kilomentor

How thinking about Separating Acetic acid and Acetic Anhydride can sharpen our Chemical Process Development Skills

kilomentor | 16 December, 2011 10:50

The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/12/how-thinking-about-separating-acetic-acid-and-acetic-anhydride-can-sharpen-our-chemical-process-development-skills

 

An Example of a Possible Kilomentor Type Separation at Scale

kilomentor | 22 November, 2011 10:22

The Kilomentor Blog is now being continued and updated at www.kilomentor.com

Hi Marto,

 
Thanks for the problem. Although you do not provide enough information to exactly identify the compounds that is OK. I understand there may be intellectual property or privacy issues. I think I can make some suggestions that are at least mentally stimulating and which certainly exemplify the kilomentor approach.

Marto has asked for suggestions of how to achieve a particular separation.

He wrote: “
I am having a problem in the isolation of mixture containing biphenyl benzylacetate compound along with diarylated benzylacetate copound. I have been carrying out this reaction on 100 g- 200 g scale, the ratio of biphenyl and diaryl compounds is 10:1, isolation by recrystallization was unsuccessful. Both have similar retention factor in TLC. Suggest me any purification method for the isolation of these two compounds.”

First, I would hydrolyze the acetates. When compounds are strongly hydrophobic, separation should most often be tried on the most polar functional groups available.

In the case where there is a difference between the number of substituents ortho to the primary alcohol function, the compounds can probably be separated by the difference in the rates they form the O-sulfate derivatives. Sulfonate the mixture with only enough sulfonating agent ( say chlorosulfonic acid in one of the solvents pyridine or dimethylaniline; see the kilomentor blog on making O-sulfonates). The sulfonated material and the non-sulfonated are easily separated by acid-base extraction and the sulfonation is easily reversedto give two separated alcohols.

In the situations where there is no difference in the number of ortho substituents between the alcohols one must depend upon a difference in inductive and electronic effects and the best chance comes when the primary alcohol mixture is converted into two carboxylic acids. The required hydrolysis and oxidations of the esters can be done together without isolation and the mixture of two carboxylic acids can be obtained cleanly and easily by simple acid-base extraction.

I think there will be a good chance that these acids can be separated by what is called extractive crystallization. (kilomentor has also written a blog about extractive crystallization). Extractive crystallization works by taking advantage of any small difference in pKas of the two acids augmented by any small difference in the solubilities of the two acids in an immiscible organic solvent selected to augment this pKa difference. The goal is to get one compound overwhelmingly as a salt in water and the other compound overwhelmingly as free acid in the organic solvent.

In any case, even if this cannot be made to work, as free acids there are many more salts, both organic and inorganic, that are accessible to find substances that do fractionally crystallize.

Also when one has a mixture of acids one can screen a portfolio of enzymes to find one that esterifies only one of these acids. Thus one uses the most discriminating of reagents, enzymes, catalytically in their favorite reversible reaction, ester formation/ hydrolysis.  

Once separated the alcohol-acetates can easily be reformed if that is what is required. The extra steps in both directions are simply probably high yield and the separations are trivial acid/base extractions.

If you are reforming the acetates remember that the ester (non alcohol) can probably be easily separated from any residual alcohol by treatment with lithium bromide or calcium bromide or calcium chloride in hexanes where the alcohol is likely to form an insoluble inorganic complex leaving the ester in hexane solution.

What Might be the Best Solvent for Difficult Cleaning Jobs on the Reactor Walls of a Plant Reactor

kilomentor | 24 October, 2011 07:36

The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/10/what-might-be-the-best-solvent-for-difficult-cleaning-jobs-on-the-reactor-walls-of-a-plant-reactor




The Importance of Understanding Process Validation for Pharmaceutical Process Chemists

kilomentor | 17 October, 2011 05:15


The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/10/the-importance-of-understanding-process-validation-for-pharmaceutical-process-chemists



 

Is Glycerin a General Green Solution to Solvent Recovery and Replacement for Process Chemistry?

kilomentor | 13 June, 2011 07:15

 The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/06/is-glycerin-a-general-green-solution-to-solvent-recovery-and-replacement-for-process-chemistry

 

 

 

More Information about using Inorganic Salt Complexes to simply Purify Alcohols at Scale

kilomentor | 16 May, 2011 08:19

The Kilomentor Blog is now being continued and updated at www.kilomentor.com this particular article can be found at http://www.kilomentor.com/2011/05/more-information-about-using-inorganic-salt-complexes-to-simply-purify-alcohols-at-scale

Saturated Calcium Chloride Brine for Separations?

kilomentor | 11 May, 2011 15:54

 The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/05/saturated-calcium-chloride-brine-for-separations

 

 

 

Use of free radical inhibitors or antioxidants to increase the overall yield of organic synthesis steps.

kilomentor | 25 March, 2011 13:30

 The Kilomentor Blog is now being continued and updated at www.kilomentor.com this particular article can be found at http://www.kilomentor.com/2011/03/use-of-free-radical-inhibitors-or-antioxidants-to-increase-the-overall-yield-of-organic-synthesis-steps

The Pharmaceutical Salt called Pamoate or Embonate

kilomentor | 26 February, 2011 14:47

The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article appears as http://www.kilomentor.com/2011/06/is-glycerin-a-general-green-solution-to-solvent-recovery-and-replacement-for-process-chemistry

 

Simple, Rapid Optimization of a Chemical Process Step

kilomentor | 10 February, 2011 14:53

 The Kilomentor Blog is now being continued and updated at www.kilomentor.com http://www.kilomentor.com/2011/02/simple-rapid-optimization-of-a-chemical-process-step

 

Experiment # Yield Rank Yield Rank (100-Rank)/(N+1)
1 41 11 1 7.1
2 50 14 2 14.3
3 11 25 3 21.4
4 14 34 4 28.6
5 80 41 5 35.7
6 34 59 6 42.9
7 84 61 7 50.0
8 25 70 8 57.1
9 85 73 9 64.3
10 73 80 10 71.5
11 70 84 11 78.5
12 61 85 12 86.7
13 88 88 13 92.8

Optimization continued

kilomentor | 10 February, 2011 14:50

This particular article part can be found at http://www.kilomentor.com/2011/02/optimization-continued

 

Results B

Experiment # Yield Rank Yield Rank (100-Rank)/(N+1)
1 30 15 1 7.1
2 63 23 2 14.3
3 65 26 3 21.4
4 26 30 4 28.6
5 37 37 5 35.7
6 15 42 6 42.9
7 50 50 7 50.0
8 23 63 8 57.1
9 75 65 9 64.3
10 94 75 10 71.5
11 42 76 11 78.5
12 91 91 12 86.7
13 78 94 13 92.8
Results C
Experiment # Yield Rank Yield Rank (100-Rank)/(N+1)
1 0 0 1 7.1
2 45 0 2 14.3
3 0 11 3 21.4
4 11 15 4 28.6
5 15 23 5 35.7
6 32 24 6 42.9
7 53 32 7 50.0
8 33 33 8 57.1
9 44 42 9 64.3
10 24 44 10 71.5
11 60 45 11 78.5
12 42 53 12 86.7
13 23 60 13 92.8
 

The Kilomentor Approach-More Easily Isolated Intermediates-Fewer Technically Demanding Physical Separations.

kilomentor | 01 February, 2011 09:19

  The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/02/the-kilomentor-approachmore-easily-isolated-intermediatesfewer-technically-demanding-physical-separations

 

 

Chemistry related Poetry

kilomentor | 10 January, 2011 13:17

The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2011/01/chemistry-related-poetry

 

Reducing Reaction Time by Adjusting Concentration during the Process in Chemical Process Development

kilomentor | 29 December, 2010 05:48

This particular article can be found at http://www.kilomentor.com/2010/12/reducing-reaction-time-by-adjusting-concentration-during-the-process-in-chemical-process-development. The kilomentor blog has moved to www.kilomentor.com.

 

Dichloroacetic Acid Solvent

kilomentor | 24 December, 2010 07:30

The Kilomentor Blog is now being continued and updated at www.kilomentor.com This particular article can be found at http://www.kilomentor.com/2010/12/dichloroacetic-acid-solvent

 

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