Hydrogen-bonded systems solutions

The photodecomposition and thermodecomposition of nitromethane have been extensively studied as model systems in combustion, explosion and atmosphere pollution processes[l]. On another hand, nitromethane was selected as a model solvent in experiments aimed at examining non hydrogen-bonded solvent effects in a general acid-base theory of organic molecules [2.3]. This selection is based on the electronic and structural characteristics of nitromethane that has a high dielectric constant, and at the same time cannot form hydrogen bonds with solute molecules. 

Seiler [250] proposed a way of estimating the extent of hydrogen bonding in solute partitioning between water and a lipid phase by measuring the so-called A log P parameter. The latter parameter is usually defined as the difference between the partition coefficient of a solute measured in the octanol-water system and that measured in an inert alkane-water suspension AlogP = log Kp oet — log Kp aik. 

One of the most prominent hydrogen-bonded systems is DNA. Despite numerous experimental and theoretical investigations on vibrational spectra of nucleic acid bases [7-13], information on inter- and intramolecular interactions in base pairs and DNA oligomers is still limited [14-25]. A recent example is the work on single adenine-uracil (AU) base pairs in the Watson-Crick geometry in solution, which showed an enhancement of vibrational energy... 

The validity of the two approaches sketched above has been quite amply tested against the ability of reproducing various molecular properties of hydrogen-bonded systems (see elsewhere in this book) including vibrational spectroscopies [11,54-56], For example, in Figure 2.11 calculated versus experimental IR spectra of gallic acid in water solution are reported for different levels of treatment of the specific solute-solvent interaction [54],... 

A variety of studies have been performed in which the chirality induced in ketone chromophores has been characterized by CD spectroscopy. CD has been induced in the n-+ r transition of cyclohexanone upon its dissolution into several alcoholic and ester-functionalized solvent systems [5]. In this work it was established that hydrogen bonding between solute and solvent was not required for the generation of solvent-induced CD. In a more comprehensive work, the CD induced in 20 compounds containing a ketone chromophore was studied in approximately 15 chiral solvent systems [6]. It proved difficult to develop general rules for the observation (or lack thereof) of solvent-induced CD, with the rotational strengths being found to be solvent, temperature, and... 

First consider LSC systems where hydrogen bonding between solute and solvent molecules cannot occur (no proton-donor molecules). 

Within the quadrupolar hydrogen-bonding systems, three aspects are significant (1) the action of the association in diluted liquid solution, (2) the ordering in the solid state, most of all the mechanical properties of the associates, and (3) methods to investigate and prove the ordering process. The latter is strongly related to electric- and optical properties. 

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