Moreover, the electron density at the BCPs is a good measure to evaluate
the H-bond length and strength. Thus, there is correlation between the
interaction energy and topological parameters at the BCPs [50]. The
electron density decreases as a result of the elongation of the
corresponding bond, while the opposite occurs when the bond length
shortens. For instance, the H-bond length of
O4…HO3-O3 in the
conjugate base of L-fucose (formed from its deprotonation at
C4-HO4) is 1.78 Å and the electron
density at its BCPs is 0.0439 a.u., while the H-bond length of
O1…HO2-O2 (formed
from deprotonation of L-fucose at
C1-HO1) is 1.97 Å and electron density
at its BCPs decreases to 0.0289 a.u.. In addition, the values of
electron density at BCPs of H-bonds in the conjugate bases of
aldo-pentose decrease as intramolecular H-bond length increases. There
is a good correlation between electron density, Laplacian of electron
density, H-bond energy, sum of stabilization energy values, and
intramolecular H-bond length in the conjugate bases of Deoxy-hexose
sugars studied herein (stabilization energy will be explained in NBO
analyses in the next section). Figure 4 presents the linear correlation
between the values of\(\ \rho_{(r)}\), , andE(2) with bond length in conjugate bases of
L-fucose. Figure 5 presents the linear correlation between electron
density ,\(\text{\ ρ}_{(r)}\) (e/au3), at H-bond BCPs
and interaction energyand stabilization energyE(2) in the conjugate bases of D-ribose.