Chapter 9 Alcohols, Ethers and phenols 9.1 IUPAC Nomenclature of Alcohols, Ethers and Phenols 9.1.1 Naming Alcohols 9.1.2 Naming Phenols 9.1.3 Naming Ethers 9.2 Preparation of alcohols,Ethers and Phenols 9.2.1 Preparation of alcohols A. Preparation of alcohols by reduction of carbonyl compounds (1) Hydrogenation of aldehydes and ketones by catalysis of metals (2) Reduction of carbonyl compounds by metal hydrides B. Preparation of diols 9.2.2 Preparation of Ethers A. Ethers by intermolecular dehydration of alcohols B. Williamson Synthesis of Ethers 9.2.3 Preparation of phenols A. Laboratory synthesis B. Industrial synthesis 9.3 Reactions of Alcohols The sites of reactions of a Alcohol 9.3.1 Acidity and Basicity of Alcohols 9.3.2 Conversion of alcohols to ethers 9.3.3 Oxidation of alcohols A. Oxidation of primary alcohols B. Oxidation of secondary alcohols C. Oxidation of vicinal diols 9.4 Reactions of phenols 9.4.1 Acidity of Phenols 9.4.2 Electrophilic aromatic substitutions 9.4.3 Acylation of phenols Fries rearrangement 9.4.4 Kolbe-Schmitt reaction 9.4.5 Preparation of aryl ethers 9.4.6 Cleavage of aryl ethers by hydrogen halides 9.4.7 Claisen rearrangement of allyl aryl ethers 9.4.8 Oxidation of phenols: Quinones 9.5 Reactions of Ethers 9.5.1 Acid-catalyzed cleavage of ethers 9.5.2 Preparation of epoxides A.Epoxidation of alkenes by reaction with peroxy acids B. Conversion of vicinal halodrins to epoxides 9.5.3 Reactions of Epoxides A. Base-catalyzed ring opening B. Acid-catalyzed ring opening Compounds with O-containing functional groups O ROH ROR' ArOH R C H O R C R' Alcohol Ether Phenol Aldehyde Ketone 醇 醚 O R C OH 酚 O X, R C Y Carboxylic Carboxylic acid acid derivatives Y 羧酸 醛 羧酸衍生物 OR, 酮 Acetyl halides 酰卤 Esters 酯 O Carboxylic acid C R anhydrides 酸酐 The interplay of these Amides NR' 2 compounds is fundamental 酰胺 to organic chemistry and biochemistry Compounds that have hydroxyl C OH group bonded to a saturated, sp3-C atom-Alcohols. Compounds that have hydroxyl OH group bonded to a aromatic ring-Phenols. Compounds that have a oxygen R O R' atom bonded to two carbon atom -Ethers Class of Ethers: Class of Alcohols: R'' RCH2OH RCHR' OH RCR' C OH Primary Secondary Tertiary alcohols alcohols alcohols O C R O R'Ethers CH2 H2C O Epoxides 9.1 IUPAC Nomenclature of Alcohols, Ethers and Phenols P252,8.1 9.1.1 Naming Alcohols Common name: Alkyl + alcohol Substitutive name: Suffix: e ol CH3 • Number: begin at the end nearer the hydroxyl group. CH3COH CH2OH Benzyl alcohol (苄醇) H2C CHCH2OH Allyl alcohol (烯丙醇) 2-Propen-1-ol Phenyl methanol (2-丙烯-1-醇) (苯甲醇) CH3 tert-Butylalcohol (叔丁醇) 2-Metyl-2-propanol (2-甲基-2-丙醇) HOCH2CH2OH HOCH2CHCH2OH ClCH CH CH OH 2 2 2 Ethyl glycol OH 3-Chloro-1-propanol (乙二醇) 1,2-Ethanediol Glycerol(甘油) OH (3-氯-1-丙醇) 1,2,3-Propanetriol (CH ) C C(CH ) 9.1.2 Naming Phenols Phenol is the base name: o-, m-, p-: substitutent OH CH3 4-Methylphenol p-Methylphenol p-Cresol(甲酚) Cl OH OH CH3 BHT OH OH OH 1,2-Benzenediol Catechol 1,3-Benzenediol Resorcinol (儿茶酚) (邻苯二酚) (间苯二酚) 3 3 3 3 CH3 OH 5-Chloro2-methylphenol (2-甲基-5-氯 苯酚) OH 1,4-Benzenediol Hydroquinone (对苯二酚) (氢醌) OH OH OH OH HO OH Pyrogallol 1,3,5-benzenetriol (连苯三酚) OH (均苯三酚) OH 1-Naphthol α- Naphthol 2-Naphthol β- Naphthol (1-萘酚) (2-萘酚) 9.1.3 Naming of Ethers Functional class IUPAC names Diethyl ether P253 Tetrahydrofuran Anisole (THF) phenyl ether (乙醚) (四氢呋喃) Methyl (茴香醚) CH3CH2OCH3 CH3 (苯甲醚) Ethyl methyl ether C6H5O C CH3 (甲乙醚) Symmetrical ethers (单醚) CH3 Unsymmetrical (Mixed) ethers (混醚) tert-Butyl phenyl ether (苯叔丁基醚) Substitutive IUPAC CH3CHCH2CH2CH3 OCH3 Alkoxy (烷氧基) CH3 CH3CH2O 1-Ethoxy-4-methylbenzene 2-Methoxypentane (4-甲基-1-乙氧基苯) (2-甲氧基戊烷) Suffix:yl oxy Cyclic ethers: O O O 1,4-Dioxane Oxane 1,4-二氧六环 烷 二 烷 9.2 Preparation of alcohols, Ethers and Phenols 9.2.1 Preparation of Alcohols Transformation of the several functional groups to alcohols: C ROH P258,8.4 C RX O C R'(H) A. Preparation of Alcohols by Reduction of Carbonyl Compounds O C Reducing agent C OH (1) Hydrogenation of aldehydes and ketones by Catalysis of metals O RC H + H2 Aldehydes O RC R' + H2 Ketones CH3O Pt, Pd, Ni, or Ru RCH2OH Primary alcohols RCHR' Pt, Pd, Ni, or Ru OH Secondary alcohols O H2, Pt C H EtOH CH3O H C H OH p-Methoxybenzaldehyde p-Methoxybenzyl alcohol(92%) (2) Reduction of carbonyl compounds by metal hydrides P259, 8.5 Metal hydrides: H Na + H B H H Li+ H H Al H H Sodium borohydride NaBH4 Lithium aluminum hydride LiAlH4(LAH) (硼氢化钠) (四氢铝锂) •Reaction of NaBH4 with aldehydes and ketones O O CH CH33CH CH22CH CH22CH CH Butanal NaBH NaBH44 H H22O O CH CH33CH CH22CH CH22CH CH22OH OH O 1-Butanol (87%) OH NaBH4 CH3CCH2C(CH3)3 EtOH 4,4-Dimethyl2-pentanone O NaBH4 H2O CH3CHCH2C(CH3)3 4,4-Dimethyl2-pentanol(85%) OH An aqueous or alcoholic solution •Reaction of LiAlH4 with Aldehydes and Ketones (1) LiAlH4 / Et2O (CH3)3CCHCH3 (2) H2O OH O 3,3-Dimethyl-2-butanone 3,3-Dimethyl-2-butanol (CH3)3CCCH3 •Reaction of LiAlH4 with carboxylic acids and esters 4 RCO2H + 3 LiAlH4 Et2O [(RCH2O)4Al]Li + 4 H2 + 2 LiAlO2 H2O O C OH 1. LiAlH4 / Et2O 2. H2O 4 RCH2OH + Al (OH)3 + LiOH CH2OH Cyclopropanecarboxylic Cyclopropylmethanol (环丙基甲醇)(78%) Acid (环丙基甲酸) O RC OR' 1. LiAlH4 / Et2O 2. H2O O 1. LiAlH4 / Et2O COC2H5 2. H2O RCH2OH + R'OH CH2OH + C2H5OH Ethyl benzoate Benzyl alcohol (苯甲酸乙酯) (苄醇)(90%) RCOOH RCOOR' 1°Alcohols Characteristics of reactions: • Selective reduction: NaBH4 does not reduce C=C, C C and -COOH, -COOR。 LiAlH4 does not reduce C=C, C C Reduced by LiAlH4 Reduced by NaBH4 O O O O O RC O < RC OH < RC OR' < RC R' < RC H Ease of reduction O O COC2H5 O NaBH4 H3+O CH3OH 1. LiAlH4,ether CH3CH2CH CHCOCH3 2. H3O+ H OH COOC2H5 CH3CH2CH CHCH2OH + CH3OH Methyl 2-pentenoate 2-Penten-1-ol(91%) • Solvents: NaBH4 Solvents: H2O, ROH LiAlH4 Et2O, THF LiAlH4 reacts violently with water. B. Preparation of diols Vicinal diols CH2CH2 OH OH CH3CHCH2 OHOH 1,2-Ethanediol Ethylene glycol 1,2-Propanediol Propylene glycol 1,2-乙二醇(甘醇) 1,2-丙二醇 CH3 H3C C O OH CH3 , OsO4(Cat) RCHCH2 OH, OH OH HO OsO4 Alkaline Osmium tetraoxide tert-butyl hydroperoxide (碱性) RCH CH2 (四氧化锇) (叔丁基氢过氧化物) HO (CH3)3COOH, OsO4 (Cat) (CH3)3COH, HO Hydroxylation Syn-addition HO H H KMnO4 / OH- (cold) 9.2.2 Preparation of Ethers A. Ethers by intermolecular dehydration of alcohols Substrate: Primary alcohols Acid-catalyzed Products: symmetric ethers P261, B. The Williamson Synthesis of Ethers 8.6 Sodium alkoxide,Alkyl halide and derivatives Mixed ethers R O Na + R' L R O R' + Na L L: Br, I, OSO2R'' or OSO2OR'' CH3CH2CH2OH + Na Propyl alcohol CH3CH2CH2O Na + 1/2 H2 Sodium propoxide CH3CH2I CH3CH2CH2OCH2CH3 + Na I Ethyl propyl ether (70%) The reaction characteristic: 1. SN2 reaction 2. The best substrate is primary alkyl halide (CH3)2CHONa + CH2Cl (CH3)2CHOCH2 CH2ONa + (CH3)3CHCl + NaCl Alexander W. Williamson (1824-1904) Alexander W. Williamson was Born in London, England, and received his Ph.D. at the University of Giessen in 1846.His ability to work in laboratory was hampered by a childhood injury that caused the loss of an arm. From 1849,utill 1887, he was professor of Chemistry at University College, London. Bonding in organic compounds at that time was thought to be of either the water type, as in alcohols, ROH, or of the radical type, as in ethers which would be given the formula RO. But Williamson, by his ether synthesis, showed that mixed ethers, with two different alkyl groups, could be prepared. Ethers thus has to have the water-type formula ROR', and oxygen had the equivalent weight of 8 but the atomic weight of 16. By this type of argument he established and rationalised the structures of many of the families of simple organic compounds. Thus, in 1850 he predicted the existence of acetic anhydride, which was prepared in 1851.We still have some examples of his early apparatus, and his copper pelicans, in which he prepared ether, are shown at right. When you realise the scale on which these reactions were carried out, and the fact that the pelican was heated over a charcoal brazier, it is remarkable that we do not seem to have records of catastrophic accidents taking place. Later on Williamson, again with people such as Liebig, was responsible for the introduction of much of the glassware which we are familiar with today, except that it was usually fitted together with corks rather than ground glass joints. Standard joints, blown in a mould, as we know them today did not come into use until the middle of the last (20th) century. Towards the end of his period as Head of Department, Williamson became very much involved in College and University politics, and his research suffered. This was the period when the other London colleges - Kings, Birkbeck, Queen Mary, what is now Imperial College, and so on were combined into a federal university, and presumably Williamson felt the need to fight the University College corner. 9.2.3 Preparation of phenols From aniline: A. Laboratory synthesis N2+ NH2 OH H3+O£¬¡÷ NaNO2, H2SO4 NO2 0~5¡æ NO2 NO2 (80%) B. Industrial synthesis (1) Reaction of benzenesulfonic acid with NaOH SO3H SO3 H2SO4 CH3 Toluene OH 1. NaOH, 300¡æ 2. H3+O CH3 CH3 p-Toluenesulfonic p-methylphenol acid (72%) 碱熔法 (2) Hydrolysis of chlorobenzene Cl 1. NaOH, H2O, 370¡æ + 2. H 3. From cumene(枯烯) + CH3CH 无水 AlCl3 CH2 85 ~ 95 ¡æ Friedel-Crafts alkylation CH3 CH + O2 CH3 OH 卤苯水解 CH3 CH CH3 Cumene 枯烯 CH3 95 ~ 135 ¡æ C O OH CH3 Cumene hydroperxide (氢过氧化枯烯) Cumene is oxidized to cumene hydroperoxide CH3 C O OH CH3 O 10% H2SO4 OH ~ 90¡æ 异丙苯法 9.3. Reactions of Alcohols + CH3CCH3 •The sites of reactions of a Alcohol: H C O H Nucleophilic substitution H C O C C Elimination H Nu: C H C Oxidation O Weak basicity Protonation H A H H O H Weak acidity 9.3.1 Acidity and Basicity of Alcohols Like water, alcohols are both weakly basic and weakly acidic. P256,8.3 As a weak base: Reversible protonated by strong acids to yield oxonium ions( 离子): H O H+H A R O H + A R An alcohol An oxonium ion As a weak acid: H H R O + H O O H + O R H An alcohol An Alkoxide Hydronium H ion(烷氧负离子) ion(水合离子) Acid (base) conjugate conjugate base acid TABLE. pKa Values for In any proton-transfer some weak acids process: ACID CH3OH H 2O CH3CH2OH (CH3)3COH HC CH H2 NH3 CH3CH3 P257, Table 8.1 K>1 Stroger Stroger + pKa acid base Weaker + Weaker 15.5 acid base 15.74 16.0 18.0 25 35 38 50 Relative acidity: H2O > ROH > RC C H > H2 > NH3 > RH Relative basicity: R- > NH2- > H- > C C > RO > OH R 2 CH3CH2OH + 2 Na 2 CH3CH2O Na + H2 CH3 CH3 2 H3 C C OH + 2 K 2 H3 C C O K + H2 CH3 CH3 NaH, NaNH2 P263.8.7 9.3.2 Conversion of Alcohols to Ethers H2SO4 180 C 2 CH 2=CH 2 + 2H2O H2SO4 140 C CH3CH2-O-CH2CH3 + H2O 2CH3CH2OH 2 CH3CH2CH2CH2OH H+ ¡÷ Dehydration CH3CH2CH2CH2OCH2CH2CH2CH3 + H2O Characteristics of the reaction: 1. Condensation(缩合反应) 2. Only for primary alcohols 3. The temperature of condensation is lower than elimination. 4. SN2 mechanism HOCH2CH2CH2CH2CH2OH H2SO4 ¡÷ O 1,5-Pentanediol (1,5-戊二醇) + H2O Oxane ( 烷)(76%) 9.3.3 Oxidation of alcohols A. Oxidation of primary alcohols O R-CH2OH [O] FCH2CH2CH2OH RCH2OH PCC CrO3 + HCl + K2Cr2O7 H2SO4,H2O O R C H N O R-C-H 3-Fluoro-1-propanol (3-氟-1-丙醇) P 263 [O] R-C-OH O FCH2CH2 C OH 3-Fluoropropanoic acid (3-氟丙酸) (74%) PCC reagent is soluble in CH2Cl2 N H CrO3Cl Pyridinium chlorochromate ( PCC) CH3 (C2H5)2C CH2OH + PCC CH2Cl2 25 C CH3 O (C2H5)2C C PCC doesn’t attack C=C bond O PCC CH2OH CH Cl 2 2 C H Citronellol Citronellal (82%) (香茅醇) (香茅醛) B. Oxidation of secondary alcohols Secondary [O] ketones alcohols RCHR' OH K2Cr2O7 H2SO4,H2O RCR' O Chromic acid H2CrO4 H R OH O R' C Na2 Cr2O7 H2SO4,H2O Cyclohexanol OH [O] No rection R" Cyclohexanone(85%) AgIO3 C. Oxidation of vicinal diols Vicinal diols react with HIO4, the C-C bond is broken to form carbonyl compounds Ch.P225,(3) O RCHOH + O I OH R'CHOH O -H2O OH O RCH O I OH R'CH O OH RCHO + HIO 3 R'CHO AgNO3 is added to identify the vicinal diols 9.4 Reactions of phenols The sites of reactions Acylation Acidity Formation of aryl ethers Aromatic Electrophilic substitution 9.4.1 Acidity of Phenols P256,8.3 O OH pKa = 18 OH CH3C OH pKa = 9.89 pKa = 4.74 TABLE 1 The acidity constants of phenols pKa (25℃) Substimptuents o- -H -CH3 -Cl -NO2 -OCH3 9.89 10.20 8.11 7.17 9.98 9.89 10.01 8.80 8.28 9.65 Substituents 9.89 2,4-Dinitro 10.17 2,4,6-Trinitro 9.20 (picric acid) (苦味酸) 7.15 10.21 pKa (25℃) 3.96 0.38 Substituted phenols: Electron - releasing group Substuents Acidity is decreased Electron – withdrawing on the position group o- or pAcidity is increased O H O + H pka = 10 Electron delocalization in phenoxide ion: O O O O O 9.4.2 Electrophilic aromatic P266; Ch.P322,(2) substitutions A hydroxyl group is a very powerful activating substituent: Bromination: OH OH H2O + 3 Br2 Br (white) + 3HBr Br Br (100%) Sulfonation: OH 25¡æ OH (concd)H2SO4 SO3H OH Rate control 100¡æ 100¡æ SO3H Equilibrium control 9.4.3 Acylation of phenols Acylating agents: acyl halides and carboxylic acid anhydrides Ch.P319(丙) OH + CH3 H3C OCOCH3 O CH3CCl pyridine 75£¥ H3C Fries rearrangement: O OH CC6H5 OH O OCC6H5 AlCl3 Phenol benzoate + HCl CH3 Phenolic Esters (酚酯) Conversion of aryl esters to CC6H5 aryl ketones. (9%) O p-hydroxylbenzopheone + (对-羟基二苯酮)(64%) 9.4.4 Kolbe-Schmitt reaction: Carboxylaltion of phenols Sodium phenoxide CO2 Heated under pressure Salicylic acid ONa + CO2 O OCCH3 COOH 120¡æ 100 atm Aspirin (阿斯匹林) (乙酰水杨酸) Acidified OH H+ COONa OH COOH Salicylic acid (水杨酸)(79%) 9.4.5 Preparation of aryl ethers Williamson Method A Phenoxide anion A alkyl halide Alkylation of hydroxyl oxygen a phenol ArOH NaOH ArO Na O Na OH + NaOH H2O R X (X = Cl, Br, I, ArOR OSO2OR') OCH3 CH3OSO2OCH3 Me2SO4-methylating agent OCH3 + Na+X + NaOSO2OCH3 (Anisole) 茴香醚 I + CH3ONa Why? 9.4.6 Cleavage of aryl ethers by hydrogen halides Ar O concd HX ¡÷ R ¡÷ Ar OH + RX concd HX Ar X + ROH The bond of O-R was broken! OCH3 OH The bond of HO + HBr + CH3Br C-O in phenols has partial double CH3 CH3 bond character HBr 2 No reaction 9.4.7 Claisen rearrangement of allyl aryl ethers Intramolecular Heating allyl aryl ether reaction The product is o-allylphenol OCH2CH CH2 OH 200¡æ CH2CH CH2 O O via Transition state Claisen was professor in Aachen in 1890, Kiel in 1897 and Berlin in 1904. Several syntheses especially condensation reactions between aldehydes, ketones, and esters (1881-1890) are connected with Claisen´s name. He also carried out research on tautomerism and rearrangement reactions (Umlagerungsreaktionen) http://www.chemsoc.org/networks/enc/FECS/ Claisen.htm 19th Century Claisen, Ludwig Born: Köln (Germany), 1851 Died: Godesberg near Bonn (Germany), 1930 9.4.8 Oxidation of phenols: Quinones O P266 OH (醌) K2Cr2O7 H2SO4, H2O OH Hydroquionoe The sructures of quinones: O O p-Benquinone O O OH - 2e + 2H + 2e OH O O O O O CH3 CH3 CH2CH C(CH2CH2CH2CH)3CH3 CH3 Vitamin K 9.5 Reactions of Ethers P267,8.9 9.5.1 Acid-catalyzed cleavage of ethers CH3CH2OCH2CH3 + 2 HBr 2 CH3CH2Br + H2O Mechanism of the reaction: CH3CH2O CH2CH3 + Br CH3CH2OCH2CH3 + HBr CH3CH2O + CH3CH2Br H H CH3CH2OH + HBr Br CH3CH2 + CH3CH2 O H H Br + O H H 9.5.2 Preparation of epoxides A. Epoxidation of alkenes by reaction with peroxy acids (过氧酸) O O RHC CHR + R'C OH O O RCH CHR + R'C O OH Syn-addition O Peroxy acids: CH3COOH C6H5COOH Peroxyacetic acide Peroxybenzoic acide (过氧乙酸) (过氧苯甲酸) B. Conversion of vicinal halohydrins (α-卤代醇) to epoxides X R2C CR2 2 H2O R2C CR2 HO X HO R2C CR2 O Intramolecular Williamson ether synthesis: R HO R X R C C R R H O HO H + R R X R C C R O R R R C C R + X O R C C R O R H3C H C C H CH3 X 1. Br2/ H2O 2. HO H3C H C C H CH 3 O 1. Anti-addition, 2. Inversion of configuration 9.5.3 Reactions of epoxides A. Base-catalyzed ring opening CH3CH2O + H2C CHCH3 O CH3CH2OH CH3CH2OCH2CHCH3 O CH3CH2OCH2CHCH3 + CH3CH2O OH To the unsymmetric epoxide, in basecatalyzed ring-opening, attack by nucleophile occurs at less substituted carbon atom. B. Acid-catalyzed ring opening CH3 CH3OH + CH3 C CH2 O H CH3 CH3 C CH2OH OCH3 In the acid-catalyzed ring opening, the nucleophile attacks primarily at theAntimore hydroxylation substituted carbon atom. CH3 ¦Ä CH3 CH3OH + CH3 C CH2 O ¦Ä H CH3 C CH2OH OCH3 H SN2 reaction With inversion of configuration O + CH3COOH H O + H3O H H O + CH3COOH H2O H OH H H OH2 + H H OH H OH H OH H Problems to Chapter 9 P276 8.24 (c), (d) 8.25 (b), (c) 8.28 8.31(a),(b) 8.33(a), (c), (e) 8.35(a),(d) 8.36(b), (e) 8.37(b) 8.38(b), (c) 8.40 8.41 8.43 8.46 8.48 8.51 8.53 8.54(b) 8.55