The first and the last proposals will succeed but

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Unformatted text preview: Ph base OPr Me O OPr Me H2N O Me N H Cl O ? + Me ? HCl O O Me N H Purpose of the problem A chance to try out the correlation between leaving group ability and pKa explained in the textbook (p. 205). Suggested solution You need to draw mechanisms for the formation of the tetrahedral intermediate and check that it is in the right protonated form. Then you need to check which potential leaving group is the best, using appropriate estimated pKa values. The first and the last proposals will succeed but the second will not as chloride ion is a better leaving group than even a protonated amine and this reaction would go backwards. 3 4 Solutions Manual to accompany Organic Chemistry 2e O Me O OPr n-PrOH OPh base Me O Me O OPh HCl N H Me HO Me O OPr successful reaction: pKa PrOH about 18 pKa PhOH about 10 unsuccessful reaction: pKa HCl about –7 pKa R2NH2+ about 10 chloride leaves Cl N H2 HO OPr + Me OPr product H2N Me N H successful reaction: pKa PrOH about 18 pKa R2NH about 35 PrO– leaves PROBLEM 4 Suggest mechanisms for these reactions. O NH2 OH EtO O O OEt HN O RCOCl base R O N O Purpose of the problem Drawing mechanisms for nucleophilic substitution on important compounds including cyclic and dicarbonyl compounds. Suggested solution In the first reaction there are two nucleophilic substitutions and you must decide which nucleophile attacks first. The amine is a better nucleoph...
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