A new Ba(OH)2 catalyst for synthesis of diacetone alcohol

The application of new Ba(OH)₂ catalysts for the preparation of diacetone alcohol is described. No loss of activity is observed when they are stored in a dessiccator over NaOH. The same yield as that described in the literature is obtained, but in a much shorter reaction time (9.5 h against 72–120 h)

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Ba(OH)₂ . NaOH . , , (9,5 72–120 ).

     

Potential energy surface for the CCl4 + H --> CCl3 + ClH reaction: kinetics and dynamics study

An analytical potential energy surface for the gas-phase CCl4 + H --> CCl3 + ClH reaction was constructed with suitable functional forms to represent vibrational modes. This surface is completely symmetric with respect to the permutation of the four chlorine atoms and is calibrated with respect to experimental thermal rate constants available over the temperature range 297-904 K. On this surface, the thermal rate constants were calculated using variational transition-state theory with semiclassical transmission coefficients over a wider temperature range 300-2500 K, therefore obtaining kinetics information at higher temperatures than are experimentally available. This surface was also used to analyze dynamical features, such as tunneling and reaction-path curvature. In the first case, the influence of the tunneling factor is very small since a heavy chlorine atom has to pass through the barrier. In the second, it was found that vibrational excitation of the Cl-H stretching mode can be expected in the exit channel.     

Kb/Ka X-ray intensity ratios in calcium and potassium compounds

Summary Kb/Ka X-ray intensity ratios of some K and Ca compounds were studied. The samples were excited with 59.5 keV g-rays emitted from 75 mCi ²⁴¹Am radioisotope source and characteristic K X-ray from the samples were counted by means of an Si(Li) detector which has a resolution 155 eV at 5.9 keV. We found that Kb/Ka X-ray intensity ratios are changed by chemical effect for different K and Ca compounds. The experimental values were compared with the calculated theoretical values for elemental K and Ca.     

Efficient synthesis of 3H-imidazo[4,5-b]pyridines from malononitrile and 5-amino-4-(cyanoformimidoyl)imidazoles

1-Aryl-5-amino-4-(cyanoformimidoyl)imidazoles 2 were reacted with malononitrile under mild experimental conditions and led to 3-aryl-5,7-diamino-6-cyano-3H-imidazo[4,5-b]pyridines 5, when the reaction was carried out in the presence of DBU, or to 3-aryl-5-amino-6,7-dicyano-3H-imidazo[4,5-b]pyridines 3, in its absence. Both reactions evolved from the adduct formed by nucleophilic attack of the malononitrile anion to the carbon of the cyanoformimidoyl substituent. A 5-amino-1-aryl-4-(1-amino-2,2-dicyanovinyl)imidazole 4 was isolated when this reaction was carried out in the presence of DBU. The structure of compound 4 was confirmed by spectroscopic methods and by reaction with triethyl orthoformate and with acetic anhydride, leading respectively to 9-aryl-6-(cyanomethylidene)purines 11 and 12. Imidazole 2b was also reacted with ethyl acetoacetate, a carbon acid with a pK(a) comparable to that of malononitrile. Similar reaction conditions were used and the product isolated was a 6-carbamoyl-1,2-dihydropurine 10, showing that a different mechanism was operating in this case.     

Crystal engineering of urea alpha-network via I...O2N synthon and design of SHG active crystal N-4-iodophenyl-N'-4'-nitrophenylurea

Crystalline nitrodiphenyl ureas adopt the N-H...O tape alpha-network only when stabilization accrues from the I...O(2)N or C[triple bond]C-H...O(2)N synthon, otherwise the ureanitro motif is preferred; soft, weak interactions can direct polar self-assembly in strong N-HO hydrogen-bonded crystals.     

Critical Analysis of Hypothesis Tests in Federal Information Processing Standard (140-2)

This work presents an analysis of the existing dependencies between the tests of the FIPS 140-2 battery. Two main analytical approaches are utilized, the first being a study of correlations through the Pearson’s correlation coefficient that detects linear dependencies, and the second one being a novel application of the mutual information measure that allows detecting possible non-linear relationships. In order to carry out this study, the FIPS 140-2 battery is reimplemented to allow the user to obtain p-values and statistics that are essential for more rigorous end-user analysis of random number generators (RNG).     

Antioxidant Activity of Polyphenols,from Mauritia flexuosa (Aguaje), Based on Controlled Dehydration

Plant polyphenols offer several benefits for the prevention of diverse illnesses. Fruit’s edible and inedible parts (pulp, seeds, peels, stems, flowers) are important sources of polyphenols. Different industrial processes for fruit treatment and commercialization affect the total polyphenol content (TPC), and probably the biological activity. The purpose of the present work was to determine the TPC and antioxidant activity (by DPPH) of polyphenols extracted from the pulp and seeds of Mauritia flexuosa (aguaje), in fresh and dehydrated forms, in order to determine the possible connection with the quantity of polyphenols and their specific antioxidant activity. The highest phenolic content for M. flexuosa seeds in fresh form (non-dehydrated) was 270.75 mg GAE/100 g with a 96-h extraction. With respect to the dehydrated samples, the best yield was quantified in the 96-h dehydrated seed sample. For all pulp and seeds, dehydrated for 24, 48, and 96 h, TPC showed a slightly decreasing pattern. The DPPH results were the highest in the 96-h dehydrated samples and the differences among all dehydrated pulp and seed samples were minimal. More studies testing the presence of other antioxidant components could help in understanding the detailed antioxidant activity, and related more to the specific action, rather than only total polyphenol content.     

Oxonitrogenated Derivatives of Eremophilans and Eudesmans: Antiproliferative and Anti-Trypanosoma cruzi Activity

Cancer is one of the most important causes of death worldwide. Solid tumors represent the vast majority of cancers (>90%), and the chemotherapeutic agents used for their treatment are still characterized by variable efficacy and toxicity. Sesquiterpenes are a group of natural compounds that have shown a wide range of biological activities, including cytotoxic and antiparasitic activity, among others. The antiproliferative activity of natural sesquiterpenes, tessaric acid, ilicic acid, and ilicic alcohol and their semisynthetic derivatives against HeLa, T-47D, WiDr, A549, HBL-100, and SW1573 cell lines were evaluated. The effect of the compounds on Trypanosoma cruzi epimastigotes was also assessed. The selectivity index was calculated using murine splenocytes. Derivatives 13 and 15 were the most antiproliferative compounds, with GI₅₀ values ranging between 5.3 (±0.32) and 14 (±0.90) μM, in all cell lines tested. The presence of 1,2,3-triazole groups in derivatives 15–19 led to improvements in activity compared to those corresponding to the starting natural product (3), with GI₅₀ values ranging between 12 (±1.5) and 17 (±1.1) μM and 16 being the most active compound. In relation to the anti-T. cruzi activity, derivatives 7 and 16 obtained from tessaric acid and ilicic acid were among the most active and selective compounds with IC₅₀ values of 9.3 and 8.8 µM (SI = 8.0 and 9.4), respectively.     

Insecticidal Activity of Organic Extracts of Solidago graminifolia and Its Main Metabolites (Quercetin and Chlorogenic Acid) against Spodoptera frugiperda: An In Vitro and In Silico Approach

Spodoptera frugiperda (S. frugiperda) remains a global primary pest of maize. Therefore, new options to combat this pest are necessary. In this study, the insecticidal activity of three crude foliar extracts (ethanol, dichloromethane, and hexane) and their main secondary metabolites (quercetin and chlorogenic acid) of the species Solidago graminifolia (S. graminifolia) by ingestion bioassays against S. frugiperda larvae was analyzed. Additionally, the extracts were phytochemically elucidated by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Finally, an in silico study of the potential interaction of quercetin on S. frugiperda acetylcholinesterase was performed. Organic extracts were obtained in the range from 5 to 33%. The ethanolic extract caused higher mortality (81%) with a half-maximal lethal concentration (LC₅₀) of 0.496 mg/mL. Flavonoid secondary metabolites such as hyperoside, quercetin, isoquercetin, kaempferol, and avicularin and some phenolic acids such as chlorogenic acid, solidagoic acid, gallic acid, hexoside, and rosmarinic acid were identified. In particular, quercetin had an LC₅₀ of 0.157 mg/mL, and chlorogenic acid did not have insecticidal activity but showed an antagonistic effect on quercetin. The molecular docking analysis of quercetin on the active site of S. frugiperda acetylcholinesterase showed a −5.4 kcal/mol binding energy value, lower than acetylcholine and chlorpyrifos (−4.45 and −4.46 kcal/mol, respectively). Additionally, the interactions profile showed that quercetin had π–π interactions with amino acids W198, Y235, and H553 on the active site.     

Selective CO2 reduction into formate using Ln-Ta oxynitrides combined with a binuclear Ru(Ⅱ)complex under visible light

Hybrid materials constructed from a visible-light-absorbing semiconductor and a functional metal complex have attracted attention as efficient photocatalysts for CO₂ reduction with high selectivity to a desired product.In this work,defect fluorite-type Ln-Ta oxynitrides LnTaO_xN_y(Ln=Nd,Sm,Gd,Tb,Dy and Ho)were examined as the semiconductor component in a hybrid photocatalyst system combined with known Ag nanoparticle promoter and binuclear ruthenium(Ⅱ)complex(RuRu’).Among the LnTaO_xN_y examined,TbTaO_xN_y gave the highest performance for CO₂ reduction under visible light(k>400 nm),with a Ru Ru0-based turnover number of 18 and high selectivity to formate(>99%).Physicochemical analyses indicated that high crystallinity and more negative conduction band potential of Ln Ta O_xN_ywith the absence of Ln-4 f states in the band gap structure contributed to higher activity of the hybrid photocatalyst.