Page 1 of 1
basic pH can change the pi-pi conjugation system
Posted: Sun Dec 27, 2009 5:28 am
by praveenpaliwal
Hellow,
I want to know 'can basic pH change the pip-pi conjugation system of any compound'
Means cis and trans isomeric form .
praveen
Posted: Sun Dec 27, 2009 11:55 am
by HW Mueller
If the system is highly activated, such that an allylic H is quite acidic, as an example, one can imagine that changes in the conjugation and cis-trans isomerization occur.
The idea, though, that this is the right place to learn organic chemistry seems a bit adventurous.
pi-pi conjugation
Posted: Sun Dec 27, 2009 5:35 pm
by praveenpaliwal
Sir,
My compound is one of sodium salt Ist I dissolve it in 0.1N NaOH I got two peaks with same UV-spectra but when I dissolve it in 0.01N NaOH I got a single peak but it's UV spectra is also same as earlier peaks UV-spectra . This I want to know from u that at a certain pH is it possible to change in pi-pi conjugative system
If u send me ur e mail ID I will send u the complete detail of my experiments[/code][/quote][/url]
Posted: Mon Dec 28, 2009 9:54 am
by HW Mueller
Take a look at pH indicators (phenolphthaleine, etc.) to get an idea of how pH can change UV/Vis spectra. Since we all try to learn something with this forum I would prefer that you continue here, however, there is no problem in handing out my e-mail address.
Posted: Mon Dec 28, 2009 11:03 am
by Peter Apps
If you are injecting samples dissolved in 0.1M sodium hydroxide there are all sorts of reasons why you might get two peaks - and if your column is silica-based you shuld not expect it to last very long.
Peter
Posted: Mon Dec 28, 2009 5:09 pm
by praveenpaliwal
I repeat three conjugative runs I got repeatability with 0.01N NaOH.
I am also looking the possibility to form zwitterions.
But main thing where I also go and stop why there is no difference in UV-spectra and this one tell me that there is some change in pi-pi conjugative system as mullar say's.
The Phenolphthalene gives us some clue but here in this molecule what is going one?
praveen
Posted: Mon Dec 28, 2009 9:30 pm
by DJ
Is there perhaps some degradation going on?
Distinct UV spectra for the ionized and neutral form of a compound probably depends on the proximity of the chromophore to the site of ionization.
Posted: Tue Dec 29, 2009 8:53 am
by HW Mueller
Why don´t you tell us what this compound is. It also might be helpful to see the spectra, and to know whether you can repeat the results at 0.1M NaOH (especially after you change contact time).