Page 288 - MODERN ELECTROCHEMISTRY

224 CHAPTER 2

MICRO RESEARCH PROBLEMS
1. Define electrostriction.
In the functioning of drugs, the physiological effects are dependent on the
precise structure of the molecule. Among other reasons, this is because of the
need to “fit” onto the structure of a relevant enzyme. In work on theoretical drug
designs, some computations are made on models of the organic molecules
constituting the drug in a force-free field, i.e., in a hypothetical vacuum.

Consider an group associated with a designer drug. What happens to
the group when it is introduced into a saline solution 0.4 M in NaCl? Examine
the likely hydration in respect to energy and structure. Calculate the change in
volume of the group due to electrostriction. Examine carboxypeptides
(Fig. 2.4) and make computations that would lead to an estimate of the stabili-
zation energy due to hydration.
2. (a) The origin of the hydrogen bond is the intermolecular dipole interaction
caused by the polarized covalent bond. The existence of this additional intermo-
lecular force accounts for the abnormally high boiling point for water. Using the
electronegativity data provided, try to rationalize semiquantitatively the
elevation of boiling point in terms of bond polarization for a series of hydrides
(Fig. 1). H 2.2; N 3.0; O 3.4; F 4.0; Zn 1.6. Hint: The total intermolecular
force caused by the H bond is proportional to the total number of H bonds and
dipole moment of an individual H bond, which in turn vary approximately with
X. (b) The elevation of boiling point is by no means unique to hydrogen. Explain
the abnormal boiling point of in the light of the “zinc bond.” Compare the
“zinc bond” with the hydrogen bond in (a) and account for the especially strong
effect of the “zinc bond” on boiling point. (Assume that each molecule can
form 6 Zn bonds.)