Nucleophilic addition vs. Electrophilic addition

[Enginever]

So I'm reviewing an old diagnostic, and the question pretty much asks "What kind of reaction is aldol condensation?"

The answer is nucleophilic addition, but how can you distinguish nucleophilic addition and electrophilic addition??? Every addition needs an a nucleophile and electrophile, does it not?

For example, in the aldol, the enolate is the nucleophile, and the carbonyl is the electrophile.

What am I missing here?

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[docelh]

You are technically correct. I suppose it's just convention when determining which perspective to take.

McMurry groups Aldol into an enolate condensation reaction, separate from the NP addition reactions listed for ketones and aldehydes.

 

[joshto]

i think when the nucleophile attacks the electrophile the result is a nucleophilic substitution. on the other hand, when the electrophile (ex a double bond) attacks a nucleophile, you have electrophilic addition.

not too sure, thougj.

 

[loveoforganic]

Technically, the elctrons and thus Nucleophile does the attacking. And yeah, I'm pretty sure it's a semantic argument with no clear answer

 

[wanderer]

Certain reactions, like addition of an alkyl group to benzene are considered electrophilic, because the electrophile is being added to the molecule of interest (to us the aromatic ring is a lot more important in those kinds of reactions.)
When attacking a halide and turning it into an alcohol for example, it is the nucleophile that is being added to the base molecule, and we call that a nucleophilic substitution.
Although it can become a game of semantics it is usually pretty clear whether the substitution or addition is considered electrophilic or nucleophilic. In the case of aldol, the nucleophile and the electrophile are equally important, so calling it either is a bit ridiculous.

 

[IH8ColdWeath3r]

i think when the nucleophile attacks the electrophile the result is a nucleophilic substitution. on the other hand, when the electrophile (ex a double bond) attacks a nucleophile, you have electrophilic addition.

not too sure, thougj.

A double bond is not an electrophile. A double bond is electron rich and thus acts as a nucleophile. A double bond acts as a nucleophile and attacks electrophiles, not the other way around as you mentioned...just to clear things up for the OP. Basically, electrophilic addition is the same thing as nucleophilic addition; just different jargon.

An with benzenes, that is electrophilic aromatic substitution, which generates a strong electrophile that is desperately seeking electrons from the stable benzene ring. I guess you can think of it has electrophilic addition, but technically its electrophilic substitution. Hope this helps