CHAPTER 24 PHEN○LS SOLUTIONS TO TEXT PROBLEMS 4.1 (b) A benzyl group(CH-CH2)is ortho to the phenolic hydroxyl group in o-benzylphenol (c) Naphthalene is numbered as shown. 3-Nitro-1-naphthol has a hydroxyl group at C-1 and a nitro group at C-3 (d) Resorcinol is 1, 3-benzenediol. 4-Chlororesorcinol is therefore 676 Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
676 CHAPTER 24 PHENOLS SOLUTIONS TO TEXT PROBLEMS 24.1 (b) A benzyl group (C6H5CH2G) is ortho to the phenolic hydroxyl group in o-benzylphenol. (c) Naphthalene is numbered as shown. 3-Nitro-1-naphthol has a hydroxyl group at C-1 and a nitro group at C-3. (d) Resorcinol is 1,3-benzenediol. 4-Chlororesorcinol is therefore OH Cl OH OH NO2 Naphthalene 3-Nitro-1-naphthol 5 4 8 1 3 2 6 7 OH CH2C6H5 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
PHENOLS 677 4.2 Intramolecular hydrogen bonding between the hydroxyl group and the ester carbonyl can occur when these groups are ortho to each other. Methyl salicylate Intramolecular hydrogen bonds form at the expense of intermolecular ones, and intramolecularly hydrogen-bonded phenols have lower boiling points than isomers in which only intermolecular hydrogen-bonding is possible 24.3(b) A cyano group withdraws electrons from the ring by resonance. A p-cyano substituent is con- jugated directly with the negatively charged oxygen and stabilizes the anion more than does an m-cyano substituent p-Cyanophenol is slightly more acidic than m-cyanophenol, the Ka values being 1.0 X 10 and 2. X 10, respectively (c) The electron-withdrawing inductive effect of the fluorine substituent will be more pronounced at the ortho position than at the para. o-Fluorophenol(a=1.9 x 10)is a stronger acid han p-fluorophenol(K=1.3 10) 24.4 The text points out that the reaction proceeds by the addition-elimination mechanism of nucleophilic aromatic substitution Under the strongly basic conditions of the reaction, p-toluenesulfonic acid is first converted to its H,C HOH alfonic acid Hydroxide Toluenesulfonate ion Water Nucleophilic addition of hydroxide ion gives a cyclohexadienyl anion intermediate. OH C SO,+ OH H,C p-Toluenesulfonate ion Hydroxide Cyclohexadienyl anion Loss of sulfite ion(SO 2)gives p-cresol gC OH SO Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
24.2 Intramolecular hydrogen bonding between the hydroxyl group and the ester carbonyl can occur when these groups are ortho to each other. Intramolecular hydrogen bonds form at the expense of intermolecular ones, and intramolecularly hydrogen-bonded phenols have lower boiling points than isomers in which only intermolecular hydrogen-bonding is possible. 24.3 (b) A cyano group withdraws electrons from the ring by resonance. A p-cyano substituent is conjugated directly with the negatively charged oxygen and stabilizes the anion more than does an m-cyano substituent. p-Cyanophenol is slightly more acidic than m-cyanophenol, the Ka values being 1.0 108 and 2.8 109 , respectively. (c) The electron-withdrawing inductive effect of the fluorine substituent will be more pronounced at the ortho position than at the para. o-Fluorophenol (Ka 1.9 109 ) is a stronger acid than p-fluorophenol (Ka 1.3 1010). 24.4 The text points out that the reaction proceeds by the addition–elimination mechanism of nucleophilic aromatic substitution. Under the strongly basic conditions of the reaction, p-toluenesulfonic acid is first converted to its anion. Nucleophilic addition of hydroxide ion gives a cyclohexadienyl anion intermediate. Loss of sulfite ion (SO3 2) gives p-cresol. p-Cresol H3C OH SO3 2 Cyclohexadienyl anion H3C SO3 OH OH p-Toluenesulfonate ion Hydroxide H3C SO3 Cyclohexadienyl anion H3C SO3 OH H3C SO O O H p-Toluenesulfonic acid H3C SO O O p-Toluenesulfonate ion OH Hydroxide ion HOH Water O CN O C N OCH3 O O C H Methyl salicylate PHENOLS 677 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
PHENOLS It is also possible that the elimination stage of the reaction proceeds as follows + ho H,C- OH Cyclohexadienyl anion H H OH H C so,+ H,o p-Methylphenoxide ion 24.5 The text states that the hydrolysis of chlorobenzene in base follows an elimination-addition mechanism H + Ho+c Chlorobenzene -OH Benzyne 24.6 (b) The reaction is Friedel-Crafts alkylation. Proton transfer from sulfuric acid to 2-methyl- propene gives tert-butyl cation. Because the position para to the hydroxyl substituent already bears a bromine, the tert-butyl cation attacks the ring at the position ortho to the sOa B 2-Methylpropene methylphenol (c) Acidification of sodium nitrite produces nitrous acid, which nitrosates the strongly activated aromatic ring of phenols H HC HC 2-lsopropyl-5-methylphenol 2-Isopropyl-5-methyl-4-nitrosophenol isolated yield, Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
678 PHENOLS It is also possible that the elimination stage of the reaction proceeds as follows: 24.5 The text states that the hydrolysis of chlorobenzene in base follows an elimination–addition mechanism. 24.6 (b) The reaction is Friedel–Crafts alkylation. Proton transfer from sulfuric acid to 2-methylpropene gives tert-butyl cation. Because the position para to the hydroxyl substituent already bears a bromine, the tert-butyl cation attacks the ring at the position ortho to the hydroxyl. (c) Acidification of sodium nitrite produces nitrous acid, which nitrosates the strongly activated aromatic ring of phenols. CH(CH3)2 OH H3C NaNO2 HCl, H2O CH(CH3)2 OH N O H3C 2-Isopropyl-5-methylphenol 2-Isopropyl-5-methyl-4-nitrosophenol (isolated yield, 87%) H2SO4 (CH3)2C OH CH3 CH2 Br (CH3)3C OH CH3 Br 4-Bromo-2- methylphenol 4-Bromo-2-tert-butyl- 6-methylphenol (isolated yield, 70%) 2-Methylpropene OH OH Phenol OH Benzyne H2O OH H2O Cl H Cl Chlorobenzene Benzyne H2O Cyclohexadienyl anion intermediate H3C SO3 OH H H3C SO3 O H H H SO3 2 H2O OH H3C H H O OH p-Methylphenoxide ion H3C O HO Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
PHENOLS 679 (d) Friedel-Crafts acylation occurs ortho to the hydroxyl group CCHCH Ch3CHaCCI H3 p-Cresol 1-(2-Hydroxy-5-methylpher 24.7(b) The hydroxyl group of 2-naphthol is converted to the corresponding acetate ester OH OCCH CH3COCCH3 CH CONa 2-Naphthol Acetic anhydride 2-Naphthyl acetate Sodium acetate (c) Benzoyl chloride acylates the hydroxyl group of phenol CCI t HCl Phenol Benzoyl chloride Phenyl benzoate 24.8 Epoxides are sensitive to nucleophilic ring-opening reactions. Phenoxide ion attacks the less hin- dered carbon to yield l-phenoxy-2-propanol ④“政mm OCH-CHCH Phenoxide ion 1, 2-Epoxypropane l-Phenoxy-2-propanol 24.9 The aryl halide must be one that is reactive toward nucleophilic aromatic substitution by the addition-elimination mechanism. p-Flt trobenzene is far more reactive than fluorobenzene The reaction shown yields p-nitrophenyl phenyl ether in 92%o yield. p-Nitrophenyl phenyl ether 24.10 Substituted allyl aryl ethers undergo a Claisen rearrangement similar to the reaction described in text Section 24.13 for allyl phenyl ether. 2-Butenyl phenyl ether rearranges on heating to give o-(1 meth oH enolization 2-Butenyl phenyl Methyl-2 Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(d ) Friedel–Crafts acylation occurs ortho to the hydroxyl group. 24.7 (b) The hydroxyl group of 2-naphthol is converted to the corresponding acetate ester. (c) Benzoyl chloride acylates the hydroxyl group of phenol. 24.8 Epoxides are sensitive to nucleophilic ring-opening reactions. Phenoxide ion attacks the less hindered carbon to yield 1-phenoxy-2-propanol. 24.9 The aryl halide must be one that is reactive toward nucleophilic aromatic substitution by the addition–elimination mechanism. p-Fluoronitrobenzene is far more reactive than fluorobenzene. The reaction shown yields p-nitrophenyl phenyl ether in 92% yield. 24.10 Substituted allyl aryl ethers undergo a Claisen rearrangement similar to the reaction described in text Section 24.13 for allyl phenyl ether. 2-Butenyl phenyl ether rearranges on heating to give o-(1- methyl-2-propenyl)phenol. O H OH o-(1-Methyl-2-propenyl)- phenol rearrangement enolization 2-Butenyl phenyl ether O OK Potassium phenoxide F NO2 p-Fluoronitrobenzene O NO2 p-Nitrophenyl phenyl ether 150C OCH2CHCH3 OH 1-Phenoxy-2-propanol O Phenoxide ion HO, H2O 1,2-Epoxypropane H2C O CHCH3 Phenyl benzoate OC O Phenol OH Benzoyl chloride O CCl Hydrogen chloride HCl NaOH 2-Naphthyl acetate OCCH3 O 2-Naphthol OH Sodium acetate CH3CONa O Acetic anhydride CH3COCCH3 O O AlCl3 OH CH3 O CH3CH2CCl p-Cresol Propanoyl chloride CCH2CH3 OH CH3 O 1-(2-Hydroxy-5-methylphenyl)- 1-propanone (isolated yield, 87%) PHENOLS 679 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
680 PHENOLS 24.11 (a) The parent compound is benzaldehyde Vanillin bears a methoxy group(CH O)at C-3 and a hydroxyl group(HO)at C-4 Vanillin (b, c) Thymol and carvacrol differ with respect to the position of the hydroxyl group CH(CH3) CH(CH) (2-isopropyl-5-methylphenol) (5-isopropyl-2-methylphenol) (d) An allyl substituent is-CH, CH=CH, OCH CHCH=CH Eugenol (e) Benzoic acid is CHCO, H. Gallic acid bears three hydroxyl groups, located at C-3, C-4, and C-5 COH HO allic acid (3, 4, 5-trihydroxybenzoic Benzyl alcohol is CsHS CH,OH. Salicyl alcohol bears a hydroxyl group at the ortho position Salicyl alcohol (o-hydroxybenzyl alcohol) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
24.11 (a) The parent compound is benzaldehyde. Vanillin bears a methoxy group (CH3O) at C-3 and a hydroxyl group (HO) at C-4. (b, c) Thymol and carvacrol differ with respect to the position of the hydroxyl group. (d) An allyl substituent is GCH2CH?CH2. (e) Benzoic acid is C6H5CO2H. Gallic acid bears three hydroxyl groups, located at C-3, C-4, and C-5. (f ) Benzyl alcohol is C6H5CH2OH. Salicyl alcohol bears a hydroxyl group at the ortho position. Salicyl alcohol (o-hydroxybenzyl alcohol) CH2OH OH Gallic acid (3,4,5-trihydroxybenzoic acid) CO2H HO OH OH 1 2 3 4 5 6 OH OCH3 CH2CH CH2 1 2 3 4 5 6 Eugenol (4-allyl-2-methoxyphenol) HO CH3 CH(CH3)2 3 2 1 6 5 4 Thymol (2-isopropyl-5-methylphenol) HO CH3 CH(CH3)2 3 2 1 6 5 4 Carvacrol (5-isopropyl-2-methylphenol) OCH3 C O H OH 3 2 1 6 5 4 Vanillin (4-hydroxy-3-methoxybenzaldehyde) 680 PHENOLS Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
681 24.12 (a) The compound is named as a derivative of phenol. The substituents(ethyl and nitro) are cited n alphabetical order with numbers assigned in the direction that gives the lowest number at the first point of difference OH CH,CH3 (b) An isomer of the compound in part(a) is 4-ethyl-3-nitrophenol CH3 (c) The parent compound is phenol. It bears, in alphabetical order, a benzyl group at C-4 and a chlorine at C-2 (d) This compound is named as a derivative of anisole, C6HsOCH3 Because multiplicative pre- H-C CH (e) The compound is an aryl ester of trichloroacetic acid. The aryl group is 2, 5-dichlorophenyl Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
24.12 (a) The compound is named as a derivative of phenol. The substituents (ethyl and nitro) are cited in alphabetical order with numbers assigned in the direction that gives the lowest number at the first point of difference. (b) An isomer of the compound in part (a) is 4-ethyl-3-nitrophenol. (c) The parent compound is phenol. It bears, in alphabetical order, a benzyl group at C-4 and a chlorine at C-2. (d) This compound is named as a derivative of anisole, C6H5OCH3. Because multiplicative pre- fixes (di, tri-, etc.) are not considered when alphabetizing substituents, isopropyl precedes dimethyl. (e) The compound is an aryl ester of trichloroacetic acid. The aryl group is 2,5-dichlorophenyl. 2,5-Dichlorophenyl trichloroacetate Cl Cl 1 2 3 4 5 6 OCCCl3 O 4-Isopropyl-2,6- dimethylanisole OCH3 H3C CH3 CH(CH3)2 1 2 3 4 5 6 Cl HO CH2 1 2 3 4 6 5 4-Benzyl-2-chlorophenol OH NO2 CH2CH3 1 2 3 4 5 6 4-Ethyl-3-nitrophenol 3-Ethyl-4-nitrophenol OH CH2CH3 NO2 1 2 3 4 5 6 PHENOLS 681 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
682 PHENOLS 24.13(a)The reaction is an acid-base reaction. Phenol is the acid; sodium hydroxide is the base. (ONa+ Ho Pheno Sodium Sodium phenoxide (weaker acid) (b) Sodium phenoxide reacts with ethyl bromide to yield ethyl phenyl ether in a Williamson reaction. Phenoxide ion acts as a nucleophile C6H ONa CH CH, Br CHOCH CH NaBr Sodium Ethyl phenyl ether Sodi (c) p-Toluenesulfonate esters behave much like alkyl halides in nucleophilic substitution reac tions. Phenoxide ion displaces p-toluenesulfonate from the primary carbor H_ ONa CH3CH,CH, CH,O C6H-OCH, CH, CH, CH3 NaoS SycH Sodium Butyl p-toluenesulfonate Butyl phenyl ether Sodium p-toluenesulfonate (d) Carboxylic acid anhydrides react with phenoxide anions to yield aryl esters CH,ONa CH, COCCH C.HOCCH,+CH,CONa Sodium Acetic anhydride Phenyl acetate Sodium (e) Acyl chlorides convert phenols to aryl esters CC t HCl o-cresol Benzoyl chloride 2-Methylphenyl benzoate Hydrogen (f) Phenols react as nucleophiles toward epoxides. CH H, C +H2C—CH DCH,CH,OH m-cresol 2-(3-Methylphenoxy )ethanol Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
24.13 (a) The reaction is an acid–base reaction. Phenol is the acid; sodium hydroxide is the base. (b) Sodium phenoxide reacts with ethyl bromide to yield ethyl phenyl ether in a Williamson reaction. Phenoxide ion acts as a nucleophile. (c) p-Toluenesulfonate esters behave much like alkyl halides in nucleophilic substitution reactions. Phenoxide ion displaces p-toluenesulfonate from the primary carbon. (d ) Carboxylic acid anhydrides react with phenoxide anions to yield aryl esters. (e) Acyl chlorides convert phenols to aryl esters. ( f ) Phenols react as nucleophiles toward epoxides. CH3 OH m-Cresol Ethylene oxide H2C CH2 O 2-(3-Methylphenoxy)ethanol H3C OCH2CH2OH OH OC HCl CH3 CH3 CCl O O o-Cresol Benzoyl chloride 2-Methylphenyl benzoate Hydrogen chloride C6H5ONa C CH3COCCH3 6H5OCCH3 CH3CONa Sodium phenoxide Acetic anhydride Phenyl acetate Sodium acetate O O O O C6H5ONa C CH3CH2CH2CH2OS 6H5OCH2CH2CH2CH3 NaOS Sodium phenoxide Butyl p-toluenesulfonate Sodium Butyl phenyl ether p-toluenesulfonate O O O O CH3 CH3 C CH3CH2Br 6H5ONa C 6H5OCH2CH3 NaBr Sodium phenoxide Sodium bromide Ethyl bromide Ethyl phenyl ether OH NaOH ONa H2O Phenol (stronger acid) Water (weaker acid) Sodium hydroxide (stronger base) Sodium phenoxide (weaker base) 682 PHENOLS Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
683 The reaction as written conforms to the requirements of the problem that a balanced equation be written. Of course, the reaction will be much faster if catalyzed by acid or base, but the cat- all (g) Bromination of the aromatic ring of 2, 6-dichlorophenol occurs para to the hydroxy group. The more activating group(Oh) determines the orientation of the product. Cl 2. 6-Dichlorophenol Bromine (h) In aqueous solution bromination occurs at all the open positions that are ortho and para to the hydroxyl group. Br H,O 2Br 2HBr p-Cresol Bromine 2, 6-Dibromo-4. Hydrogen (i Hydrogen bromide cleaves ethers to give an alkyl halide and a phenol. OCH(CH3)2+ HBr OH + CH,)2 CHBr Isopropyl phenyl ether Phenol 24. 14(a) Strongly electron-withdrawing groups, particularly those such as-NO2, increase the acidity of phenols by resonance stabilization of the resulting phenoxide anion. Electron-releasing substituents such as-CH3 exert a very small acid-weakening effect. ON NO 2,4, 6-Trinitrophenol, 2,4, 6-Trimethylphenol more acidic less acidic (K2=3.8×10-1,pKa=04) (K2=1.3×10-1,pK2=10.9) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
The reaction as written conforms to the requirements of the problem that a balanced equation be written. Of course, the reaction will be much faster if catalyzed by acid or base, but the catalysts do not enter into the equation representing the overall process. (g) Bromination of the aromatic ring of 2,6-dichlorophenol occurs para to the hydroxy group. The more activating group (GOH) determines the orientation of the product. (h) In aqueous solution bromination occurs at all the open positions that are ortho and para to the hydroxyl group. (i) Hydrogen bromide cleaves ethers to give an alkyl halide and a phenol. 24.14 (a) Strongly electron-withdrawing groups, particularly those such as GNO2, increase the acidity of phenols by resonance stabilization of the resulting phenoxide anion. Electron-releasing substituents such as GCH3 exert a very small acid-weakening effect. OH H3C CH3 CH3 2,4,6-Trimethylphenol, less acidic (Ka 1.3 1011, pKa 10.9) OH O2N NO2 NO2 2,4,6-Trinitrophenol, more acidic (Ka 3.8 101 , pKa 0.4) Hydrogen bromide HBr Isopropyl phenyl ether OCH(CH3)2 Isopropyl bromide (CH3)2CHBr Phenol OH heat OH CH3 CH3 Br Br 2Br 2HBr 2 OH p-Cresol 2,6-Dibromo-4- Bromine methylphenol Hydrogen bromide H2O OH Br Br HBr 2 Cl Cl OH Cl Cl 2,6-Dichlorophenol Bromine 4-Bromo-2,6- dichlorophenol Hydrogen bromide PHENOLS 683 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
684 PHENOLS Picric acid (2, 4, 6-trinitrophenol) is a stronger acid by far than 2, 4, 6-trimethylphenol All three nitro groups participate in resonance stabilization of the picrate anion O O (b) Stabilization of a phenoxide anion is most effective when electron-withdrawing groups are present at the ortho and para positions, because it is these carbons that bear most of the nega rge in phenoxide 2, 6-Dichlorophenol is therefore expected to be(and is)a stronger acid than 3, 5-dichloro- OH 2, 6-Dichlorophenol, more acidic 3. 5-Dichlorophenol, less acidic (K2=1.6×10-7,pK=68) NO2 (K2=4.1×10-9,pK=84) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
Picric acid (2,4,6-trinitrophenol) is a stronger acid by far than 2,4,6-trimethylphenol. All three nitro groups participate in resonance stabilization of the picrate anion. (b) Stabilization of a phenoxide anion is most effective when electron-withdrawing groups are present at the ortho and para positions, because it is these carbons that bear most of the negative charge in phenoxide anion. 2,6-Dichlorophenol is therefore expected to be (and is) a stronger acid than 3,5-dichlorophenol. (c) The same principle is at work here as in part (b). A nitro group para to the phenol oxygen is directly conjugated to it and stabilizes the anion better than one at the meta position. OH NO2 4-Nitrophenol, stronger acid (Ka 1.0 108 , pKa 7.2) OH NO2 3-Nitrophenol, weaker acid (Ka 4.1 109 , pKa 8.4) OH Cl Cl 3,5-Dichlorophenol, less acidic (Ka 6.5 109 , pKa 8.2) OH Cl Cl 2,6-Dichlorophenol, more acidic (Ka 1.6 107 , pKa 6.8) O O O O N N O O O O O O N O N N O O O O O O N O N N O O O O O N O O N N O O O O O N O O 684 PHENOLS Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
PHENOLS 685 (d) A cyano group is strongly electron-withdrawing, and so 4-cyanophenol is a stronger acid than phenol CN Phenol. less acidic (K2=1.1×10-8,pK2=80)(K2=1×10-10,pK2=10) There is resonance stabilization of the 4-cyanophenoxide anion. (e) The 5-nitro group in 2, 5-dinitrophenol is meta to the hydroxyl group and so does not stabilize the resulting anion as much as does an ortho or a para nitro group ON NO ON 2. 6-Dinitrophenol, more acidi 0-4,pK2=3.7) 24.15 (a) The rate-determining step of ester hydrolysis in basic solution is formation of the tetrahedral ntermediat ArOccH +Ho ArOCCH ecause this intermediate is negatively charged, there will be a small effect favoring its for mation when the aryl group bears an electron-withdrawing substituent. Furthermore, this in termediate can either return to starting materials or proceed to products HO ArO→CCH Aro ChcoH Aro CH, co The proportion of the tetrahedral intermediate that goes on to products increases as the leav g group Aro becomes less basic. This is strongly affected by substituents; electron withdrawing groups stabilize ArO. The prediction is that m-nitrophenyl acetate undergoes hydrolysis in basic solution faster than phenol. Indeed, this is observed to be the case; m-nitrophenyl acetate reacts some ten times faster than does phenyl acetate at 25C. OCCH HO 0+ CH- COH han phenoxide because it is less basic) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(d) A cyano group is strongly electron-withdrawing, and so 4-cyanophenol is a stronger acid than phenol. There is resonance stabilization of the 4-cyanophenoxide anion. (e) The 5-nitro group in 2,5-dinitrophenol is meta to the hydroxyl group and so does not stabilize the resulting anion as much as does an ortho or a para nitro group. 24.15 (a) The rate-determining step of ester hydrolysis in basic solution is formation of the tetrahedral intermediate. Because this intermediate is negatively charged, there will be a small effect favoring its formation when the aryl group bears an electron-withdrawing substituent. Furthermore, this intermediate can either return to starting materials or proceed to products. The proportion of the tetrahedral intermediate that goes on to products increases as the leaving group ArO becomes less basic. This is strongly affected by substituents; electronwithdrawing groups stabilize ArO. The prediction is that m-nitrophenyl acetate undergoes hydrolysis in basic solution faster than phenol. Indeed, this is observed to be the case; m-nitrophenyl acetate reacts some ten times faster than does phenyl acetate at 25°C. HO OCCH3 O2N O m-Nitrophenyl acetate (more reactive) CH3COH O O O2N m-Nitrophenoxide anion (a better leaving group than phenoxide because it is less basic) ArO CH3COH O CH3CO ArO O ArO CCH3 O OH HO ArOCCH3 O OH ArOCCH3 O HO slow OH O2N NO2 2,6-Dinitrophenol, more acidic (Ka 2.0 104 , pKa 3.7) OH NO2 O2N 2,5-Dinitrophenol, less acidic (Ka 6.0 106 , pKa 5.2) O CN O C N OH CN 4-Cyanophenol, more acidic (Ka 1.1 108 , pKa 8.0) OH Phenol, less acidic (Ka 1 1010, pKa 10) PHENOLS 685 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
