THE EVALUATION OF PROTONATION ENERGY OF MOLECULES IN TERMS OF QUANTUM THEORETICAL DESCRIPTORS - Theoretical and Computational Research in the 21st Century - page 216

For this reason, in recent years, much attention has been given to the
possibility of calculating proton affi nities through some quantum mechan-
ical as well as DFT models [43,57,76-78]. Modern computational chemi-
cal methods can yield very accurate values for the proton affi nity of mol-
ecules composed of fi rst-row elements [43]. Fontaine et al. [79] performed
HF calculations for a number of small molecules.
From the study of the vast literature on the determination of PAs and
effect of protonation on molecules, it reveals that the physicochemical pro-
cess of protonation is a complex phenomenon and the determination of PA
is not a simple procedure—both experimentally and theoretically. There-
fore, there is enough scope of exploring some other methods—namely
modeling and simulation—an well-known procedure for scientifi c study.
In this study, we have resorted to modeling and simulation in the study
of physicochemical process of protonation. We have introduced modeling
to calculate PA.

10.7 METHOD OF COMPUTATION

MULTILINEAR REGRESSION (MLR) IN MODELING TO
SUGGEST ALGORITHM FOR THE EVALUATION OF
PROTONATION ENERGY.

As we have mentioned earlier in Section 10.6 that still there is some dif-
ficulties in both the theoretical and experimental procedures of evaluating
the protonation energy. In this backdrop, we have ventured to explore a
model toward the evaluation of protonation energy with an intention to
overcome such problems as are found inherent in the methods already
available.
Since we have found that the individual quantum chemical descrip-
tors such as ionization potential (I), global softness (S), chemical potential
(μ), and electrophilicity index (ω) to correlate with protonation energy, we
have used these parameters as the components of our modeling.
In this project, we have modeled and given a mathematical relation
with the above-mentioned quantum chemical descriptors for the evalua-
tion of protonation energy. We have taken recourse to the method of mul-
tilinear regression (MLR) to obtain good parameters because, it is known
that as the number of components (here descriptors) increased, the method
were automatically reached to a good result.