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Topic: what's more basic EtNH2 or MeCN?  (Read 8115 times)

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Offline bioch

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what's more basic EtNH2 or MeCN?
« on: April 13, 2014, 01:06:47 PM »
Which is the more basic molecule: EtNH2 or MeCN?

My attempt: EtNH2 is more basic as the nitrogen is sp3 hybridised whereas the Nitrogen atom in MeCN is sp hydbirdized. This makes MeCN more acidic as the negative charge can be held closer to the nucleus.

Is this correct? is there any other reasons or logic?
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #1 on: April 13, 2014, 01:15:08 PM »
How about the C triple bond N, with an additional N lone pair.  Holds a lot of electron density over just a Nitrogen lone pair huh? :).
                -Zack
« Last Edit: April 13, 2014, 01:52:56 PM by zsinger »
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Offline bioch

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Re: what's more basic EtNH2 or MeCN?
« Reply #2 on: April 13, 2014, 01:45:36 PM »
Quote from: zsinger on April 13, 2014, 01:15:08 PM
Also, how about the C triple bond N, with an additional N lone pair.  Holds a lot of electron density over just a Nitrogen lone pair huh? :).
                -Zack
so wouldn't that mean MeCN is more basic?
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #3 on: April 13, 2014, 01:52:09 PM »
Yep!  :o :o :o
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Offline orgopete

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Re: what's more basic EtNH2 or MeCN?
« Reply #4 on: April 13, 2014, 01:58:04 PM »
No, the amine was right (most basic) the first time. Just look at a pKa table
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Offline kriggy

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Re: what's more basic EtNH2 or MeCN?
« Reply #5 on: April 13, 2014, 04:39:45 PM »
Isnt MeCN in fact an acid?
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #6 on: April 13, 2014, 07:52:33 PM »
No way….think of the lewis structure of Methyl Cyanide.  No labile hydrogens stabilized.  Are you sure about that Orgo?  Am I missing something?
                -Z
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #7 on: April 13, 2014, 07:58:30 PM »
pKb of CH3CN is -11
            -Zack
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Offline orgopete

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Re: what's more basic EtNH2 or MeCN?
« Reply #8 on: April 13, 2014, 08:10:44 PM »
Quote from: zsinger on April 13, 2014, 07:52:33 PM
No way….think of the lewis structure of Methyl Cyanide.  No labile hydrogens stabilized.  Are you sure about that Orgo?  Am I missing something?
                -Z

The pKa of the protonated species are
EtNH3(+), 10.6
PhCNH(+), -10
http://evans.harvard.edu/pdf/evans_pKa_table.pdf

In HCl, very little of benzonitrile is protonated while in neutral water, most of ethylamine would be.
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #9 on: April 13, 2014, 08:53:42 PM »
Pete,
I dont understand your response to what I said? PM me.
             -Z
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #10 on: April 13, 2014, 09:32:17 PM »
Additionally, many charts indicate that HCl is stronger than Sulfuric, which, by thermodynamic data is false…..
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Offline orgopete

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Re: what's more basic EtNH2 or MeCN?
« Reply #11 on: April 13, 2014, 09:56:18 PM »
Quote from: bioch on April 13, 2014, 01:06:47 PM
Which is the more basic molecule: EtNH2 or MeCN?

My attempt: EtNH2 is more basic as the nitrogen is sp3 hybridised whereas the Nitrogen atom in MeCN is sp hydbirdized. This makes MeCN more acidic as the negative charge can be held closer to the nucleus.

Is this correct? is there any other reasons or logic?

Basically, this is correct. Because EtNH2 is more basic, it's conjugate acid is only a weak acid, pKa 10.6. PhCN is a very weak base so it's conjugate acid is a very strong acid, pKa -10.
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #12 on: April 13, 2014, 10:04:35 PM »
But he is not talking about phenolic cyanide, but rather methyl.  Im confused…..
            Z
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Offline discodermolide

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Re: what's more basic EtNH2 or MeCN?
« Reply #13 on: April 13, 2014, 10:13:00 PM »
Methyl cyanide = acetonitrile. A well known solvent for chromatography.
It is not basic.
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Offline zsinger

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Re: what's more basic EtNH2 or MeCN?
« Reply #14 on: April 13, 2014, 10:42:33 PM »
I stand corrected.
        -Z
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