Chemistry Reference
In-Depth Information
HT hierarchy of aromaticity according to the
π
values of Table
11.10
(ninth column),
for calibrated Hückel-DFT [-
β
] integral:
π
HT
π
HT
¯
DFT
(
A
04)
>
¯
DFT
(A05)
π
HT
π
HT
>
¯
DFT
(A09)
>
¯
DFT
(A02)
π
HT
π
HT
>
DFT
(A03)
>
DFT
(A07)
π
HT
π
HT
>
¯
DFT
(A08)
>
¯
DFT
(A11)
(11.65)
π
HT
π
HT
>
¯
DFT
(A10)
>
¯
DFT
(A12)
π
HT
>
DFT
(
A
01)
π
HT
>
¯
DFT
(
A
06)
The principal points which arise from the aromaticity scale are:
There is an agreement between the DFT and Hückel chemical hardness
scales, (except for the case of the displacement and the inversion of
the 4-N, N'-dimethylaminoaniline/A06 and monochlorohydrate of 4-N, N'-
dimethylaminoaniline/A01 in the HT scheme), and also with the aromatic-
ity/stability/reactivity scale for the molecules of interest, using experimental or
other presented theoretical methods;
Unlike the DFT counterpart scale of aromaticity, the mixed DFT-Hückel chemical
hardness scale of aromaticity further inverts and departs the two forms of Naphtol
(A04 & A05) and the Pyridine & Pyrimidine (A10 & A11) pairs considered;
The inversion of the Phenol/A09 and Naphtalene/A07 with Benzene/A12 struc-
tural inertia in reactivity (aka aromaticity), as an effect of the delocalization energy
per pi electrons is present in both realizations as HT and HT-DFT scales;
Only the A
Phenol
>
A
Aniline
ordering is appearing to be the only invariant across
above aromaticity.
Overall, the chemical hardness although custom to be considered a versatile tool
in assessing reactivity and aromaticity, conceptually superior to the classical delo-
calization energy per pi electrons index, it is currently challenged by the bondonic
chemistry insight, especially regarding the bondonic mass and gravity production
that can reshape the aromaticity concept itself.; however, the DFT approach paral-
lels remarkably well with the simple Hückel quantum picture of organic molecules,
which nevertheless appears to be more “spectroscopically reach” in bondonic peaks
of information.
11.5
On Reducing Character of Mono- and Polyhydroxy Arens
Selected for their usage to obtain artificial resins, medicines and azo dyes,
hydroxyarenes has properties of both hydroxyl groups and the aromatic rings (Avram
1995
, Chap. 32). Hückel and DFT specific calculations were performed for these sys-
tems in which the conjugation between non participating electrons of oxygen of the
