Mechanism of transformation of protons in the process of creating aqueous-alcoholic mixtures.

Механізм трансформації протонів у процесі створення водно-спиртових сумішей

Introduction. The aim of the publication is to study the mechanisms of transformation of ethanol protons (ethyl rectified spirit - ERS) and water (drinking water) in the process of creating aqueous-alcoholic mixtures (AAM) by 1H NMR spectroscopy. Materials and methods. 1H NMR analysis was conducted with the usage of the following: FT-NMR Bruker Avance II spectrometer with operating frequency at 1H - 400 MHz; specially shaped capillary with acetone-d6 (atomic fraction of deuterium - 99,88 %; chemical shift of the residual proton 1H - δ=2,75 ppm); high accuracy ampoules № 507-HP for high resolution NMR's spectroscopy (400 MHz); volumetric pipette; dispenser; ERS; drinking water; AAM from ERS and drinking water. Work methodology: 0,3 ml of a AAM prepared with a volumetric pipette with a predetermined strength (40,0 ± 0,2) % vol.; external standard separated from the testing substance which is required for LOCK's system operation (acetone-d6) of NMR's deuterium stabilization spectrometer) is added in a special form of a capillary into an ampoule. The obvious advantage of using the external standard is the fact that standard substance's molecules and test's solution do not interact with each other; 1H NMR spectra records and data processing were performed according to the instruction of FT-NMR Bruker Avance II spectrometer (400 MHz). Results and discussion. In this paper, we have established fundamentally new features in the process of creating AAM that are directly dependent on the time of contact with water and ERS. As a results we have evidence of a complex dynamic of achievement processes of solution equilibrium for AAM prepared in drinking water with pH=7,01 and ERS. At the same time pH of obtained AAM is pH=8,32. Hydroxyl proton of ethanol (EtOH) exchange rate is in intermediate area. It happens during the first 48 hours when the concentration of alcohol is constant (strength AAM - 39,94 % vol.) and the system is thermostatic (t=23,5 ºC). Signals are separately located. Protons' exchange is accelerated due to the rearrangement of system's structure, during the interval of τ=48 h to 120 h. Since τ=120 h, there is only one common signal of mobile protons of asymmetrical shape. The size of chemical shift of the summed signal δEtОН+Н2О=4,74 ppm (τ=120 h) is starting to grow and shifts to the «weak fields» with the value of δEtОН+Н2О=4,81 ppm (τ=312 h). Conclusion. In this paper, we have established fundamentally new features in the process of creating AAM that are directly dependent on the time of contact with drinking water and ERS. [ABSTRACT FROM AUTHOR]