213 9. 13 (b) Addition of hydrogen chloride to vinyl chloride gives the geminal dichloride 1, 1 H C=CHCI CH3CHCI2 Vinyl chloride L.I-Dichloroethane (c) Since 1, I-dichloroethane can be prepared by adding 2 mol of hydrogen chloride to acetylene Is shown in the sample solution to part(a), first convert 1, l-dibromoethane to acetylene by dehydrohalogenation NaNH, NH, CH CHBI HC≡CH 2HCI 2.H,O CH3CHCI 1.l-Dibromoethane 1.l-Dichloroethane 9. 14 The enol arises by addition of water to the triple bond. CH3C=CHCH3 CHC≡CCH3+H2O CHaCCH,CH3 2-Butyne 2-Buten-2-ol (enol form) 2-Butanone The mechanism described in the textbook Figure 9.6 is adapted to the case of 2-butyne hydration as H CH3CH=CCH3 O: CH,-CCH CH CHCCH Hydronium 2-Buten-2-ol CH CH,-CCH3 +:O CH2CH2CCH3+H一 Carbocation Water 2-Butanone Hydronium ion 9. 15 Hydration of 1-octyne gives 2-octanone according to the equation that immediately precedes this problem in the text. Prepare 1-octyne as described in the solution to Problem 9.9, and then carry out its hydration in the presence of mercury(f) sulfate and sulfuric acid Hydration of 4-octyne gives 4-octanone. Prepare 4-octyne as described in the solution to Problem 9.9 9.16 Each of the carbons that are part of-CO, H groups was once part of a-C=C-unit. The two fragments CH3 (CH,)CO, H and HO, CCH,CH, CO, H account for only 10 of the original 16 carbons The full complement of carbons can be accommodated by assuming that two molecules of CHa(CH,)CO, H are formed, along with one molecule of HO, CCH, CH,CO, H. The starting alkyne is therefore deduced from the ozonolysis data to be as shown: CH,(CH2),C#,_ CH,C3C(CH)CH, CHa(CH2)4CO,H HO, CCH,CH,CO,H HO, C(CH,)4CH3 Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website9.13 (b) Addition of hydrogen chloride to vinyl chloride gives the geminal dichloride 1,1- dichloroethane. (c) Since 1,1-dichloroethane can be prepared by adding 2 mol of hydrogen chloride to acetylene as shown in the sample solution to part (a), first convert 1,1-dibromoethane to acetylene by dehydrohalogenation. 9.14 The enol arises by addition of water to the triple bond. The mechanism described in the textbook Figure 9.6 is adapted to the case of 2-butyne hydration as shown: 9.15 Hydration of 1-octyne gives 2-octanone according to the equation that immediately precedes this problem in the text. Prepare 1-octyne as described in the solution to Problem 9.9, and then carry out its hydration in the presence of mercury(II) sulfate and sulfuric acid. Hydration of 4-octyne gives 4-octanone. Prepare 4-octyne as described in the solution to Problem 9.9. 9.16 Each of the carbons that are part of @CO2H groups was once part of a @C>C@ unit. The two fragments CH3(CH2)4CO2H and HO2CCH2CH2CO2H account for only 10 of the original 16 carbons. The full complement of carbons can be accommodated by assuming that two molecules of CH3(CH2)4CO2H are formed, along with one molecule of HO2CCH2CH2CO2H. The starting alkyne is therefore deduced from the ozonolysis data to be as shown: CH3(CH2)4CO2H HO2C(CH2) HO2CCH2CH2CO2H 4CH3 CH3(CH2)4C C(CH2) CCH2CH2C 4CH3 Carbocation 2-Butanone CH3CH2CCH3 O Water O H H Hydronium ion H O H H CH3CH2 CCH3 O H Water O H H Carbocation CH3CH2 CCH3 OH CH3CH2CCH3 OH Hydronium ion 2-Buten-2-ol CH3CH CCH3 OH O H H H CH3C CCH3 H2O 2-Butyne 2-Butanone CH3CCH2CH3 O 2-Buten-2-ol (enol form) CH3C CHCH3 OH HC CH Acetylene CH3CHCl2 1,1-Dichloroethane CH3CHBr2 1,1-Dibromoethane 2HCl 1. NaNH2, NH3 2. H2O H CHCl 2C Vinyl chloride CH3CHCl2 1,1-Dichloroethane HCl ALKYNES 213 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website