not seeing this...? maybe I am?

[BoneMental]

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Let's say I have a ketone.

If I add a negative carbon compound, will I displace the original carbonyl?

For example, let's say I have acetone.
I add a Grignard reagent to yield a negative carbon (RMgX), which attacks the carbonyl. You could also add a CH3O- with the negative on the carbon.
I add acid to protonate and make water, a leaving group.


What happens? Do I form an alkene? I know that ammonia derivatives can displace the carbonyl, so I wasn't sure if this happened with other compounds..

Someone help me clear this up! 😕😕😕

Edit: I think this may be impossible. You cannot have a negative carbon compound such as -CH3O because the oxygen will carry the negative, correct? If you added a Grignard Reagent, the R will add, but it s sp3 hybridized and its not like it will form a double bond with your compound. You'd get a nucleophilic addition product...right?

 

[stefspets]

Grignard and amine reactions with ketones/aldehydes are not the same.

When you react a ketone/aldehyde with an amine, you replace the oxygen on the carbonyl with a nitrogen (forming an imine or enamine).

When you react the grignard with the ketone/aldehyde, the Grignard attacks the carbonyl carbon and the electrons move to the oxygen. The oxygen now has three lone pairs and a negative charge. You add acid to protonate the negatively-charged oxygen, making an alcohol. You don't make H2O/a leaving group. The carbonyl does not reform in this case.

 

[BoneMental]

Yeah I just noticed that. I was just curious because the reason it works with NH3 is because water is a weaker base than NH3 is...so I was like, well I know if you had a negative carbon that's a super strong base, so maybe it would do the same thing...

 

[stefspets]

I said that in my first post but changed when I edited it. CH3O- carries the charge on the oxygen, not the carbon. It is a strong base and I think could attack the carbonyl but the carbonyl would just reform kicking it back off.

 

[BoneMental]

Thank you for helping me walk through this 😛