Ketones and nucleophilicity Is there anyone who can give me a convincing argument about the ketone, or the carbonyl oxygen in the ketone being nucleophile or not? . I really don't know what to write anymore. Everyone says something different. My instructor said that the Ketone oxygen can be protonated, thus reacting as a nucleophile. Others says that  Protonating the ketone in fact makes it more electrophilic.

Here is the molecule I'm working with (attached) and I have to mention all the nucleophilic sites - I've done that. This is the only one that really is confusing me. Hoping for some clarification. 

http://imgur.com/a/20NAw
Everyone says something different


Well, actually they don't. A ketone has a nucleophilic and an electrophilic center. The carbonyl carbon is electrophilic and can be attacked by nucleophiles, the oxygen itself can act as a nucleophile and can, for example, be protonated. And yes, if we protonate the oxygen the "ketone", or better the carbonyl carbon, get's more electrophilic.

An example would be the Luche reduction. In this case the carbonyl oxygen coordinates to cerium chloride, thus acting as nucleophile, and makes the carbonyl carbon even more reactive towards nucleophiles.