Use clues provided by the products of reactions, such as ozonolysis, to determine the

Predict the major products of the following reactions, and propose mechanisms to support your predictions. (a) pent-1-ene + HCl (b) 2-methylpropene + HCl (c) 1-methylcyclohexene + HI (d) 4-methylcyclohexene + HBr

(a) When 1 mole of buta-1,3-diene reacts with 1 mole of HBr, both 3-bromobut-1-ene and 1-bromobut-2-ene are formed. Propose a mechanism to account for this mixture of products. (b) When 1-chlorocyclohexene reacts with HBr, the major product is 1-bromo1-chlorocyclohexane. Propose a mechanism for this reaction, and explain why your proposed intermediate is more stable than the other possible intermediate.

Predict the major products of the following reactions, and propose mechanisms to support your predictions. 1-methylcyclopentene + HBr + CH3 C O O C CH3 O O (a) (phenyl = Ph = ) (b) 1-phenylpropene + HBr + di-tert-butyl peroxide

Show how you would accomplish the following synthetic conversions. (a) but@1@ene 1@bromobutane (b) but@1@ene 2@bromobutane (c) 2@methylcyclohexanol 1@bromo@1@methylcyclohexane (d) 2@methylbutan@2@ol 2@bromo@3@methylbutane

Propose a mechanism to show how 3,3-dimethylbut-1-ene reacts with dilute aqueous H2SO4 to give 2,3-dimethylbutan-2-ol and a small amount of 2,3-dimethylbut-2-ene.

Predict the products of the following hydration reactions. (a) 1@methylcyclopentene + dilute acid (b) 2@phenylpropene + dilute acid (c) 1@phenylcyclohexene + dilute acid

(a) Propose a mechanism for the following reaction. (b) Give the structure of the product that results when this intermediate is reduced by sodium borohydride.

Predict the major products of the following reactions. (a) 1@methylcyclohexene + aqueous Hg(OAc)2 (b) the product from part (a), treated with NaBH4 (c) 4@chlorocycloheptene + Hg(OAc)2 in CH3OH (d) the product from part (c), treated with NaBH4

Show how you would accomplish the following synthetic conversions. (a) \(\text { but-1-ene } \rightarrow \text { 2-methoxybutane }\) (b) \(\text { 1-iodo-2-methylcyclopentane } \rightarrow \text { 1-methylcyclopentanol }\) (c) \(\text { 3-methylpent-1-ene } \rightarrow \text { 3-methylpentan-2-ol }\) Explain why acid-catalyzed hydration would be a poor choice for the reaction in (c).

Predict the major products of the following reactions. (a) propene + BH3 # THF (b) the product from part (a) + H2O2>OH(c) 2@methylpent@2@ene + BH3 # THF (d) the product from part (c) + H2O2>OH(e) 1@methylcyclohexene + BH3 # THF (f) the product from part (e) + H2O2>OH

Show how you would accomplish the following synthetic conversions. (a) but@1@ene S butan@1@ol (b) but@1@ene S butan@2@ol (c) 2@bromo@2,4@dimethylpentane S 2,4@dimethylpentan@3@ol

In the hydroboration of 1-methylcyclopentene shown in Solved Problem 8-3, the reagents are achiral, and the products are chiral. The product is a racemic mixture of trans-2- methylcyclopentanol, but only one enantiomer is shown. Show how the other enantiomer is formed.

Predict the major products of the following reactions. Include stereochemistry where applicable. (a) \(\text { 1-methylcyclohentene }+\mathrm{BH}_{2} \cdot \text { THF then } \mathrm{H}_{2} \mathrm{O}_{2} \mathrm{OH}^{-}\) (b) \(\text { trans-4,4-dimethylpent-2-ene }+\mathrm{BH}_{3} \cdot \mathrm{THF} \text {, then } \mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{OH}^{-}\) (c)

(a) When (Z)-3-methylhex-3-ene undergoes hydroborationoxidation, two isomeric products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the relationship between these isomers? (b) Repeat part (a) for (E)-3-methylhex-3-ene. What is the relationship between the products formed from (Z)-3-methylhex-3-ene and those formed from (E)-3-methylhex-3-ene?

Show how you would accomplish the following transformations.

(a) When HBr adds across the double bond of 1,2-dimethylcyclopentene, the product is a mixture of the cis and trans isomers. Show why this addition is not stereospecific. (b) When 1,2-dimethylcyclopentene undergoes hydroborationoxidation, one diastereomer of the product predominates. Show why this addition is stereospecific, and predict the stereochemistry of the major product.

Give mechanisms to account for the stereochemistry of the products observed from the addition of bromine to cis- and trans-but-2-ene (Figure 8-5). Why are two products formed from the cis isomer but only one from the trans? (Making models will be helpful.)

Propose mechanisms and predict the major products of the following reactions. Include stereochemistry where appropriate. (a) \(\text { cycloheptene }+\mathrm{Br}_{2} \text { in } \mathrm{CH}_{2} \mathrm{Cl}_{2}\) (b) (c) \(\text { (E)-dec-3-ene }+\mathrm{Br}_{2} \text { in } \mathrm{CCl}_{4}\) (d) \(\text { (Z)-dec-3-ene }+\mathrm{Br}_{2} \text { in } \mathrm{CCl}_{4}\)

Propose a mechanism for the addition of bromine water to cyclopentene, being careful to show why the trans product results and how both enantiomers are formed.

The solutions to Solved Problem 8-5 and Solved Problem 8-6 showed only how one enantiomer of the product is formed. For each product, show how an equally probable reaction forms the other enantiomer.

Predict the major product(s) for each reaction. Include stereochemistry where appropriate. (a) 1@methylcyclohexene + Cl2>H2O (b) 2@methylbut@2@ene + Br2>H2O (c) cis@but@2@ene + Cl2>H2O (d) trans@but@2@ene + Cl2>H2O (e) 1@methylcyclopentene + Br2 in saturated aqueous NaCl

Show how you would accomplish the following synthetic conversions. (a) 3-methylpent-2-ene \(\rightarrow\) 2-chloro-3-methylpentan-3-ol (b) chlorocyclohexane \(\rightarrow\) trans-2-chlorocyclohexanol (c) 1-methylcyclopentanol \(\rightarrow\) 2-chloro-1-methylcyclopentanol

Give the expected major product for each reaction, including stereochemistry where applicable. (a) but@1@ene + H2>Pt (b) cis@but@2@ene + H2>Ni (c) (c) + H2/Pt (d) (d) + excess H2/Pt

One of the principal components of lemongrass oil is limonene, C10H16. When limonene is treated with excess hydrogen and a platinum catalyst, the product is an alkane of formula C10H20. What can you conclude about the structure of limonene?

The chiral BINAP ligand shown in Figure 8-8 contains no asymmetric carbon atoms. Explain how this ligand is chiral.

Predict the carbenoid addition products of the following reactions. (a) \(\text { trans-hex-3-ene }+\mathrm{CH}_{2} \mathrm{I}_{2}, \mathrm{Zn}(\mathrm{Cu})\) (b) \(\text { cis-hept-2-ene }+\mathrm{CH}_{2} \mathrm{I}_{2}, \mathrm{Zn}(\mathrm{Cu})\)

Predict the carbene addition products of the following reactions. (a) cyclohexene + CHCl3, 50% NaOH>H2O (b) + CH2I2, Zn(Cu) (b) H3C OH (c) (c) CHBr2 + 50% NaOH/H2O

Show how you would accomplish each of the following synthetic conversions. (a) trans@but@2@ene trans@1,2@dimethylcyclopropane H Br (b) cyclopentene (c) cyclohexanol Cl Cl

Predict the products, including stereochemistry where appropriate, for the m-chloroperoxybenzoic acid epoxidations of the following alkenes. (a) cis-hex-2-ene (b) trans-hex-2-ene (c) cis-cyclodecene (d) trans-cyclodecene

(a) Propose a mechanism for the conversion of cis-hex-3-ene to the epoxide (3,4-epoxyhexane) and the ring-opening reaction to give the glycol, hexane-3,4-diol. In your mechanism, pay particular attention to the stereochemistry of the intermediates and products. (b) Repeat part (a) for trans-hex-3-ene. Compare the products obtained from cis- and trans-hex-3-ene. Is this reaction sequence stereospecific?

Magnesium monoperoxyphthalate (MMPP) epoxidizes alkenes much like mCPBA. MMPP is more stable, however, and it may be safer to use for large-scale and industrial reactions. Propose a mechanism for the reaction of trans-2-methylhept-3-ene with MMPP, and predict the structure of the product(s).

Predict the major products of the following reactions. (a) cis@hex@2@ene + mCPBA in chloroform (b) trans@hex@3@ene + peroxyacetic acid (CH3CO3H) in water (c) 1@methylcyclohexene + MMPP in ethanol (d) trans@cyclodecene + peroxyacetic acid in acidic water (e) cis@cyclodecene + mCPBA in CH2Cl2, then dilute aqueous acid

When 1,2-epoxycyclohexane (cyclohexene oxide) is treated with anhydrous HCl in methanol, the principal product is trans-2-methoxycyclohexanol. Propose a mechanism to account for the formation of this product.

Predict the major products of the following reactions, including stereochemistry. (a) cyclohexene + KMnO4>H2O (cold, dilute) (b) cyclohexene + peroxyacetic acid in water (c) cis@pent@2@ene + OsO4>H2O2 (d) cis@pent@2@ene + peroxyacetic acid in water (e) trans@pent@2@ene + OsO4>H2O2 (f) trans@pent@2@ene + peroxyacetic acid in water

Show how you would accomplish the following conversions. (a) cis-hex-3-ene to meso-hexane-3,4-diol (b) cis-hex-3-ene to (d,l)-hexane-3,4-diol (c) trans-hex-3-ene to meso-hexane-3,4-diol (d) trans-hex-3-ene to (d,l)-hexane-3,4-diol

Give structures of the alkenes that would give the following products upon ozonolysis reduction. O O CH3 C CH2 CH2 CH2 C CH2 CH3 (a) and CH2 C O H O cyclohexanone CH3 CH2 (b) and O CH3 CH2 C CH2 CH2 CH2 CH3 O (c) CH3 CH2 C H

Predict the major products of the following reactions. (a) (E)@3@methyloct@3@ene + ozone, then (CH3)2S (b) (Z)@3@methyloct@3@ene + warm, concentrated KMnO4 O3, then (CH3) (c) + 2S (d) 1@ethylcycloheptene + ozone, then (CH3)2S (e) 1@ethylcycloheptene + warm, concentrated KMnO4 (f) 1@ethylcycloheptene + cold, dilute KMnO4

(a) Propose a mechanism for the following reaction. 2 (CH3)2CCHCH3 + cat. H+ 2,3,4,4@tetramethylhex@2@ene (b) Show the first three steps (as far as the tetramer) in the BF3@catalyzed polymerization of propylene to form polypropylene.

When cyclohexanol is dehydrated to cyclohexene, a gummy green substance forms on the bottom of the flask. Suggest what this residue might be, and propose a mechanism for its formation (as far as the dimer).

Show the intermediate that would result if the growing chain added to the other end of the styrene double bond. Explain why the final polymer has phenyl groups substituted on alternate carbon atoms rather than randomly distributed.

The structures of three monomers are shown. In each case, show the structure of the polymer that would result from polymerization of the monomer. Vinyl chloride is polymerized to “vinyl” plastics and PVC pipe. Tetrafluoroethylene polymerizes to Teflon®, used as non-stick coatings and PTFE valves and gaskets. Acrylonitrile is polymerized to Orlon®, used in sweaters and carpets.

Draw a mechanism for a base-catalyzed polymerization of methyl a@methacrylate to give the Plexiglas polymer. C C H COOCH3 H CH3 methyl -methacrylate

Propose a mechanism for the triolefin process using a metal alkylidene as the catalyst.

Show what reagents would be needed to synthesize the pheromone of the omnivorous leafroller (OLR) using olefin metathesis to assemble the molecule at the double bond.

Show how you would synthesize each compound, starting with alkenes or cycloalkenes that contain no more than six carbon atoms. You may use any additional reagents you need.

Use the extended version of Markovnikov’s rule to predict the regiochemistry (orientation) of electrophilic additions to alkenes.

Show how to control the stereochemistry and regiochemistry (orientation) of additions to alkenes to obtain the products we want.

Show how to control the hydration of alkenes to give alcohols with either Markovnikov or anti-Markovnikov orientation, depending on the reagents. (Problems 8-46, 49, 50, 51, and 79)

Predict the products of halogenations, oxidations, reductions, and cleavages of alkenes, including the orientation (regiochemistry) and the stereochemistry of the reaction. (Problems 8-46, 47, 48, 54, 55, 61, 65, 66, and 75)

Predict the stereochemistry observed in the hydroboration, halogenation, and dihydroxylation reactions of alkenes. (Problems 8-46, 50, 51, 55, and 66)

Propose logical mechanisms to explain the observed products of alkene reactions, including regiochemistry and stereochemistry. (Problems 8-56, 57, 58, 59, 64, 67, 70, 71, 76, 77, 78, and 79)

Use retrosynthetic analysis to solve multistep synthesis problems with alkenes as reagents, intermediates, or products. (Problems 8-49, 50, 51, 55, and 61) Problem-Solving Strategy: Organic Synthesis (Problems 8-49, 50, 51, 55, and 61)

Use clues provided by the products of reactions, such as ozonolysis, to determine the structure of an unknown alkene.

Show how metathesis interchanges the alkylidene (=CHR) groups in alkenes, forming new and different alkenes. (Problems 8-46, 52, and 53)

Given a particular monomer unit, draw the structure of the resulting polymer. (Problems 8-72, 73, and 74)

Predict the major products of the following reactions, and give the structures of any intermediates. Include stereochemistry where appropriate. (a) (a) HCl (b) (b) Br2 CCl4 (c) (c) (1) BH3 THF (2) H2O2, OH (d) (1) O3 (d) (78 C) (2) (CH3) 2S (e) (e) HBr ROOR (f) HCl ROOR (f) (g) (g) PhCO3H (h) (h) OsO4 H2O2 (i) (i) KMnO4, OH (cold, dil.) (j) (j) CH3CO3H H+, H2O (k) (k) KMnO4, OH (warm, concd.) (l) (l) (1) O3 (78 C) (2) (CH3) 2S (m) (m) H2 Pt (n) H+ (n) , H2O (o) [M] CHR (o) (p) (p) (1) Hg(OAc)2, H2O (2) NaBH4 (q) (q) Cl2 H2O

Limonene is one of the compounds that give lemons their tangy odor. Show the structures of the products expected when limonene reacts with an excess of each of these reagents. limonene (a) borane in tetrahydrofuran, followed by basic hydrogen peroxide (b) m-chloroperoxybenzoic acid (c) ozone, then dimethyl sulfide (d) a mixture of osmic acid and hydrogen peroxide (e) hot, concentrated potassium permanganate (f) peroxyacetic acid in acidic water (g) hydrogen and a platinum catalyst (h) hydrogen bromide gas (i) hydrogen bromide gas in a solution containing dimethyl peroxide (j) bromine water (k) chlorine gas (l) mercuric acetate in methanol, followed by sodium borohydride (m) CHBr3 and 50% aq. NaOH

Give the products expected when the following compounds are ozonized and reduced. (a) (b) (c) (d)

Show how you would make the following compounds from a suitable cyclic alkene. (a) H CH3 OH OH (a) (b) (b) OH OH (c) (c) Br Br (d) (d) Cl OH (e) (e) OH (f) (f) OCH3

Using 1,2-dimethylcyclohexene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.) If a chiral product is shown, assume that it is part of a racemic mixture. 1,2-dimethylcyclohexene (a) Br (b) OH (c) Br CH3 CH3 Br (e) OH CH3 CH3 OH (g) CH3 CH3 Br OH (d) CH3 CH3 OH OH (f) CH3 OH (h) O O (i) 1,2-dimethylcyclohexene (a) Br (b) OH (c) Br CH3 CH3 Br (e) OH CH3 CH3 OH (g) CH3 CH3 Br OH (d) CH3 CH3 OH OH (f) CH3 OH (h) O O

Show how you would synthesize each compound using methylenecyclohexane as your starting material. (a) (c) OH (d) O (g) (b) Br OCH3 (e) OH Cl O

Show what products you would expect from the following metathesis reactions, using the Schrock or Grubbs catalysts. O [M] CHR (a) HO OCH3 CH2OH CH2OH [M] CHR (c) eugenol + O O O O [M] CHR

Show how you might use olefin metathesis to assemble the following alkenes from smaller units:

Professor Patrick Dussault (University of Nebraska at Lincoln) has developed an alternative to the standard two-step ozonolysis procedure requiring reduction of the ozonide in a second step. He uses 2 to 3 equivalents of pyridine, a mildly basic organic solvent, in a one-step process (Organic Letters, 2012, 14, 2242). Show the products you expect from the following examples. (a) (a) O3 pyridine ? 78 C 93% yield (b) (b) O3 pyridine t-Bu ? 78 C 85% yield (c) (c) (CH2)7COCH3 O (CH2)7CH3 O3 pyridine ? 78 C 78% yield (d) (d) O3 pyridine ? 78 C 81% yield O CH2

Complete each synthesis by providing the structure of the major product at each step, including any important stereochemistry. (a) (a) Br2 H2O A B excess NH3 (b) (b) (1) Hg(OAc)2, H2O (2) NaBH4 C D E H2SO4 OsO4 H2O2 (c) (c) excess HBr ROOR F G H excess KO-t-Bu 2) (CH3)2S 1) excess O3 78 C (d) (d) Br2 J 2) H2O2, NaOH 1) excess BH3 THF K C13H16 L (ignore stereoisomers)

Propose mechanisms consistent with the following reactions. (a) (a) Br HBr ROOR (b) H2 (b) SO4 H2O OH (c) HBr (c) Br + Br (d) CHBr3 NaOH (d) Br Br (e) (e) Br Br + Cl Br HCl CH3CH2OH OCH2CH3 (f) O CH3CH2 H+, H2O H OH H OH CH2CH3 CH2CH3 CH2CH3

Draw an approximate reaction-energy diagram showing the curves for the two possible pathways for ionic addition of HBr to 1-methylcyclohexene. (a) Formation of the major product, 1-bromo-1-methylcyclohexane, and (b) formation of the minor product, 1-bromo-2-methylcyclohexane. Point out how these curves show that 1-bromo-1-methylcyclohexane should be formed faster.

Cyclohexene is dissolved in a solution of lithium chloride in chloroform. To this solution is added one equivalent of bromine. The material isolated from this reaction contains primarily a mixture of trans-1,2-dibromocyclohexane and trans-1-bromo-2-chlorocyclohexane. Propose a mechanism to show how these compounds are formed.

Draw a reaction-energy diagram for the propagation steps of the free-radical addition of HBr to isobutylene. Draw curves representing the reactions leading to both the Markovnikov and the anti-Markovnikov products. Compare the values of \(\Delta G^{\circ}\) and \(E_a\) for the rate-limiting steps, and explain why only one of these products is observed.

Unknown X, C5H9Br, does not react with bromine or with dilute KMnO4. Upon treatment with potassium tert-butoxide, X gives only one product, Y, C5H8. Unlike X, Y decolorizes bromine and changes KMnO4 from purple to brown. Catalytic hydrogenation of Y gives methylcyclobutane. Ozonolysisreduction of Y gives dialdehyde Z, C5H8O2. Propose consistent structures for X, Y, and Z. Is there any aspect of the structure of X that is still unknown?

One of the constituents of turpentine is \(\alpha \text {-pinene }\), formula \(\mathrm{C}_{10} \mathrm{H}_{16}\). The following scheme (called a “road map”) gives some reactions of \(\alpha \text {-pinene }\). Determine the structure of \(\alpha \text {-pinene }\) and of the reaction products A through E.

The sex attractant of the housefly has the formula C23H46. When treated with warm potassium permanganate, this pheromone gives two products: CH3(CH2)12COOH and CH3(CH2)7COOH. Suggest a structure for this sex attractant. Explain which part of the structure is uncertain.

In contact with a platinum catalyst, an unknown alkene reacts with three equivalents of hydrogen gas to give 1-isopropyl4-methylcyclohexane. When the unknown alkene is ozonized and reduced, the products are the following: H C H O H C CH2 C C CH3 O O O CH3 C CH2 C H O O Deduce the structure of the unknown alkene.

Propose a mechanism for the following reaction. O OH H2SO4 H2O

The two butenedioic acids are called fumaric acid (trans) and maleic acid (cis). 2,3-Dihydroxybutanedioic acid is called tartaric acid. HOOC H H COOH C C fumaric acid HOOC H H COOH C C maleic acid HOOC CH CH COOH OHOH tartaric acid Show how you would convert (a) fumaric acid to ({)@tartaric acid. (b) fumaric acid to meso-tartaric acid. (c) maleic acid to ({)@tartaric acid. (d) maleic acid to meso-tartaric acid.

The compound BD3 is a deuterated form of borane. Predict the product formed when 1-methylcyclohexene reacts with BD3 # THF, followed by basic hydrogen peroxide.

A routine addition of HBr across the double bond of a vinylcyclopentane gave a small amount of an unexpected rearranged product. Propose a mechanism for the formation of this product, and explain why the rearrangement occurs. HBr CH3 Br CH3

An unknown compound decolorizes bromine in carbon tetrachloride, and it undergoes catalytic reduction to give decalin. When treated with warm, concentrated potassium permanganate, this compound gives cis-cyclohexane-1,2-dicarboxylic acid and oxalic acid. Propose a structure for the unknown compound.

Many enzymes catalyze reactions that are similar to reactions we might use for organic synthesis. Enzymes tend to be stereospecific in their reactions, and asymmetric induction is common. The following reaction, part of the tricarboxylic acid cycle of cell respiration, resembles a reaction we might use in the laboratory; however, the enzyme-catalyzed reaction gives only the (S) enantiomer of the product, malic acid. (a) What type of reaction does fumarase catalyze? (b) Is fumaric acid chiral? Is malic acid chiral? In the enzyme-catalyzed reaction, is the product (malic acid) optically active? (c) If we could run the preceding reaction in the laboratory using sulfuric acid as the catalyst, would the product (malic acid) be optically active? (d) Do you expect the fumarase enzyme to be a chiral molecule? (e) When the enzyme-catalyzed reaction takes place in \(D_2O\), the only product is the stereoisomer just pictured. No enantiomer or diastereomer of this compound is formed. Is the enzyme-catalyzed reaction a syn or anti addition? (f) Assume that we found conditions to convert fumaric acid to deuterated malic acid using hydroboration with \(\mathrm{BD}_{3} \cdot \mathrm{THF}\), followed by oxidation with \(D_2O_2\) and NaOD. Use Fischer projections to show the stereoisomer(s) of deuterated malic acid you would expect to be formed.

(a) The following cyclization has been observed in the oxymercurationdemercuration of this unsaturated alcohol. Propose a mechanism for this reaction. (1) Hg(OAc)2 (2) NaBH4 OH O (b) Predict the product of formula C7H13BrO from the reaction of this same unsaturated alcohol with bromine. Propose a mechanism to support your prediction.

A graduate student attempted to form the iodohydrin of the alkene shown below. Her analysis of the products showed a good yield of an unexpected product. Propose a mechanism to explain the formation of this product. I2 H2O O OH O O I O O I side view

Propose a mechanism for reaction of the first three propylene units in the polymerization of propylene in the presence of a peroxide.

When styrene (vinylbenzene) is commercially polymerized, about 1–3% of 1,4-divinylbenzene is often added to the styrene. The incorporation of some divinylbenzene gives a polymer with more strength and better resistance to organic solvents. Explain how a very small amount of divinylbenzene has a marked effect on the properties of the polymer.

The cationic polymerization of isobutylene (2-methylpropene) is shown in Section 8-16A. Isobutylene is often polymerized under free-radical conditions. Propose a mechanism for the free-radical polymerization of isobutylene.

Ozonolysis can be applied selectively to different types of carbon–carbon double bonds. The compound shown below contains two vinyl ether double bonds, which are electron-rich because of the electron-donating alkoxy groups. Ozone reacts more quickly with electron-rich double bonds and more slowly with hindered double bonds. At \(-78^{\circ} \mathrm{C}\), this compound quickly adds two equivalents of ozone. Immediate reduction of the ozonide gives a good yield of a single product. Show the expected ozonolyis product, and label the functional groups produced, some of which are not typical from ozonolysis of simple alkenes.

Propose mechanisms to explain the opposite regiochemistry observed in the following two reactions.

An inexperienced graduate student treated dec-5-ene with borane in THF, placed the flask in a refrigerator, and left for a party. When he returned from the party, he discovered that the refrigerator was broken and that it had gotten quite warm inside. Although all the THF had evaporated from the flask, he treated the residue with basic hydrogen peroxide. To his surprise, he recovered a fair yield of decan-1-ol. Use a mechanism to show how this reaction might have occurred. (Hint: The addition of \(BH_3\) is reversible.)

We have seen many examples where halogens add to alkenes with anti stereochemistry via the halonium ion mechanism. However, when 1-phenylcyclohexene reacts with chlorine in carbon tetrachloride, a mixture of the cis and trans isomers of the product is recovered. Propose a mechanism, and explain this lack of stereospecificity. Cl2 CCl4 Cl Ph Ph H Cl Ph Cl H Cl + and 1,2-dichloro-1-phenylcyclohexane 1-phenylcyclohexene cis- trans

The bulky borane 9-BBN was developed to enhance the selectivity of hydroboration. In this example, 9-BBN adds to the less hindered carbon with 99.3% regioselectivity, compared with only 57% for diborane. (a) Show the two organic products generated when the trialkylborane is oxidized with \(H_2O_2\)/NaOH. (b) 9-BBN is synthesized by adding \(BH_3\) across a symmetric, cyclic diene. What is the structure of the diene?