Question

when p-ethenlybenzoic acid is treated with mercuric acetate and water followed by reduction with sodium borohydride, the IR spectrum of the product shows a strong broad absorption at 3400cm^-1. the isolated material is then treated with PBr₃, and the mass spectrum of the resulting product has a molecular ion with two peaks roughly equal intensity at m/z values of 228 and 230. The NMR spectrum showed the following information.

                         A. Singlet at 11.5 ppm- integration of 1

                         B. 2 peak multiplet at 7.5-8.1 ppm- integration of 4

                         C. Quartet at 4.9 ppm- integration of 1

                         D. Doublet at 2.0 ppm- integration of 3

How many degrees of unsaturation are in the product?

What is the structure of the product? Assign the peaks for the NMR spectrum on your structure.

Answer 1

Ethenyl benzoic acid upon treatment with mercuric acetate and water gives an intermediate with mercury associated with which upon reduction with the sodium borohydride gives an alcohol which further treating with PBr3 gives bromo derivative. PBr3 brings one bromine atom in the place of hydroxy group.

3400cm-1 in IR spectrum shows the presence of hydroxy group after sodium boro hydride reduction.

Presence of Bromine is indecated by the mass spectrum of the resulting product has a molecular ion with two peaks roughly equal intensity at m/z values of 228 and 230.