ALCOHOLS. DIOLS AND THIOLS 369 15.14 Thiols may be prepared from the corresponding alkyl halide by reaction with thiourea followed by treatment of the isothiouronium salt with base RBr (hnC=s Isothiouronium salt RSH bromide Thus, an acceptable synthesis of 1-hexanethiol from 1-hexanol would be 1.(H2N)2C= CH(CH,)CH,OH CH3(CH,)CH,Br CH3(CH2)4CH,SH 1-Hexanol 1-Hexanethiol 15.15 The three main components of"essence of skunk"are H2C、 CH,CHCH, CH,SH CH SH 3-Methyl-1-butanethiol is- 2-Butene.l-thiol 15.16 The molecular weight of 2-methyl-2-butanol is 88. A peak in its mass spectrum at m/z 70 corre ponds to loss of water from the molecular ion. The peaks at m/z 73 and m/z 59 represent stable cations corresponding to the cleavages shown in the equation CH, CH3 CH3+ CH3 CCH, CH3 CH2CCH3+“CH2CH m/z73 m/259 15.17 (a) The appropriate alkene for the preparation of 1-butanol by a hydroboration-oxidation sequence is 1-butene. Remember, hydroboration-oxidation leads to hydration of alkenes with a regioselectivity opposite to that seen in acid-catalyzed hydration. L B CH, CHCH=CH2 2.H202HO CH CHCH.OH 1-Butene 1-Butanol (b) 1-Butanol can be prepared by reaction of a Grignard reagent with formaldehyde. CH3 CH,CH,CH,OH CHaCH,CH2+ HCH An appropriate Grignard reagent is propylmagnesium bromide CH CH,CH, Br CH CH, CH,Mgl 1-Bromopropane Propylmagnesium bromide Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE WebsiteALCOHOLS, DIOLS, AND THIOLS 369 15.14 Thiols may be prepared from the corresponding alkyl halide by reaction with thiourea followed by treatment of the isothiouronium salt with base. Thus, an acceptable synthesis of 1-hexanethiol from 1-hexanol would be 15.15 The three main components of “essence of skunk” are 15.16 The molecular weight of 2-methyl-2-butanol is 88. A peak in its mass spectrum at mz 70 corre￾sponds to loss of water from the molecular ion. The peaks at mz 73 and mz 59 represent stable cations corresponding to the cleavages shown in the equation. 15.17 (a) The appropriate alkene for the preparation of 1-butanol by a hydroboration–oxidation sequence is 1-butene. Remember, hydroboration–oxidation leads to hydration of alkenes with a regioselectivity opposite to that seen in acid-catalyzed hydration. (b) 1-Butanol can be prepared by reaction of a Grignard reagent with formaldehyde. An appropriate Grignard reagent is propylmagnesium bromide. 1. diethyl ether 2. H3O CH3CH2CH2MgBr CH 3CH2CH2CH2OH 1-Butanol HCH O Mg diethyl ether CH3CH2CH2Br CH3CH2CH2MgBr 1-Bromopropane Propylmagnesium bromide CH3CH2CH2CH2OH HCH CH3CH2CH2 O CH3CH2CH CH2 CH3CH2CH2CH2OH 1. B2H6 2. H2O2, HO 1-Butene 1-Butanol CH3 CH2CH3 CH3 OH C CH3 CH3CCH2CH3 OH CH3CCH3 OH CH2CH3 m/z 73 m/z 59 C C H3C H CH2SH H trans-2-Butene-1-thiol H H C C H3C CH2SH 3-Methyl-1-butanethiol cis-2-Butene-1-thiol CH3CHCH2CH2SH CH3 CH3(CH2)4CH2OH 1-Hexanol CH3(CH2)4CH2Br 1-Bromohexane CH3(CH2)4CH2SH 1-Hexanethiol PBr3 HBr, heat 1. (H2N)2C S 2. NaOH Isothiouronium salt (not isolated) NaOH RBr Alkyl bromide (H2N)2C S Thiourea RSH Thiol Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website