behaviour of analyte in mobile phase!

[amaryl]

My analyte Glimepiride is practically insoluble in water. Its a non-polar highly hydrophobic drug.


IUPAC name - 3-Ethyl-2,5-dihydro-4-methyl-N-[2-[4-[[[[(trans-4-methylcyclohexyl)-amino]carbonyl]amino]sulfonyl]phenyl]ethyl]2-oxo-1H-pyrrole-1-carboxamide.

well its stated in one artilce it exhibits a pH dependent low solubility. in acidic and neutral aqueous media (<0.004 mg/ml) and in media of pH > 7 the solbility of drug is increased to pH 7.8 (0.02 mg/ml).

i could not find any literature stating its a acidic or basic drug. well based on its pka i used a mobile phase of ACN : phophate buffer pH 3.0 for analysis.

working at higher pH (4 and 6 ) the RT decreased (more decrease at pH 6.0) suggesting its getting ionised...but at what point in the structure?

Can anyone suggest me how my analyte is behaving at my working mobile phase conditions?

whether its acidic or basic?


thanx for the suggestions

regards

amaryl


well i tried but could not place the structure of my analyte on the post.

[Uwe Neue]

I would not have guessed this from the structure either, but the evidence is clear: it is acidic. I think that the acid function is the aryl-SO2-NH-CO-NH-R entity.

[Mark Tracy]

Indeed it is. This is analogous to the acidic moieties in saccharin or acesulfame. Ironically, artificial sweeteners.

[amaryl]

thanx for the reply

so i can state off its an acidic drug with pka 6.2.


thanking you

regards

amaryl

[amaryl]

I would not have guessed this from the structure either, but the evidence is clear: it is acidic. I think that the acid function is the aryl-SO2-NH-CO-NH-R entity.

thanx for the reply

so i can state off its an acidic drug!

thanking you


regards

amaryl

[amaryl]

I would not have guessed this from the structure either, but the evidence is clear: it is acidic. I think that the acid function is the aryl-SO2-NH-CO-NH-R entity.

thanx for the reply

so i can state off its an acidic drug!

thanking you


regards

amaryl

[amaryl]

I would not have guessed this from the structure either, but the evidence is clear: it is acidic. I think that the acid function is the aryl-SO2-NH-CO-NH-R entity.

thanx for the reply

so i can state off its an acidic drug!

thanking you


regards

amaryl

[amaryl]

I would not have guessed this from the structure either, but the evidence is clear: it is acidic. I think that the acid function is the aryl-SO2-NH-CO-NH-R entity.

thanx for the reply

so i can state off its an acidic drug!

thanking you


regards

amaryl

[amaryl]

well i found one literature ...it exist in anionic form as stated by dr Neue being an arylsulfonylurea the H atom attached to nitrogen is donated so its a Brownsted acid. but its not acid according to lewis acid base concept.
Since lewis acid is a substance which accepts a electron pair. So what should i state. Is it acid or basic in my work.

thanking you

regards

amaryl

[HW Mueller]

Hm, can´t think of any acid that does not fit the Lewis definition. Your "donated" proton is an electron pair acceptor.

[amaryl]

All brownsted bases are also lewis bases but all brownsted acids are not lewis acids.

lewis bases generally contain one or more lone pair of electrons and, therefore they can also accept a proton (brownsted base). Thus, all lewis bases are also brownsted bases. On the other hand, brownsted acids are those which can give a proton, for example, HCL, H2SO4. but they are not capable of accepting a pair of electrons.

Hence all brownsted acids are not Lewis acids.

[HW Mueller]

I guess I would be shouting also if that confused. A humble suggestion: Check this Forum on Brönsted, Lewis, and Arrhenius.