Hydroquinone Molecules Research Articles

Crystal structure of a clathrate inclusion compound of hydroquinone and hydrogen sulphide

The crystal structure of a β-hydroquinone clathrate of stoicheiometry 3C6H4(OH)2·xH2S (x= 0.768) has been determined from three-dimensional X-ray data. The hydrogen-bonded [OH]6hexagonal rings are nearly but not exactly planar, and a difference map revealed an ordered proton arrangement. The clathration cavity is roughly, spherical with a free diameter of ca. 4.8 Å. Analysis of the thermal parameters showed that the hydroquinone molecule behaves as a rigid body, and that vibration of the S atom is very pronounced, particularly in the direction of the c axis.

Stoichiometry and kinetics of the reaction between manganese(III) and hydroquinone in acid perchlorate solution

The stopped-flow method has been used to investigate the kinetics of the rapid reaction between manganese(III) and hydroquinone in aqueous perchlorate solution at 25°. The sole oxidation product was p-benzoquinone using spectrophotometric analysis, and the stoichiometry of the reaction corresponded to 2Mn(III)+ p-C6H4(OH)2→ 2Mn(II)+ p-C6H4O2+ 2H+. The reaction rate was first-order in each reactant, and was independent of variations in [Mn(III)]0, [p-hydroquinone]0, [Mn(II)], total ionic strength, [NaClO4], [NaNO3] and the presence of oxygen, at fixed acidity. Variation of acidity in the range [HClO4]= 0.60–3.60 M was used to determine the rate constants k1= 0.48 × 104 M–1 sec–1 and k1′= 3.28 × 104 M–1 sec–1 for reaction of Mn3+aq and MnOH2+aq with the hydroquinone molecule, respectively.

Influence of Quaternary Salts on the Adsorption of Hydroquinone by Metallic Silver

AbstractThe adsorption of hydroquinone by metallic silver in the presence of a long chain alkylammonium quaternary salt was examined at three different pH values corresponding to the hydroquinone molecule, the mono- and the di-anion, and the results were correlated with those obtained from measurements of the development activity of these same species. The combined results indicate that a complex is formed of the hydroquinone di-anion and the quaternary salt which is readily adsorbed by silver, thus providing a substantial shortening of the induction period and acceleration of development.

Electrometric acid-base titrations by means of the quinhydrone electrode and its application under physiological conditions.

It has recently been shown that an acid solution containing equimolecular proportions of benzoquinone and hydroquinone, a condition which is most easily obtained by dissolving the crystalline addition product, benzoquinhydrone, in the medium under examination, promptly produces a stable and reproducible oxidation-reduction potential on a properly prepared inert electrode, preferably of gold. In acid solutions the observed potential has been shown to be a linear function of the PH and may, therefore, serve as a very simple means of determining hydrogen ion concentrations. For measurements on this system and references to the literature see. Using this method, Biilmann has shown that the potential is stable in a phosphate buffer at PH 6.81, but unstable in an alkaline borate solution at PH 9.24, and further that the method possesses the distinct advantage that it may be used where the platinum black hydrogen electrode is inapplicable, e.g., in the presence of certain mild oxidizing agents as 0.1 M nitric acid or unsaturated compounds of the acryhic acid type. We have made a study of the quinhydrone electrode in order to determine more definitely the range of its applicability under physiological conditions. The validity of the method depends upon maintaining the ratio of the concentrations or more correctly of the activities of the quinone and hydroquinone strictly equal to unity or to some other constant and known value. The factors which may upset this relationship are: (A) Deviations from the simple oxidation-reduction equation of Peters due to hydroquinone acting as a weak dibasic acid. (13) Changes in the activities of the dissolved quinone or hydroquinone molecules due to the presence of salts. (C) The presence of other oxidizing or reducing substances which react with the quinone substances with measurable velocity.