5. Conclusions
This investigation represents the study of various non-competitive and
competitive reactions utilizing QTAIM and stress tensor analyses.
Examination of four reactions in order to distinguish and quantify the
TSIC and TSOC paths were performed. In this framework, we have used four
disparate cyclobutenes skeleton-based named 1-chlorocyclobut-1-ene,
3-chloro-4-methylcyclobut-1-ene, 3-methoxy-4-methylcyclobut-1-ene,
3-chloro-4-methoxycyclobut-1-ene that identified as Reactions
(1-4) respectively. The results from the exploration of QTAIM and
stress tensor scalar reveal that each reaction response differently by
showing degeneracy or non-degeneracy of the plots. Generally, we
conclude that the ξ(r b) and the
ℙσ would be useful indicators to predict whether the
reaction is competitive or non-competitive following the degeneracy of
the results. Overwhelmingly, the determination of these four reactions
display that Reaction 1 is a competitive reaction whilst in
contrast Reaction 2 , Reaction 3 , and Reaction
4 are non-competitive reactions. Other stress tensor and QTAIM scalar
for instance, the stress tensor eigenvalue λ3σ, the
bond-path length (BPL), and the total local energy densityH (rb ) also provided the same results in
confirmation with metallicity ξ(r b) and stress
tensor polarizability ℙσ. Furthermore, illustration of
the metallicity ξ(r b) and stress tensor
polarizability ℙσ demonstrate that the maximum values
and the transition state points do not occur simultaneously in agreement
with transition state theory and our previous investigations for other
ring-opening (electrocyclic) reactions.
On the other side of this investigation, we used helicity length H with
the purpose of predicting the TSIC or TSOC preferences based on data
from experiments. Helicity length H plots for non-competitive reactions,Reactions (2-4) , could correctly predict the torquoselectivity
preferences of either TSIC or TSOC. As a result, that the greater
helicity lengths H for shared-shell ring-opening BCP s bond-paths
could assist to significantly predict both TSIC or TSOC for these three
reactions, Reactions (2-4) , exhibit that preference ofReaction 2 is TSOC, Reaction 3 is TSOC, andReaction 4 is TSIC. The advantage of using H is back to where
it is constructed. To make it transparent,e2 corresponds to the easiest direction
or even mention as the most preferred direction, therefore given that H
is constructed from a vector representation of the ellipticity ε, longer
values of H for the TSIC or TSOC would predict the path such as
torquoselectivity. The other benefit of the variation of H relevant to
the shared-shell ring-opening BCP s bond-paths is that instead of
only tracking alternation at the BCP it could track slight
changes along the length of the whole ring-opening bond-path(r ).