Kinetics of Deuterium Exchange on Resorcinol in D₂O at High Pressure and High Temperature

Abstract

The kinetics of deuteration of resorcinol in pure D2O were studied for the first time using a flow-through capillary tubular reactor with on-line, proton, and deuterium NMR detection at high temperatures and high pressure. The global rate constants for hydrogen/deuterium (H/D) exchange were determined from temperatures of 200−450 °C (723 K) at a pressure of ∼400 bar (the critical temperature and pressure of water are 374.2 °C and 218.3 bar, respectively). The H/D exchange rate in resorcinol (1,3-dihydroxybenzene) under these extreme conditions was determined using proton NMR as a function of the resorcinol residence time in a capillary tubular reactor, which also served as a high-pressure NMR cell. The 1H and 2H NMR results indicate that H/D exchange in resorcinol for the ring protons was observed at temperatures as low as 200 °C. The kinetics of H/D exchange in resorcinol and the activation energy was extracted from the experimental 1H NMR data.

Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water

“…As an example of the compounds that have similarly reactive phenyl protons, the deuteration of resorcinol ͑1,3-benzenediol͒ in hydrothermal D 2 O was investigated recently. 35 In that study, however, the site-selective deuteration of similarly reactive protons at ␣ and ␣Ј positions were not achieved at supercritical temperatures as high as 450°C. The topological control of the siteselective deuteration is then desirable to be established for the sites that have similar reactivities in monosubstituted benzenes such as phenol, by taking advantage of the unique nature of supercritical aqueous medium.…”

“…The reaction under hydrothermal conditions is a possible answer to the clean H/D conversion with desired site selectivity. The H/D exchange reaction under hydrothermal conditions have been investigated recently for various chemicals with or without catalysts, [25][26][27][28][29][30][31][32][33][34][35] as reviewed in brief by Savage. 16 Hot water is a convenient and effective reaction medium since it serves both as a reactive species and as a solvent by surrounding the reactant and lowering the activation energy of the transition state.…”

Trends in the Hydrogen−Deuterium Exchange at the Carbon Centers. Preparation of Internal Standards for Quantitative Analysis by LC-MS

“…Based on this technique several MS standards of bleomycin A2 for quantitative MS analysis were successfully prepared in D 2 O after a two-minute heating at 165 °C [ 40 ]. Additionally, some physicochemical reports have been published in which the kinetics of noncatalyzed HDX and energetic investigations were described [ 41 ].…”

Prediction of flow effects in quantitative NMR measurements

“…The most common approach in flow NMR spectroscopy is to connect the investigated process with the spectrometer by a sample loop [1,7,8]. Also other techniques for NMR spectroscopic reaction and process monitoring have been described in the literature [9][10][11][12][13][14][15][16][17]. All these applications benefit from the non-invasive characteristics of NMR spectroscopy making it a powerful tool for online monitoring.…”