22 Replies
@Dexter
Note for OP
+solved @user1 @user2... to close the thread when your doubt is solved. Mention the users who helped you solve the doubt. This will be added to their stats.2 things
i) is it not 4 because NMe2 is bulky and both cant enter at the same time because of steric hindrance?
ii) i don't understand the 2nd step
The second step seems S_ngp
yeah its NGP, also ping me if anyone gets the answer for the 1st question about why it cant be (4)
so intramolecular nucleophile attack (i just looked this mech up i may not understand it entirely, correct me if im wrong)
why would NMe2 attack the pi bond?
you'd expect it to attack only if there was a clear partial positive on the victim(:kekw:) carbon
my theory is that the probability of one NMe2 attaching itself and then setting off this chain of events is just much larger than both NMe2 coming on in the correct spot at the same time
chemistry is intrinsically tied to probabilities
the more jee answer would probably be steric hindrance, since i suppose 2 methyl groups indicate hindrance
source: chemical kinetics
Nah, hindrance is low here
ek sec @Nimboi [ping if answering] dont mark it as solved if you get it anytime soon, imma look at this tmrw around night
Ok, so, i actually think the explanation for this is bs. It's completely arbitrary. You could get (4) even with NGP because the ring is small enough to enable intramolecular nucleophilic attack onto the second bromine-adjacent carbon by the nitrogen l.p.
So, by that logic (4) is just as feasible.
._.
ill look up NGP at a deeper level then get back to this
Whenever someone mentions "this is NGP" i lose my sanity
it's the one type of reaction which i genuinely hate from the bottom of my heart 🥰
(cuz i wasn't taught in depth bout it)
This question was my doubt as well but uh never asked it -_-
is this reasoning correct that, in 3rd if you see there is extended resonance stabilization which makes it more stable? in 4th there is lone pair repulsion of both the nitrogen? @Opt
The nitrogens are closer in 3 than in 4. Which means that repulsion is greater in 3 than in 4. This logic doesn't seem to work.
ahh got it
but is it not the pi bond that actually executes the NGP mech on the bromine
since its closer to the bromine
it seems like the triangle intermediate is being formed by NMe2, while the pi bond is doing the NGP
unique case
(confirm pls)
Okay, I'm not very sure about this, but after substitution of one NMe2 group, if you try to do NGP by double bond w/o rearrangement, you would get a bicyclo-compound with a four membered and three membered ring which is very unstable
As opposed to the rearranged one, where by NMe2 you only get one 3-ringed intermediate which is comparitively a lot stable.
maybe the final product is more stable.
hm
i think i got my answer
+solved SirLancelotDuLac Opt trin
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