[alrob8a]

Hey guys.

In uni lab we performed a perkin reaction to for a-phenylcinnamic acids. After separating the E and Z isomers, we dissolved the Z isomer in boiling water for recrystallization. However there was an amount of precipitate that did not dissolve. I held onto this filtrate for IR analysis.

Running IR on all 3 samples, I came out with the following:

e-isomer


z-isomer


Z-filtrate


First, am I correct in guessing that the "z filtrate" is actually the e-isomer, based on similarities in IR? Mainly due to the absence of the  peaks at 2924.90 and 2854.48? But more importantly, I'm guessing these peaks are present in the Z isomer due to the trans configuration. If so, why does the change in conformation create these peaks?

Thanks.

[orgopete]

By my looking at these spectra, their fingerprint regions are all virtually the same. I suggest you compare the fingerprint region of your compounds with those of authentic samples.