Stability and reactivity of dimethylethoxysilane

The chemistry of the compound dimethylethoxysilane (DMES) is discussed especially as it relates to waterproofing silica surfaces. Some of the desirable properties of this compound are that it readily reacts with silica in the vapor phase, it is a low boiling point liquid (54 C), and the by-product of its reaction with silica is the rather inert substances ethanol. It is currently used by NASA to re-waterproof the HRSI shuttle tiles before relaunching the vehicle. Very little information is available on this particular compound in the literature or even on related silane compounds that have both a hydride group and an alkoxy group. Since the close proximity of two groups often drastically affects the chemical behavior of each group, chemical reactions were carried out in the laboratory with DMES to verify the expected behavior of these two functional groups located on DMES. Some of the reactions tested would be potentially useful for quantitative or qualitative measurements on DMES. To study the reactions of DMES with silica surfaces, cabosil was used as a silica substrate because of its high surface area and the ease of detection by infrared spectroscopy as well as other techniques

Mol-CycleGAN - a generative model for molecular optimization

Designing a molecule with desired properties is one of the biggest challenges in drug development, as it requires optimization of chemical compound structures with respect to many complex properties. To augment the compound design process we introduce Mol-CycleGAN - a CycleGAN-based model that generates optimized compounds with high structural similarity to the original ones. Namely, given a molecule our model generates a structurally similar one with an optimized value of the considered property. We evaluate the performance of the model on selected optimization objectives related to structural properties (presence of halogen groups, number of aromatic rings) and to a physicochemical property (penalized logP). In the task of optimization of penalized logP of drug-like molecules our model significantly outperforms previous results

Virtual chemical reactions for drug design

Two methods for the fast, fragment-based combinatorial molecule assembly were developed. The software COLIBREE® (Combinatorial Library Breeding) generates candidate structures from scratch, based on stochastic optimization [1]. Result structures of a COLIBREE design run are based on a fixed scaffold and variable linkers and side-chains. Linkers representing virtual chemical reactions and side-chain building blocks obtained from pseudo-retrosynthetic dissection of large compound databases are exchanged during optimization. The process of molecule design employs a discrete version of Particle Swarm Optimization (PSO) [2]. Assembled compounds are scored according to their similarity to known reference ligands. Distance to reference molecules is computed in the space of the topological pharmacophore descriptor CATS [3]. In a case study, the approach was applied to the de novo design of potential peroxisome proliferator-activated receptor (PPAR gamma) selective agonists. In a second approach, we developed the formal grammar Reaction-MQL [4] for the in silico representation and application of chemical reactions. Chemical transformation schemes are defined by functional groups participating in known organic reactions. The substructures are specified by the linear Molecular Query Language (MQL) [5]. The developed software package contains a parser for Reaction-MQL-expressions and enables users to design, test and virtually apply chemical reactions. The program has already been used to create combinatorial libraries for virtual screening studies. It was also applied in fragmentation studies with different sets of retrosynthetic reactions and various compound libraries

Chemistry of pyrrolizines; reactions with cyanogen bromide and trifluoroacetic anhydride

Interaction of the pyrrolizine 3 with cyanogen bromide in a tetrahydrofuran/water mixture affords addition to the enamine double bond with formation of 5 which can be aromatized to 6 by silica gel. Reaction of 6 with cyanogen bromide in the same solvent mixture yields the indoline 8a which structure is proved in a chemical way by conversion of the product into the aldehyde 8d. The different reaction pathway is discussed in terms of steric hindrance by the ester groups. Treatment of 6 with trifluoroacetic anhydride gives the trifluoroacetylated compound 11. Removal of the sterically hindered ester groups in 6, with acetic acid in quinoline at 200°, is accompanied by the simultaneous decarboxylation to yield the pyrrolo[1,2-a]indole 1

Chemical profiling and chemical standardization of Vitex negundo using 13C NMR

Chemical profiling and standardization of the defatted methanol extract of the leaves of Vitex negundo L. were carried out using 13C nuclear magnetic resonance (NMR) analysis followed by chemometric analysis of the chemical shift data. Chemical profile was obtained using a k-means cluster profile and chemical standardization which was achieved using a multivariate control chart. The V. negundo samples were made up of four groups: the training set, submitted samples from production farms, commercial samples, such as tablets, capsules and teas, and experimental samples (samples which were allowed to degrade). Four groups were generated in k-means cluster, which generally corresponded to the four types of samples. The multivariate control chart identified samples whose quality exceeded the upper control limit, all of which were commercial samples and experimental samples. The samples were also analyzed by quantitative thin layer chromatography (qTLC) using agnuside as marker compound. Comparison of the qTLC results with the k-means cluster and the multivariate control chart showed poor correspondence. This means that a univariate analysis of a plant sample using a marker compound is useful only for quantification of the target compound. On the other hand, chemical profiling and standardization of medicinal plants should use a multivariate method

Synthesis and Characterization of HPMpFBP Using Raman Spectroscopy, Nuclear Magnetic Resonance (NMR) Spectroscopy, and FTIR

Synthesis is one of the models for the formation of a new drug or compound with the aim of obtaining better activity at an economical price. HPMpFBP has been synthesized by mixing of 1-phenyl-3-methyl-5-pyrazolone and 4-fluorobenzoyl chloride. In the synthesis of HPMpFBP, a new compound namely 1-phenyl-3-methyl-4-(4-fluorobenzoyl)-5-pyrozolone has been obtained. The sample then characterized by non-invasive methods using Raman spectroscopy, Nuclear Magnetic Resonance (NMR) Spectroscopy and FTIR. Through this characterization process, wavelength information, chemical shift, and functional groups (chemical structure) of HPMpFBP samples were obtained. HPMpFBP has a chemical structure of C17H13N2O2F, the highest wavelength carried out by characterization using Raman is 1643.91 cm-1, the highest chemical shift characterized by using NMR (Nuclear Magnetic Resonance) is 7.8628 ppm, and the functional groups identified by using FTIR are (O-H, C-H, C=C, C=O, C-N). Information from the HPMpFBP sample characterization process using mentioned characterization methods was compared with previously reported results

Volatility of Secondary Organic Aerosol from β-Caryophyllene Ozonolysis over a Wide Tropospheric Temperature Range

We investigated secondary organic aerosol (SOA) from β-caryophyllene oxidation generated over a wide tropospheric temperature range (213–313 K) from ozonolysis. Positive matrix factorization (PMF) was used to deconvolute the desorption data (thermograms) of SOA products detected by a chemical ionization mass spectrometer (FIGAERO-CIMS). A nonmonotonic dependence of particle volatility (saturation concentration at 298 K, C298K*) on formation temperature (213–313 K) was observed, primarily due to temperature-dependent formation pathways of β-caryophyllene oxidation products. The PMF analysis grouped detected ions into 11 compound groups (factors) with characteristic volatility. These compound groups act as indicators for the underlying SOA formation mechanisms. Their different temperature responses revealed that the relevant chemical pathways (e.g., autoxidation, oligomer formation, and isomer formation) had distinct optimal temperatures between 213 and 313 K, significantly beyond the effect of temperature-dependent partitioning. Furthermore, PMF-resolved volatility groups were compared with volatility basis set (VBS) distributions based on different vapor pressure estimation methods. The variation of the volatilities predicted by different methods is affected by highly oxygenated molecules, isomers, and thermal decomposition of oligomers with long carbon chains. This work distinguishes multiple isomers and identifies compound groups of varying volatilities, providing new insights into the temperature-dependent formation mechanisms of β-caryophyllene-derived SOA particles