[Wald_ron]

Hello Chemical Forums,

I've run several Proton NMR of a long chain carboxylic acid  (C18, alkene at 9-10, COOH at 1) and after acid catalyzed fischer methylation, what I had originally suspected to be a non terminal alkene exhibits doublet of a doublet shifts in deutoro benzene.

Initial analysis of the double bond peak in deutoro(sp) Chloroform via HNMR was inconclusive. Literature data of the expected shift characteristic was completed in Chloroform-D.

Would deutero benzene influence the splitting pattern of the double bond characteristic to such an extent that it would influence the splitting pattern?

MS data of expected product is comparable. Is there an instrumental method which I haven't considered which would allow me to draw a conclusion about my alkene? I've run IR, GC/MS, HNMR, 2DNMR(DCCl3),CNMR(DCCl3). IR confirmed a successful esterfication.

[Cesium-137]

Peaks shift all over the place when changing solvents... always compare your peaks to literature in the same solvent as the literature uses. I might suggest trying DMSO as your NMR solvent. I've had good luck with peak resolution in DMSO when other solvents gave ambiguous peaks (CDCl3, Acetone-D6, MeOD, etc). As for other instrumentation, maybe give HPLC a shot and compare ret. times w/ literature.

[Wald_ron]

Cesium 137,

Thank you for your reply, honestly I was casually fishing to see if there is a common trend of the effects of benzene on alkenes in comparison to DCCl3 in relation to Cis Trans isomerism.

[discodermolide]

Cesium 137,

Thank you for your reply, honestly I was casually fishing to see if there is a common trend of the effects of benzene on alkenes in comparison to DCCl3 in relation to Cis Trans isomerism.

Benzene causes aromatic induced solvent shifts in the nmr, especially of those goups containing pi electrons. So you may well see different splitting patterns.