Question

14. Explain the difference in the appearance of the two mass spectra below: 31 43 El-MS CH2COCZH6CHO 60 | 55 97 | | | 61 122 لالالالالا 157 15/ Abundance 120 140 160 180 200 220 240 40 60 80 100 100 7 CI-MS (METHANE) 123 M = 200 للننليلنا 141 201 100 120 160 180 200 220 240 140 miz

Answer 1

Solution:

First mass spectra has been proposed by using electron impact or electron ionization mass spectrometry while second mass spectra is proposed by using chemical ionization mass spectrometry.

First mass spectra:

Electron impact method: Electron ionization is one of the method in which high energy electrons are bombarded with atoms or molecules to produce gas phase ions.

In first spectra molecular peak is 157 which tells about molecular mass of molecule assosciated with given spectra with base peak(tallest peak) with highest intensity of 55 with some other small fragment peaks.

Second mass spectra:

Chemical Ionization method:  In this method gas molecules are ionized by electron ionization which further react by analyte molecule in gas phase in order to have ionization. It is a low energy process than electron impact method.

In second mass spectra molecular peak is 201 which tells about molecular mass of molecule assosciated with given spectra with base peak(highest intensity) peak of 123.