344 ORGANOMETALLIC COMPOUNDS removed because it is the most acidic, having a pK of approximately 2s Vne. The proton at C-1 is 14.6 Ethyl anion reacts as a Bronsted base to remove a proton from the alky CH2CH2+H-C≡CCH2CH2CH2CH3—CH2CH3+:C≡ CCHCH2CH2CH I-Hexyne Ethane Conjugate base of 1-hexyne 14.7(b) The target alcohol is tertiary and so is prepared by addition of a grignard reagent to a ketone. The retrosynthetic transformations are: CH3-C--CH3 CH CHiCH Because two of the alkyl groups on the hydroxyl-bearing carbon are the same(methyl), only two, not three, different ketones are possible starting materials O CH,Mgl+ CCH 1. diethyl ether CCH 2.H3O CH Methylmagnesium diethyl ether MgBr CH,CCH -CCH Acetone 2-Phenyl-2-propand 14.8(b) Recall that the two identical groups bonded to the hydroxyl-bearing carbon of the alcohol arose from the Grignard reagent. That leads to the following retrosynthetic analysis (C6H5)2 COR t 2CHs MgX Thus, the two phenyl substituents arise by addition of a phenyl grignard reagent to an ester of cyclopropanecarboxylic acid. L diethyl ether 2CH-MgBr COCH 2. H,o+(CH3)2C ChOH Phenylmagnesium carboxylate diphenylmethanol 14.9(b) Of the three methyl groups of 1, 3, 3-trimethylcyclopentene, only the one connected to the double bond can be attached by way of an organocuprate reagent Attachment of either of Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website344 ORGANOMETALLIC COMPOUNDS 14.6 Ethyl anion reacts as a Brønsted base to remove a proton from the alkyne. The proton at C-1 is removed because it is the most acidic, having a pKa of approximately 25. 14.7 (b) The target alcohol is tertiary and so is prepared by addition of a Grignard reagent to a ketone. The retrosynthetic transformations are: Because two of the alkyl groups on the hydroxyl-bearing carbon are the same (methyl), only two, not three,different ketones are possible starting materials: 14.8 (b) Recall that the two identical groups bonded to the hydroxyl-bearing carbon of the alcohol arose from the Grignard reagent. That leads to the following retrosynthetic analysis: Thus, the two phenyl substituents arise by addition of a phenyl Grignard reagent to an ester of cyclopropanecarboxylic acid. 14.9 (b) Of the three methyl groups of 1,3,3-trimethylcyclopentene, only the one connected to the double bond can be attached by way of an organocuprate reagent. Attachment of either of 1. diethyl ether 2. H3O (C6H5)2C OH Cyclopropyl￾diphenylmethanol CH3OH Methanol O COCH3 Methyl cyclopropanecarboxylate 2C6H5MgBr Phenylmagnesium bromide (C6H5)2C OH O COR 2C 6H5MgX MgBr CH3CCH3 O Phenylmagnesium bromide Acetone CCH3 1. diethyl ether 2. H3O OH CH3 2-Phenyl-2-propanol CH3MgI CCH3 CCH3 1. diethyl ether 2. H3O O OH CH3 Methylmagnesium iodide Acetophenone 2-Phenyl-2-propanol CH3 C O CH3 C OH CH3 CH3 CH3CCH3 O CH3CH3 1-Hexyne Ethane H C CCH2CH2CH2CH3 Ethyl anion CH3CH2 Conjugate base of 1-hexyne C CCH2CH2CH2CH3 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website