Chromatography Forum

Ok ,

Now tell me what is the easier way ??? the which u told me earlier. If yes hen how can I tell the person about un reacted p-cresol,.AS per your hexane extraction it can not be tell exactly.
If u have more better why then tell me because extraction process does not gives me a perfect idea about un reacted p-cresol.
AS my initial mail I told that I have demonstrate the person that X % of p-cresol is remaining and Y% of Na-salt of p-cresol is formed.
So do not tell us story and give me the fact answer if u know ??? I am quite sure the RP HPLC technique may be one of right way to do this job. If u object it gave me the facts or relative literature.

Praveen

If you have the cresol sodium salt in solution, you can calculate the portion of p-cresol that is not ionized the pKa of p-cresol is 10.12. The pKb for NaOH is 0.2. The rest is the calculations used for equilibrium chemistry - used for computing buffers as well.

Remember that you are forming an acid/base salt rather than a covalently bonded compund. So, in solution it is in constant equilibrium, unless you can do something like remove all water formed by making the salt.

If you are using an aquesous solution, I would suggest three measurements: 1) sodium concentraiton, 2) total p-cresol concentration and 3) pH. Unless there are other components present, the sodium hydroxide present and the p-cresol present will establish the pH.

If you are using the solid, I would look the usability of the melting point (202 deg. C - from antoher web site). A sharp mepting point typically indicates pure material. Any inclusion of impurity causes the melting point to be lower and broader. (And a melting point measurement is relatively quick and easy.)

Hi Praveen

It might be worth checking whether the free cresol and the sodium salt have different absorption spectra - there might be a set of wavelengths that can tell you how much of each you have. You can do this measurement using your PDA if you do not have a stand alone spectometer.

Like other posters I am concerned that if you try to do any chemical reactions or separations the equilibrium will shift and your result will not reflect the composition of the original sample.

Peter