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Alcohols Chemistry PowerPoint Presentation

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On : Dec 09, 2014

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  • Slide 1 - Alcohols R-O-H Classification CH3, 1o, 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)
  • Slide 2 - 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
  • Slide 3 - Physical properties of alcohols: polar + hydrogen bonding relatively higher mp/bp water insoluble! (except for alcohols of three carbons or less) CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2-OH hydrophobic hydrophilic
  • Slide 4 - Oldest known organic synthesis: “fermentation” Sugar + yeast  ethyl alcohol + CO2 Grape juice => “wine” Barley => “beer” Honey => “mead” Rice => “sake” ~5-11% ethanol
  • Slide 5 - 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)
  • Slide 6 - 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)
  • Slide 7 - Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1o) 5. 6. 7. 8.
  • Slide 8 - R-H R-X R-OH Acids Bases Active metals Oxidation Reduction Halogens
  • Slide 9 - Alcohols, reactions: R-|-OH With HX With PX3 (later) RO-|-H As acids Ester formation Oxidation
  • Slide 10 - 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 > 1o c) May be acid catalyzed d) Rearrangements are possible except with most 1o alcohols.
  • Slide 11 - 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
  • Slide 12 - Mechanism? CH3-OH and most 1o 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”
  • Slide 13 - Whenever an oxygen containing compound is placed into an acidic solution, the oxygen will be protonated, forming an oxonium ion.
  • Slide 14 - Mechanism for reaction of an alcohol with HX: CH3OH or 1o alcohols:
  • Slide 15 - Mechanism for reaction of an alcohol with HX: 2o or 3o alcohols:
  • Slide 16 - 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.
  • Slide 17 - 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
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  • Slide 19 - Most 1o? If large steric requirement… CH3 CH3 CH3CCH2-OH + HBr  CH3CCH2CH3 CH3 Br neopentyl alcohol 2-bromo-2-methylbutane   CH3 CH3 CH3 CH3CCH2-OH2+  CH3CCH2+  CH3CCH2CH3 CH3 CH3 + 1o carbocation 3o carbocation [1,2-CH3]
  • Slide 20 - With PX3 ROH + PX3  RX PX3 = PCl3, PBr3, P + I2 No rearrangements ROH: CH3 > 1o > 2o CH3 CH3 CH3CCH2-OH + PBr3  CH3CCH2-Br CH3 CH3 neopentyl alcohol 2,2-dimethyl-1-bromopropane 
  • Slide 21 - Dehydration (later)
  • Slide 22 - As acids. With active metals: ROH + Na  RONa + ½ H2  With bases: ROH + NaOH  NR! CH4 < NH3 < ROH < H2O < HF
  • Slide 23 - CH3CH2OH + NaOH  H2O + CH3CH2ONa WA WB SA SB CH3CH2OH + CH3MgBr  CH4 + MgBr(OCH2CH3) SA SB WA WB CH3OH + NaNH2  NH3 + CH3ONa SA SB WA WB
  • Slide 24 - Ester formation. CH3CH2-OH + CH3CO2H, H+  CH3CO2CH2CH3 + H2O CH3CH2-OH + CH3COCl  CH3CO2CH2CH3 + HCl CH3-OH + CH3SO2Cl  CH3SO3CH3 + HCl Esters are alkyl “salts” of acids.
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  • Slide 29 - oxidation states of carbon - oxidation  CH4 CH3OH CH2O HCO2H CO2 -4 -2 0 +2 +4  reduction -
  • Slide 30 - 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.
  • Slide 31 - Primary alcohols can also be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl  CH3CH2CHO pyridinium chlorochromate aldehyde or CH3CH2CH2-OH + K2Cr2O7, special conditions 
  • Slide 32 - Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1o) 5. 6. 7. 8.
  • Slide 33 - Alcohols, reactions: R-|-OH With HX With PX3 (later) RO-|-H As acids Ester formation Oxidation

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