The way I see it, the -R (alkyl part) obtains a negative charge and the MgX obtains a net positive charge on bond dissociation. So a nucleophile and an electrophile both are obtained simultaneously. So why is Grignard reagent a nucleophile and not an ambiphile? Where am I wrong?
$\begingroup$
$\endgroup$
8
-
4$\begingroup$ R- doesn't like being R- and MgX+ is fine with it. $\endgroup$– Safdar FaisalCommented Apr 23, 2021 at 9:12
-
2$\begingroup$ There are some cases where the Mg cation binds to the Grignard substrate activating it or directing the nucleophilic attack, so you could say in these instances it is an ambiphile. $\endgroup$– WaylanderCommented Apr 23, 2021 at 9:42
-
1$\begingroup$ @Safdar Faisal would that mean R- would be a better nucleophile? Ready to get rid of that charge instantly? $\endgroup$– Saumya ChaturvediCommented Apr 23, 2021 at 10:12
-
$\begingroup$ @Waylander ah can you give me an example? $\endgroup$– Saumya ChaturvediCommented Apr 23, 2021 at 10:13
-
1$\begingroup$ @SaumyaChaturvedi The Grignard addition to nitriles is arguably one. $\endgroup$– WaylanderCommented Apr 23, 2021 at 13:30
|
Show 3 more comments
1 Answer
$\begingroup$
$\endgroup$
In fact a Grignard reagent reacting with, let us say, a ketone, is ambiphilic. However, the electrophilic component of the reaction, in which the positively charged magnesium combines with the carbonyl oxygen, does not figure into the organic product on workup. See this answer.
answered Jul 7, 2022 at 23:45