3-methyl-2pentanone 1. The two El mass spectra shown below are of 3-methyl-2-pentanone and 4-methyl-2- pentanone. Unfortunately, the mass spectrometer operator failed to label them (1) Please assign the proper structure for each of them. (1) Write reasonable structures for the following mass peaks: in spectrum A: m/z 85, 58; in spectrum B, m/272, 43. (iii) Propose reaction mechanisms to account for the formation of the abovementioned four fragment peaks (use curly arrows to clearly indicate the electron flow). 100- (A) 80- 4-methyl-2 pentakone 60 Relative Intensity 40 20 10 20 30 40 50 60 70 100 100- (B) 80 50 Relative htensity 20- otto 10 20 30 40 50 60 70 80 90 100 m/z