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Topic: Basic Nature Of Amines  (Read 3198 times)

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Offline SHREY PATEL

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Basic Nature Of Amines
« on: September 01, 2018, 10:25:19 AM »
Question: Which one is more basic in nature- Me3N or Et3N ?
(where Me denotes Methyl and Et denotes Ethyl group.)

My Attempt:
I think Me3N is more basic as if we consider the reaction:
Me3N + H+  :rarrow: Me3NH+
In the product, the positive(+) charge is on Nitrogen atom.
So now we will check for stability of (+) charge.
Using the concept of hyperconjugation, Me has more no. of α-Hydrogen than Et.
So more hyperconjugation in case of Me.
Thus more Stabilisation of (+) charge.
This shows Me3N is more basic.

But answer is Et3N.

Please clear my concepts and help me where am I wrong.
Thank you :)

Offline Babcock_Hall

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Re: Basic Nature Of Amines
« Reply #1 on: September 01, 2018, 10:40:04 AM »
What about taking an empirical approach?  In other words by experiment which one is more basic?  One other thing to consider is that measurements of basicity in the gas phase sometimes provide different answers than in solution phase.

Offline SHREY PATEL

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Re: Basic Nature Of Amines
« Reply #2 on: September 01, 2018, 01:51:15 PM »
I am just a highschool student and I dont have access to either of the compounds...so cant find it out experimentally ;D
In the question, there is nothing mentioned about the phase, so is it to be taken in gaseous phase by default?
I am thinking if Inductive effect could be the reason.
but i am confused, whether inductive effect will dominate or hyperconjugation?

Offline Babcock_Hall

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Re: Basic Nature Of Amines
« Reply #3 on: September 01, 2018, 02:28:34 PM »
What I meant was that you look up a tabulated quantity.  Which quantity correlates with acid strength?  I would assume that the question referred to aqueous solution, unless it was specified as something else.

Offline SHREY PATEL

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Re: Basic Nature Of Amines
« Reply #4 on: September 03, 2018, 01:10:57 PM »
Okay! got it  ;D
Thank you :)

Offline wildfyr

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Re: Basic Nature Of Amines
« Reply #5 on: September 03, 2018, 06:56:36 PM »
Hyperconjugation is taught in high school? I never heard of it until grad school, yeesh.

Offline krishnaraj

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Re: Basic Nature Of Amines
« Reply #6 on: September 04, 2018, 03:14:50 AM »
That's India!

Offline krishnaraj

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Re: Basic Nature Of Amines
« Reply #7 on: September 04, 2018, 03:17:13 AM »
What I meant was that you look up a tabulated quantity.  Which quantity correlates with acid strength?  I would assume that the question referred to aqueous solution, unless it was specified as something else.
OP is preparing for an exam where such questions are asked without providing any relevant data, ideally we are looking for a solution which compares the basic reason behind order of basicity being higher or lower

Offline Babcock_Hall

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Re: Basic Nature Of Amines
« Reply #8 on: September 04, 2018, 09:48:45 AM »
@OP,
Are you familiar with the inductive effect?

Offline krishnaraj

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Re: Basic Nature Of Amines
« Reply #9 on: September 06, 2018, 08:49:54 AM »
Yes he is, the major confusion was why hyperconjugation is not playing a role (which is usually more dominant than inductive effect) but then we realized N doesn't have the vacant p orbitals needed for hyperconjugation so inductive effect would be observed which gives the correct answer. Your last message was what we were looking for, but we ended up finding this out since this post took longer since it had ambiguity in the form of the answer. Thanks a lot for confirming our train of thought :D

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