The structure and vibrational features of proton disolvates in water-ethanol solutions of HCl: the combined spectroscopic and theoretical study

Abstract

The infrared (IR) spectra of water–ethanol (EtOH) solutions of HCl are measured over a wide range of acid concentration at fixed H2O―EtOH ratios (1 : 1, 1 : 2, and 1 : 40). In these systems, different proton disolvates with (quasi)symmetrical H‐bonds are formed. Their structure and vibrational features are revealed by the density functional theory method coupled with the polarizable continuum model of solvation. In dilute acidic solutions, the Zundel‐type H5O2+ ion is mainly formed. In concentrated HCl solutions, the ions (H2O···H···O(H)Et)+ and (Et(H)O···H···O(H)Et)+ with the quasi‐symmetrical O···H+···O unit having O···O separation <2.45 Å appear. The first ion characterized by the IR‐intensive band around 1800 cm−1 is mainly formed in the 1 : 1 water–ethanol systems. The second ion exists in the 1 : 2 and 1 : 40 water–ethanol systems. Its spectroscopic signatures are the groups of the IR‐intensive bands around 800 and 1050 cm−1. In highly concentrated HCl solutions with the 1 : 40 water–ethanol ratio, a neutral Et(H)O···H+···Cl− complex exists. Copyright © 2013 John Wiley & Sons, Ltd.

Quantification of Conventional and Nonconventional Charge-Assisted Hydrogen Bonds in the Condensed and Gas Phases

“…The strengthening of “conventional” XH···A (where X = O, N, or another very electronegative atom) and “non-conventional” CH···A hydrogen bonds (H-bonds) that occurs when either XH or A subunits (or both) are electrically charged − is an essential element for molecular recognition in a vast array of chemical and biological processes. − Consequently, quantifiable information on this phenomenon is regarded as essential for rational design of selective ligands, organocatalysts, drugs, and pesticides. Quantum chemical computations and gas-phase experiments have provided quantitative assessments of such charge-assisted H-bonds (CAHBs) in the gas phase, but their strength in the condensed phase has been investigated surprisingly little until now.…”

Green Recycle of Copper Ions in Saccharin Sodium Wastewater by Direct Electrodeposition Using Rotating Thin Copper Disc Electrode

“…The process of (CuCl 4 ) 2− dissociation could take place when (CuCl 4 ) 2− is diffused to the cathodic electrode surface, during which the concentration of Cl − should decline because of the electrostatic force between Cl − and cathode electrode which drives Cl − away. 17,18 Under this assumption, the method that enhanced the gradient of Cl − could increase the electrodeposition current theoretically. Inspired by the rotating disk electrode (RDE) method to enhance the mass transfer during the classic electrochemical tests, a method with scaled-up RDE to enhance the mass transfer, from the solution to the electrode surface especially in the diffusion layer, could artificially control the capacitance of the electrochemical reaction in theory, thus controlling the distribution of Cl − ions and finally the format of (CuCl x ) (2−X)− .…”

“…However, the state of (CuCl 4 ) 2– became unstable and dissociate to (CuCl 3 ) − , (CuCl 2 ) 0 , (CuCl) + , and even Cu 0 , while the Cl – decreases. The process of (CuCl 4 ) 2– dissociation could take place when (CuCl 4 ) 2– is diffused to the cathodic electrode surface, during which the concentration of Cl – should decline because of the electrostatic force between Cl – and cathode electrode which drives Cl – away. , Under this assumption, the method that enhanced the gradient of Cl – could increase the electrodeposition current theoretically. Inspired by the rotating disk electrode (RDE) method to enhance the mass transfer during the classic electrochemical tests, a method with scaled-up RDE to enhance the mass transfer, from the solution to the electrode surface especially in the diffusion layer, could artificially control the capacitance of the electrochemical reaction in theory, thus controlling the distribution of Cl – ions and finally the format of (CuCl x ) (2– X )– . , Therefore, the direct electrodeposition of (CuCl 4 ) 2– could probably be enhanced by the controlled mass-transfer electrodeposition methods of the above RDE, via which fast reduction of current and rapid generation of recycled copper should be theoretically possible. , On the basis of the hypothesis, green recycled and reused copper as the raw material of CuSO 4 for original manufacturing process has become possible, in which high concentration of copper ions could be efficiently reused without a significant neutralization of HCl.…”

Fast Structural Dynamics in Concentrated HCl Solutions: From Proton Hopping to the Bulk Viscosity

“…Because of a distinct focus on proton transport in acid solutions, less attention has been directed to studying the overall structural dynamics of the liquid, i.e., the complex, transient system of solvated hydronium cations, anions, and water molecules. Theoretical models, neutron and X-ray diffraction experiments, ,− X-ray, IR, Raman, and terahertz spectroscopy techniques − have been used to describe concentration-dependent solvation shells around ions semiquantitatively. However, the results vary remarkably, depending on the technique used.…”