Bài giảng Hoá học hữu cơ alcohol

ALCOHOL I.Introduction II.Physical Properties III.Synthesis IV.Reaction I.1.Structure of Alcohols • Hydroxyl (OH) functional group • Oxygen is sp3 hybridized => I.2 Classification • CH3 • Primary (1o): carbon with –OH is bonded to one other carbon • Secondary (2o) : carbon with –OH is bonded to two other carbons • Tertiary (3o): carbon with –OH is bonded to three other carbons • Aromatic (phenol): -OH is bonded to a benzene ring Classify these alcohols: CH3 CH3 CH3 CH CH2OH CH3 C OH CH3 OH OH CH3 CH CH2CH3 I.3.IUPAC Nomenclature • Find the longest carbon chain containing the carbon with the -OH group • Drop the -e from the alkane name, add -ol • Number the chain, starting from the end closest to the -OH group • Number and name all substituents Name these: CH3 CH3 CH CH2OH 2-methyl-1-propanol OH CH3 CH CH2CH3 2-butanol CH3 CH3 OH C OH CH3 2-methyl-2-propanol Br CH3 3-bromo-3-methylcyclohexanol Unsaturated Alcohols • Hydroxyl group takes precedence Assign that carbon the lowest number • Use alkene or alkyne name OH CH2 CHCH2CHCH3 4-penten-2-ol (old) pent-4-ene-2-ol (1997 revision of IUPAC rules) Hydroxy Substituent • When -OH is part of a higher priority class of compound, it is named as hydroxy • Example: OH CH2CH2CH2COOH 4-hydroxybutanoic acid Common Names • Alcohol can be named as alkyl alcohol • Useful only for small alkyl groups • Examples: CH3 CH3 CH CH2OH isobutyl alcohol OH CH3 CH CH2CH3 sec-butyl alcohol => Naming Diols • Two numbers are needed to locate the two -OH groups • Use -diol as suffix instead of -ol OH HO 1,6-hexanediol => "Lasso" chemistry O + R C O H O CH3C O H acetic acid H-O-R' + H+ O + R C O R' CH3 H-O CHCH3 isopropyl alcohol H+ H2O O + H2O CH3C CH3 O CHCH3 isopropyl acetate acid chloride + alcohol > ester O R C Cl + O CH3C Cl H-O-R' + H+ O + R C O R' CH3 H-O CHCH3 acetyl chloride isopropyl alcohol H+ HCl O + HCl CH3C CH3 O CHCH3 isopropyl acetate Sulfonate ester O R S Cl O sulfonyl chloride + H-O-R alcohol O R S O-R + HCl O sulfonate ester IV.6 Oxidation CH4 -4 oxidation states of carbon - oxidation  CH3OH CH2O HCO2H -2 +2  reduction - CO2 +4 Oxidizing agents: KMnO4, K2Cr2O7, CrO3, NaOCl, etc Primary alcohols: CH3CH2CH2-OH + KMnO4, etc  CH3CH2CO2H carboxylic acid Secondary alcohols: OH O CH3CH2CHCH3 + K2Cr2O7, etc  CH3CH2CCH3 ketone Teriary alcohols: no reaction Primary alcohols ONLY can be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl  pyridinium chlorochromate (PCC) CH3CH2CHO aldehyde or CH3CH2CH2-OH + K2Cr2O7, special conditions Oxidation of Alcohol in the Body  Enzymes in the liver oxidize ethanol  The aldehyde produced impairs coordination  A blood alcohol level over 0.4% can be fatal O || CH3CH2OH CH3CH 2CO2 + H2O Ethyl alcohol acetaldehyde Oxidation of alcohols in liver acetaldehydedehydrogenase alcoholdehydrogenase O CH3CH2OH CH3C ethyl alcohol ethanol O CO2 + H2O CH3C H OH acetaldehyde ethanal acetic acid ethanoic acid alcoholdehydrogenase CH3OH metyl alcohol methanol O HC H formaldehyde methanal O HC OH formic acid methanoic acid reacts with proteins causing denaturation great toxicity to humans not toxic to horses and rats Effect of Alcohol on the Body Breathalyzer test • K2Cr2O7 (potassium dichromate) • This orange colored solution is used in the Breathalyzer test (test for blood alcohol level) • Potassium dichromate changes color when it is reduced by alcohol • K2Cr2O7 oxidizes the alcohol Breathalyzer reaction orange-red green 8H++Cr2O72-+3C2H5OH→2Cr3++3C2H4O+7H2O dichromate ethyl ion (from K2Cr2O7) alcohol chromium (III) acetaldehyde ion OH O [O] H3C C H ethyl alcohol H H3C + C H acetaldehyde H2O Oxidation of Thiols • Mild oxidizing agens remove two hydrogen atoms from two thiol molecules • The remaining pieces of thiols combine to form a new molecule, disulfide, with a covalent bond between two sulfur atoms • R – S – H H – S – R+I2 → RS – SR+2HI • RSH + H2O2 → RS – SR + H2O The chemistry of the “permanent” waving of hair • • • • • • • • Hair is protein, and it is held in shape by disulfide linkages between adjacent protein chains The first step involves the use of lotion containing a reducing agent such as thioglycolic acid, HS – CH2 – COOH The wave lotion ruptures the disulfide linkages of the hair protein The hair is then set on curles or rollers and is treated with a mild oxidizing agent such as hydrogen peroxide (H2O2) Disulfide linkages are formed in new positions to give new shape to the hair Exactly the same chemical process can be used to straighten naturally curly hair The change in hair style depends only on how one arranges the hair after the disulfide bonds have been reduced and before the reoxidation takes place Permanent Hair Wave (http://www.elmhurst.edu/~chm/vchembook/568hairwave.html) Highly applied alcohols • Ethanol is made by hydration of ethylene (ethene) in the presence of acid catalyst H H C H [H+] + HOH C H H H H C C H OH H Production of ethanol from grain by fermentation • Grain seeds are grounded and cooked → mash • Malt (the dried sprouts of barley) or special mold is added → source of the enzyme diastase that catalyzes the conversion of starch to malt sugar, maltose diastase (C6H10O5)2x + H2O → x C12H22O11 starch maltose • Pure yeast culture is added C12H22O11 + H2O → C6H12O6 maltoseglucose C6H12O6 → CH3CH2OH + CO2 glucose ethanol carbon dioxide Isopropyl alcohol • is produced by addition of water to propylene (1-propene) H3C H C [H+] CH2 + HOH H3C H C CH3 OH (Markovnikov's rule) CH3CH2CH2OH propyl alcohol is never formed Methanol • is made commercially from carbon monoxide and hydrogen • CO + 2H2 → CH3OH [...]... dilute acid protonates the alkoxide to produce an alcohol R C O R C O R C OH HOH => OH Synthesis of 1° Alcohols Grignard + formaldehyde yields a primary alcohol with one additional carbon CH3 H3C C CH2 C H H CH3 H H MgBr C O H CH3 CH2 C O MgBr H CH3 CH3 CH CH2 H CH CH2 H CH2 C O H HOH H => Synthesis of 2º Alcohols Grignard + aldehyde yields a secondary alcohol CH3 H3C C CH2 C H H CH3 H3C H MgBr C O H... H => Synthesis of 3º Alcohols Grignard + ketone yields a tertiary alcohol CH3 H3C C CH2 C H H CH3 H3C H MgBr C O H3C CH3 CH2 C O MgBr CH3 CH3 CH3 CH CH2 CH3 CH CH2 CH3 CH2 C O H HOH CH3 => How would you synthesize OH CH3CH2CHCH2CH2CH3 CH2OH OH OH CH3 C CH3 CH2CH3 => Grignard Reactions with Acid Chlorides and Esters • Use two moles of Grignard reagent • The product is a tertiary alcohol with two identical... is a 1º alcohol with 2 additional carbons O O MgBr + CH2 CH2CH2 CH2 HOH O H CH2CH2 => MgBr Limitations of Grignard • No water or other acidic protons like O-H, N-H, S-H, or -C—C-H Grignard reagent is destroyed, becomes an alkane • No other electrophilic multiple bonds, like C=N, C—N, S=O, or N=O => Reduction of Carbonyl • Reduction of aldehyde yields 1º alcohol • Reduction of ketone yields 2º alcohol. .. Methyl phenols are cresols OH H3C Cl 3-chlorophenol meta-chlorophenol 4-methylphenol para-cresol => II.Physical Properties • Unusually high boiling points due to hydrogen bonding between molecules • Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases => Boiling Points => Solubility in Water Solubility decreases as the size of the alkyl group increases... of esters or carboxylic acids O C H H H C H O + H H3O O H C H => Lithium Aluminum Hydride • Stronger reducing agent than sodium borohydride, but dangerous to work with • Converts esters and acids to 1º alcohols O C OCH3 H LAH H3O+ C O H H =>