July 04, 2020, 12:22:24 PM
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Topic: Schotten-Baumann Benzoylation of Diamines  (Read 325 times)

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Offline jr620

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Schotten-Baumann Benzoylation of Diamines
« on: June 04, 2020, 08:57:48 PM »
I am an undergraduate student currently studying organic chemistry and i'm trying to come up with a full reaction mechanism (including electron movement) for benzoyl chloride + ethylene diamine. I have chosen Schotten-Baumann benzoylation as the method but i am unsure how NaOH works in this reaction, in some examples OH- reacts directly with the acidic hydrogen of the tetrahedral intermediate to form water and in other examples proton transfer occurs between the nitrogen and the carbonyl group and chloride ions remove the H from the resulting unstable C=O-H group. I have attached my progress so far, any advice or input would be appreciated.

Offline wildfyr

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #1 on: June 04, 2020, 09:46:41 PM »
It's an acid scavenger. It's there so suck up any protons that would prevent reaction or cause something to be reversible.

So anything that can't react in protonated form, or if protonated could reverse react.

Offline jr620

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #2 on: June 04, 2020, 09:57:53 PM »
So in this case is it just neutralizing the HCl, or is it soaking up the acidic hydrogen of the amine?

Offline wildfyr

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #3 on: June 17, 2020, 09:19:57 AM »
Its really 6 of one, half a dozen of the other.

Offline rolnor

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #4 on: June 17, 2020, 10:52:29 AM »
I dont see the neccesity of using excess benzoylchloride?

Offline wildfyr

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #5 on: June 17, 2020, 03:02:19 PM »
Usually some of it does get hydrolyzed to carboxylic acid, doesn't hurt to use an excess.

Offline phth

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #6 on: June 18, 2020, 03:33:48 AM »
S-B conditions are lit. I was able to get better results using their conditions compared to anhydrous conditions:

THF: ~20%

THF/NaOH/NaCl, 0 C, biphasic: ~50%

Water has an amazing heat capacity, and carbonyl chlorides are stable enough when cold :-)

Offline rolnor

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #7 on: June 18, 2020, 05:51:26 AM »
Do you only get 50%? I would use DCM/NaHCO3(aq) and 1:2ratio amine/acid chloride, then wash with dil. HCl(aq) after reaction is complete, it should be very fast.
« Last Edit: June 18, 2020, 09:01:32 AM by rolnor »

Offline kriggy

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Re: Schotten-Baumann Benzoylation of Diamines
« Reply #8 on: June 19, 2020, 07:18:15 AM »
Do you only get 50%? I would use DCM/NaHCO3(aq) and 1:2ratio amine/acid chloride, then wash with dil. HCl(aq) after reaction is complete, it should be very fast.

Seconded. I used same conditions few times and worked well. Even using NaOH as a base without any problems. Colleague of mine did lots of those and she just mix all in DCM in sep funnel, then add aq. NaOH shake few times and its done

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