366 ALCOHOLS, DIOLS. AND THIO Any alkyl group may be attached to the oxygen of the ester function. In the following example, it is a methyl group I LiANHe CH3OCCH, CHCH,COCH 2.H2O HOCHCHCHCHCHOH 2CH,, OH CH H3 Dimethyl 3-methyl-1, 5-pentanedioate 3-Methyl-1, 5-pentanediol Methanol 15.6 Hydroxylation of alkenes using osmium tetraoxide is a syn addition of hydroxyl groups to the dou- ble bond. cis-2-Butene yields the meso diol OsOa(CH:)COOH H3C CH3 H,C CH cis-2-Butene trans-2-Butene yields a racemic mixture of the two enantiomeric forms of the chiral diol OH H H3C OsO4(CH3),COOH H3C (2R, 3R).2, 3-Butanediol (2S, 3S)2,3-Butanediol The Fischer projection formulas of the three stereoisomers are CH HO-H H H3 H3 meso-2, 3-Butanediol (2R, 3R)-2 3-Butanediol (2S.3S)-2, 3-Butanediol 15.7 The first step is proton transfer to 1, 5-pentanediol to form the corresponding alkyloxonium ion HOCH2CH_CH_CH2CH2OH HT-OSO2OH HOCH2CHCH2CH,CH2一 OSO.OH 1. 5-Pentanediol Sulfuric acid Conjugate acid of 1, 5-pentanediol Hydrogen sulfate Rewriting the alkyloxonium ion gives H HQ一CH2CH2CH2CH2CH2O is equivalent to H Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website366 ALCOHOLS, DIOLS, AND THIOLS Any alkyl group may be attached to the oxygen of the ester function. In the following example, it is a methyl group. 15.6 Hydroxylation of alkenes using osmium tetraoxide is a syn addition of hydroxyl groups to the dou￾ble bond. cis-2-Butene yields the meso diol. trans-2-Butene yields a racemic mixture of the two enantiomeric forms of the chiral diol. The Fischer projection formulas of the three stereoisomers are 15.7 The first step is proton transfer to 1,5-pentanediol to form the corresponding alkyloxonium ion. Rewriting the alkyloxonium ion gives HO is equivalent to CH2CH2CH2CH2CH2 O H H O H O H H HOCH2CH2CH2CH2CH2 OH 1,5-Pentanediol H OSO2OH Sulfuric acid OSO2OH Conjugate acid of 1,5-pentanediol Hydrogen sulfate HOCH2CH2CH2CH2CH2 O H H CH3 CH3 H HO H OH (2S,3S)-2,3-Butanediol CH3 CH3 HO H OH H (2R,3R)-2,3-Butanediol CH3 CH3 H H OH OH meso-2,3-Butanediol C C H3C H H CH3 trans-2-Butene OsO4, (CH3)3COOH (CH3)3COH, HO (2R,3R)-2,3-Butanediol (2S,3S)-2,3-Butanediol C HO OH C H3C H H CH3 HO OH C H H3C H3C H C C C H3C H CH3 H cis-2-Butene OsO4, (CH3)3COOH (CH3)3COH, HO meso-2,3-Butanediol C H3C CH3 H H HO OH C 1. LiAlH4 2. H2O HOCH2CH2CHCH2CH2OH Dimethyl 3-methyl-1,5-pentanedioate 3-Methyl-1,5-pentanediol CH3OCCH2CHCH2COCH3 O O CH3 CH3 2CH3OH Methanol Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website