Phase hydrogen bonding

M. Mons, I. Dimicoli, and F. Piuzzi, Gas phase hydrogen bonded complexes of aromatic molecules Photoionization and energetics. Int. Rev. Phys. Chem. 21, 101 135 (2002). 

Detailed microwave spectroscopic analysis of gas-phase hydrogen-bonded adducts can yield the hydrogen-bond energy with precision, e.g. for HCN HF, (NHF) = 26.1 1.6kJmol-i (Legon et al 1980). Sadly, few systems are susceptible to this approach. 

Although the gas-phase hydrogen-bonded dimer (MeF)2H" is held by a strong hydrogen bond (McMahon and Kebarle, 1986) this is a rare exception to the previous statement regarding covalently bonded fluoride. More typical are the perfluorocarbons, which are among the weakest hydrogenbonding substances known, as their physical properties and uses clearly demonstrate. 

Curtiss LA, Blander M (1988) Thermodynamic properties of gas-phase hydrogen-bonded complexes. Chem Rev 88 827-841... 

In Section 22.3 the main types of interactions occurring between the enantiomeric analytes and the stationary phase (hydrogen bonding, charge transfer, and inclusion complexes) was described. In the following section,... 

Authors indicated that as the descriptors in Eq.(36) refer to particular properties of the solutes, the coefficients in the equation will correspond to specific properties of the solid phase as follows r - refers to the ability of the phase to interact with solute ir- and n-electron pairs s to the phase dipolarity/polarisability a to the phase hydrogen-bond basicity b to the phase acidity, and 1 to the phase lipophilicity. Analysis of these coefficients lead authors to the statement that solute dipolarity/polarisability, hydrogen-bond acidity, and general dispersion interactions influenced adsorption. The examined fullerene was weakly polarisable and had some hydrogen-bond basicity. 

Coherent Low-frequency Motions in Condensed Phase Hydrogen Bonding and Transfer... 

Hermanek and co-workers (6) first reported the general importance of liquid phase hydrogen-bonding effects for adsorption on alumina. These workers cited several examples of the inversion of sample separation order... 

Secondary Solvent Effects from Liquid Phase Hydrogen Bonding in Adsorption on Silica [data of Klouwen et al. (15)]... 

The master retention equation of the solvation parameter model relating the above processes to experimentally quantifiable contributions from all possible intermolecular interactions was presented in section 1.4.3. The system constants in the model (see Eq. 1.7 or 1.7a) convey all information of the ability of the stationary phase to participate in solute-solvent intermolecular interactions. The r constant refers to the ability of the stationary phase to interact with solute n- or jr-electron pairs. The s constant establishes the ability of the stationary phase to take part in dipole-type interactions. The a constant is a measure of stationary phase hydrogen-bond basicity and the b constant stationary phase hydrogen-bond acidity. The / constant incorporates contributions from stationary phase cavity formation and solute-solvent dispersion interactions. The system constants for some common packed column stationary phases are summarized in Table 2.6 [68,81,103,104,113]. Further values for non-ionic stationary phases [114,115], liquid organic salts [68,116], cyclodextrins [117], and lanthanide chelates dissolved in a poly(dimethylsiloxane) [118] are summarized elsewhere. 

Figure 2.9. Influence of temperature on the system constants (A) and contributions of individual intermole-cular interactions to the retention of octan-2-one (B) for the hydrogen-bond acid stationary phase PSF6. For (B) 1 = contribution from cavity formation and dispersion interactions (2) contribution from dipole-type interactions (3) contribution from solute hydrogen-bond base and stationary phase hydrogen-bond acid interactions and (4) contribution from lone pair electron repulsion. Note for PSF6 there are no contributions from stationary phase hydrogen-bond base interactions since the a system constant is zero. (From ref. [81] Elsevier)...

In this phase, hydrogen bonds are created between the bases of the probe and the complementary sequences inside targeted nucleic acids. The stringency of the hybridization depends on many conditions such as the temperature of the hybridization. The hybridization is usually performed at 37 °C for 1-3 h or overnight, and increasing the temperature enhances the stringency. A low salt concentration and a high formamide concentration in the hybridization buffer also increase the specificity of hybridization. 

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