The software then uses the Karplus relationship to estimate the vicinal H-H coupling, which is compared with the value measured by the students in their 1 H nmr spectra of the product.
Students also follow the rate of reaction by nmr.
A Diels-Alder reaction between tetraphenylcyclopentadienone and dimethylacetylenedicarboxylate yields, after reverse cheleotropic loss of CO, dimethyl tetraphenyl phthalate. Modeling reveals the propeller shape of the product, which helps to explain its unusual 1 H and 13 C nmr spectra. Here is a picture of the very crowded product, with the atoms drawn to full scale of their van der Waals radii. The four peripheral benzene rings are twisted at about 30 degrees relative to the central one, whereas the two ester functions are essentially orthogonal to the ring. Modeling of the methyl m-nitrobenzoate product of nitration of methyl benzoate reveals the ring hydrogen between the two substituents to lie in the anisotropic deshielding zone of the nitro group, which is coplanar with the ring.