Dolbier HW Solutions 225

Dolbier HW - reactions The alkynide nucleophile displaces the p-toluenesulfonate leaving group from ethyl p-toluenesulfonate 1 Phenylacetylide ion

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9.29 The alkane formed by hydrogenation of ( S )-3-methyl-1-pentyne is achiral; it cannot be optically active. The product of hydrogenation of ( S )-4-methyl-1-hexyne is optically active because a stereogenic center is present in the starting material and is carried through to the product. Both ( S )-3-methyl-1-pentyne and ( S )-4-methyl-1-hexyne yield optically active products when their triple bonds are reduced to double bonds. 9.30 ( a ) The dihaloalkane contains both a primary alkyl chloride and a primary alkyl iodide functional group. Iodide is a better leaving group than chloride and is the one replaced by acetylide. ( b ) Both vicinal dibromide functions are converted to alkyne units on treatment with excess sodium amide. ( c ) The starting material is a geminal dichloride. Potassium tert -butoxide in dimethyl sulfoxide is a suf f ciently strong base to convert it to an alkyne. ( d ) Alkyl p -toluenesulfonates react similarly to alkyl halides in nucleophilic substitution
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Unformatted text preview: reactions. The alkynide nucleophile displaces the p-toluenesulfonate leaving group from ethyl p-toluenesulfonate. 1 Phenylacetylide ion C C 2 Ethyl p-toluenesulfonate OS O O CH 2 CH 3 CH 3 1-Phenyl-1-butyne C CCH 2 CH 3 KOC(CH 3 ) 3 , DMSO heat CCH 3 Cl Cl 1,1-Dichloro-1-cyclopropylethane CH C Ethynylcyclopropane BrCH 2 CHCH 2 CH 2 CHCH 2 Br 1,2,5,6-Tetrabromohexane 1. excess NaNH 2 , NH 3 2. H 2 O HC CCH 2 CH 2 C CH Br Br 1,5-Hexadiyne ClCH 2 CH 2 CH 2 CH 2 CH 2 CH 2 I 1 NaC CH ClCH 2 CH 2 CH 2 CH 2 CH 2 CH 2 C CH Sodium acetylide 1-Chloro-6-iodohexane 8-Chloro-1-octyne H 2 Pt H H 3 C CH 2 C CH 3 CH 2 CH ( S )-4-Methyl-1-hexyne CH 2 CH 2 CH 3 H H 3 C CH 3 CH 2 ( S )-3-Methylhexane C C H 2 Pt CH 3 CH 2 CHCH 2 CH 3 CH 3 3-Methylpentane (does not have a stereogenic center; optically inactive) H H 3 C C CH CH 3 CH 2 ( S )-3-Methyl-1-pentyne C ALKYNES 219...
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This note was uploaded on 09/26/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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