Molecular structure-reactivity study of Para-methyl maleanilic acid using mass spectrometry, thermal analyses and semi-empirical molecular orbital calculation

Abstract EN

The chemistry and reactivity of maleanilic acid (MA) derivatives have always been of great interest because of their importance and biological activities.

In the present work p-methyl maleanilic acid (C11H11NO3) compound (P-MMA) was investigated using thermal analyses (TA) measurements (TG/DTA) in comparison with EI mass spectral (MS) fragmentation at 70 and at some different low energies 10,11,12eV.

Semi-empirical MO calculations using PM3 procedure have been carried out on P-MMA both as neutral molecule and the corresponding positively charged molecular ion.

These include molecular geometry, bond order, and charge distribution, heats of formation and ionization energy.

It is concluded that this compound passed through two steps of fragmentation via rupture of the weakest bond C1-C2 to give CO2 gas molecule by decomposition of COOH functional group.

As a result of this rupture active ingredient of mole mass 160 or fragment ion m/z=160 is formed.

It is followed by the rupture of the second weak bond C4-N8 which leads to thermal fragment of mole mass 106 and competitive active mass fragment ions of m/z=106 or 107.

This study is thought to be helpful in establishing a quantitative and qualitative structure—activity relationship for the given compound, which is the main objective of the present work.