Question

2. Propose a structure for a molecule whose mass spectrum shows a parention at m/z 86 with a base peak at m/z 29. an IR peakat 1720 cm and which gave the following 'H NMR spectrum. PPM e a narention at m/z 86 with a base peak at mvz 43, an IR peak at

Can someone please explain how to do this? Thanks in advance!

Answer 1

Integration 2H with quartet is an indication of -CH₂- group attached to -CH₃

Integration 3H with triplet is an indication of -CH₃ group attached to -CH₂-

-CH₂- group further attached to a carbon without hydrogens and also chemical shift value ~2.5 ppm indicates electron withdrawing group present as neighbor such as carbonyl group (Please refer 1H NMR chemical shift table for this purpose)

so far we found -CH₂-CH₃ group is present and molar mass of this group = m/z 29, but given m/z is 86, so we can expect twice this group, so that m/z = 2 x 29 = 58 and we have also deduced C=O group is present (m/z = 28)

so total = 58 + 28 = 86 matched

Hence we found the compound as 3-pentanone

2. Propose a structure for a molecule whose mass spectrum shows a parention at m/z 86 with a base peak at m/z 29. an IR peakat 1720 cm and which gave the following 'H NMR spectrum. 1720 cm-1 due to C=0 stretch PPM e a narention at m/z 86 with a base peak at mvz 43, an IR peak at

Hope this helped you!

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