp2 hybridization of
carbocations.)
2.16 Unlike SN2 mechanisms, SN1 mechanisms exhibit minimal nucleophile selectivity. That is,
if there is more than one nucleophile present, a SN1 mechanisms show little discrimination
between a strong nucleophile and a weak nucleophile. However, a SN2 mechanism exhibits a
significant discrimination. (a) Suggest an explanation for these observations. (b) Discuss how
your explanation applies to the following reactions. The reaction of n-butyl chloride with dilute
sodium cyanide in ethanol primarily yields CH3CH2CH2CH2CN. Under the same conditions, tbutyl chloride primarily yields (CH3)3OCH2CH3.
2.17 What are the IUPAC names for each of the following compounds?
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(a) CH3 CH2 CH2
H
C
CH3
(b)
C
CH3 CH2
H
CH3
2.18 Show how cyclopropene could be synthesized from each of the following reactants.
(a) 1,2-dichlorocyclopentane (b) bromocyclopentane
(c) cyclopentanol
2.19 Show how propene could be synthesized from each of the following reactants.
(a) propyl chloride
(c) isopropyl alcohol (e) 1,2-dibromopropane
(b) 2-chloropropane (d) propyl alcohol
2.20 The dehydrohalogenation of trans-1-bromo-2-methylcyclohane gives 3-methylcyclohexene
as the major product. The acid-catalyzed dehydration of trans-2-methylcyclohexanol yields 1methylcyclohexene as the major product. These reactions are:
Explain why the different products result.
2.21 Draw structural formulas for the products of each of the following reactions. If more than
one product is possible, indicate which would be the major product.
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2.22 How does the heat of hydrogenation of cis-cyclooctene compare to the heat of
hydrogenation of trans-cyclooctene (in kJ/mole)? Explain your prediction.
2.23 Each of the following alkyl halides will undergo dehydrohalogenation when reacted with an
ethanol solution of sodium ethoxide. Draw the structural formulas for each of the alkenes that
may form. In this problem, you do not need to consider cis-trans isomerism.
(a) CH3CHBrCH2CH2CH3
(b) CH3CH2CHBrCH2CH3
(d) CH3CHBrCH(CH3)CH3
(c) CH3CH2CH(CH3)CH2Br
2.24 Outline the synthesis for each of the following compounds (as the only, or the major
product). Begin with the appropriate base and alky halide. (a) 3-methyl-1-butene
(b) 4-methylcyclohexene
2.25 Draw the structural formulas for the alcohol or alcohols that, upon dehydration, would yield
the following alkenes as the major product. (a) 1-metyylcyclopentene (b) 2,3-dimethyl-2-butene
(c) 2-methylpropene
2.26 (a) Which of the two possible isomers will form when 1,2-dimethylcyclopentene is
hydrogenated in the presence of a platinum catalyst. (b) Under similar conditions, what is the
major product for the hydrogenation of 1,2-dimethylcyclohene? Draw the conformational
formula of the product. (c) The reaction of cyclohexene with deuterium (D2) in the presence of a
platinum catalyst produces which isomer?
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2.27 Heating borneol in 50% sulfuric acid produces camphene not the expected bornylene. This
reaction is:
Write a step-by-step mechanism illustrating the formation of camphene. It may be useful to use
models.
2.28 The compound caryophyllene, C15H24, is present in oil of cloves. Hydrogenation of this
compound with excess hydrogen in the presence of a platinum catalyst produces C15H28.
Determine the number of rings and the number of double bonds in caryophyllene.
2.29 (a) Which reagent(s) are necessary to convert 2-butyne to cis-2-butene? (b) Which
reagent(s) are necessary to convert 2-butyne to trans-2-butene?
2.30 Examine the rearrangement occurring in the following acid catalyzed dehydration:
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CH3
CH3
20
CH3
11
H
3
HO
10
5
4
CH3
H
9
1
2
12
13
19
14
CH3
18
H
15
21
22
17
16
8
CH3
CH3
7
H+
6
3 -friedelanol
CH3
CH3
CH3
CH3
CH3
CH3
H
CH3
13(18)-oleanene
H
CH3 CH
3
The reaction begins with the formation of a carbocation followed by a number of migrations of
both methyl groups and hydrogen atoms before the loss of a H+ yields the product. All of the
migrations are 1-2 shifts of a methanide ion (CH3:-) or a hydride ion (H:-). Use curved arrows to
indicate how each shift occurs.
2.31 Dehydrohalogenation of an alkyl halide with the formula C7H15Br produces a single alkene
(no cis-trans isomers). The same product results when either potassium t-butoxide in t-butyl
alcohol or sodium methoxide in methyl alcohol is used. Draw the alkyl halide.
2.32 Derive a mechanism for each of the following reactions. Explain the relative proportions of
each of the isomers formed.
(a)
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CH3
CH3
CH3
OH
CH2
H+
CH3
heat
+
major
CH3
CH3
CH3
+
minor
(b)
2.33 Explain the statement “a sp2 hybridized carbon atom (alkene) is ‘more electronegative’ than
a sp3 hybridized carbon atom (alkane).” How does this relate to the observation that ethene (pKa
= 44) is a stronger acid than ethane (pKa = 50)? How would the pKa of acetylene compare to that
of ethene and ethane?
EXAM 3
3.1 Define each of the following and give examples to illustrate the meaning.
(a) structural isomers (f) diastereomers
(k) plane of symmetry
(b) isomers
(g) meso compound (l) dextrorotatory
(c) enantiomers
(h) chiral atom
(m) optical activity
(d) racemate
(i) achiral molecule (n) retention of configuration
(e) stereoisomers
(j) chiral molecule
3.2 Below are several pairs of structures. Describe the relationship between the two members of
each pair. (Are the members of each pair enantiomers, diastereomers, structural isomers, or two
views of the same compound?)
(a)
(b)
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(c)
(d)
(e)
CH3
CH3
H
Br
H
Cl
H
Cl
H
Br
CH3
(f)
(g)
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CH3
16
(h)
(i)
(j)
(k)
(l)
(m)
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CH3
CH3
CH3
CH3
(n)
CH3
CH3
CH3
CH3
(o)
(p)
(q)
3.3 Draw the stereochemical formulas for all expected products for each of the following
reactions. It may be helpful for you to use models.
(a)
(b)
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(c)
(d)
(e)
(f)
3.4 Determine the R/S designation (configuration) for each different compound produced in
problem 3.3.
3.5 (a) Predict which stereoisomer would result from the catalyzed hydrogenation of 1,2dimethylcyclopentene. (b) Is the product optically active? (c) Is it possible to resolve the
product?
3.6 Compound E is an optically active hydrocarbon with the molecular formula C5H8. Catalytic
hydrogenation converts compound E into the optically inactive compound F (C5H10). It is not
possible to resolve compound F. Determine the structures of compounds E and F.
3.7 Two compounds, G and H, have the molecular formula C7H14. Both of these compounds are
optically active, and rotate plane polarized light in the same direction. Catalytic hydrogenation
of either compound produces optically active compound K, C7H16. What are the structures of G,
H, and K?
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3.8 Decide which of the following reactions will undergo retention of configuration, undergo
inversion of configuration, or undergo racemization. Explain your decision on each case.
(a) (+)CH3CH2CH2CHDBr + :CN- Æ CH3CH2CH2CHDCN + Br(b) (-)CH3CH2CH(CH3)CH2Cl
OH /SN
NH
CH3Ch2CH(CH3)CH2OH
CH3CH(OH)C(NH2)O
(c) (+)CH3CH(OH)CClO
(d) (-)C6H13CHBrCH3 + I- Æ C6H13CHICH3 + BrH O
(e) (-)C6H13CH(OH)CH3
C6H13CH(OH)CH3
(f) (+)CH3CH2CI(CH3)CH2CH2CH3 CH3OHÆCH3CH2C(OCH3)(CH3)CH2CH2CH3 + HI
(g) (-)CH3CH(OH)CHO
B
/H O
CH3CH(OH)COOH
3.9 Both maleic acid and fumaric acid have the general formula HOOCCH=CHCOOH.
Treatment of fumaric acid with cold dilute KMnO4 produces (±)-tartaric acid. Under the same
conditions, maleic acid produces meso-tartaric acid. Determine the stereochemical formulas of
maleic acid and fumaric acid.
3.10 Compound A is optically active (assume it to be dextrorotatory), and has the formula
C7H11Br. In the absence of peroxides, compound A will react with hydrogen bromide to yield
two isomers (B and C) with the formula C7H12Br2. Compound B is optically active, and
compound C is not optically active. One mole of potassium t-butoxide converts compound B
into (+)A. Under the same conditions, potassium t-butoxide converts compound C into (±)A.
Compound A reacts with potassium t-butoxide to form compound D (C7H10). When one mole of
compound D undergoes ozonolysis followed by treatment with zinc and water it produces two
moles of formaldehyde and one mole of the following compound. Outline the reactions involved
and predict the stereochemical formulas for A, B, C, and D.
3.11 The reaction of 2-iodooctane (C6H13CHICH3) with radioactive iodine (*I-) produces the
chemically equivalent compound C6H13CH*ICH3. When a pure sample of either enantiomer
reacts, the rate of racemization is exactly double the rate of incorporation of radioactive iodine.
This experiment is considered proof that a SN2 with inversion of configuration is occurring. (a)
Why is true? (b) How would the relative rates of racemization and iodine incorporation compare
if the mechanism were SN1?
3.12 Draw the structural formula for the products that result when 1-pentene reacts with each of
the following.
(a) HCl
(g) O3, then Zn, H2O
(m) cold con H2SO4
(b) HBr
(h) THF:BH3, then H2O2, OH(n) Br2 in CCl4, then KI in acetone
(c) HI
(i) dilute KMnO4, OH-, cold
(o) KMnO4, OH-, heat then H+
(d) D2, Pt
(j) OsO4, then Na2SO3/H2O
(p) THF:BH3, then CH3COOH
(e) HBr, peroxides
(k) Br2 in CCl4, room temperature (q) 1) Hg(OAc)2, H2O 2) NaBH4
(f) H+, H2O, heat
(l) cold con H2SO4, then H2O and heat
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3.13 Derive a possible mechanism for the following reaction.
3.14 Outline a practical method of synthesizing each of the following. You may begin with 2butene and any other reagents.
(a) CH3CHO
(h) CH3CHBrCHBrCH3
(o) CH3CH(OH)CH(OH)CH3
(b) CH3COOH
(i) CH3CHBrCH(OH)CH3 (p) CH3CH2CH(OH)CH3
(c) octane
(j) CH3CH2CH2CH2D
(q) CH3CH2CH2CH2Br
(d) 3-methylheptane
(k) CH3CH2CHFCH3
(r) CH3CH2CH2CH2CN
(l) CH3CH2CH2CH3
(s) CH3CH2CH2CH2OCH3
(e) CH3CHDCH2CH3
(m) CH3CH2CHBrCH3
(t) CH3CHDCH(OH)CH3
(f) CH3CH2CH2CH2OH
(g) CH3CHDCHTCH3
(n) CH3CH2CH=CH2
3.15 Draw the structural formulas for the products of each of the following reactions.
(a) cyclohexene + (1) OsO4 (2) NaHSO3
(b) 1-methylcyclopentene + (1) KMnO4/OH- heat (2) H+
(c) cyclohexene + (1) peroxybenzoic acid (2) H+/H2O
(d) 1-butene + Br2/CCl4
(e) cis-3-hexene + KMnO4/OH-/heat
(f) 1,2-bibromopentane + Zn/C2H5OH
(g) ethene + con H2SO4, cold
(h) product of (g) + H2O
(i) 2-butanol + con H2SO4/hot
(j) 2-methyl-2-pentene + HI
(k) cyclohexene + dil KMnO4/OH- cold
(l) bromocyclopentane + KOH/alcohol/heat
(m) 2-methylpropene + THF:BH3
(n) product of (m) + NaOH/H2O2
(o) 2,3-dimethyl-1-butene + HBr/heat (in the presence of a free radical inhibitor)
(p) 1,2-dimethylcyclopentene + HCl
(q) 1-hexene + HCl/heat
(r) cis-3-hexene + O3
(s) product of (r) + Zn/H2O
(t) 1-methylcyclopentene + Cl2/H2O
(u) 1-methylcyclopentene + H2/Pt
(v) 1-hexene + HBr/peroxides
(w) 1-methylcyclopentene + O3
(x) product of (w) + Zn/H2O
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3.16 Many animals, especially insects, secrete substances known as pheromones. These
compounds produce a specific response. Some pheromones are warning substances, others are
sex attractants, and others induce members of a species to aggregate. The sex attractant
pheromone has been identifies and synthesized. This compound is unusual in that it attracts both
male and female gypsy moths. This pheromone is potentially useful in pest control of gypsy
moths. The last step in the laboratory synthesis of this pheromone is the reaction of cis-2methyl-7-octadecene with a peroxy acid. Draw the structure of the gypsy moth pheromone.
3.17 The alarm pheromone of the green peach aphid has the molecular formula C15H24. During
catalytic hydrogenation of this compound, it absorbs four moles of hydrogen and produces
2,6,10-trimethyldodecane. With ozonolysis, followed by treatment with zinc and water, one
mole of the pheromone produces one mole of acetone, two mole of formaldehyde, and one mole
of each of the following two compounds:
Propose a structure for the green peach aphid alarm pheromone. Neglect possible cis-trans
isomerism.
3.18 Derive a possible mechanism for the following reaction;
(This is a good mechanism question.)
3.19 Outline the reaction(s) necessary to convert each of the following to 1-pentyne.
(a) 1-chloropentane (c) 1,1-dichloropentane
(e) 1-chloro-1-pentene
(b) 1-pentene
(d) 1-bromopropane and acetylene
3.20 What are the IUPAC names of the following alkynes?
(a) sec-butyl methylacetylene
(b) diisopropylacetylene
(c) di-tert-butylacetylene
(d) CH3CH(CH3)C≡CH
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3.21 Outline a reasonable synthesis for each of the following compounds. You may begin with
coke, water, methane, lime, any compound synthesized in another part, or any inorganic
reagents.
(a) acetylene
(d) 2,2-dichloropropane
(g) 1-butene
(b) propene
(e) cis-2-butene
(h) sec-butyl alcohol
(c) acetone
(f) trans-2-butene
(i) racemic-2,3-dibromobutane
3.22 Draw the structure of each product that would form when 1-pentyne reacts with each of the
following.
(i) H2, Ni2B (P-2)
(a) two molar equivalents of HCl
(e) Cu(NH3)2OH
(b) one molar equivalent of HCl
(f) Ag(NH3)2OH
(j) (1) (Sia)2BH (2) CH3COOH
(c) one molar equivalent of Br2
(g) NaNH2 inNH3(l) (k) (1) (Sia)2BH (2) OH-, H2O2
(d) H2O, H+, Hg2+
(h) (g)then CH3I
(l) one molar equivalent HBr and
peroxides
3.23 Draw the structure of each product that would form when 3-hexyne reacts with each of the
following.
(g) H2, Ni2B (P-2)
(m) (1) (Sia)2BH (2) CH3COOH
(a) one molar equivalent of Br2
(b) two molar equivalents of Br2
(h) H2O, H+, Hg2+
(n) (1) (Sia)2BH (2) OH-, H2O2
(c) one molar equivalent of HCl
(i) Ag(NH3)2OH
(o) NaNH2 inNH3(l)
(d) two molar equivalents of HCl
(j) Cu(NH3)2OH
(p) (1) KMnO4, OH- (2) H+
(q) two molar equivalents H2/Pt
(e) one molar equivalents of HBr
(k) NaOH, H2O
(f) Li/NH3
(l) O3, H2O
(r) HgSO4, H2SO4, H2O
3.24 It is possible to differentiate the compounds in each of the following pairs with a simple
test. In each case, what would you see in the test, and what are the reactions involved?
(a) propyne and propane
(b) propyne and propene
(c) 2-bromobutane and 2-butyne
(d) 2-bromopropene and 1-bromopropene
(e) 2-bromo-2-butene and 2-butyne
(f) 2-bromo-2-butene and 1-butyne
(g) CH3CH2CH2CH2OH and CH3C≡CCH2OH
(h) CH3CH2CH2CH2OH and CH3CH=CHCH2OH
(i) 2-bromobutane and 2-butyne
3.25 Synthesize each of the following compounds beginning with 3-methyl-1-butyne and any
inorganic reagents. (a) (CH3)2CHCH2CH2Br (b) (CH3)2CHCHClCH3 (c) (CH3)2CHCOOH
3.26 Suggest a method for carrying out each of the following.
(a) convert cyclohexylacetylene into methyl cyclohexyl ketone
(b) convert methyl cyclohexyl ketone into 2-cyclohexylethanal
3.27 Heating (R)-2-butanol in aqueous strong acid causes a gradual loss in optical activity.
Prolonged heating yields a solution of (±)-2-butanol. Develop a mechanism to explain this.
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3.28 Three compounds (A, B, and C) have the molecular formula C5H8. All three compounds
are soluble in cold concentrated sulfuric acid, all give a positive Baeyer’s test, and all three
decolorize bromine in carbon tetrachloride rapidly. Upon treatment with ammoniacal silver
nitrate, only compound A gives a precipitate. When compounds A and B react with excess
hydrogen in the presence of a catalyst, both will produce pentane. Compound C reacts with
excess hydrogen in the presence of a catalyst to produce C5H10. (a) Draw the structures of A, B,
and C. (b) Are there alternate structures for B and C? (c) When compound B undergoes
oxidative cleavage with hot basic KMnO4, the products after acidification are acetic acid and
propionic acid. What is the structure of B? (d) Ozonolysis of compound C, followed by
acidification, gives HOOCCH2CH2CH2COOH. What is the structure of C?
3.29 Develop a reaction scheme to carry out the following transformations. If deuterium is
necessary, you may use D2, (BD3)2, or CH3COOD.
O
(a) CH3 CH2 C
CH
CH3 CH2 C
CH3
CH3 CH2
(b) CH3 CH2 C
CH
H
C
C
H
D
CH3
(c) CH3 C
C
CH3
CH3
C
D
C
D
O
(d)
C
CH
CH2 CH
EXAM 4
4.1 In each of the following cases, use the spectral data provided to propose a structure for the
compound.
1
H NMR
(a) Formula: C4H10O
Singlet,
δ1.28 (9H)
Singlet,
δ1.35 (1H)
1
(b) Formula: C3H7Br
H NMR
Doublet,
δ1.71 (6H)
Septet,
δ4.32 (1H)
1
(c) Formula: C4H9Cl
H NMR
Doublet,
δ1.04 (6H)
Multiplet,
δ1.95 (1H)
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(d) Formula: C4H8O
(e) Formula: C7H8O
(f) Formula:
C15H14O
(g) Formula: C4H7BrO2
(h) Formula: C8H10
(i) Formula:
C4H8O3
(j) Formula:
C3H7NO2
(k) Formula: C4H10O2
Doublet,
δ3.35 (2H)
1
H NMR
Triplet,
δ1.05 (3H)
Singlet,
δ2.13 (3H)
Quartet,
δ2.47 (2H)
IR spectrum
1720 cm-1
1
H NMR
Singlet,
δ2.43 (1H)
Singlet,
δ4.58 (2H)
Multiplet,
δ7.28 (5H)
IR spectrum
Broad peak in 3200-3550 cm-1 region
1
H NMR
Singlet,
δ2.20 (3H)
Singlet,
δ5.08 (1H)
Multiplet,
δ7.25 (10H)
IR spectrum
Strong peak near 1720 cm-1
1
H NMR
Triplet,
δ1.08 (3H)
Multiplet,
δ2.07 (2H)
Triplet,
δ4.23 (1H)
Singlet,
δ10.97 (1H)
IR spectrum
Broad peak in 2500-3000 cm-1 region
Peak at 1715 cm-1
1
H NMR
Triplet,
δ1.25 (3H)
Quartet,
δ2.68 (2H)
Multiplet,
δ7.23 (5H)
1
H NMR
Triplet,
δ1.27 (3H)
Quartet,
δ3.66 (2H)
Singlet,
δ4.13 (2H)
Singlet,
δ10.95 (1H)
IR spectrum
Broad peak in 2500-3000 cm-1 region
Peak at 1715 cm-1
1
H NMR
Doublet,
δ1.55 (6H)
Septet,
δ4.67 (1H)
1
H NMR
Singlet,
δ3.25 (6H)
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Singlet,
(l) Formula:
C5H10O
(m) Formula: C8H9Br
δ3.45 (4H)
1
H NMR
Doublet,
δ1.10 (6H)
Singlet,
δ2.10 (3H)
Septet,
δ2.50 (1H)
IR spectrum
Strong peak near 1720 cm-1
1
H NMR
Doublet,
δ2.0 (3H)
Quartet,
δ5.15 (1H)
Multiplet,
δ7.35 (5H)
4.2 Draw the structure of the product(s) of each of the following reactions of ethylene oxide.
(a) + KI/H2O Æ C2H5IO
(b) + NH3 Æ C2H7NO
(c) + H+/CH3OH Æ C3H8O2
(d) + CH3ONa/CH3OH Æ C3H8O2
(e) + H+/EtOH Æ C4H10O2
4.3 The reaction of propene oxide with sodium ethoxide in ethanol produces 1-ethoxy-2propanol and a very small amount of 2-ethoxy-1-propanol. Discuss what factor leads to this
observation.
4.4 Draw the structure of the product(s) of each of the following reactions of E-2-pentene. (Use
N.R. to indicate no reaction.)
(a) MCPBA
(b) BH3•THF/H3O+
(c) KMnO4/KOH
(d) O3/H2O2
4.5 (a) How many sets of equivalent hydrogen atoms are in each of the following compounds?
(b) What would be the observed proton NMR splitting of each set? (i.e., singlets, doublets, etc.)
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4.6 (a) How many sets of equivalent hydrogen atoms are in each of the following compounds?
(b) What would be the observed proton NMR splitting of each set?
(1) 1-pentene
(6) cis-1,2-dimethylcyclopropane
(2) CH3CH2OH
(7) trans-1,2-dimethylcyclopropane
(3) CH3CH=CH2
(8) 1,2-dibromopropane
(4) CH3CH2CH2CH3
(9) trans-2-butene
(5) 1,1-dimethylcyclopropane (10) 1-butene
4.7 Compound A has the molecular formula of C6H8. In the presence of a catalyst, compound A
will react with two molar equivalents of hydrogen to form compound B. The formula of
compound is C6H12. The proton decoupled C-13 NMR of compound A has two singlets. One
singlet is at 26.0, and the other is at 124.5. In the C-13 off resonance NMR of compound A, the
26.0 signal splits into a triplet, and the other signal splits into a doublet. What are the structures
of A and B?
4.8 Compound C has a molecular formula C4H8O2. The proton NMR of a CDCl3 solution of
compound C has four signals. There is a doublet at δ1.35, a singlet at δ2.15, a broad singlet at
δ3.75 (1H), and a quartet at δ4.25 (1H). In D2O, the NMR signal is similar, except that the δ3.75
signal is no longer present. In the infrared spectrum, Compound C has a strong absorption near
1720 cm-1. (a) Draw the structure of compound C. (b) Why is the δ3.75 signal not present in
D2O?
4.9 Compound D has the molecular formula C9H10. Compound D will decolorize a Br2/CCl4
solution. The infrared spectrum contains the following peaks:
3035 cm-1 (m)
2853 cm-1 (w)
915 cm-1 (s)
1640 cm-1 (m)
740 cm-1 (s)
3020 cm-1 (m)
-1
-1
2925 cm (m)
990 cm (s)
695 cm-1 (s)
The proton NMR has:
Doublet
δ3.1(2H)
Multiplet
δ5.1 Multiplet
δ7.1(5H)
Multiplet
δ4.8
Multiplet
δ5.8
There is a peak in the ultraviolet spectrum at 255 nm. (a) What is the structure of compound D?
(b) Assign each of the infrared peaks.
4.10 Compound E contains carbon, hydrogen, chlorine, and no other elements. The infrared
spectrum is simple and contains the following peaks:
3125 cm-1 (m)
1280 cm-1 (m)
695 cm-1 (s)
-1
-1
820 cm (s)
1625 cm (m)
The proton NMR of compound E contains a singlet at δ6.3. (a) What is the structure of
compound E? (b) Assign each of the infrared peaks.
4.11 What is a simple chemical test that would distinguish between the members of each of the
following pairs?
(a) allyl propyl ether and dipropyl ether
(b) phenol and benzyl alcohol
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(c) cyclohexane and cyclohexanol
(d) cyclohexene and cyclohexanol
4.12 Retrosynthetic analysis – Give a reasonable synthesis for each of the following compounds
from the indicated starting materials.
(a) 1-phenylethanol from styrene
(b) 2-phenylethanol from styrene
(c) 1-methoxy-2-phenylethane fro styrene
(d) ethyl 1-phenylethyl ether from 1-phenylethasnol
(e) 2-phenylethanol from phenylacetic acid
(f) 1-phenylethanol from methyl phenyl ketone
(g) 2-phenylethanol from methylphenylacetate
4.13 Retrosynthetic analysis – Give a reasonable synthesis for each of the following compounds
from the indicated starting materials. Outline the synthesis of each of the following beginning
with 1-butanol and any inorganic reagents.
(a) 1-butanol
(i) 1-butene
(b) 3-methyl-3-heptanol
(j) octane
(c) 1-hexene
(k) butyllithium
(d) 1-pentanol
(l) dibutyl ether
(e) 2-bromobutane
(m) butyl sec-butyl ether
(f) 1-bromobutane
(n) pentanoic acid
(g) 2-butanone
(o) 3-methyl-4-heptanol
(h) 2-butanol
(p) 4-octanol
4.14 Give the MAJOR organic products for each of the following reactions:
(a) 1-propanol + methylsulfonyl chloride
(f) 1-propanol + KMnO4/OH-/hot
(b) 1-propanol + reflux with con HBr
(g) 1-propanol + p-toluenesulfonyl chloride
(h) 1-propanol + acetyl chloride
(c) 1-propanol + H2SO4/140°C
(d) 1-propanol + thionyl chloride
(i) 1-propanol + sodium metal
(j) 1-propanol + (1) sodium metal
(e) 1-propanol + PCl3
(2) 1-bromobutane
4.15 Give the MAJOR organic products for each of the following reactions:
(a) cyclohexanol + acetic anhydride
(b) benzyl alcohol + KMnO4/OH-/hot
(c) benzyl alcohol + NaH
(d) benzyl alcohol + PCC
(e) cis-3-hexene + MCPBA
(f) product of (e) + H3O+/H2O
(g) propylene oxide + H3O+/H2O
(h) ethanol + ethylene oxide/OH-
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4.16 Give a suitable mechanism to explain the following. Use curved arrows to show flow of
electrons. The process follows first order kinetics.
CH3
CH3
CH3
OH
H3O+
CH3
4.17 Give a suitable mechanism to explain the following. Use curved arrows to show flow of
electrons. The product shown is the only product.
4.17 Compound F has the molecular formula C10H14O. This compound is insoluble in aqueous
sodium bicarbonate, but it is soluble in aqueous sodium hydroxide. Bromine water converts
compound F into C10H12Br2O. In the 3000-4000 cm-1 region, compound F has a broad peak at
about 3250 cm-1. There is also a strong peak at 830 cm-1. The proton NMR has the following:
Singlet δ1.3(9H)
Singlet δ4.9 (1H)
Multiplet
δ7.0(4H)
Draw the structure of compound F.
4.18 Beginning with D2O, magnesium, dry ether, and t-butyl bromide outline a synthesis for the
following compound.
4.19 The following is the mass spectrum of an organic liquid that does not absorb in the UV.
Determine the structure of the compound.
m/e
Relative
m/e
Relative
m/e
Relative
Intensity
m/e
Relative
m/e
Relative
27
7.5
44
6.0
71
1.0
28
7.3
45
0.2
72
1.2
29
7.6
55
1.0
86
100.
30
14.0
56
5.2
87
5.9
31
0.2
57
1.0
88
0.1
41
2.5
58
12.0
100
8.0
42
10.0
59
0.4
101
21.0
43
1.5
70
2.0
102
1.7
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FINAL REVIEW
Look over all assigned problems. You will not have time to re-work all of them. However, you
should re-work (without looking at the solution), any problem you do not immediately recognize.
Review all exams, pay particular attention to any question for which you did not receive full
credit.
Review “thought questions,” “exam questions,” and “asides” from the class notes.
The ACS final includes basic lab questions.
F.1 Draw the structure of propanal and predict the hybridization about each carbon atom.
F.2 Sketch and label energy level diagrams for each of the following. (a) a free radical
bromination (b) a SN1 mechanism (c) a SN2 mechanism (d) an E1 mechanism (e) an E2
mechanism Which steps are endothermic and which are exothermic? Write the general rate law
for mechanisms b-e.
F.3 Rank the following classes of compounds in order from the strongest acid to the weakest
acid (strongest base). (a) alkane (b) alkene (c) terminal alkyne (d) ether (e) alcohol (f) phenol (g)
carboxylic acid (h) primary amine (i) secondary amine (j) tertiary amine
F.4 Draw the structural formula for the products that result when 2-pentene reacts with each of
the following.
(a) HCl
(g) O3, then Zn, H2O
(m) cold con H2SO4
(b) HBr
(h) THF:BH3, then H2O2, OH-, H2O (n) Br2 in CCl4, then KI in acetone
(o) KMnO4, OH-, heat then H+
(c) HI
(i) dilute KMnO4, OH-, cold
(d) D2, Pt
(j) OsO4, then Na2SO3/H2O
(p) THF:BH3, then CH3COOH
(q) 1) Hg(OAc)2, H2O 2) NaBH4
(e) HBr, peroxides
(k) Br2 in CCl4, dark
F.5 (a) Which reagent(s) are necessary to convert 2-pentyne to E-2-pentene? (b) Which
reagent(s) are necessary to convert 2-pentyne to Z-2-pentene?
F.6 Rank the following carbocations in order of increasing stability. Explain why you placed
them in the order you chose.
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(A)
(C)
CH3CHCH2CHCH2CH3
CH3CHCH2CHCH2CH3
Cl
CH3
(B)
(D)
CH3CHCH2CHCH2CH3
CH3
CH3CHCH2CCH2CH3
CH3
F
F.7 Below are several pairs of structures. Describe the relationship between the two members of
each pair. (Are the members of each pair enantiomers, diastereomers, structural isomers, or two
views of the same compound?) In each case, identify any chiral carbon atoms (stereogenic
carbon atoms = stereocenters).
(a)
CH3
CH3
HO
H
H
OH
HO
H
H
OH
CH2 CH3
CH2 CH3
CH3
CH3
(b)
(c)
H
H
HO
OH
HO
OH
H
H
CH2 CH3
CH2 CH3
(d)
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CH3
CH3
HO
H
H
OH
H
OH
HO
H
CH2 CH3
CH2 CH3
F.8 Draw the structure of each product that would form when 1-pentyne reacts with each of the
following. (a) (Sia)2BH (2) CH3COOH (b) (Sia)2BH (2) OH-, H2O2 (c) HgSO4, H2SO4, H2O
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