Anti-hydrogen bond

Hobza P, Spirko V, Havlas Z, Buchhold K, Reimann B, Barth H-D, Brutschy B (1999) Anti-hydrogen bond between chloroform and fluorobenzene. Chem Phys Lett 299 180-186... 

Cubero E, Orozco M, Hobza P, Luque FJ (1999) Hydrogen bond versus anti-hydrogen bond A comparative analysis based on the electron density topology. J Phys Chem A 103 6394-6401... 

P. Hobza, V. Spirko, H. L. Selzle, and E. W. Schlag, Anti-hydrogen bond in the benzene dimer and other carbon proton donor complexes, J. Phys. Chem. A 102, 2501-2504 (1998). 

E. Cubero, M. Orozco, and F. J. Luque, Electron density topological analysis of the C—H O anti-hydrogen bond in the fluoroform-oxirane complex, Chem. Phys. Lett. 310, 445-450 (1990). 

Hobza, P., and Spirko, V., Anti-hydrogen bond in the benzene dimer and other carbon proton... 

An example where electrostatics does fail to predict the correct minimum structure is the complex formed by HF and CIF. This complex is experimentally found to exist in the anti-hydrogen bonded HF- - -CIF configuration rather than in the hydrogen-bonded structure CIF- - -HF predicted by electrostatic arguments analogous to those discussed for the HF dimer. 

Blue-shifted. - Cubero et used AIM to examine the nature of what they termed the anti-hydrogen bond interaction . Upon formation of the anti H-bond the X-H bond shortens and its vibrational frequency blue-shifts contrary to a H-bond. Amongst others the topological properties of p have been determined for a series of C-H... n complexes, which exhibit either anti H-bond or normal H-bond character. According to a set of topological criteria utilized to characterize conventional H-bonds no relevant difference was found in the two classes of C-H... 71 complexes. Since the anti H-bonds are just a special type of H-bond the qualifier anti is misleading and was abandoned in later work. 

MuchalP " focused on the the anti-hydrogen bond in aromatic iV-sulfinylamines with ortho H atoms. From AIM she learns that a C-H... 0 bonding interaction exists that meets all the characteristics of an anti-hydrogen bond. 

In the excited electronic state correlating to OH A(v=0) + Ar, the potential exhibits deep minima in the linear hydrogen-bonded OH-Ar and anti-hydrogen-bonded Ar-OH configurations. A contour diagram of the ab initio potential for OH (A + Ar is shown in Fig. 4. The potential is strongly... 

The structure of the adduct favors this because in similar molecules it is known that they are anti hydrogen bonded, meaning that the hydrogen atoms point away from the halogens. The prompt departure of the H atom also eliminates the possibility that in reactions initiated, e.g., by photolysis of BrH-C02, which is hydrogen bonded, the heavy Br atom stays around and may play an unintended guest role. 

P. Hobza, Z. Havlas, The fluoroform center dot center dot center dot ethylene oxide complex exhibits a C-H center dot center dot center dot O anti-hydrogen bond. Chem. Phys. Lett. 303(3 ), 447 52 (1999)... 

Construct molecular models of the gauche and anti conformations of 1 2 ethanediol and explore the possibility of intramolecular hydrogen bond formation in each one... 

The two peptides form a symmetrical dimer stabilized by four hydrogen bonds (red dashes) and hydrophobic contacts. The two monomers form a four-stranded, anti-parallel pleated sheet. 

The NMR spectrum of the syn isomer shows evidence of a diamagnetic ring current, based on both the relatively low-field position of the vinylic hydrogens and the upfield shift of the methylene hydrogens. The anti isomer shows much less pronounced shifts. The X-ray crystal structure of the syn isomer shows a moderate level of bond alternation, ranging ftom 1.36 to 1.45 A (Fig. 9.4A). In the anti isomer, bond alternation is more pronounced, vith the double bond in the center ring being essentially a localized double bond (Fig. 9.4B). 

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