9. (a) A compound with chemical formula C₂H₂CIBr shows the proton NMR spectrum consisting of two doublets with J-7.3 Hz. What is the molecular structure of this compound? (b) The proton chemical shifts of the two doublets from the previous question differ by 0.3 ppm. Can you consider the proton spectrum as the first order one?

The mass spectrum of n-octane shows a prominent molecular ion peak (m>z 114). There is also a large peak at m>z 57,but it is not the base peak. The mass spectrum of 3,4-dimethylhexane shows a smaller molecular ion, and the peak atmass 57 is the base peak. Explain these trends in abundance of the molecular ions and the ions at mass 57, and predict theintensities of the peaks at masses 57 and 114 in the spectrum of 2,2,3,3-tetramethylbutane.1

The 1H NMR spectrum of chloromethane recorded on a 300 Hz NMR spectrometer consists of signals at 444 Hz and 1071 Hz  downfield from TMS. Calculate the chemical shift of each absorption. Give answer in parts per million.

-·|· 4.0 Match the peaks in this spectrum with hydrogens on the structure below. A) I: 0.91 ppm II: 3.29 ppm III: 1.52 ppm IV: 3.23 ppm H3C | 3.0 || H₂ CH3 CH CH3 III IV 2.0 ppm 1.0 B) I: 0.91 ppm II: 3.29 ppm III: 3.23 ppm IV: 1.52 ppm C) 1: 3.23 ppm II: 3.29 ppm +