Dolbier HW Solutions 471

Dolbier HW Solutions 471 - 565 CARBOXYLIC ACID DERIVATIVES...

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Unformatted text preview: 565 CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION 20.34 The first step is acid hydrolysis of an acetal protecting group. Step 1: O H2O, H Compound A heat HOC(CH2)5CH CH(CH2)7CH2OH HO OH Compound B (C16H32O5) All three alcohol functions are converted to bromide by reaction with hydrogen bromide in step 2. Step 2: O HBr Compound B HOC(CH2)5CH CH(CH2)7CH2Br Br Br Compound C (C16H29Br3O2) Reaction with ethanol in the presence of an acid catalyst converts the carboxylic acid to its ethyl ester in step 3. Step 3: O Compound C ethanol H2SO4 CH3CH2OC(CH2)5CH Br CH(CH2)7CH2Br Br Compound D (C18H33Br3O2) The problem hint points out that zinc converts vicinal dibromides to alkenes. Of the three bromine substituents in compound D, two of them are vicinal. Step 4 is a dehalogenation reaction. Step 4: O Compound D Zn ethanol CH3CH2OC(CH2)5CH CH(CH2)7CH2Br Compound E (C18H33BrO2) Step 5 is a nucleophilic substitution of the SN2 type. Acetate ion is the nucleophile and displaces bromide from the primary carbon. Step 5: O Compound E NaOCCH3 CH3CO2H O O CH3CH2OC(CH2)5CH CH(CH2)7CH2OCCH3 Compound F (C20H36O4) Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website ...
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