350 ORGANOMETALLIC COMPOUNDS By retrosynthetically disconnecting the butyl group from the carbon that bears the hydroxy substituent, we see that the appropriate starting ketone is 2-butanone CH3 CH CH, CH CH+C-CH,CH,> CH,CH, CH,Mgx+CCH,CH, Butylmagnesium halide Therefore CHa CH, CH,CH,MgBr CH CCH, CH3 CH3 CH, CH,CH,CCH,CH3 Butylmagnesium bromide 2-Butanone 3.Methyl-3-heptanol (e) 1-Butylcyclobutanol is a tertiary alcohol. The appropriate ketone is cyclobutanone L diethyl ether CHCHCH-CH CHCH,CH,CH, MgBr 2.H.O Buty magnesium bromide Cyclobutanone 1-Butylcyclobutanol 14.19 In each part of this problem in which there is a change in the carbon skeleton, disconnect the phenyl group of the product to reveal the aldehyde or ketone precursor that reacts with the grignard reagent derived from bromobenzene. Recall that reaction of a Grignard reagent with formaldehyde H,C=O)yields a primary alcohol, reaction with an aldehyde(other than formaldehyde) yields a secondary alcohol, and reaction with a ketone yields a tertiary alcohol. (a) Conversion of bromobenzene to benzyl alcohol requires formation of the corresponding Grignard reagent and its reaction with formaldehyde. Retrosynthetically can be seen 3CH.OH MgX hC=O Therefore diethyl Phenylmagnesium Benzyl alcohol (b) The product is a secondary alcohol and is formed by reaction of phenylmagnesium bromide with hexanal FCH(CH,).CH MgX HC(CH))4CH I-Phenyl-l-hexanol Phenylmagnesium Hexanal CHCH,CHCHCH,CH3 CHaCH, CH,CH,CH,CH diethyl ether H,O Hexane Phenyl-l-hexanol Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE WebsiteBy retrosynthetically disconnecting the butyl group from the carbon that bears the hydroxyl substituent, we see that the appropriate starting ketone is 2-butanone. Therefore (e) 1-Butylcyclobutanol is a tertiary alcohol. The appropriate ketone is cyclobutanone. 14.19 In each part of this problem in which there is a change in the carbon skeleton, disconnect the phenyl group of the product to reveal the aldehyde or ketone precursor that reacts with the Grignard reagent derived from bromobenzene. Recall that reaction of a Grignard reagent with formaldehyde (H2C?O) yields a primary alcohol, reaction with an aldehyde (other than formaldehyde) yields a secondary alcohol, and reaction with a ketone yields a tertiary alcohol. (a) Conversion of bromobenzene to benzyl alcohol requires formation of the corresponding Grignard reagent and its reaction with formaldehyde. Retrosynthetically, this can be seen as Therefore, (b) The product is a secondary alcohol and is formed by reaction of phenylmagnesium bromide with hexanal. Hexanal 1-Phenyl-1-hexanol MgBr Phenylmagnesium bromide CH3CH2CH2CH2CH2CH OH CHCH2CH2CH2CH2CH3 O 1. diethyl ether 2. H3O Phenylmagnesium halide Hexanal MgX HC(CH2)4CH3 1-Phenyl-1-hexanol O CH(CH2)4CH3 OH Br Bromobenzene Phenylmagnesium bromide MgBr Benzyl alcohol CH2OH 2. H3O 1. HCH O Mg diethyl ether CH2OH MgX H 2C O Butylmagnesium bromide CH3CH2CH2CH2MgBr 1-Butylcyclobutanol OH 1. diethyl ether CH2CH2CH2CH3 2. H3O Cyclobutanone O CH3CH2CH2CH2MgBr CH CH3CCH2CH3 3CH2CH2CH2CCH2CH3 Butylmagnesium bromide 2-Butanone 3-Methyl-3-heptanol 1. diethyl ether 2. H3O O OH CH3 Butylmagnesium halide CH3CH2CH2CH2 C CH2CH3 CH3CH2CH2CH2MgX OH CH3 2-Butanone CCH2CH3 CH3 O 350 ORGANOMETALLIC COMPOUNDS Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website