Dissociation and microsolvation of bisulfate anion

Abstract

Bisulfate anion has vast applications in industrial and environmental chemistry. Its dissociation to sulfate anion has been studied computationally and by size-selected clusters. In this study, Micro-Raman spectroscopy is applied at different relative humidity (RH)% on small droplets of aqueous solutions of NaHSO 4 , NH 4 HSO 4 , and H 2 SO 4 to explore the dissociation of HSO 4 experimentally in bulk and supersaturated state. Our cumulative experimental results support the conclusion obtained from gas-phase cluster study that HSO 4 starts dissociating at very low number of water molecules (H 2 O~1). However, dissociation of HSO 4 is found dependent on the cation attached with this weak acid. The magnitude of dissociation is found as NH 4 HSO 4 ≈ H 2 SO 4 > NaHSO 4 . In addition, studying the hydration process of HSO 4 − in the presence of three different cations enabled us to observe various species in three systems. Theoretical values obtained from extended aerosol inorganic model supports the experimental results. K E Y W O R D S dissociation, Raman spectroscopy, E-AIM

Electrochemical Strategy for the Simultaneous Production of Cyclohexanone and Benzoquinone by the Reaction of Phenol and Water

“…Meanwhile, two new Raman signals appeared at 1410 and 1606 cm –1 , which were, respectively, associated with the CH bending and CC stretching vibrations of the conjugated ketene structure in the 2,4-cyclohexadienone (Figure A1, inset) generated from the tautomerization of phenol . This isomerization was driven by the HSO 4 – anion-derived proton, which could be supported by the observed red-shift (from 980 to 971 cm –1 ) and enhanced peak intensity of the SO 4 2– anion, due to the electrostatic interaction from the above working protons . Experimentally, these typical Raman signals with regard to the proton-driven tautomerization were not observed without the catalyst on the electrode (Figure S13A1), or with the incident light focusing on the bulk electrolyte solution (Figure S13A2), or when the power was switched off during the reaction (Figure A1, SHUTOFF), indicating the electrocatalytic characteristic of the phenol reduction process over the catalyst.…”

“…53 This isomerization was driven by the HSO 4 − anion-derived proton, which could be supported by the observed red-shift (from 980 to 971 cm −1 ) and enhanced peak intensity of the SO 4 2− anion, due to the electrostatic interaction from the above working protons. 51 Experimentally, these typical Raman signals with regard to the proton-driven tautomerization were not observed without the catalyst on the electrode (Figure S13A1), or with the incident light focusing on the bulk electrolyte solution (Figure S13A2), or when the power was switched off during the reaction (Figure 3A1, SHUTOFF), indicating the electrocatalytic characteristic of the phenol reduction process over the catalyst. To further discover the essence of the ERP reaction, we carried out the Raman measurements using H 2 and NaBH 4 as the reductants in the power-off condition of the reaction system (Figure 3A3), and their spectra exhibited no representative signals of the ERP reaction, ruling out the thermocatalytic mechanism of the phenol reduction.…”

“…As shown in the Raman spectra (Figure 3A1), the power-off reaction system exhibited peaks at 980, 1049, 1610, and 1635 cm −1 that could be, respectively, assigned to the SO 4 2− anion, SOH stretching of bisulfate, a stretching vibration of the aromatic π bonds in phenol, and a broad water OH bending vibration (Figure 3A1, OFF). 51,52 After the power is turned on, the broad water OH peak disappeared (Figure 3A2), and the SOH stretching peak weakened, which indicated that the HSO 4 − anions on the catalytic active sites were replaced by the phenol molecules, in light of the enhanced stretching vibration of the aromatic π bonds (Figure 3A1, ON_5min). Meanwhile, two new Raman signals appeared at 1410 and 1606 cm −1 , which were, respectively, associated with the CH bending and CC stretching vibrations of the conjugated ketene structure in the 2,4cyclohexadienone (Figure 3A1, inset) generated from the tautomerization of phenol.…”

Aerosol pH and Ion Activities of HSO4– and SO42– in Supersaturated Single Droplets

“…The calibration measurements were performed by adding 100 μL of solution onto a coverslip (0.12 mm thickness, Paul Marienfeld GmbH & Co. KG) placed over the objective that focuses the 532 nm excitation laser of the AOT–Raman system with the laser power set to 50 mW. The peaks at 981 and 1050 cm –1 originate from the stretching vibrations of SO 4 2– and HSO 4 – , respectively, − and the broad bands centered at around 3400 cm –1 are related to the OH stretching of water , (Figure c,d). The upper and lower limits of integration for the OH band were set to 3000 and 3850 cm –1 with the LARA program of AOT.…”