Vibrational Stark Fields in Carboxylic Acid Dimers

Carboxylic acids form exceptionally stable dimers and have been used to model proton and double proton transfer processes. The stabilization energies of the carboxylic acid dimers are very weakly dependent on the nature of the substitution. However, the electric field experienced by the OH group of a particular carboxylic acid is dependent more on the nature of the substitution on the dimer partner. In general, the electric field was higher when the partner was substituted with electron-donating group and lower with electron-withdrawing substituent on the partner. The Stark tuning rate (∆μ) of the O–H stretching vibrations calculated at the MP2/aug-cc-pVDZ level was found to be weakly dependent on the nature of substitution on the carboxylic acid. The average Stark tuning rate of O–H stretching vibrations of a particular carboxylic acid when paired with other acids was 5.7 cm–1 (MV cm–1)–1, while the corresponding average Stark tuning rate of the partner acids due to a particular carboxylic acid was 21.9 cm–1 (MV cm–1)–1. The difference in the Stark tuning rate is attributed to the primary and secondary effects of substitution on the carboxylic acid. The average Stark tuning rate for the anharmonic O–D frequency shifts is about 40-50% higher than the corresponding harmonic O–D frequency shifts calculated at B3LYP/aug-cc-pVDZ level, much greater than the typical scaling factors used, indicating the strong anharmonicity of O–H/O–D oscillators in carboxylic acid dimers. Finally, the linear correlation observed between pKa and the electric field was used to estimate the pKa of fluoroformic acid to be around 0.9.

Photodegradation of Dyes From Cual Batik Waste Using TiO2 Photocatalyst From Ilmenite Bangka

Cual batik is one of the local products of the Bangka Belitung Islands. The expansion of cual batik in Bangka Belitung continues to increase, resulting in an increase in the production of cual batik cloth. Cual batik contains remasol dyes which are carcinogenic so that waste handling is appropriate and safe for the surrounding environment. One of them is using the TiO2 photocatalytic method from ilmenite Bangka. The results of XRF characterization showed that the TiO2 content after magnetic separator and HCl washing reached 69,975% and 77,260%. The results of XRD characterization showed that the optimal temperature of calcination was at 700ºC with the peak diffraction intensity of anatase TiO2 crystals at 2θ 48.9º, 53.53º and 53.92º. In FTIR characterization, there is a functional group spectrum of titanium dioxide (TiO2) at the absorption wave number 795 cm-1 showing Ti-O-Ti stretching vibrations, at wavenumber 2326 cm-1 showing Ti-O stretching vibrations. The results of photodegradation of cual batik waste showed a decrease in the dye content of remazol briliant blue when exposed to UV lamps and sunlight at contact times of 30, 60, and 90 minutes 85.21%, 82,75%, and 86,72% (UV light); 70,75%, 78,92%, and 93.51% (sunlight).

IR-Spectroscopic Study of Complex Formation of Nitrogen Oxides (NO, N2O) with Cationic Forms of Zeolites and the Reactivity of Adsorbed Species in CO and CH4 Oxidation

The formation of complexes and disproportionation of nitrogen oxides (NO, N2O) on cationic forms of LTA, FAU, and MOR zeolites was investigated by diffuse-reflectance IR spectroscopy. N2O is adsorbed on the samples under study in the molecular form and the frequencies of the first overtone of the stretching vibrations ν10–2 and the combination bands of the stretching vibrations with other vibrational modes for N2O complexes with cationic sites in zeolites (ν30–1 + ν10–1, ν10–1 + δ0–2) are more significantly influenced by the nature of the zeolite. The presence of several IR bands in the region of 2400–2600 cm−1 (the ν10–1 + δ0–2 transitions) for different zeolite types was explained by the availability of different localization sites for cations in these zeolites. The frequencies in this region also depend on the nature of the cation (its charge and radius). The data can be explained by the specific geometry of the N2O complex formed, presumably two-point adsorption of N2O on a cation and a neighboring oxygen atom of the framework. Adsorption of CO or CH4 on the samples with preliminarily adsorbed N2O at 20–180 °C does not result in any oxidation of these molecules. NO+ and N2O3 species formed by disproportionation of NO are capable of oxidizing CO and CH4 molecules to CO2, whereas NOx is reduced simultaneously to N2 or N2O. The peculiarities in the behavior of cationic forms of different zeolites with respect to adsorbed nitrogen oxides determined by different density and localization of cations have been established.

Features of the Chemical Interaction of 2-Furaldehyde and 1,3,5-Trihydroxybenzene in an Alkaline Medium to Obtain a Plasticizing Additive

The paper presents data on the study of the polycondensation of 2-furaldehyde and 1,3,5-trihydroxybenzene in an alkaline medium to obtain a plasticizing additive. Results are presented on the study of the products of the separate interaction of 1,3,5-trioxybenzene and 2-furaldehyde with NaOH, and the joint polycondensation of 1,3,5-trioxybenzene with 2-furaldehyde with NaOH by UV spectroscopy. The structure of the product of the interaction of 1,3,5-trioxybenzene with 2-furaldehyde in an alkaline medium was studied by IR spectroscopy. Stronger C–H bonds appear in the IR spectrum and stretching vibrations of the C = O group are not observed, which confirms the production of a new compound. The optimal dosage of the developed plasticizing additive has been established as 0.3% of the cement mass (calculated on dry matter). The developed plasticizing additive can significantly reduce the water-cement ratio while maintaining the strength characteristics of cement compositions. In addition, when using the additive, the strength characteristics are significantly increased with a reduced water-cement ratio.

SYNTHESIS AND PROPERTIES OF ORGANOSILICON EPISULFIDES

A study was made of the interaction of thiourea with saturated and unsaturated organosilicon oxiranes in absolute methyl alcohol in a medium of potassium hydroxide, and methods were developed for the synthesis of unsaturated and unsaturated organosilicon silicides with a yield of 65–75%.The studies carried out revealed that the synthesized organosilicon episulfides are very reactive compounds and can react with nucleophilic and electrophilic reagents, while forming the corresponding silicon derivatives. The IR- spectra of the products were studied. It should be noted that, when comparing the IR- spectra of oxiranes and episulfides, it was revealed that the stretching vibrations of the CH2 group of the episulfide ring are underestimated by 50–70 cm-1 in comparison with the oxirane ring

Synthesis and study of oligohexamethyleneguanidine hydroiodide as a radiopaque substance

Diagnosis of complex injuries, such as splinter fractures and wounds, skull injuries accompanied by internal injuries that are inaccessible to visual control, presents the greatest difficulties during X-ray examination. Therefore, it is relevant to develop a drug that can help localize the site of a pathological lesion with high accuracy, relying only on the results of an X-ray study, which is possible when a reference point (substance) is applied to the patient’s skin. A radiopaque contrast compound based on an iodinated polymeric matrix with iodine as the contrasting component and polyguanidine as the carrier has been proposed to be used as a reference point substance. The choice of this class of polymers stemmed from the fact that a positive charge is localized to a greater extent on the carbon atom of the guanidine group, which allows loading iodine anions into it. Protonation of pure guanidine with hydroiodic acid has helped obtain guanidine hydroiodide. This finding was confirmed by IR spectroscopy methods (a decrease in the intensity of bands in the region of 1,380, 880 cm−1 in comparison with guanidine, as well as broadening of the band of stretching vibrations of amino groups characteristic of guanidine salts) and X-ray phase analysis. Polyhexamethylene guanidine hydroiodide was synthesized based on hexamethylenediamine and iodine-containing guanidine salt using melt polycondensation. The results show that the aqueous solutions of samples under study absorb X-radiation and are the X-ray-positive substances (exposure radiation dosage E = 0.04 mSV).

Setting up the HyDRA blind challenge for the microhydration of organic molecules

The procedure leading to the first HyDRA blind challenge for the prediction of water donor stretching vibrations in monohydrates of organic molecules is described. A training set of 10 monohydrates with experimentally known and published water donor vibrations is presented and a test set of 10 monohydrates with unknown or unpublished water donor vibrational wavenumbers is described together with relevant background literature. The rules for data submissions from computational chemistry groups are outlined and the planned publication procedure after the end of the blind challenge is discussed.