(a) Draw a detailed mechanism for the FeBr3-catalyzed

Phenolphthalein, a common nonprescription laxative, is also an acid–base indicator that is colorless in acid and red in base. Phenolphthalein is synthesized by the acid-catalyzed reaction of phthalic anhydride with 2 equivalents of phenol. (a) Propose a mechanism for the synthesis of phenolphthalein. (b) Propose a mechanism for the conversion of phenolphthalein to its red dianion in base. (c) Use resonance structures to show that the two phenolic oxygen atoms are equivalent (each with half a negative charge) in the red phenolphthalein dianion.

Problem 1P Step 2 of the iodination of benzene shows water acting as a base and removing a proton from the sigma complex. We did not consider the possibility of water acting as a nucleophile and attacking the carbocation, as in an electrophilic addition to an alkene. Draw the reaction that would occur if water reacted as a nucleophile and added to the carbocation. Explain why this type of addition is rarely observed.

Problem 2P Propose a mechanism for the aluminum chloride–catalyzed reaction of benzene with chlorine.

Problem 5P (a) Draw a detailed mechanism for the FeBr3-catalyzed reaction of ethylbenzene with bromine, and show why the sigma complex (and the transition state leading to it) is lower in energy for substitution at the ortho and para positions than it is for substitution at the meta position. (b) Explain why m-xylene undergoes nitration 100 times faster than p-xylene.

Problem 3P p-Xylene undergoes nitration much faster than benzene. Use resonance forms of the sigma complex to explain this accelerated rate.

Problem 4P Use resonance forms to show that the dipolar sigma complex shown in the sulfonation of benzene has its positive charge delocalized over three carbon atoms and its negative charge delocalized over three oxygen atoms.

Problem 6P Styrene (vinylbenzene) undergoes electrophilic aromatic substitution much faster than benzene, and the products are found to be primarily ortho- and para-substituted styrenes. Use resonance forms of the intermediates to explain these results.

Problem 7P Propose a mechanism for the bromination of ethoxybenzene to give o- and p-bromoethoxybenzene.

Problem 8P Draw all the resonance forms for the sigma complexes corresponding to bromination of aniline at the ortho, meta, and para positions.

Problem 9P When bromine is added to two beakers, one containing phenyl isopropyl ether and the other containing cyclohexene, the bromine color in both beakers disappears. What observation could you make while performing this test that would allow you to distinguish the alkene from the aryl ether?

Problem 11P Draw all the resonance forms of the sigma complex for nitration of bromobenzene at the ortho, meta, and para positions. Point out why the intermediate for meta substitution is less stable than the other two.

Problem 12P Predict the mononitration products of the following compounds. (a) o-nitrotoluene (b) m-chlorotoluene (c) o-bromobenzoic acid (d) p-methoxybenzoic acid (e) m-cresol (m-methylphenol) (f) o-hydroxyacetophenone

Problem 10P In an aqueous solution containing sodium bicarbonate, aniline reacts quickly with bromine to give 2,4,6-tribromoaniline. Nitration of aniline requires very strong conditions, however, and the yields (mostly m-nitroaniline) are poor. (a) What conditions are used for nitration, and what form of aniline is present under these conditions? (b) Explain why nitration of aniline is so sluggish and why it gives mostly meta substitution. (c) Although nitration of aniline is slow and gives mostly meta substitution, nitration of Acetanilide (PhNHCOCH3) goes quickly and gives mostly para substitution. Use resonance forms to explain this difference in reactivity.

Predict the mononitration products of the following aromatic compounds. (a) -methylanisole (b) -nitrochlorobenzene (c) -chlorophenol (d) -nitroanisole

Biphenyl is two benzene rings joined by a single bond. The site of substitution for a biphenyl is determined by (1) which phenyl ring is more activated (or less deactivated), and (2) which position on that ring is most reactive, using the fact that a phenyl substituent is activating and ortho, para-directing. (a) Use resonance forms of a sigma complex to show why a phenyl substituent should be ortho, para-directing. (b) Predict the mononitration products of the following compounds.

Problem 15P Propose products (if any) and mechanisms for the following AlCl3-catalyzed reactions: (a) chlorocyclohexane with benzene (b) methyl chloride with anisole *(c) 3-chloro-2,2-dimethylbutane with isopropylbenzene

Problem 16P For each reaction, show the generation of the electrophile and predict the products. (a) benzene + cyclohexene + HF (b) tert-butyl alcohol + benzene + BF3 (c) tert-butylbenzene + 2-methylpropene + HF (d) propan-2-ol + toluene + BF3

Problem 17P Predict the products (if any) of the following reactions. (a) (excess) benzene + isobutyl chloride + AlCl3 (b) (excess) toluene + butan-1-ol + BF3 (c) (excess) nitrobenzene + 2-chloropropane + AlCl3 (d) (excess) benzene + 3,3-dimethylbut-1-ene + HF

Problem 18P Which reactions will produce the desired product in good yield? You may assume that aluminum chloride is added as a catalyst in each case. For the reactions that will not give a good yield of the desired product, predict the major products. (a) n-butylbenzene benzene + n-butyl bromide (b) p-ethyl-tert-butylbenzene ethylbenzene + tert-butyl chloride (c) p-bromoethylbenzene bromobenzene + ethyl chloride (d) benzamide (PhCONH2) + CH3CH2Cl p-ethylbenzamide (e) toluene + HNO3, H2SO4, heat 2,4,6-trinitrotoluene (TNT)

Problem 19P Show how you would synthesize the following aromatic derivatives from benzene. (a) p-tert-butylnitrobenzene (b) p-toluenesulfonic acid (c) p-chlorotoluene

Fluoride ion is usually a poor leaving group because it is not very polarizable. Fluoride serves as the leaving group in the Sanger reagent (2,4-dinitrofluorobenzene), used in the determination of peptide structures (Chapter 24). Explain why fluoride works as a leaving group in this nucleophilic aromatic substitution, even though it is a poor leaving group in the \(S_{N} 1\) and \(S_{N} 2\) mechanisms. Equation transcription: Text transcription: S{N} 1 S{N} 2

Show how you would use the Friedel–Crafts acylation, Clemmensen reduction, and or Gatterman–Koch synthesis to prepare the following compounds: \(\mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\) \(C\left(C H_{3}\right)_{3}\) (d) ????-methoxybenzaldehyde (e) 3-methyl-1-phenylbutane (f) 1-phenyl-2,2-dimethylpropane (g) ????-butylbenzene \(H_{3} C\) \(\mathrm{CH}_{3}\) Equation transcription: Text transcription: {CH}{2}{CH}({CH}{3}){2} C(C H{3}){3} H{3} C {CH}{3}

Problem 25P The highly reactive triple bond of benzyne is a powerful dienophile. Predict the product of the Diels–Alder reaction of benzyne (from chlorobenzene and NaOH, heated) with cyclopentadiene.

Problem 22P Propose a mechanism that shows why p-chlorotoluene reacts with sodium hydroxide at 350 °C to give a mixture of p-cresol and m-cresol.

What products would you expect from the following reactions? \(O C H_{3}\) \(\mathrm{CuLi}\) \(\mathrm{PH}_{2} \mathrm{CuLi} \rightarrow\) Equation transcription: Text transcription: O C H{3} {CuLi} {PH}{2}{CuLi} rightarrow

Problem 24P Nucleophilic aromatic substitution provides one of the common methods for making phenols. (Another method is discussed in Section 19-17.) Show how you would synthesize the following phenols, using benzene or toluene as your aromatic starting material, and explain why mixtures of products would be obtained in some cases. (a) p-nitrophenol (b) 2,4,6-tribromophenol (c) p-chlorophenol (d) m-cresol (e) p-n-butylphenol

What organocuprate reagent would you use for the following substitutions? \(I\) \(\text { Br }\) Equation transcription: Text transcription: I { Br }

What products would you expect from the following reactions? \(\frac{P d C I_{2}}{P P h_{3}, E t_{3} N}\) \(\mathrm{OCH}_{3}\) \(\frac{P d(O A c)_{2}}{P P h_{3}, E T_{3} N}\) Equation transcription: Text transcription: frac{P d C I{2}}{P P h{3}, E t{3} N} {OCH}{3} frac{P d(O A c){2}}{P P h{3}, E T{3} N}

What substituted alkene would you use in the Heck reaction to make the following products? \(\mathrm{CH}_{3}\) \(\frac{P d(O A c)_{2}}{P P h_{3}, E t_{3} N}\) \(\mathrm{OCH}_{3}\) \(B r+? \frac{P d(O A c)_{2}}{P P h_{3}, E t_{3} N}\) Equation transcription: Text transcription: {CH}{3} frac{P d(O A c){2}}{P P h{3}, E t{3} N} {OCH}{3} B r+? frac{P d(O A c){2}}{P P h{3}, E t{3} N}

What products would you expect from the following Suzuki coupling reactions? \(\frac{\mathrm{Pd}(\mathrm{OAc})_{2}}{\mathrm{~K}_{3} \mathrm{PO}_{4}}\) \(\frac{P d\left(P P h_{3}\right)_{4}}{N a O H}\) Equation transcription: Text transcription: frac{{Pd}({OAc}){2}}{{~K}{3}{PO}{4}} frac{P d(P P h{3}){4}}{N a O H}

Predict the major products of the following reactions. (a) toluene + excess \(\mathrm{CI}_{2}\) (heat, pressure) (b) benzamide \(\left(\mathrm{PhCONH}_{2}\right)\) + Na (liquid \(\mathrm{NH}_{3}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\)) (c) ????-xylene + \(H_{2}\) (1000 psi, 100 °C, Rh catalyst) (d) ????-xylene + Na (liquid \(\mathrm{NH}_{3}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\)) \(\mathrm{CH}_{3} \mathrm{O}\) \(O C H_{3}\) \(\frac{\mathrm{NH}_{3}(\mathrm{l}) / \mathrm{THF}}{\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}}\) Equation transcription: Text transcription: {CI}{2} ({PhCONH}{2}) {NH}{3},{CH}{3}{CH}{2}{OH} H_{2} {NH}{3},{CH}_{3}{CH}{2}{OH} {CH}{3}{O} O C H_{3} frac{{NH}{3}({l}) /{THF}}{({CH}{3}){3}{COH}}

Show how you would use Suzuki reactions to synthesize these products from the indicated starting materials. You may use any additional reagents you need. \(B r\) Equation transcription: Text transcription: B r

Problem 32P Propose mechanisms for the Birch reductions of benzoic acid and anisole just shown. Show why the observed orientation of reduction is favored in each case.

Predict the major products of treating the following compounds with hot, concentrated potassium permanganate, followed by acidification with dilute HCl. (a) isopropylbenzene (b) ????-xylene

Problem 35P Propose a mechanism for the bromination of ethylbenzene shown above.

Problem 36P What would be the ratio of products in the reaction of chlorine with ethylbenzene if chlorine randomly abstracted a methyl or methylene proton? What is the reactivity ratio for the benzylic hydrogens compared with the methyl hydrogens?

Predict the major products when the following compounds are irradiated by light and treated with (1) 1 equivalent of \(B r_{2}\) and (2) excess \(B r_{2}\). (a) isopropylbenzene Equation transcription: Text transcription: B r{2}

Propose a mechanism for the reaction of benzyl bromide with ethanol to give benzyl ethyl ether (shown above). \(C H_{2}-B r\) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}, \triangle(\text { heat })\) \(\mathrm{CH}_{2}-\mathrm{OCH}_{2} \mathrm{CH}_{3}\) Equation transcription: Text transcription: C H{2}-B r {CH}{3}{CH}_{2}{OH}, triangle({ heat }) {CH}{2}-{OCH}{2}{CH}{3}

Show how you would synthesize the following compounds, using the indicated starting materials. (a) 3-phenylbutan-1-ol from styrene \(\mathrm{CH}_{3}-\mathrm{CH}-\mathrm{OCH}_{3}\) \(\mathrm{OCH}_{3}\) \(O_{2} N\) \(\mathrm{CH}_{2} \mathrm{CN}\) Equation transcription: Text transcription: {CH}{3}-{CH}-{OCH}{3} {OCH}{3} O{2} N {CH}{2}{CN}

Problem 39P (a) Based on what you know about the relative stabilities of alkyl cations and benzylic cations, predict the product of addition of HBr to 1-phenylpropene. (b) Propose a mechanism for this reaction. (c) Based on what you know about the relative stabilities of alkyl radicals and benzylic radicals, predict the product of addition of HBr to 1-phenylpropene in the presence of a free-radical initiator. (d) Propose a mechanism for this reaction.

The bombardier beetle defends itself by spraying a hot quinone solution from its abdomen (see photo). This solution is formed by the enzyme-catalyzed oxidation of hydroquinone by hydrogen peroxide. Write a balanced equation for this oxidation. When threatened, the bombardier beetle mixes hydroquinone and \(\mathrm{H}_{2} \mathrm{O}_{2}\) with enzymes. Peroxide oxidizes hydroquinone, and the strongly exothermic reaction heats the solution to boiling. The hot, irritating liquid sprays from tip of the insect’s abdomen. Equation transcription: Text transcription: {H}{2}{O}{2}

Predict the products formed when m-cresol (????-methylphenol) reacts with (a) \(\mathrm{NaOH}\) and then ethyl bromide \(\mathrm{CH}_{3}\) (c) bromine in \(C C I_{4})u in the dark (d) excess bromine in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) in the light (e) sodium dichromate in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (f) two equivalents of tert-butyl chloride and \(A I C L_{3}\) Equation transcription: Text transcription: {NaOH} {CH}{3} C C I_{4} {H}{2}{SO}{4} {H}{2}{SO}{4} A I C L{3}

Problem 44SP Predict the major products formed when benzene reacts (just once) with the following reagents. (a) tert-butyl bromide, AlCl3 (b) 1-chlorobutane, AlCl3 (c) isobutyl alcohol + BF3 (d) bromine + a nail (e) isobutylene + HF (f) fuming sulfuric acid (g) 1-chloro-2,2-dimethylpropane + AlCl3 (h) benzoyl chloride + AlCl3 (i) iodine + HNO3 (j) nitric acid + sulfuric acid (k) carbon monoxide, HCl, and AlCl3/CuCl (l) CH2(COCl)2, AlCl3

Indane can undergo free-radical chlorination at any of the alkyl positions on the aliphatic ring. (a) Draw the possible monochlorinated products from this reaction. (b) Draw the possible dichlorinated products from this reaction. (c) What instrumental technique would be most helpful for determining how many products are formed, and how many of those products are monochlorinated and how many are dichlorinated? (d) Once the products have been separated, what instrumental technique would be most helpful for determining the structures of all the dichlorinated products?

Problem 43P 1,4-Benzoquinone is a good Diels–Alder dienophile. Predict the products of its reaction with (a) buta-1,3-diene (b) cyclopenta-1,3-diene

Predict the major products of the following reactions. (a) 2,4-dinitrochlorobenzene + NaOCH3 (b) phenol + tert-butyl chloride + AlCl3 (c) nitrobenzene + fuming sulfuric acid (d) nitrobenzene + acetyl chloride + AlCl3 (e) ????-methylanisole + acetyl chloride + AlCl3 (f) ????-methylanisole + Br2, light (g) 1,2-dichloro-4-nitrobenzene + NaNH2 (h) ????-nitrotoluene + Zn + dilute HCl (i) ????-ethylbenzenesulfonic acid + steam>H+ (j) ????-ethylbenzenesulfonic acid + HNO3, H2SO4

Predict the major products of bromination of the following compounds, using \(B r_{2}\) and \(\mathrm{FeBr}_{3}\) in the dark. \(\mathrm{NO}_{2}\) \(O C H_{3}\) Equation transcription: Text transcription: B r{2} {FeBr}{3} {NO}{2} O C H{3}

What products would you expect from the following coupling reactions? \(B r\) \(\text { Culi }\) \(\frac{\mathrm{PaCl}_{2}}{\mathrm{Na}_{2} \mathrm{CO}_{3}, \mathrm{H}_{2} \mathrm{O}}\) Equation transcription: Text transcription: B r { Culi } frac{{PaCl}{2}}{{Na}{2}{CO}{3},{H}{2}{O}} frac{P d(O A c){2}}{P P h{3} E t{3} N{:}} {NO}{2}

Give the structures of compounds A through H in the following series of reactions.

A student added 3-phenylpropanoic acid \(\left(\mathrm{PhCH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\right)\) to a molten salt consisting of a 1:1 mixture of \(\text { NaCL }\) and \(A I C L_{3}\) maintained at 170 °C. After 5 minutes, he poured the molten mixture into water and extracted it into dichloromethane. Evaporation of the dichloromethane gave a 96% yield of the product whose spectra follow. The mass spectrum of the product shows a molecular ion at ????/???? 132. What is the product? Equation transcription: Text transcription: ({PhCH}{2}{CH}{2}{COOH}) A I C L_{3} { NaCL }

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the ???? position. Predict the major products of the reactions of naphthalene with the following reagents. (a) \(H M O_{3}, H 2 \mathrm{SO}_{4}\) (b) \(B r_{2}, F e B r_{3}\) (c) \(\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COCl}, \mathrm{AICL}_{3}\) (d) isobutylene and HF (e) cyclohexanol and \(B F_{3}\) (f) fuming sulfuric acid Equation transcription: Text transcription: H M O{3}, H 2{SO}{4} B r{2}, F e B r{3} {CH}{2}{CH}{2}{COCl},{AICL}{3} B F{3}

The following compound reacts with a hot, concentrated solution of \(\mathrm{NaOH}\) (in a sealed tube) to give a mixture of two products. Propose structures for these products, and give a mechanism to account for their formation. \(\frac{\mathrm{NaOH}, \mathrm{H}_{2} \mathrm{O}}{350^{\circ} \mathrm{C}}\) Equation transcription: Text transcription: {NaOH} frac{{NaOH},{H}{2}{O}}{350^{circ}{C}}

????-Tetralone undergoes Birch reduction to give an excellent yield of a single product. Predict the structure of the product, and propose a mechanism for its formation. \(\frac{\mathrm{Na}, \mathrm{NH}_{3}(l)}{\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}}\) Equation transcription: Text transcription: frac{{Na},{NH}{3}(l)}{{CH}{3}{CH}{2}{OH}}

Show how you would use a Suzuki reaction to synthesize Bombykol, the sex hormone of the silk moth, from cis-1-bromopent-1-ene and the acetylenic alcohol shown below. \(B r\) \(H-C=C-\left(C H_{2}\right)_{8}-C H_{2} O H\) \(\left(\mathrm{CH}_{2}\right)_{8}-\mathrm{CH}_{2} \mathrm{OH}\) Equation transcription: Text transcription: B r H-C=C-\left(C H_{2}\right)_{8}-C H_{2} O H ({CH}{2}){8}-{CH}{2}{OH}

The most common selective herbicide for killing broadleaf weeds is 2,4-dichlorophenoxyacetic acid (2,4-D). Show how you would synthesize 2,4-D from benzene, chloroacetic acid \(\left(\mathrm{CICH}_{2} \mathrm{COOH}\right)\), and any necessary reagents and solvents. \(\mathrm{CICH}_{2} \mathrm{COOH}\) Equation transcription: Text transcription: {CICH}{2}{COOH}) {CICH}{2}{COOH}

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran. (a) Propose mechanisms for the bromination of furan at the 2-position and at the 3-position. Draw the resonance forms of each sigma complex, and compare their stabilities. (b) Explain why furan undergoes bromination (and other electrophilic aromatic substitutions) primarily at the 2-position.

Problem 58SP (a) Draw the three isomers of benzenedicarboxylic acid. (b) The isomers have melting points of 210 °C, 343 °C, and 427 °C. Nitration of the isomers at all possible positions was once used to determine their structures. The isomer that melts at 210 °C gives two mononitro isomers. The isomer that melts at 343 °C gives three mononitro isomers. The isomer that melts at 427 °C gives only one mononitro isomer. Show which isomer has which melting point.

Bisphenol A is an important component of many polymers, including polycarbonates, polyurethanes, and epoxy resins. It is synthesized from phenol and acetone with HCl as a catalyst. Propose a mechanism for this reaction. \(O H\) \(\mathrm{CH}_{3}\) \(\text { HO }\) Equation transcription: Text transcription: O H {CH}{3} { HO }

Problem 61SP When 1,2-dibromo-3,5-dinitrobenzene is treated with excess NaOH at 50 °C, only one of the bromine atoms is replaced. Draw an equation for this reaction, showing the product you expect. Give a mechanism to account for the formation of your proposed product.

Problem 60SP Unlike most other electrophilic aromatic substitutions, sulfonation is often reversible (see Section 17-4). When one sample of toluene is sulfonated at 0 °C and another sample is sulfonated at 100 °C, the following ratios of substitution products result: Reaction Temperature Isomer of the Product 0 °C 100 °C o-toluenesulfonic acid 43% 13% m-toluenesulfonic acid 4% 8% p-toluenesulfonic acid 53% 79% (a) Explain the change in the product ratios when the temperature is increased. (b) Predict what will happen when the product mixture from the reaction at 0 °C is heated to 100 °C. (c) Because the SO3H group can be added to a benzene ring and removed later, it is sometimes called a blocking group. Show how 2,6-dibromotoluene can be made from toluene using sulfonation and desulfonation as intermediate steps in the synthesis.

Problem 62SP When anthracene is added to the reaction of chlorobenzene with concentrated NaOH at 350 °C, an interesting Diels–Alder adduct of formula C20H14 results. The proton NMR spectrum of the product shows a singlet of area 2 around ? 3 and a broad singlet of area 12 around ? 7. Propose a structure for the product, and explain why one of the aromatic rings of anthracene reacted as a diene.

In Chapter 14, we saw that Agent Orange contains (2,4,5-trichlorophenoxy) acetic acid, called 2,4,5-T. This compound is synthesized by the partial reaction of 1,2,4,5-tetrachlorobenzene with sodium hydroxide, followed by reaction with sodium chloroacetate, \(\mathrm{CICH}_{2} \mathrm{CO}_{2} \mathrm{Na}\). (a) Draw the structures of these compounds, and write equations for these reactions. (b) One of the impurities in the Agent Orange used in Vietnam was 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD), often incorrectly called “dioxin.” Propose a mechanism to show how 2,3,7,8-TCDD is formed in the synthesis of 2,4,5-T. (c) Show how the TCDD contamination might be eliminated, both after the first step and on completion of the synthesis. \(\mathrm{OCH}_{2} \mathrm{COOH}\) Equation transcription: Text transcription: {CICH}{2}{CO}{2}{Na}

Problem 64SP Phenol reacts with three equivalents of bromine in CCl4 (in the dark) to give a product of formula C6H3OBr3. When this product is added to bromine water, a yellow solid of molecular formula C6H2OBr4 precipitates out of the solution. The IR spectrum of the yellow precipitate shows a strong absorption (much like that of a quinone) around 1680 cm-1. Propose structures for the two products.

Starting with benzene and any other reagents you need, show how you would synthesize the compound shown here. (Hint: Consider a Pd-catalyzed coupling for the final step.)

A graduate student tried to make ????-fluorophenylmagnesium bromide by adding magnesium to an ether solution of ????-fluorobromobenzene. After obtaining puzzling results with this reaction, she repeated the reaction by using as solvent some tetrahydrofuran that contained a small amount of furan. From this reaction, she isolated a fair yield of the compound that follows. Propose a mechanism for its formation. \(B r\) Equation transcription: Text transcription: B r

Show how you would use a Suzuki reaction to synthesize the following biaryl compound. As starting materials you may use the two indicated compounds, plus any additional reagents you need. \(\mathrm{OCH}_{3}\) \(B r\) Equation transcription: Text transcription: {OCH}{3} B r

The antioxidants BHA and BHT are commonly used as food preservatives. Show how BHA and BHT can be made from phenol and hydroquinone. \(\mathrm{OH}\) \(\mathrm{C}\left(\mathrm{CH}_{3}\right)_{3}\) \(\mathrm{OCH}_{3}\) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}\) \(\mathrm{CH}_{3}\) Equation transcription: Text transcription: {OH} {C}({CH}{3}){3} {OCH}{3} ({CH}{3}){3}{C} {CH}{3}

A common illicit synthesis of methamphetamine involves an interesting variation of the Birch reduction. A solution of ephedrine in alcohol is added to liquid ammonia, followed by several pieces of lithium metal. The Birch reduction usually reduces the aromatic ring (Section 17-14C), but in this case it eliminates the hydroxyl group of ephedrine to give methamphetamine. Propose a mechanism, similar to that for the Birch reduction, to explain this unusual course of the reaction. \(\text { OH }\) \(\mathrm{CH}_{3}\) \(\mathrm{NHCH}_{3}\) \(\frac{L i}{N H_{3}(l), E t O H}\) Equation transcription: Text transcription: { OH } {CH}{3} {NHCH}{3} frac{L i}{N H{3}(l), E t O H}

Problem 70SP Triphenylmethanol is insoluble in water, but when it is treated with concentrated sulfuric acid, a bright yellow solution results. As this yellow solution is diluted with water, its color disappears and a precipitate of triphenylmethanol reappears. Suggest a structure for the bright yellow species, and explain this unusual behavior.