Please answer the following as detailed as possible and assign the cis or trans
ID: 1045132 • Letter: P
Question
Please answer the following as detailed as possible and assign the cis or trans isomer to spectra A and B. (PLEASE do not answer if you are uncertain of the answer, thank you)
The partial proton NMR spectra (A and B) are given for the cis and trans isomers of the com- pound shown below (the bands for the three phenyl groups are not shown in either NMR) Draw the structures for each of the isomers and use the magnitude of the coupling constants to assign a structure to each spectrum. It may be helpful to use a molecular modeling program to determine the dihedral angles for each compound. The finely spaced doublet at 3.68 ppm in spectrum A is the band for the O-H peak. Assign each of the peaks in spectrum A to the struc ture. The O-H peak is not shown in spectrum B, but assign the pair of doublets to the structure using chemical shift information. Unknown #5 5 Ph Ph Ph OH Spectrum A Spectrum B 4.30 (ppm)Explanation / Answer
When coupling constant is < 10, it is cis and when coupling constant > 10, it is trans.
In the given NMR spectrum,
The coupling constant between the two peaks of the doublet's appearing for the H's have a larger distance between them. Thus the compiund has cis-configuration of the two hydrogens. Coupling constant = higher frequency shift - lower frequency shift.