Question

The 13C NMR spectra A and B for two molecules, each with a formula C5H8, are shown below. One of them is for a molecule with conjugated double bonds, the other is for a structure that is not conjugated.

CHM 26200 Problem Set 2 Spring 2020 Due Feb 19 1) (30 points) The 13C NMR spectra A and B for two molecules, each with a formula CsHx, are shown below. One of them is for a molecule with conjugated double bonds, the other is for a structure that is not conjugated. 206'100' ido toho 1606 2 6 LUU rom 200' 0' ido to ho 100' ab 'ob .ub.ab. a) Which spectrum is which, and how do you know?

Answer 1

solution - i Given molecule CSHE a) since given we can calculate the degree of comeba satura non as, Degree of men ginstruction -(C+1) - HEREN 2 where, ca number of catims ! H. NO. OF H-atoms To No-Ofhologeas.. Ne NÖ OF Aitrogens .. ! for crH8! (0-0) = (5+1) - 87010 = 6-u (6.0) =2 So. possible structeire are:- r i plane of symmetry unconjugake.08 forces conjugated moleccele. won-congugaked in HB) * since there is a plane of symmetry in non- conjugated molecule. we get only is peaks in 13 C-NMR

In conjugated mole ale we get & peaks in 13 en so A in question, belongs p con gugated male te belongs to un conjugaled molecule. so, the non- conjugated molecule in ca) is. ..CH CH M '8'-spectrum Hot 01 we get, 3-pears for H₂ ca uoppm noben CH + 120 ppm CH₂ y 7 Poppm nuoppřesto! conjugaled structures B. P ji 'key'reatures:- ; sa@ molecular weignt i required for better o understanding. 6 molecular formula is required a long with splining pattern. and coupling constant values.