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Historically, Hammett constants have been extremely effective in describing the influence of substituents on chemical reactivity and other physical and chemical properties, whereas variables derived from quantum chemical calculations have generally been less effective. Taking the experimental pK(a)s of substituted anilines as a representative(More)
Invoking the known link between impact sensitivity and compressibility, we have expanded upon an earlier preliminary study of the significance of the available free space per molecule in the unit cell, ΔV. We express ΔV as V(eff) - V(int), where V(eff) corresponds to zero free space, V(eff) = molecular mass/density. V(int) is the intrinsic gas phase(More)
Halogen bonding refers to the non-covalent interactions of halogen atoms X in some molecules, RX, with negative sites on others. It can be explained by the presence of a region of positive electrostatic potential, the sigma-hole, on the outermost portion of the halogen's surface, centered on the R-X axis. We have carried out a natural bond order B3LYP(More)
A halogen bond is a highly directional, electrostatically-driven noncovalent interaction between a region of positive electrostatic potential on the outer side of the halogen X in a molecule R-X and a negative site B, such as a lone pair of a Lewis base or the pi-electrons of an unsaturated system. The positive region on X corresponds to the(More)
Halogen bonding (XB) is a type of noncovalent interaction between a halogen atom X in one molecule and a negative site in another. X can be chlorine, bromine or iodine. The strength of the interaction increases in the order Cl<Br<I. After a brief review of experimental evidence relating to halogen bonding, we present an explanation for its occurrence in(More)
A σ-hole bond is a noncovalent interaction between a covalently-bonded atom of Groups IV-VII and a negative site, e.g. a lone pair of a Lewis base or an anion. It involves a region of positive electrostatic potential, labeled a σ-hole, on the extension of one of the covalent bonds to the atom. The σ-hole is due to the anisotropy of the atom's charge(More)
We have carried out B3PW91 and MP2-FC computational studies of dimethyl sulfoxide, (CH(3))(2)SO, and dimethyl sulfone, (CH(3))(2)SO(2). The objective was to establish quantitatively the basis for their high polarities and boiling points, and their strong solvent powers for a variety of solutes. Natural bond order analyses show that the sulfur-oxygen(More)
A synchronous, concerted chemical process is rigorously divided by the reaction force F(R), the negative gradient of V(R), into "reactant" and "product" regions which are dominated by structural changes and an intervening "transition" region which is electronically intensive. The reaction force constant κ(R), the second derivative of V(R), is negative(More)
In a previous study we investigated the effects of aromatic fluorine substitution on the strengths of the halogen bonds in halobenzene…acetone complexes (halo = chloro, bromo, and iodo). In this work, we have examined the origins of these halogen bonds (excluding the iodo systems), more specifically, the relative contributions of electrostatic and(More)
Halogen bonding is a noncovalent interaction that is receiving rapidly increasing attention because of its significance in biological systems and its importance in the design of new materials in a variety of areas, for example, electronics, nonlinear optical activity, and pharmaceuticals. The interactions can be understood in terms of(More)