Molecular electrostatic potential (MEP) indicates the net electrostatic
effect produced at a point by the total charge distribution of themolecule.
It correlates with the dipole moment, electronegativity, partial charge and chemical reactivity of the molecules. It provides a visual
method to depict the size, shape, charge density and the sites of chemical
reactivity of the molecules. The molecular electrostatic potential
(MEP) Maps shown in Fig. 6 were used to visualize the atomic charge
density distribution of 6a–g. MEP values increase in the order
red b orange b yellow b green b blue. The MEP Map showed the most
negative (red) regions around the carbonyl oxygen and N atoms while
the maximum positive (blue) regions are localized on the hydrogen
atoms of the NH group. MEP regions with red are the most suitable for
electrophilic attack. In contrast, the blue spaces represent the sites of
the highest reactivity towards the nucleophilic attack [45]. MEP is
used to understand the relative polarity of themolecule. The dipole moment
of the studied compounds is 1.9528D (6a), 1.5229 D (6b), 2.2394
D (6g) and 4.8758 D (6i).We could conclude that 6iwhich has the largest
number of heteroatoms has the highest polarity.