Question

2. Below is the observed ESR spectrum of the butadiene anion radical. Interpret the spectrum (i.e., What nucleus / nuclei are responsible for coupling with the unpaired electron? Also explain the origins of the multiplet of multiplets, the number of signals in each multiplet, and the relative signal intensities within each multiplet.)

Answer 1

I - w CH 4 H Butadiene anion radical Since the negative charge is delocalized in P₂ orbital of the 4-Carbon atom. Hence the total number of spectral linea initial obtain is (2nI+1). hello Number of linea = 2x4x2 + 2 = 5 lines. Since there are two different type of proton present in the system lie proton on C8C₃ are same type and proton of a & Ca Que same type). Each five line forther split into (202+1) = (2x 2 x + 2 + 1) = 3 lines Linea intensity ratio is given by pascal triangle. The inital five line formed have ratio 1:4:6:4:1 then each line split into triplet (with ratio 1:2:1)

Pascal Triangle No. of Line Ratio A arnt al 1:2:1 1: 3: 3:1 1:4 : 6:4:1 & The spectrum is a quinteto of triplet dat because first five line will form and then each line split into triplet. Ich ③ There are three signals present present in in each each multiplet o ③ The relative signal intensities is - for initial five lines then each intensities 1:4: 6:4:1 into triplet with line split 1:2:1