Compounds that form acids in water?? 5pointsss!!?

Let us take as a typical anhydride, acetic anhydride. Often written by organic chemists as AcOAc (Ac = CH3CO). If you think about it, this molecule contains two electrophilic carbon atoms (the two carbonyl carbon atoms), both of which can undergo reaction with nucleophiles. Now, if a nucleophile such as water reacts at one of these sites, it undergoes an addition-elimination process. If you think about it, there is a rather good leaving group ready to depart (CH3COO- - the acetate ion). It is a relatively good leaving group due to the fact that it has two canonical structures. Remember, according to resonance theory, the more resonance structures that you can form, the more stable a structure is likely to be. Removal of this acetate moiety results ultimately in the formation of the carboxlic acid. In other words, you end up with two molecules of acetic acid. It is for this reason that acid anhydrides need to be kept very dry, otherwise they undergo hydrolysis and cannot be used. I want to get you to consider something else. Esters (e.g. AcOMe - methyl acetate) do not undergo such facile hydrolysis (requiring acid catalysis and heat). Do you have any ideas why this might be the case? Think about the -OMe (methoxy) functionality as a leaving group relative to the acetate functionality. Furthermore, in thinking about the formation of esters from carboxylic acids, if you want to start with the carboxylic acid and react it with an alcohol, you need an acid catalyst and often heat (Fischer esterification). The reason for this is that the -OH group attached to the carboxylic acid is not at all a good leaving group (how many resonance structures can you draw for it?). The role of the acid catalyst is to cause a protonation resulting in the formation of a good leaving group. If you have any further questions, please feel free to ask.