Alcohols - Organic Chemistry I - Lecture Slides, Slides of Organic Chemistry

Download Alcohols - Organic Chemistry I - Lecture Slides and more Slides Organic Chemistry in PDF only on Docsity! Alcohols R-O-H Classification CH3, 1 o, 2o, 3o Nomenclature: Common names: “alkyl alcohol” IUPAC: parent = longest continuous carbon chain containing the –OH group. alkane drop -e, add –ol prefix locant for –OH (lower number for OH) docsity.com CH3 CH3 CH3CHCH2CHCH3 CH3CCH3 OH OH 4-methyl-2-pentanol tert-butyl alcohol 2-methyl-2-propanol 2o 3o CH3 HO-CHCH2CH3 CH3CH2CH2-OH sec-butyl alcohol n-propyl alcohol 2-butanol 1-propanol 2o 1o docsity.com Distillation of fermented beverages to produce “distilled spirits” with a greater percentage of ethyl alcohol (bp 78.3 oC). Ethyl alcohol forms a binary azeotrope with water: 95% ethanol + 5% water (bp 78.15oC) Diluted with water => “vodka” 40% ethyl alcohol in water. “proof”: when aqueous alcohol is placed on a sample of gunpowder and ignited, the gunpowder will burn at a minimum concentration of 50% alcohol. This is called “100-proof”. (proof = 2 * alcohol percent) docsity.com Add oil of juniper => gin Add peat smoke => scotch Age in a burned barrel => whiskey Add peppermint => schnapps Etc. Ethyl alcohol is a poison. LD50 = ~10g/Kg orally in mice. Nausea, vomiting, flushing, mental excitement or depression, drowsiness, impaired perception, loss of coordination, stupor, coma, death may occur. (intoxication) docsity.com Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1 o) 5. 6. 7. 8. docsity.com 1. Reaction of alcohols with HX: (#1 synthesis of RX) R-OH + HX  R-X + H2O a) HX: HI > HBr > HCl b) ROH: 3o > 2o > CH3 > 1 o c) May be acid catalyzed d) Rearrangements are possible except with most 1o alcohols. docsity.com CH3CH2CH2CH2-OH + NaBr, H2SO4, heat  CH3CH2CH2CH2-Br n-butyl alcohol n-butyl bromide 1-butanol 1-bromobutane CH3 CH3 CH3C-OH + HCl  CH3C-Cl (room temperature) CH3 CH3 tert-butyl alcohol tert-butyl chloride 2-methyl-2-propanol 2-chloro-2-methylpropane CH3CH2-OH + HI, H +, heat  CH3CH2-I ethyl alcohol ethyl iodide ethanol iodoethane docsity.com Mechanism? CH3-OH and most 1 o alcohols react with HX via SN2 mechanism 3o and 2o react with HX via SN1 mechanism Both mechanisms include an additional, first step, protonation of the alcohol oxygen: R-OH + H+  R-OH2 + “oxonium ion” docsity.com Mechanism for reaction of an alcohol with HX: 2o or 3o alcohols: SN1 1) R-OH + HX R-OH2 + X 2) R-OH2 R + H2O RDS 3) R + X R-X docsity.com May be catalyzed by acid. SN2 rate = k [ ROH2 + ] [ X- ] SN1 rate = k [ ROH2 + ] Acid protonates the -OH, converting it into a better leaving group (H2O), increasing the concentration of the oxonium ion, and increasing the rate of the reaction. docsity.com Rearrangements are possible (except with most 1o alcohols): CH3 CH3 CH3CHCHCH3 + HBr  CH3CCH2CH3 OH Br   Br- CH3 CH3 [1,2-H] CH3 CH3CHCHCH3  CH3CHCHCH3  CH3CCH2CH3 OH2+ + + 2o carbocation 3o carbocation docsity.com 2. With PX3 ROH + PX3  RX a) PX3 = PCl3, PBr3, P + I2 b) No rearrangements c) ROH: CH3 > 1 o > 2o CH3 CH3 CH3CCH2-OH + PBr3  CH3CCH2-Br CH3 CH3 neopentyl alcohol 2,2-dimethyl-1-bromopropane  docsity.com 3. Dehydration (later) docsity.com 4) As acids. a) With active metals: ROH + Na  RONa + ½ H2  b) With bases: ROH + NaOH  NR! CH4 < NH3 < ROH < H2O < HF docsity.com R C OH O R C ONa O R C OR' O carboxylic acid sodium salt ester R S O O OH R S O O OK R S O O OR' sulfonic acid potassium salt ester HO P O OH OH HO P O OH OR HO P O OR OR RO P O OR OR phosphoric acid monoester diester triester docsity.com "Lasso" chemistry R C O H O R C O R' O H-O-R' H+ + + H2O CH3C O O H + H-O CHCH3 CH3 H+ CH3C O O CHCH3 CH3 + H2O acetic acid isopropyl alcohol isopropyl acetate docsity.com R C Cl O R C O R' O H-O-R' H+ + + HCl CH3C O Cl + H-O CHCH3 CH3 H+ CH3C O O CHCH3 CH3 + HCl acetyl chloride isopropyl alcohol isopropyl acetate acid chloride + alcohol --> ester docsity.com 6. Oxidation 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. docsity.com Primary alcohols can also be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl  CH3CH2CHO pyridinium chlorochromate aldehyde or CH3CH2CH2-OH + K2Cr2O7, special conditions  docsity.com Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1 o) 5. 6. 7. 8. docsity.com