2013-5-10 10:08 PM
2013-5-12 03:37 AM
Q1: In mechanisms of acid-catalysed hydrolysis of ester and amide, the first step is the protonation of the carbonyl group. Why the lone pair electrons on O atom is used to attract the H+ ion (the red part of picture 1 and 2)? However, when I studied AL, my teacher taught me that it should be the pi electrons are used to attract the H+ ion because the pi electrons are more diffused than the lone pair electrons on O atom so that it should be the carbonyl C atom bears the positive charge. Which one is correct?
Q2: In the mechanism of acid-catalysed hydrolysis of amide, the amine group is protonated first before the carbon-oxygen double bond is reformed (the blue part of picture 2) while in the mechanism of base-catalysed hydration of amide, no such kind of protonation of the amine group when the carbon-oxygen double bond is reformed (the blue part of picture 3). Why?
Q3: In the mechanism of aldol condensation (the green part of picture 4), hydroxide is a poor leaving group, protonation of the hydroxy group is required before ejecting it. However, as the reaction condition is basic, protonation cannot be achieved. Why the hydroxide still can be ejected even though it is a poor leaving group?
Q4: When converting an alcohol to a alkyl halide, e.g.ethanol to 1-bromoethane, can I just simply suggest HBr instead of PBr3, PBr5 or NaBr+conc. H2SO4?
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