Question

Help on Mass Spectrometry Data Analysis. Please explain.

For the following mass spec data: a) Circle the structure(s) consistent with the mass spectrum (more than one answer may be possible): b) Draw the structure(s) of the most abundant fragments (base peaks) in the mass spectrum. If two compounds are consistent with the spectrum, please draw the base peak for each structure)

Answer 1

7a) Firstly, we should remember Nitrogen rule which can gives some hint regarding the no of nitrogen

here, the molecular ion is appeared at around 86 m/z, is conforming that nitrogen must be even, the given alkyl amine having only one nitrogen here, thus Ist compound is not shown by given mass spectra.

other three compounds having molecular mass 86. so all stracture can show given mass spectra.

7b) Let start from second stracture:

CH3- C(CH3)2-CH2-CH3 the tertiary carbocation is more stable, will show base peak,

CH3-C(CH3)2+ would be the ion shows base peak

In normal alkane compound the most intance peak are due to C3 and C4 ions at m/e 43 and m/e 57respectively. C4H9+ will show the base peak.

In last one alpha cleavage is most prefeared so CH3-CH2-CO+ shows base peak.