Catalytic sulfation of betulin with sulfamic acid : experiment and DFT calculation

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst(®)15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835–841 cm(−1); in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K(1) and K(2) of a solution of the betulin disulfate H(+) form has been found to be 3.86 × 10(–6) ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data

Optimisation of Siberian Larch (Larix sibirica) Galactoglucomannan Sulfation Process with Sulfamic Acid in DMSO

Изучено влияние температуры, продолжительности процесса сульфатирования галактоглюкоманнана древесины лиственницы и количества сульфатирующего комплекса на содержание серы (мас.%) в сульфатах галактоглюкоманнана при сульфатировании сульфаминовой кислотой в ДМСО в присутствии мочевины. Путем математической оптимизации по плану Бокса-Бенкена установлены условия сульфатирования, позволяющие достичь высокого содержания серы в сульфатах галактоглюкоманнана. Оптимальными условиями сульфатирования галактоглюкоманнана древесины лиственницы являются температура 89,5 °C, продолжительность 2,3 часа, количество сульфатирующего комплекса на 1 г галактоглюкоманнана 55,4 ммоль. Высокое качество аппроксимации доказано высоким значением R 2 adj = 92,9 %, а также значениями P<0,0019 (с допустимым диапазоном значений 0,05). Введение сульфатной группы в молекулу галактоглюкоманнана подтверждено методами ИК‑спектроскопии и элементного анализаThe influence of temperature, duration of the process of sulfation of larch wood galactoglucomannan, and the amount of the sulfating complex on the sulfur content (wt %) in galactoglucomannan sulfates during sulfation with sulfamic acid in DMSO in the presence of urea was studied. By mathematical optimization according to the Box-Behnken plan, sulfation conditions were established to achieve a high sulfur content in galactoglucomannan sulfates. The optimal conditions for sulfation of larch wood galactoglucomannan are temperature 89.5 °C, duration 2.3 hours, amount of sulfating complex per 1 g galactoglucomannan 55.4 mmol. The high quality of the approximation is proved by the high value of R 2adj = 92.9 %, as well as by the values P<0.0019 (with an allowable range of 0.05). The introduction of a sulfate group into the galactoglucomannan molecule was confirmed by FTIR spectroscopy and elemental analysi

Sulfation of Wheat Straw Soda Lignin with Sulfamic Acid over Solid Catalysts

Soda lignin is a by-product of the soda process for producing cellulose from grassy raw materials. Since a method for the industrial processing of lignin of this type is still lacking, several research teams have been working on solving this problem. We first propose a modification of soda lignin with sulfamic acid over solid catalysts. As solid catalysts for lignin sulfation, modified carbon catalysts (with acid sites) and titanium and aluminum oxides have been used. In the elemental analysis, it is shown that the maximum sulfur content (16.5 wt%) was obtained with the Sibunit-4&reg; catalyst oxidized at 400 &deg;C. The incorporation of a sulfate group has been proven by the elemental analysis and Fourier-transform infrared spectroscopy. The molecular weight distribution has been examined by gel permeation chromatography. It has been demonstrated that the solid catalysts used in the sulfation process causes hydrolysis reactions and reduces the molecular weight and polydispersity index. It has been established by the thermal analysis that sulfated lignin is thermally stabile at temperatures of up to 200 &deg;C. According to the atomic force microscopy data, the surface of the investigated film consists of particles with an average size of 50 nm. The characteristics of the initial and sulfated &beta;-O-4 lignin model compounds have been calculated and recorded using the density functional theory

Comprehensive Study of the Ammonium Sulfamate–Urea Binary System

The physicochemical properties of binary systems are of great importance for the application of the latter. We report on the investigation of an ammonium sulfamate–urea binary system with different component ratios using a combination of experimental (FTIR, XRD, TGA/DSC, and melting point) and theoretical (DFT, QTAIM, ELF, RDG, ADMP, etc.) techniques. It is shown that, at a temperature of 100 °C, the system under study remains thermally and chemically stable for up to 30 min. It was established using X-ray diffraction analysis that the heating time barely affects the X-ray characteristics of the system. Data on the aggregate states in specified temperature ranges were obtained with thermal analysis and determination of the melting point. The structures of the ammonium sulfamate–urea system with different component ratios were optimized within the density functional theory. The atom-centered density matrix propagation calculation of the ammonium sulfamate–urea system with different component ratios was performed at temperatures of 100, 300, and 500 K. Regardless of the component ratio, a regular increase in the potential energy variation (curve amplitude) with an increase in temperature from 100 to 500 K was found

Сульфатирование диэтиламиноэтилцеллюлозы хлорсульфоновой кислотой в 1,4-диоксане

Sulfation of diethylaminoethylcellulose with chlorosulfonic acid in 1,4-dioxane was studied. It is shown that with an increase in the amount of chlorosulfonic acid and the duration of the process, an increase in the sulfur content in diethylaminoethylcellulose sulfate is observed. The maximum sulfur content (13.8 wt.%) in DEAE‑cellulose sulfate is observed at a ratio of ClSO3H:(DEAEC) of 20.22:1 (mmol: g) and a process duration of 180 min. The introduction of a sulfate group into the DEAEC molecule was confirmed by elemental analysis and FTIR spectroscopy. In the FTIR spectra of ethylaminoethylcellulose sulfate there are absorption bands related to stretching vibrations υ(C–O–S) at 810–815 cm‑1 and asymmetric stretching vibrations υas(O=S=O) at. 1249–1254 cm‑1. Using X‑ray phase analysis and optical microscopy, it was shown that during the sulfation of diethylaminoethylcellulose, amorphization of the material is observed. It has been shown by gel permeation chromatography that with an increase in the duration of the sulfation process, glycosidic bond cleavage reactions are also observed with the formation of products with a lower molecular weight and greater polydispersityИзучено сульфатирование диэтиламиноэтилцеллюлозы хлорсульфоновой кислотой в 1,4-диоксане. Показано, что с увеличением количества хлорсульфоновой кислоты и продолжительности п роцесса наблюдается увеличение содержания серы в сульфате диэтиламиноэтилцеллюлозы. Максимальное содержание серы (13.8 мас.%) в сульфате ДЭАЭ‑целлюлозы наблюдается при соотношении ClSO3H:(ДЭАЭЦ) 20,22:1 (ммоль: г) и продолжительности процесса 180 мин. Введение сульфатной группы в молекулу ДЭАЭЦ- подтверждено данными элементного анализа и ИК-Фурье-спектроскопии. В ИК‑спектрах сульфата этиламиноэтилцеллюлозы присутствуют полосы поглощения, относящиеся к валентным колебаниям υ(C–O–S) при 810–815 см‑1 и асимметричным валентным колебаниям υas(O=S=O) при 1249–1254 см‑1. Методами рентгенофазового анализа и оптической микроскопией показано, что в процессе сульфатирования диэтиламиноэтилцеллюлозы наблюдается аморфизация материала. Методом гель-проникающей хроматографии показано, что с увеличением продолжительности процесса сульфатирования также наблюдаются реакции разрыва гликозидных связей с образованием продуктов с меньшей молекулярной массой и большей полидисперсность