Showing papers in "Journal of the American Chemical Society in 1964"

Isolation, Structure, and Partial Synthesis of an Active Constituent of Hashish

Abstract: strongly solvated than triple ions,lb-5 the difference being greater for cations of smaller radii, leading to a trend to smaller K with decreasing cationic radii. Both effects, in opposite directions, should operate in solution. The directions of the effects can be similarly rationalized if ionic association is incomplete, but the arguments are slightly more complex. The quantitative measurements were spectrophotometric. Figure 1 gives the forms of the spectra of stilbene, stilbene-, and stilbene-2 in tetrahydrofuran, 2-methyltetrahydrofuran, and 1,2-dime thoxye thane. By suitable choices of solvent, metal ion, and amount of metal allowed to react with the stilbene, extinction coefficients for all three species could be directly determined. These appeared to be rather insensitive to solvent variation. K was calculated directly from the equilibrium expression and was sensibly constant for a given solvent and metal ion. The concentrations of hydrocarbons and ions employed in these experiments ranged about 1()-4 M. All experiments were done at

An x-ray diffraction study of nonplanar carbanion structures.

Abstract: X-ray diffraction of ammonium tricyanomethide and pyridinium dicyanomethylide shows nonplanar carbanion structure

Solvent Deuterium Isotope Effects on Acid-Base Equilibria

Abstract: The glass electrode affords precision measurements of aciditics in mixed H/sub 2/O-D/sub 2/O solvents. Using electrodes standardized for H/sub 2/O solutions, the pL, the generalized equivalent of pH (where L includes all the isotopically different hydrogen ions), in solvent of deuterium atom fraction n is given by pL - (meter reading) + 0.3314n + 0 0766n/sup 2/. Ionization constants in the mixed solvents were determined for phosphoric and arsenic acids and for the aqueous solvent itself. For water, pK/sub n/, -pK/sub H/ = 0.663n + 0.146n/ sup 2/. The apparent failure of the Gross equation to fit the data in these cases is shown to be due to the fact that the simple equation does not hold for polybasic acids. General equations, depending on the number and character of exchangeable protons in the acid and conjugate base, were derived with the aid of the rule of the geometiic mean and without added assumptions about fractionation factors. Equations in which the solvated lyon is treated is L/sub 3/O/sup +/ and that employ a value of the exchange constant of L = 11.0 satmsfactorily fit all available data, whereas the linear equation for unspecified solvation fails in the case of the ionizationmore » of water. Several kinetic applications of mixed solvent studies are discussed, including acid-catalyzed ester hydrolysis. (auth)« less