The Absorption Spectra of Naphthalene Sulfonic Acid Derivatives

Abstract

1) The absorption spectra of some naphthalene sulfonic acid derivatives have been determined in various pH solutions. 2) The remarkable spectral change revealed by the variation in pH value can be interpreted in terms of the process of the proton association and dissociation of the functional groups. 3) The pH region in which the process takes place is characteristic of the kinds, –NH2, –OH, and the number of the functional groups and their locations on the naphthalene skeleton. 4) The relative pH regions have been explained in outline by taking into account the effects of the sulfonic group, the intramolecular hydrogen bond formed between the functional groups, and the resonance of the functional group to the link. 5) The band assignment concerning the transition direction of the derivatives has been decided; the first and the second band correspond, respectively, to the 1La and 1Bb of naphthalene. 6) The order of the magnitude of the substitution effect has been clarified as –NH3+< –OH<–NH2<–O−.

Kinetics of Hydrolysis of Dichlorotriazinyl Reactive Azo Dyes

“…The reaction mechanism of hydrolysis of the dichlorotriazinyl reactive dyes is a nucleophilic bimolecular mechanism with the attack of the nucleophile on the electron-deficient carbon atom [4,11,17,18] (Table II). Table II shows that, the apparent acid dissociation constant for the loss of a proton K, is in the range of the phenolic hydroxyl group [8,20] (1, K. -2.84 x 10-'0, pl(, -9.55; ~ ~ -3.95 x 10-'0, pK, -9.40; Ie, Ko = 1.92 x 10-1°, pK, = 9.72). The acid dissociation constant of the phenolic hydroxyl group of H-acid is pK, = 8.827 [13].…”

Photo-Induced Assembly of Nanostructures Triggered by Short-Lived Proton Transfers in the Excited-State

“…These changes are analogous to those observed in solutions of NS only at different pH (Figure b). The dependence of NS spectra on pH has previously been interpreted as the presence of two balancing states: the NS naphthol form and its deprotonated naphtholate counterpart . The isosbestic points observed at λ = 238 nm, λ = 262 nm, and λ = 309 nm correspond to wavelengths equally absorbed by either NS form.…”

“…The dependence of NS spectra on pH has previously been interpreted as the presence of two balancing states: the NS naphthol form and its deprotonated naphtholate counterpart. 51 The isosbestic points observed at λ = 238 nm, λ = 262 nm, and λ = 309 nm correspond to wavelengths equally absorbed by either NS form. Thus, photoexcitation triggers a process of progressive enrichment of the NS naphthol form in the ground-state over the naphtholate form.…”