The acidity constants of 5-uracilmethylphosphonic acid, H2(5Umpa), and 6-uracilmethylphosphonic acid, H2(6Umpa), were determined by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 M, NaNO3). Comparison of these constants with those of related uracil derivatives (partly taken from the literature) allows the conclusion that an intramolecular hydrogen bond is formed between (N1)H ...

the concept of resonance assisted hydrogen bond (rahb), which usually occurs in b diketons, has a remarkable role in chemistry. these molecules, which contain heteroatom particularly o and n, are species with biological interest in protein folding and dna pairing. therefore, the amplification of hydrogen bonds strength by substituents may be important in life sciences. in the current research, ...

The effect of pressure on the crystal structure of salicylaldoxime has been investigated. The ambient-pressure phase (salicylaldoxime-I) consists of pairs of molecules interacting through oximic OH...O hydrogen bonds; taken with phenolic OH...N intramolecular hydrogen bonds, these dimers form a pseudo-macrocycle bounded by an R4 4(10) motif. The dimers interact principally via pi...pi stacking ...

Profiling of eight stereoisomeric T. cruzi growth inhibitors revealed vastly different in vitro properties such as solubility, lipophilicity, pKa, and cell permeability for two sets of four stereoisomers. Using computational chemistry and NMR spectroscopy, we identified the formation of an intramolecular NH→NR3 hydrogen bond in the set of stereoisomers displaying lower solubility, higher lipoph...

From an equimolar dipeptide/xanthosine mixture in water/methanol, only the nucleoside crystallized in anhydrous form, space group P2,2,2, with a = 17.406 (5) A, 6 = 12.378 (4), c= 5.350 (2) A, Z = 4, C|0H 12O6N4, FW = 284.26, D x = 1.639 g • cm-3. The structure was deter­ mined by direct methods on the basis of 984 X-ray data and refined to an agreement index of R = 3.9%. Xanthosine occurs in t...

the one-dimensional model of lippincott and schroeder for hydrogen bond has been re-examined and it has been shown that o-h bond distance depends on repulsive van der waals and attractive electrostatic potentials.it has been shown that constant b in the van der waals repulsion potential is not transferable to all hydrogen bonds. the possibility of obtaining the semi-empircal parameters in the l...

in 0.1 M ionic strength aqueous solution at 120 for the following: 2,4-dihydroxy4'-nitroazobenzene (I), 2,4-dihydroxy-4'-sulfonateazobenzene (II), and p-(2hydroxy-l-naphthylazo) benzenesulfonic acid (III). The reported values of k231 were 4O X 105, 3.6 X 105, and 3.6 X 106 M-1 sec-1. They attributed the much lower values of k23, for these acids than the value3 k23, 2 X 109 M-1 sec-1 kn,' for th...

New guanidine-derived superbases with TBD-functionalized alkyl side chains have been developed using a computational DFT approach. Exploiting the high hydrogen bond basicity of TBD allowed access to systems with strong charge-assisted intramolecular hydrogen bonds in the protonated state. The enhanced stability of such guanidines is mirrored in their gas-phase basicities, which cover the range ...

The title compound, C(17)H(18)N(2)OS, adopts a trans-cis geometry of the thio-urea group which is stabilized by intra-molecular hydrogen bonds between the O atom of the carbonyl group and the H atom of the thio-amide group. A C-H⋯S intramolecular hydrogen bond is also present. In the crystal structure, mol-ecules are linked by inter-molecular N-H⋯S hydrogen bonds to form centrosymmetric dimers.