Получение и обработка акустических откликов волн Лэмба в датчиках водных растворов базовых вкусов

The photodeprotection of formaldehyde was investigated for 3-(1-hydroxypropan-2-yl)benzophenone (3-HPBP) with ultrafast time-resolved spectroscopy. The femtosecond transient absorption results indicated the singlet excited state of 3-HPBP transformed efficiently into its triplet state by a fast intersystem crossing. In acidic (pH = 0) and basic (pH = 12.5) aqueous solutions, the triplet intermediate was a key precursor for the deprotection of formaldehyde via two different pathways. However, little photodeprotection was observed in neutral (pH = 7) aqueous solution where the triplet intermediate appeared to undergo a proton coupled electron transfer process to form a ketyl radical transient. The important benzylic biradical intermediates seen in the acidic and basic aqueous solutions were identified by time-resolved resonance Raman spectra whose vibrational frequency patterns were consistent with DFT calculation results for the benzylic biradical intermediate. The results here indicate that the β-carbon alcohol group of the triplet state 3-HPBP is deprotonated in basic aqueous solutions and this leads to a heterolytic C-C bond cleavage to deprotect formaldehyde and produce the benzylic carbanion triplet state species, whereas protonation of the carbonyl moiety of the triplet state 3-HPBP leads to direct generation of a benzylic biradical intermediate and the deprotection of formaldehyde in acidic aqueous solutions via a homolytic C-C bond cleavage.

Racemization of the phenylalaninato ligand in Λ- and Δ-[Ru(phe)(bpy)2]+ (phe; phenylalaninate anion, bpy; 2,2′-bipyridine) complexes was found in basic aqueous solutions. It was proceeding without conformational change around the ruthenium ion in the dark. The equilibrium and rate constants of the racemization were determined in basic solutions at 100 °C. The reaction was base-catalyzed and not affected by photoexcitation of the complex ions.

Ebselen is an organoselenium compound that exhibits a glutathione peroxidase-like activity. The kinetics of ebselen degradation in basic aqueous solution containing primary alcohol was investigated by HPLC. The reversible reaction of ebselen and its dimer (diselenide) was discovered as a novel redox reaction. This reaction followed first-order degradation in basic solution at a constant temperature, and the equilibrium constants of ebselen and diselenide depended on pH. Analysis of the degradation rate for the forward reaction-pH profile indicated that specific base catalysis occurs in ebselen. The mechanism of this redox reaction was investigated by HPLC, spectrophotometry and trapping the labile intermediate with trichloroethylene. Ebselen decomposes to diselenide via selenenic acid and selenol by reacting with primary alcohol. The deuterium isotope effect on the forward reaction indicated that the reaction rate depends on the strength of the hydrogen-carbon bond at the α-position of primary alcohol. On the other hand, the effect of nitrogen replacement on the reverse reaction showed that diselenide is converted into ebselen by oxidation with oxygen existing in the solution.

Kinetic study on leaching process of beryl with basic solution under microwave heating

A responsive function is significant to surfaces with special wettability, especially for breaking through their limitations in practical applications. We report a novel strategy, which is effective, scalable, versatile, and low-cost, to produce the pH-responsive superwettable surface by combining the pH-responsive branched polymer nanoparticles (PRBNs) and conventional textile materials. The PRBN exhibiting a spherical shape with strawberry-like rough surface is able to swell (diameter of 71 nm) in an acidic aqueous solution and shrink to its original size (diameter of 42 nm) in a neutral or basic aqueous solution; moreover, the swelling–shrinking transition is reversible. The deposition of PRBNs on polyester fabric provides the surface pH-responsive wettability that is superhydrophobic to a neutral or basic aqueous solution (pH ≥ 7) with a contact angle above 150° and superhydrophilic to an acidic aqueous solution (pH 1) with a contact angle of 0°. Similar to the pH-responsive behavior of nanoparticles, this superhydrophobic–supehydrophilic transition of fabric is also reversible. By adjusting the hydrophobic substituents of PRBN, the wettability of fabric has remarkable changes. The adhesion of PRBNs onto polyester fabric can be obviously enhanced by the heating-press procedure so that its washability improves. These results may provide a new horizon to design new-generation smart textiles via utilizing controllable wettability.

Theoretical reaction pathways for the formation of [Si(OH) 5] 1− and the deprotonation of orthosilicic acid in basic solution

The kinetics of the reduction of permanganate by cyanide in basic solution

The growth rates of α- and γ-glycine in basic and acidic aqueous glycine solutions were investigated systematically using in situ microscopic observations on single crystal seeds. The most unexpected observation was that inorganic bases (e.g., NaOH and KOH) and acids (e.g., H2SO4) can significantly accelerate the growth of the metastable α-glycine. This finding is contrary to the recently postulated self-poisoning mechanism, which highlights that glycine ions, generated in a basic or acidic solution, inhibit α-glycine so as to permit γ-glycine to appear. Furthermore, it was observed that, in basic solutions, γ-glycine growth remains dominated by α-glycine growth, yet γ-glycine is crystallized preferentially. This strongly implies that the relative nucleation rates, not the relative growth kinetics of the two glycine polymorphs play a dominant role in determining the polymorphic outcome, providing new insights into the riddle of glycine polymorphism. The observed effects of the base and acid additives on t...

A process, which makes it possible for polyimide resists to be developed using dilute base aqueous solutions, is reported. The process contains soft bake, UV exposure, post exposure bake and development with basic aqueous solutions. The post exposure bake at a temperature range from 140 to 160°C, which is higher than usual, is the feature of this process. The polyimide resists consist of polyamic acids and diazonaphthoquinone 4‐sulfonic acid esters, whose compositions are not novel and have appeared in several patents and papers. However, the resists consisting of polyamic acids and diazo compounds usually had only low dissolution selectivity between exposed areas and unexposed areas. It was therefore difficult to obtain fine patterns. The high temperature post exposure bake (HIT‐PEB) made it possible to obtain five patterns and three micron negative patterns were fabricated. This process is the simplest way to realize polyimide resists developable with basic aqueous solutions.

The reaction of bromoacetonitrile with 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[<TEX>$16.4.1^{2.6}.0^{1.18}.0^{7.12}$</TEX>]tricosane (<TEX>$L^{10}$</TEX>) containing a N-<TEX>$CH_2$</TEX>-N linkage produces 17-cyanomethyl-3,14-dimethyl-2,6,13,17-tetraazatetracyclo-[<TEX>$16.4.1^{2.6}.0^{1.18}.0^{7.12}$</TEX>]tricosane (<TEX>$L^{11}$</TEX>). The mono-N-functionalized macrocyclic complexes <TEX>$[ML^2]^{2+}$</TEX> (M = Ni(II) or Cu(II); <TEX>$L^2$</TEX> = 2-cyanomethyl-5,16-dimethyl-2,6,13,17-tetraazatricyclo[<TEX>$16.4.0.0^{7.12}$</TEX>]docosane) can be prepared by the reaction of <TEX>$L^{11}$</TEX> with nickel(II) or copper(II) ion in acetonitrile. The N-<TEX>$CH_2CN$</TEX> group attached to <TEX>$[ML^2]^{2+}$</TEX> readily reacts with water or methanol to yield the corresponding complexes of <TEX>$HL^3$</TEX> bearing one N-<TEX>$CH_2CONH_2$</TEX> pendant arm or <TEX>$L^4$</TEX> bearing one <TEX>$N-CH_2C(=NH)OCH_3$</TEX> group. The <TEX>$N-CH_2CONH_2$</TEX> or <TEX>$N-CH_2C(=NH)OCH_3$</TEX> group of each complex is coordinated to the central metal ion. Both <TEX>$[NiL^4(H_2O)]^{2+}$</TEX> and <TEX>$[CuL^4]^{2+}$</TEX> are quite stable in acidic aqueous solutions, but undergo hydrolysis to yield <TEX>$[Ni(HL^3)(H_2O)]^{2+}$</TEX> or <TEX>$[Cu(HL^3)]^{2+}$</TEX> in basic aqueous solutions. In contrast to <TEX>$[Cu(HL^3)]^{2+}$</TEX>, <TEX>$[Ni(HL^3) (H_2O)]^{2+}$</TEX> is readily deprotonated to form <TEX>$[NiL^3 (H_2O)]^+$</TEX> (<TEX>$L^3$</TEX> = a deprotonated form of <TEX>$HL^3$</TEX>) in basic aqueous solutions.

A computer simulation of the uracil hydrate mechanism for the photochemically induced deamination of free cytosine base in aqueous solution

Trans and gauche conformational equilibria in the side chains of aspartic acid (Asp) and asparagine (Asn) were investigated by measuring the vicinal spin−spin coupling constants of 1H NMR in acidic, neutral, and basic aqueous solutions over a wide range of temperature (5−90 °C). The standard free-energy changes ΔG0 were obtained for the trans to gauche conformational variations on the Cα−Cβ bond with respect to the α-carboxyl group and the β-carboxyl group in Asp (β-amide in Asn) and were decomposed into enthalpic ΔH0 and entropic −TΔS0 components. The hydration of ionic and polar groups in Asp competes against the large intramolecular electrostatic repulsion energy and stabilizes the gauche more than the trans conformer in correspondence to a larger degree of separation of positive and negative partial charges. In the neutral solutions, where both the carboxyl groups are negatively ionized, the hydration part even overwhelms the intramolecular repulsion and leads to a negative ΔH0. The fact that the hydr...

Change in reactivity of differently capped AuPd bimetallic nanoparticle catalysts for selective oxidation of aliphatic diols to hydroxycarboxylic acids in basic aqueous solution

Photochemistry of 3,4,9,10-perylenetetracarboxylic dianhydride dyes: visible absorption and fluorescence of the di(glycyl)imide derivative monomer and dimer in basic aqueous solutions

Rapid synthesis of submicron crystalline barium zirconate BaZrO 3 by precipitation in aqueous basic solution below 100 °C