Organic Problems

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Copyright 2008 Sevagram Enterprises

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: (a) C2H6 (b) H2O (c) CO2 (d) HCN (e) C2H4 (f) C2H2 (g) Br2 (h) H2O2 (i) N2 (j) SO4

2- (k) NCl3 (l) CH2O (m) HNO2 (n) KNO3 (o) CH4O (p) H2CO3 (q) C2H5OH (r) HC2H3O2 (s) NaHCO3 (t) CaCO3 (u) BH3 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 (g) CH3OCH3 (h) CHCl3 (i) BF3 (j) CH3OH 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. (a) CH3-NO2 (b) CH3-S-CH2

+ (c) CH2=CH-Cl (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. (a) ammonia, NH3 (e) cyanide ion, CN- (i) methylamine,CH3NH2 (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, HCOO- 2.2 Beginning with propyl bromide, and any other appropriate compounds, illustrate how a nucleophilic substitution reaction may be used to synthesize each of the following. a. CH3CH2CH2OH b. CH3CH2OCH2CH2CH3 c. CH3CH2CH2CN

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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- CH3CH2OH + I- or CH3CH2I + SH- CH3CH2SH + I- (b) CH3CH2I + CH3S-(1.0 M) CH3CH2SH + I- or CH3CH2I + CH3S-(2.0 M) CH3CH2SH + I- (c) CH3CH2CH2Br + CH3OH CH3CH2CH2OCH3 + HBr or CH3CH2CH2Br + CH3O- CH3CH2CH2OCH3 + Br- (d) CH3Br + CH3SH CH3SCH3 + HBr or CH3Br + CH3OH 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 (CH3)3COH + HBr or (CH3)3CBr + CH3OH (CH3)3COCH3 + HBr (b) (CH3)3CCl + CH3O-(0.001 M) (CH3)3COCH3 + Cl- or (CH3)3CCl + CH3O-(0.01 M) (CH3)3COCH3 + Cl- (c) (CH3)3CI + CH3OH (CH3)3COCH3 + HI or (CH3)3CCl + CH3OH (CH3)3COCH3 + HCl (d) (CH3)2C=CHCl + H2O (CH3)2C=CHOH + HCl or (CH3)3CCl + H2O (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 CH3CH2OH + H:- (b) NH3 + CH3CH2OH2

+ CH3CH2NH3+ + H2O

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(c) CH3CH=CHBr + CH3S- CH3CH=CHSCH3 + Br- (d) (CH3)3CBr + CN- (CH3)3C-CN + Br- (e) cyclopentane + H2O CH3CH2CH2CH2CH2OH 2.9 Which of the following reactions would give the higher yield of isopropyl methyl ether? Explain your choice. (a) (CH3)2CHONa + CH3I CH3OCH(CH3)2 (b) CH3ONa + (CH3)2CHI 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 + CH3O- °/CH OH

b. (CH3)3CO- + CH3I °/ CH COH

c. CH3CH2CH2CH2Br + CH3O- °/CH OH

d. CH3CH2CH2CH2Br + (CH3)3CO- °/ CH COH

e. C2H5O- + CH3CH2CHBrCH2CH3 °/CH CH OH

f. CH3CHBrCH3 + (CH3)3CO- °/ CH COH

g.

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 CH3COO- 2.12 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, t-butyl chloride primarily yields (CH3)3OCH2CH3. 2.17 What are the IUPAC names for each of the following compounds?

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CH2

C C

CH2

H

H

(a) (b)

CH3

CH3CH2

CH3

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 1-methylcyclohexene 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 (c) CH3CH2CH(CH3)CH2Br (d) CH3CHBrCH(CH3)CH3

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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HO

CH3

CH3

H

CH3

H

CH3

CH3

H

CH3

CH3 CH3

H+

H

CH3

H

CH3

CH3

CH3

CH3 CH3

CH3 CH3

13(18)-oleanene

3 -friedelanol

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34

56

7

8

9

10

1112

13

1415

16

17

18

1920

21

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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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CH3CH3

OH H+

heat

CH3

CH3

CH2

CH3

CH3

CH3

minor

++

major (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)

BrHCH3

ClH

CH3

ClHCH3

BrH

CH3 (f)

(g)

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(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 1,2-dimethylcyclopentene. (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- CH3CH2CH2CHDCN + Br-

(b) (-)CH3CH2CH(CH3)CH2Cl OH /SN CH3Ch2CH(CH3)CH2OH

(c) (+)CH3CH(OH)CClO NH

CH3CH(OH)C(NH2)O (d) (-)C6H13CHBrCH3 + I- C6H13CHICH3 + Br-

(e) (-)C6H13CH(OH)CH3 H O

C6H13CH(OH)CH3 (f) (+)CH3CH2CI(CH3)CH2CH2CH3 CH3OH CH3CH2C(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 2-butene 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 (e) CH3CHDCH2CH3 (l) CH3CH2CH2CH3 (s) CH3CH2CH2CH2OCH3 (f) CH3CH2CH2CH2OH (m) CH3CH2CHBrCH3 (t) CH3CHDCH(OH)CH3 (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-2-methyl-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. (a) two molar equivalents of HCl (e) Cu(NH3)2OH (i) H2, Ni2B (P-2) (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. (a) one molar equivalent of Br2 (g) H2, Ni2B (P-2) (m) (1) (Sia)2BH (2) CH3COOH (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+ (e) one molar equivalents of HBr (k) NaOH, H2O (q) two molar equivalents H2/Pt (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.

C CHCH2CH3CH3 CH2 C CH3

O

C CHCH2CH3

CH3 CH2

C C

H

H D

C C CH3CH3

CH3

C C

CH3

DD

C CH CH2 CH

O

(a)

(b)

(c)

(d)

EXAM 4 4.1 In each of the following cases, use the spectral data provided to propose a structure for the compound. (a) Formula: C4H10O 1H NMR Singlet, δ1.28 (9H) Singlet, δ1.35 (1H) (b) Formula: C3H7Br 1H NMR Doublet, δ1.71 (6H) Septet, δ4.32 (1H) (c) Formula: C4H9Cl 1H NMR Doublet, δ1.04 (6H) Multiplet, δ1.95 (1H)

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Doublet, δ3.35 (2H) (d) Formula: C4H8O 1H NMR Triplet, δ1.05 (3H) Singlet, δ2.13 (3H) Quartet, δ2.47 (2H) IR spectrum 1720 cm-1 (e) Formula: C7H8O 1H NMR Singlet, δ2.43 (1H) Singlet, δ4.58 (2H) Multiplet, δ7.28 (5H) IR spectrum Broad peak in 3200-3550 cm-1 region (f) Formula: C15H14O 1H NMR Singlet, δ2.20 (3H) Singlet, δ5.08 (1H) Multiplet, δ7.25 (10H) IR spectrum Strong peak near 1720 cm-1 (g) Formula: C4H7BrO2 1H 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 (h) Formula: C8H10 1H NMR Triplet, δ1.25 (3H) Quartet, δ2.68 (2H) Multiplet, δ7.23 (5H) (i) Formula: C4H8O3 1H 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 (j) Formula: C3H7NO2 1H NMR Doublet, δ1.55 (6H) Septet, δ4.67 (1H) (k) Formula: C4H10O2 1H NMR Singlet, δ3.25 (6H)

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Singlet, δ3.45 (4H) (l) Formula: C5H10O 1H NMR Doublet, δ1.10 (6H) Singlet, δ2.10 (3H) Septet, δ2.50 (1H) IR spectrum Strong peak near 1720 cm-1 (m) Formula: C8H9Br 1H 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 C2H5IO (b) + NH3 C2H7NO (c) + H+/CH3OH C3H8O2 (d) + CH3ONa/CH3OH C3H8O2 (e) + H+/EtOH C4H10O2 4.3 The reaction of propene oxide with sodium ethoxide in ethanol produces 1-ethoxy-2-propanol 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) 3020 cm-1 (m) 1640 cm-1 (m) 740 cm-1 (s) 2925 cm-1 (m) 990 cm-1 (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) 1625 cm-1 (m) 820 cm-1 (s) 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 (c) 1-propanol + H2SO4/140°C (h) 1-propanol + acetyl chloride (d) 1-propanol + thionyl chloride (i) 1-propanol + sodium metal (e) 1-propanol + PCl3 (j) 1-propanol + (1) sodium metal (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.

OHCH3CH3 CH3

CH3

H3O+

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 (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, dark (q) 1) Hg(OAc)2, H2O 2) NaBH4 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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CH3CHCH2CHCH2CH3

Cl

CH3CHCH2CHCH2CH3

CH3

CH3CHCH2CHCH2CH3

F

CH3CHCH2CCH2CH3

CH3

CH3

(A) (C)

(B) (D)

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

HO H

HHO

CH2 CH3

CH3

H OH

OHH

CH2 CH3 (b)

(c)

CH3

H H

OHHO

CH2 CH3

CH3

HO OH

HH

CH2 CH3 (d)

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CH3

HO H

OHH

CH2 CH3

CH3

H OH

HHO

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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