Hydrogen bonding solvent

Studies by the group directed by Mayoral have been limited to Diels-Alder reactions of type A. When water was not included, the rate constants correlate with the solvent hydrogen-bond-donating capacity Upon inclusion of water the solvophobidty parameter, Sp, contributed significantly in... 

Other solvents can be divided into several classes. In hydrogen bond-breaking solvents (dipolar aprotics), the simple amino, hydroxy and mercapto heterocycles all dissolve. In the hydrophobic solvents, hydrogen bonding substituents greatly decrease the solubility. Ethanol and other alcohols take up a position intermediate between water and the hydro-phobic solvents (63PMH 1)177). 

Solvent effects on chemical equilibria and reactions have been an important issue in physical organic chemistry. Several empirical relationships have been proposed to characterize systematically the various types of properties in protic and aprotic solvents. One of the simplest models is the continuum reaction field characterized by the dielectric constant, e, of the solvent, which is still widely used. Taft and coworkers [30] presented more sophisticated solvent parameters that can take solute-solvent hydrogen bonding and polarity into account. Although this parameter has been successfully applied to rationalize experimentally observed solvent effects, it seems still far from satisfactory to interpret solvent effects on the basis of microscopic infomation of the solute-solvent interaction and solvation free energy. 

The .p(30) scale of solvent polarity is sensitive to both solvent dipolarity and polarizability, as well as the solvent hydrogen-bond donor ability. 

Fig. 7. Stereoview of the crystal structure of water solvated host 5 (folded conformation). The structure is held together by host-host and host-solvent hydrogen bonding interactions. Within the solvation layer there are chains of circular H-bonds between the molecules of water (crystal data a - 8.227, b = 8.964, c - 16.945 A, a = 89.64, / = 97.51, y = 114.28°, space group Pi taken from Ref,3S>)...

Murray, J. S., and P. Politzer. 1991. Correlations Between the Solvent Hydrogen-Bond-... 

Murray, J. S., S. Ranganathan, and P. Politzer. 1991. Correlations Between the Solvent Hydrogen Bond Acceptor Parameter (3 and the Calculated Molecular Electrostatic Potential. J. Org. Chem. 56, 3734. 

Solvent hydrogen-bonding strength using Donor Number parameter (see Reference 32)... 

Hydrogen bond donor solvents are simply those containing a hydrogen atom bound to an electronegative atom. These are often referred to as protic solvents, and the class includes water, carboxylic acids, alcohols and amines. For chemical reactions that involve the use of easily hydrolysed or solvolysed compounds, such as AICI3, it is important to avoid protic solvents. Hydrogen bond acceptors are solvents that have a lone pair available for donation, and include acetonitrile, pyridine and acetone. Kamlet-Taft a and ft parameters are solvatochromic measurements of the HBD and HBA properties of solvents, i.e. acidity and basicity, respectively [24], These measurements use the solvatochromic probe molecules V, V-die lliy I -4-n i in tan iline, which acts as a HBA, and 4-nitroaniline, which is a HBA and a HBD (Figure 1.17). 

Usually, the influence of the solvent on the proton donor and acceptor interactions is relevant95. The importance of the amine/solvent hydrogen bonding interaction depends on the strength of the amine/amine hydrogen bonding interaction96. 

Kamlet MJ, Taft RW (1976) The solvatochromic comparison method. 1. The /6-scale of solvent hydrogen-bond acceptor (HBA) basicities. J Am Chem Soc 98 377-383. 

The solvatochromism of [Fe(phen)2(CN)2] and [Fe(phen)2(CN)2] has been discussed, with particular reference to solvent hydrogen-bond donor properties. Various solvation models have been applied to solvatochromism of [Fe(diimine)2(CN)2], and cormections between solvatochromism, electronic absorption spectra, and color perception parameters discussed in relation to [Fe(phen)2(CN)2]. Solvatochromic properties have been documented for [Fe(bipy)2(CN)2]>... 

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