Excited-state Deprotonation of .beta.-Naphthol in Supercritical Water

Abstract

A kinetic characterization of the excited-state deprotonation of P-naphthol in sub-and supercritical water establishes large deviations from Arrhenius behavior above 110 "C. The fluorescence decay rate constant increases much less with temperature than expected and then decreases at temperatures and pressures beyond the critical point. The loss of solvation of water above 200 "C strongly inhibits its ability to accept a proton and accelerates the reprotonation rate. Under basic conditions, where water clustering and reprotonation are much less important, the observed decay rates deviate much less significantly from the expected Arrhenius behavior. Above the critical point, the relaxation rate constants exhibit strong pressure dependence and are linearly related to the square of the solution density. In contrast with the absence of shifts in the absorption spectrum, pressure-induced shifts in the observed emission maxima near the critical region are assigned to the involvement of contact ion pairs derived from partially deprotonated molecules, and emission from the excited state of the naphtholate-potassium [NapO--K+] ion pair is observed in KOH solution at 200 "C.

Absorption and Fluorescence Studies of Acridine in Subcritical and Supercritical Water

“…13 Their results were consistent with those of Robinson up to 80°C where the proton-transfer rate followed linear Arrhenius behavior. 13 Their results were consistent with those of Robinson up to 80°C where the proton-transfer rate followed linear Arrhenius behavior.…”

Probing the Scale of Local Density Augmentation in Supercritical Fluids: A Picosecond Rotational Reorientation Study

“…Local density augmentation surrounding a solute in a supercritical fluid is well documented 1-18,23-38 and density augmentations of up to 2.5 times that of the bulk density are not uncommon. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Moreover, the local density augmentation is strongly dependent on the fluid pressure and temperature 1-18,23-38 and even the state of the solute. 62 An alternative explanation for the anomalous rotational reorientation times is based on the concerted motion of the solute and fluid cluster moving as a single entity.…”

Acid-base behavior in supercritical water: β-naphthoic acid-ammonia equilibrium

“…The equilibrium constant, KBHA, for the reaction of 13-naphthoic acid with ammonia is related to Ka, Kw, and Kb as shown in Eq. (5). In addition to the three independent reactions, there are two material balance equations m~tA = mHA + mA-…”