Both intra- and intermolecular hydrogen bonds increase the acidity of the
systems in which they occur. Stabilization of the anion formed after deprotonation
with a single intramolecular hydrogen bond causes a significant increase in the
strength of acid in question, compared to the system in which such interaction does
not exist. Hydrogen bonds, through their influence on the acid-base properties
of chemical compounds, play a key role in organic chemistry, coordination
chemistry, biochemistry and medicine. This paper comprise a review of the most
important publications on the impact of hydrogen bonds on the acidity of chemical
compounds and the relationship between the specificity of hydrogen bonds and the
strength of the resulting acid.
The relationship between intermolecular hydrogen bond energy and the pKa
value of a given complex is thoroughly discussed in this paper. It turns out that the
energy of the hydrogen bond is not related to a single value of pKa of neither the
donor nor acceptor of this bond, but rather to the relative difference of these
quantities. Namely, the strongest bonds are formed between those systems for
which the pKa’s of a donor and acid conjugated to an acceptor differ the least. The
feature that clearly correlates with the pKa value of the acid turns out to be the
hydrogen bond length. The results of crystallographic studies have shown that the
pKa values of C-H acids strongly correlate with the length
of C-H ••• O hydrogen bonds. It is worth noting here that the correlation is much
better for systems in which the formation of a hydrogen bond is not sterically
hindered. In the abundance of donor and acceptor groups in the structure of an acid
and its corresponding base, the anion formed after deprotonation is stabilized by
phenomenon known as networking. Spreading the negative charge over a larger
area of the molecule increases the stability of the anion and thus significantly
increases the strength of the corresponding acid. Acids, whose acidity is mainly
based on the networking are called SHEAs (single-centered hydrogen-bonded
enhanced acidity acids). In addition, the effect of hydrogen bonds on the acidity
of specific biochemical systems, namely nucleobases, has been discussed based on
the papers by Wetmore and collaborators. It turns out that intra- and extracellular
water molecules should not be overlooked when assessing the acidity
of biomolecules.
Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies
Informacja
SZANOWNI CZYTELNICY!
UPRZEJMIE INFORMUJEMY, ŻE BIBLIOTEKA FUNKCJONUJE W NASTĘPUJĄCYCH GODZINACH:
Wypożyczalnia i Czytelnia Główna: poniedziałek – piątek od 9.00 do 19.00