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Alcohols R-O-H Classification CH 3 , 1 o , 2 o , 3 o Nomenclature:

Alcohols R-O-H Classification CH 3 , 1 o , 2 o , 3 o 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 ).

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Alcohols R-O-H Classification CH 3 , 1 o , 2 o , 3 o Nomenclature:

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  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)

  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-butanol1-propanol 2o 1o

  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

  4. Oldest known organic synthesis: “fermentation” Sugar + yeast  ethyl alcohol + CO2 Grape juice => “wine” Barley => “beer” Honey => “mead” Rice => “sake” ~5-11% ethanol

  5. Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1o) 5. 6. 7. 8.

  6. R-H R-X R-OH Acids Bases Active metals Oxidation Reduction Halogens

  7. Alcohols, reactions: • R-|-OH • With HX • With PX3 • (later) • RO-|-H • As acids • Ester formation • Oxidation

  8. 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.

  9. 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

  10. 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”

  11. Whenever an oxygen containing compound is placed into an acidic solution, the oxygen will be protonated, forming an oxonium ion.

  12. Mechanism for reaction of an alcohol with HX: CH3OH or 1o alcohols:

  13. Mechanism for reaction of an alcohol with HX: 2o or 3o alcohols:

  14. 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.

  15. 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

  16. 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]

  17. 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 

  18. Dehydration • (later)

  19. As acids. • With active metals: • ROH + Na  RONa + ½ H2 • With bases: • ROH + NaOH  NR! • CH4 < NH3 < ROH < H2O < HF

  20. 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

  21. Ester formation. • CH3CH2-OH + CH3CO2H, H+ CH3CO2CH2CH3 + H2O • CH3CH2-OH + CH3COCl  CH3CO2CH2CH3 + HCl • CH3-OH + CH3SO2Cl  CH3SO3CH3 + HCl • Esters are alkyl “salts” of acids.

  22. oxidation states of carbon - oxidation CH4 CH3OH CH2O HCO2H CO2 -4 -2 0 +2 +4  reduction -

  23. 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.

  24. Primary alcohols ONLY can be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl CH3CH2CHO pyridinium chlorochromate (PCC)aldehyde or CH3CH2CH2-OH + K2Cr2O7,special conditions

  25. Alcohols, synthesis: 1. 2. 3. 4. Hydrolysis of alkyl halides (CH3 or 1o) 5. 6. 7. 8.

  26. Alcohols, reactions: • R-|-OH • With HX • With PX3 • (later) • RO-|-H • As acids • Ester formation • Oxidation

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