Separation of Na salt of p- Cresol with p- cresol

[praveenpaliwal]

Hi,

I want to separate Na-alt of P-cresol from p-Cresol. I did the derivatization with chloroacetyl chloride but still I got 16-20 % p-Cresol and this does not gives me full confidant. What is the actual procedure to do this on RP-HPLC column because I have only this , no another column and have only PDA detector.
CAn any body help me for this. I also have chromatogram but I do not now how it up load on this forum.

Best regards

Praveen

[DSP007]

Hi
Bad head does not rest his hands. (Russian proverb)
LC chromatograpy is a bad metod to separation the same (one) substance in a dynamic equilibrium between salt and "free acid" form.
If p-Cresol and its Na salt have a big concendration- dissolve you mix in water and extract by hexane. Cresol Na - good dissolve in Wather and small soluble in hexane , Cresol- good soluble in hexane and smaall soluble in wather. After - evaporate hexane and gravimetry , natrium salt in solvent - precipitate whith barium salt and gravimetry , permanganatometry (titrometry KMnO4) or foto-colorimetry (spectrofotometry in 450 nm) in Fe2+ compex.

[Vlad Orlovsky]

The way to do this to quantitate sodium and cresol separately and calculate how much salt you have. You will need reversed-phase cation-exchange column for that something similar to this application:
http://www.sielc.com/Application-HPLC-A ... p-100.html

[praveenpaliwal]

Sir,

This Na-salt of p-cresol is formed reaction of NaOH and p-cresol , there is free NaOH is also present in the salt. Then if I use cation exchange column I will get wrong result.
I do not have cation exchange column so please tell me is there is another way to this thing correctly.

Best regards

Praveen

[Peter Apps]

If you have free sodium hydroxide then all the cresol will be in the salt form I should think. So if you know, or can measure, total cresol then you know how much sodium salt you had.

Peter

[DSP007]

Sir,

This Na-salt of p-cresol is formed reaction of NaOH and p-cresol , there is free NaOH is also present in the salt. Then if I use cation exchange column I will get wrong result.
I do not have cation exchange column so please tell me is there is another way to this thing correctly.

Best regards

Praveen

I sayd for you . Extract of free cresol in hexane. Afther this - KMnO4 titrometry or foto-colorimetry Cresol Na salt. Its a vary old , by worked method.

If you want it to torment chromatograph and RP column - how to say "flag in your hands."
You can for example dilute your mixture into the water, enter the RP column and rinse it with water many times. Sodium hydroxide and cresol na salt peak this wash, but free cresol strongly sorbed. After that, you can also wash step gradient, for example acetonitrile.

But this is masturbation.

[Don_Hilton]

As I read the discussion, I am trying to understand the details of the question. It appears that there is a mixture of sodium hydroxide and p-cresol. It is know that some of the sodium hydroxide is unreacted - as indicated by the response to measuring the sodium content. There is concern that some of the p-cresol is unreacted, as indicated by the desire to separate the cresol from the cresol salt.

(I can't show the arrows pointing both ways to indicated an equilibrium using the keyboard, so I will use <===> in place, just let one arrow head have on line and the other arrowhead the other.)

What is described is:

CH3OC6H4OH + Na+ + OH- <===> CH3OC6H4O- + Na+ + H2O

A couple of things here.
1) This reaction happens quickly in either direction.
2) There is an equilibrium constant which will be the product of the concentrations of the items on one side of the equation divided by the concentratios of the items on the other side of the equation. The constand may change as a function of solvent and other factors, but remains part of the problem here.

If the ionized form and unionized form of the cresol are present and the reaction can occur, separation is going to be a problem. The equilibrium will continue to create whatever you remove.

So the question I have is what are you attempting to accomplish with the separation?

So, are you trying to prepare the "pure" ionized form, you need to run the reaction under conditions which drive the equilibrium to completion - and avoid running the reaction in reverse while analyzing the product. If you are trying to measure the portion in solution that is ionized as oppsed to unionized in solution, you will need some other kind of technique - such as a spectrosocpic technique.

I seem to have missed the point before, so if I've missed it again, help me understand what you are trying to accomplish.

(And on the matter of the derivitization with an acid chloride - the reaction between the acid chloride was most likely a nucleophilic atack by the ionic form of the cresol on the carbonyl portion of the acid chloride. Depending on the solvent used for the reaction, it might be possible to get nearly 100% of the cresol salt to form the ester.)

[HW Mueller]

Don, your suggestion in the last sentence in parentheses is also subject to Le Chatelier´s principle.

[DSP007]

Hello HW Mueller.
Don right (and I also) - strong alkali and weak acid in wather solution- is classical example of equilibrium.

[Don_Hilton]

My suggestion in the parenthases was for the purpose of suggesting that the derivitization was coming from ionized cresol - rather than being a measure of the unionized cresol.

The failure of the derivitization to run to completion would then be some other thing going on - such as running the reaction with the cresol salt present as a solid - which offers the potential for low reaction yields if the sodium chloride forms a coating on the ouside of the particle, keeping the material on the inside of the particle from being effectively exposed to the acid chloride.

Le Chatelier´s principle might be a bit less obvious in this case as the formation of an ester by reaction of a phenol and an acid chloride does not show a significant back reaction. The equilibration of between the nutral cresol and the sodium salt is hindered because of the problems of running a reaction with unisolved reagents or what ever else was going on to keep the reaction from running to completion.

[DSP007]

There is another problem -

Figuratively -

To praveenpaliwal must be split hens and chicks.
He comes to the chemist and says - I have a howitzer and a tactical missile. That I charge the sarin to kill only the chickens?
And he totally not comes to mind , that the missiles hens with chicks no shared ...

[HW Mueller]

Well, maybe I missed something, but this is exactly what I referred to: The dissociation of acid to replenish carboxylate (dissociated acid).

[praveenpaliwal]

Hellow every body

But the comment which was given by DSP007 is not good. It is a forum of chormatography not a mutton chicken shop. I can also give them answer in our INDIAN term but its is totally rubbish for this forum.
Now I want to tell them u all that the problem is almost solved by US.
I got answer from TLC which is RP TLC and derivatizing agent was CAC. I also get Normal Phase TLC with same derivatizing agent.
And finally we developed HPLC with derivatizing of Na-PCR with Tosyl chloride.
We got very good result and these are also reflected by TLC.
I do not know how to post chromatogram on this forum other wise I post them.
Now we are going to reproducibility analysis.
So we are believe that there is always better way to do something but u need Honesty and politeness.

Best regards

Praveen

[Vlad Orlovsky]

I am glad that somebody else has a problem with excessive quotation of meaningless ("rubbish") proverbs and catch phrases .
Just lets stay on a scientific pass and not to try be "witty" in the language which is not our native (for me and other people). The beauty of science is that it is international

[DSP007]

Maybe. Not calculated. Sorry
I wanted to say (diplomately, but clear menas* ) that you showed the wrong approach to the problem. Trying to solve the problem of difficult technique, if it has a lot of simple solutions.

RP HPLC was good and strong separation. But it is not suitable for this purpose, as not suitable missile or poison gas to separate the old chickens from the chicken. Because they are not designed for this task.

Here is another image.

After the farmer has different ways of solving this problem.
Firstly, he can immediately take away the eggs of chickens and grow them in an incubator. Replaced by a new natural technologies.

Secondly, this problem is solved with the simplest means. If the chicken is a lot of farmers come easy.

The farmer knows that the old hen can fly and love is on high ground, but the chickens still do not know how to fly and walk only on the ground.
He poses two feeders - one on the ground, another on the old desk, or other high place. Hen fly up there and do not interfere with a chicken.
There is another way, the farmer puts the bars around the feeder to the cell a half feet tall. Small chicks can climb through it to its stern, and adult hens remain outside the grid.

Finally, if the chicken brought chickens and they do not live in a chicken coop and go to the farmyard (in Indian villages are ancient way of life, and you could see this scene) - he is in no hurry to separate the chickens. Chicken will protect them from predators until the chicks will not grow.

Similarly, the farmer can easily share the ducklings and chickens, putting the tub with water. Ducks love to swim, and chickens do not like to swim.

Farmer solves this problem without the use of sophisticated means because he knows the habits of their birds, and he knows how they will later use. Leave on for reproduction, will receive with their eggs or sell the meat.

Do not you think that the problem of farmer's similar to your (share of birds of one species but of different ages). Just as you have a problem to separate one substance in a state of salt and the free state.

*But with the use of the image, understandable to those who served in the Army and were present at launch.