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Topic: Silica Chloride Catalyst for Esterification  (Read 5199 times)

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Offline Elnino

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Silica Chloride Catalyst for Esterification
« on: March 15, 2013, 09:53:46 PM »
Hello all I'm new to the forums!

I'm a undergraduate researcher who's interested in converting a carboxylic group into an ester using silica chloride as a catalyst.

Here's a link to the reaction I am interested in preforming: http://www.organic-chemistry.org/abstracts/literature/269.shtm

Anyway my question is what does 150 mg/mmol substrate mean?

Reaction scheme:

Carboxylic acid +Alcohlol ----(Silica Chloride 150 mg/mmol substrate ---> Ester

 
PS. I don't have access to the paper.

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #1 on: March 15, 2013, 10:02:07 PM »
Silica chloride, what sort of reagent is that?
150mg/mmol substrate means that you use 150mg silica chloride per mmol of the acid assuming the alcohol is in excess.
You should look up Fischer esterifiication.

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Offline Dan

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Re: Silica Chloride Catalyst for Esterification
« Reply #2 on: March 16, 2013, 05:15:18 AM »
Never heard of "silica chloride" either. It's probably a name they coined themselves for silica-supported HCl. I bet it's essentially the same as using any solid supported acid (haven't read the paper).
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Offline Elnino

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Re: Silica Chloride Catalyst for Esterification
« Reply #3 on: March 16, 2013, 09:28:23 AM »
Sorry, yes it's silica-supported chloride (HCL and SO2 released as gas when made thionyl chloride)

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #4 on: March 16, 2013, 10:01:07 AM »
Why not use conc. sulphuric acid like everyone else? It's easier to use and the work-up is simple.
Silica chloride is probably an undefined mixture and it means using thionyl chloride which is not pleasant to handle and dispose of.
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Offline Elnino

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Re: Silica Chloride Catalyst for Esterification
« Reply #5 on: March 16, 2013, 10:33:08 AM »
The alcohol I'm using is propargyl alcohol. Wouldn't the triple be hydrolyzed with the H2SO4? I believe my lab mates tried conc. H2SO4 before however I'm not sure.

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #6 on: March 16, 2013, 10:45:27 AM »
What is your esterI meant acid?
If it's methanol or ethanol you could do an extractive esterification using the alcohol, acid, heptane, conc. sulphuric acid, the ester is extracted into the heptane layer. This should be ok.
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Offline Elnino

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Re: Silica Chloride Catalyst for Esterification
« Reply #7 on: March 16, 2013, 10:47:57 AM »
3-hydroxy-4-methoxybenzoic acid + propargyl alcohol

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #8 on: March 16, 2013, 10:52:13 AM »
That should work.
Suspend everything in heptane/propargyl alcohol (slight excess) stir well and heat to reflux add conc. H2SO4. If heptane is too high use hexane. Work-up, separate layers, wash hexane/heptane with bicarbonate (gas evolution) evaporate hexane/heptane.
Crystallise ester.
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Offline Elnino

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Re: Silica Chloride Catalyst for Esterification
« Reply #9 on: March 16, 2013, 11:05:03 AM »
Thanks. I'll try this Monday! I thought about doing a fischer esterification, but never attempted it because I assumed my lab mates already tried it.

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #10 on: March 16, 2013, 11:11:00 AM »
Maybe they did, did you ask them?
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Offline Elnino

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Re: Silica Chloride Catalyst for Esterification
« Reply #11 on: March 16, 2013, 11:15:59 AM »
Nope -.- but I'll try both procedures because I'm interested

Offline discodermolide

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Re: Silica Chloride Catalyst for Esterification
« Reply #12 on: March 16, 2013, 11:19:52 AM »
OK, let us know what happens.
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