Lone pairs interaction between

Pyridazine is the most reactive in alkylation reactions and this again has its origin in the lone-pair/lone-pair interaction between the nitrogen atoms. This phenomenon is known as the a effect and is also responsible, for example, for the relatively higher reactivity of hydrogen peroxide as a nucleophile, compared with water. 

The number of water molecules in the primary solvation shell of a bivalent cation as determined by diffraction methods is always between six and eight unless either cation size or ion-pair complexes intervene to. produce smaller values. Thus the primary shell can be either an octahedral or cubic complex. Table 2.3 shows how the solvation number and orientation of water molecules in a solvation complex can vary with electrolyte concentration. The variation in 0 with the molality of is striking. Evidently lone-pair interactions between a water molecule and this cation are favored in concentrated solutions but dipolar interactions are favored in dilute solutions. 

The solvation parameter model intends to describe the free energy of transferring a solute from the mobile to the stationary phase as a series of product terms representing cavity formation (of hydrophobic solutes in the aqueous mobile phase) and dispersion interactions, plus dipole interactions, hydrogen bonding, and lone pair interactions between polar groups in the solute and polar groups on the solvated surface. 

The water molecule is represented by an antisymmetrized product of four geminals—two describing the chemical bonds 0-H and two describing the electron lone pairs. Interaction between molecules represented by geminal wave functions can be accounted for per-turbatively [24], but we employ a different scheme. The... 

The reaction of the 2,5-bis-trifluoromethyl-l,3,4-oxadiazole 212 with oxanorbomene derivatives has been recently re-evaluated for its stereoselectivity aspects, through a combination of experimental and computational studies [105], In particular, the theoretical model was able to explain the origin of stereoselectivity towards the bent product 214 caused by repulsive lone pair interactions between oxygen bridges in the transition state of the 1,3-dipolar addition (Scheme 54). 

We now come to other aspects of Kollman s work. Specifically, in our original work, we commented upon the fact that greater nonbonded attraction between lone pairs is obtained in U or Y molecules. The relative stability of isomeric U and Y systems, obviously, depends on much more than lone pair interactions. Accordingly, our original work did not deal with this topic. Thus, the statement of Kollman,... 

The remaining interesting feature of the picoline results is the direction of the compensation effect between the increased adsorption due to the nitrogen lone-pair interaction and the steric hindrance of the methyl group. The data from 3-picoline for the a exchange show that some deactivation of one position (presumably the 2-position, or ortho to the methyl) is observed, although the effect is not as pronounced as in the ortho positions of toluene. Thus, the compensation effect would appear to favor increased adsorption from the lone pair on the nitrogen and this is confirmed by the results of 4-picoline on borohydride-reduced platinum. 

The ammonia molecules occupy trigonal prismatic sites between the dichalcogen layers and NMR measurements show that they are oriented with the threefold axis parallel to the dichalcogenide layers, indicating only weak Lone Pair interactions with the layers. Careful study of the reaction stoichiometry, prompted by this observation, led to the conclusion that ammonia oxidation was involved and that the overall mechanism of reaction conld be summarized by equation (11). The reaction product has x in the range 0.1 -0.3 and contains ammonium ions solvated by nentral ammonia molecules. 

Oxidative additions can occur at all sorts of X-Y bonds, but they are most commonly seen at H-H (also H-Si, H-Sn, or other electropositive elements) and carbon-halogen bonds. In the oxidative addition of H2 to a metal, a d orbital containing a lone pair interacts with the cr orbital of Ik, lengthening and breaking the H-H cr bond. The two pairs of electrons from the metal and the II2 cr bond are used to form two new M-H bonds. C-H bonds can oxidatively add to metals in the same way, and this process, called C H bond activation, is of enormous current interest for its potential applications to petrochemical processing and green chemistry. Si-H, Si-Si, B-B, and other bonds between electropositive elements undergo oxidative addition, too. 

Lone-pair interactions. Repulsion between the electrons in the orbital of the anion or incipient anion. This interaction is thought to be important in pyridines and other azines, and may be a kinetic rather than equilibrium effect, at least in the case of lithiation. ... 

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