Proton acceptor parameter

An alternative approach uses the polarity index, P proposed by Snyder. This is based upon experimentally determined gas chromatographic retention of three test solvents on a large number of stationary phases. The test solvents selected are ethanol, 1,4-dioxane and nitromethane. As well as an overall polarity index (P), three other parameters are calculated, Xe (a proton acceptor parameter), xproton donor parameter) and x (a strong dipole parameter). 

For example, nylon 66 will dissolve in formic acid, glacial acetic acid, phenol and cresol, four solvents which not only have similar solubility parameters but also are capable of acting as proton donors whilst the carbonyl groups on the nylon act as proton acceptors (Figure 5.6). 

Note Solvent classification into groups based on solvent polarity selectivity parameters proton acceptor, proton donor, x dipole interactors) and solvent strength on alumina nd on silica gel 0. Physical constants viscosity (t)), surface tension (y), dielectric constant (8). Solvatochromic polarity parameters 7, j.(30) and Ej. ... 

The selectivity of a number of organic modifiers was examined using the predicted log k values of the log P — 3 models from each group in different organic modifier-water mixtures. The composition of the eluent was adjusted so that either the solubility parameter,1 polarity (Po), proton acceptor (Xa), proton donor (Xd), or dipole moment (Xn) values were kept constant to determine which parameter affected the selectivity. The results are summarized in Table 4.3. 

Water is the ever-present proton acceptor in the subsurface. During the dissocia-hon of an acid in subsurface water, H3O is one of the dissociation products and the acid strength is a measurable parameter. In a dilute solution the activity of the hydrated protons equals that of H3O and the pH value characterizes the H-ion achvity. Substituting for pH in Eq. 6.1, we obtain... 

Among various physicochemical methods, IR spectroscopy and NMR are most appropriate tools for the study of dihydrogen bonds in solution. However, it is worth mentioning that these methods are basically different. First, they measure physical properties that change upon complexation bond vibrations and magnetic behavior. Second, equilibrium (4.1) is usually slow on the IR spectroscopy time scale and very fast on the NMR time scale. In other words, proton donors, proton acceptor, and their complexes are detected separately in IR spectra, whereas the NMR parameters of these moieties are usually averaged. 

Un A hydrogen-bonding parameter which represents the lone-pair donor (proton acceptor) capability of the group. It is defined as the number of lone pairs on O and/or N atoms in the group. 

The QTAIM parameters may also be useful to analyze the other interactions, for example, the intramolecular DHBs. Similarly, as it is in the case of HBs where the proton donor and the proton acceptor may belong to the same species, malonalde-hyde is an example for the existence of intramolecular HB. Figure 12.6 presents the relief map of the species where intramolecular O-H—H-B interaction exists [30]. 7 This relief map is displayed in the plane of the molecule. Interestingly, the intramolecular DHBs often occur in the crystal structures. The first studies on DHBs in crystals of metal-organic compounds have also examined this type of interactions [11],... 

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