Apparent large deviations of water solutions from ideal behavior are eliminated by taking account of the number of water molecules binding to solute sufficiently strongly (13.0 ( 1.5 kcal mol -1 ) as to be removed from the "bulk" solvent. Freezing point, boiling point, vapor pressure, and osmotic pressure measurements of electrolyte solutions of chlorides, bromides, and iodides are treated successfully, as are those of nonelectrolytes, for up to 50 wt % solute and concentrations hundreds of time greater than those over which Debye-Hu ¨ckel theory applies. D-H theory focused on the behavior of ions; this work focuses on the nature of water. The nature of "free" water as solvent is changed by electrolytes. No evidence is found for ion pairs up to eutectic points. Hydration numbers (h) obtained are in agreement with many from more elaborate techniques. From freezing points, h values are as follows:

No abstract

Contrary to other recent reports, Pauling's original electronegativity equation, applied as Pauling specified, describes quite accurately homolytic bond dissociation enthalpies of common covalent bonds, including highly polar ones, with an average deviation of +/-1.5 kcal mol(-1) from literature values for 117 such bonds. Dissociation enthalpies are presented for more than 250 bonds, including 79 for which experimental values are not available. Some previous evaluations of accuracy gave misleadingly poor results by applying the equation to cases for which it was not derived and for which it should not reproduce experimental values. Properly interpreted, the results of the equation provide new and quantitative insights into many facets of chemistry such as radical stabilities, factors influencing reactivity in electrophilic aromatic substitutions, the magnitude of steric effects, conjugative stabilization in unsaturated systems, rotational barriers, molecular and electronic structure, and aspects of autoxidation. A new corollary of the original equation expands its applicability and provides a rationale for previously observed empirical correlations. The equation raises doubts about a new bonding theory. Hydrogen is unique in that its electronegativity is not constant.

Bond lengths (r, Å) of typical carbon-carbon bonds correlate linearly with bond dissociation energies (BDEs) in the full range of single, double, triple, and highly strained bonds, with BDEs ranging from 16 to 230 kcal mol -1 . The equation is r ) 1.748-0.002371(BDE), tested with 41 typical carbon-carbon bonds, ranging in length from 1.20 to 1.71 Å. This sets a maximum bond length limit of 1.75 Å for carbon-carbon bonds.

This article discusses and compares various methods for defining and measuring radical stability, including the familiar radical stabilization energy (RSE), along with some lesser-known alternatives based on corrected carbon-carbon bond energies, and more direct measures of the extent of radical delocalisation. As part of this work, a large set of R-H, R-CH(3), R-Cl and R-R BDEs (R = CH(2)X, CH(CH(3))X, C(CH(3))(2)X and X = H, BH(2), CH(3), NH(2), OH, F, SiH(3), PH(2), SH, Cl, Br, N(CH(3))(2), NHCH(3), NHCHO, NHCOCH(3), NO(2), OCF(3), OCH(2)CH(3), OCH(3), OCHO, OCOCH(3), Si(CH(3))(3), P(CH(3))(2), SC(CH(3))(2)CN, SCH(2)COOCH(3), SCH(2)COOCH(3), SCH(2)Ph, SCH(3), SO(2)CH(3), S(O)CH(3), Ph, C(6)H(4)-pCN, C(6)H(4)-pNO(2), C(6)H(4)-pOCH(3), C(6)H(4)-pOH, CF(2)CF(3), CF(2)H, CF(3), CCl(2)H, CCl(3), CH(2)Cl, CH(2)F, CH(2)OH, CH(2)Ph, cyclo-CH(CH(2))(2), CH(2)CH[double bond, length as m-dash]CH(2), CH(2)CH(3), CH(CH(3))(2), C(CH(3))(3), C[triple bond, length as m-dash]CH, CH[double bond, length as m-dash]CH(2), CH[double bond, length as m-dash]CHCH(3), CHO, CN, COCH(3), CON(CH(2)CH(3))(2), CONH(2), CONHCH(3), COOC(CH(3))(3), COOCH(2)CH(3), COOCH(3), COOH, COPh), and associated radical stability values are calculated using the high-level ab initio molecular orbital theory method G3(MP2)-RAD. These are used to compare the alternative radical stability schemes and illustrate principal structure-reactivity trends.