Hydrogen-bridge

This is known as a hydrogen-bridge structure. There are not enough electrons to make all the dotted-line bonds electron-pairs and hence it is an example of an electron-deficient compound. The structure of diborane may be alternatively shown as drawn in... 

Aluminium tetrahydridoborate is a volatile liquid. It is the most volatile aluminium compound known. It is covalent and does not contain ions but has a hydrogen-bridge structure like that of diborane, i.e. each boron atom is attached to the aluminium by two hydrogen bridges ... 

The representation of molecular properties on molecular surfaces is only possible with values based on scalar fields. If vector fields, such as the electric fields of molecules, or potential directions of hydrogen bridge bonding, need to be visualized, other methods of representation must be applied. Generally, directed properties are displayed by spatially oriented cones or by field lines. 

Fig. 5. Modes of M—H—B bonding where M—H—B represents a three-center hydrogen bridge bond for (a), (b), (c) tetrahydroborates and for (d), (e), (f)...

Localized Bonds. Because boron hydrides have more valence orbitals than valence electrons, they have often been called electron-deficient molecules. This electron deficiency is partiy responsible for the great interest surrounding borane chemistry and molecular stmcture. The stmcture of even the simplest boron hydride, diborane(6) [19287-45-7] 2 6 sufficientiy challenging that it was debated for years before finally being resolved (57) in favor of the hydrogen bridged stmcture shown. 

A mercurinium ion has both similarities and differences as compared with the intermediates that have been described for other electrophilic additions. The proton that initiates acid-catalyzed addition processes is a hard acid and has no imshared electrons. It can form either a carbocation or a hydrogen-bridged cation. Either species is electron-deficient and highly reactive. 

Due to the perfect linear arrangement of the N-H -N hydrogen bridges in 13, extremely fast cooperative proton transfers occur in solution which... 

Other names, such as hydrogen bridge, have also been used. 

Fig. 31. Complexes of type 120-126 are derivatives of M(dioxime)2 complexes 119, in which the hydrogen bridges have been replaced by diorganoboryl groups...

These energies are relative to the most stable douhly hydrogen bridged form. 

Huggins, M. L. (1936). Hydrogen bridges in organic compounds. The Journal of Organic Chemistry, 7(5), 407 56. 

Other particular theories are confined to diffusion-controlled reactions (109), to the so called cooperative processes (113), in which the reactivity depends on the previous state, or to resistance of semiconductors (102), while those operating with hydrogen bridges (131), steric factors (132), or electrostatic effects (133, 175) are capable of being generalized less or more. 

Complexes with Hydrogen-Bridged Silicon-Transition Metal Bonds... 

In 65% sugar jellies the hydrogen bridges alone are active. Such gels are easily deformed and are elastic. In calcium pectinate gels, the most effective cross links are calcium ion bonds between the carboxyl groups. The bond distances are short therefore an inelastic, rather brittle, gel results. 

I.r. spectra 4,13) and measurements of vapor pressure 4) indicate strong inter-molecular hydrogen bridging. In contrast to concentrated H2SO4 difluorophosphoric acid is a base and can be titrated conductometrically 14) ... 

The different behaviour of difluorophosphoric acid which is of a higher degree of association, is probably induced by the ability of the fluorine ligands to act, besides the 0-atoms, as bridging atoms in the hydrogen bridges. 

After evaporating the solvents and hydrogen halides the free acids can be purified by fractional distillation in vacuo. It was not possible to isolate the acid with X = J (7). The high value of the Trouton constant (25.1 cal/Mol °K) (7) seems to indicate, that H[P02FC1] and H[P02pBr] as well are associated over hydrogen bridges. 

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