“Urea oxalic acid” is not parabanic acid

We prove that the recently published “urea oxalic acid” is not parabanic acid but is in fact the well-known bis-urea oxalic acid. Hence the paper by Jeeva et al. [1] is completely erroneous.     

The bending-rotation spectrum of fulminic acid and deuterofulminic acid

A quasilinear molecular model is needed to account for the infrared absorption spectrum of HCNO and DCNO in the spectral region from 100 cm^?1 to 1000 cm^?1. The observed systems of infrared bands arising from the ν₅ vibrational manifold have all been assigned. The rotational structure of the absorption bands at 225 cm^?1, 275 cm^?1, 315 cm^?1, and 317 cm^?1 for HCNO has been resolved using a Fourier spectrometer. The rotational constants and the band centers have been determined for the above bands, which represent the transitions(0000⁰1¹)_c←0000⁰0⁰(0000⁰2²)_c,d←(0000⁰1¹)_c,dboth components(0000⁰3³)_c,d←(0000⁰2²)_c,d0000⁰2⁰←(0000⁰1¹)_c.By means of the Ritz combination principle the infrared transitions could be used to build up the vibrational energy level scheme of the ν₅ vibrational mode for HCNO and DCNO. The data are only reconcilable with a potential function for ν₅ which exhibits a low barrier opposing linearity. Preliminary values of the potential parameters were obtained using different approximate theoretical approaches.A reinterpretation of the r₈ structure parameters of fulminic acid in the light of the quasilinear model leads to an explanation of the extraordinarily short CH internuclear distance of 1.027 Å as the projection of a CH bond length of 1.060(5) Å upon the heavy-atom axis.The isotopic shift upon deuteration observed in the infrared data indicate that the ν₅ fundamental vibration is primarily an HCN bending motion. The ν₄ fundamental vibration (skeletal bending motion) of HCNO is located at 537 cm^?1 and does not exhibit any hot band structure which would be indicative of a perturbed potential function.     

Self-assembly of 5-octadecyloxyisophthalic acid and its coadsorption with terephthalic acid

The structure of the self-assembled monolayer of pure 5-octadecyloxyisophthalic acid (5OIA), and the coadsorption monolayer of 5OIA and terephthalic acid, is investigated using scanning tunneling microscopy (STM) at the liquid-solid interface. 5OIA self-assembles into a monolayer comprised of different structures. For the major phase, 5OIA molecules alternately pack with opposite enantiotopic faces in a lamella, giving lamellae with a chain-to-trough angle of ∼88°. Two adjacent lamellae are assembled together by a hydrogen-bonding network between two carboxylic acid groups from each lamella. In the self-assembled monolayer of the mixture solution of 5OIA and terephthalic acid, 5OIA molecules coadsorb with terephthalic acid and therefore form two stoichiometric multi-component domains. Each domain has a molar ratio of 2:1 for 5OIA and terephthalic acid. For each component (5OIA or terephthalic acid), the two coadsorption structures exhibit opposite chirality.     

Moving single bubble sonoluminescence in phosphoric acid and sulphuric acid solutions

The phenomenon of sonoluminescence still presents some unsolved aspects. Recently [Y.T. Didenko, K. Suslick, Molecular Emission during Single Bubble Sonoluminescence, Nature 407 (2000) 877-879.], it was found that a single cavitating air bubble in polar aprotic liquids (including formamide and adiponitrile) can produce very strong sonoluminescence while undergoing macroscopic translation movements in the resonator, a condition known as moving single bubble sonoluminescing (MSBSL). Here we describe some experiments conducted in aqueous solutions of phosphoric and sulphuric acid. In these liquid media, it is possible to reproduce MSBSL and luminescence is emitted even if a trapped bubble is subjected to a strong shape instability, named in the literature "jittering phase". When a moving and luminescing bubble was present and the acoustic pressure gradually increased, we observed the generation of a discrete lattice of trapped bubbles. The bubbles in the lattice emit very intense light flashes and can change their position while maintaining the overall spatial distribution in time. Some preliminary results, obtained from Mie-scattering and measurements of relative light intensity, are reported.     

Ultrasound-assisted extraction of oleanolic acid and ursolic acid from Ligustrum lucidum Ait

Oleanolic acid and ursolic acid are the main bioactive compounds in fruit of Ligustrum lucidum Ait, which possess anti-inflammatory, antioxidative, antiprotozoal, antimutagenic and anticancer properties. In this study, the ultrasound-assisted extraction of oleanolic acid and ursolic acid from L. lucidum Ait was investigated with HPLC-photodiode array detection. Effects of several experimental parameters, such as type and concentration of extraction solvent, ratio of liquid to material, extraction temperature and extraction time, on extraction efficiencies of oleanolic acid and ursolic acid from L. lucidum were evaluated. The influence of experimental parameters on extraction efficiency of ursolic acid was more significant than that of oleanolic acid. The optimal extraction conditions were 95% ethanol, the ratio of material to liquid at 1:20, and extraction for 10 min at 40 °C under ultrasonic irradiation. Under the optimal conditions, the yields of oleanolic acid and ursolic acid were 6.3 ± 0.25 and 9.8 ± 0.30 mg/g, respectively. The results indicated that the ultrasound-assisted extraction is a very useful method for the extraction of oleanolic acid and ursolic acid from L. lucidum.     

Sensitive femtosecond coherent anti-Stokes Raman spectroscopy discrimination between dipicolinic acid and dinicotinic acid

We demonstrate that femtosecond ultraviolet and visible coherent anti-Stokes Raman spectroscopy provides the sensitivity and specificity needed to distinguish between two similar molecules of pyridinedicarboxylic acid. The Fourier transforms of the temporal measurements provide the energy difference between the ground state vibrational modes. Quantum chemical calculations provide theoretical predictions that agree well with the measurements. The present technique allows us to distinguish 10 cm(-1) frequency shifts by using pulses ten times broader than the shifts.     

Synthesis of glycyrrhetinic acid monoglycoside by hydrolysis of glycyrrhizic acid in subcritical water

A method for the synthesis of glycyrrhetinic acid monoglycoside by hydrolysis of glycyrrhizic acid in subcritical water at temperatures ranging between 100 and 300°C is under development. The maximum yield of the target product is achieved at 160°C.     

Electron spin relaxation of radicals in γ-irradiated malonic acid and methyl malonic acid

Radicals generated by γ-irradiation of malonic acid and methyl malonic acid were studied as a function of temperature by inversion recovery, echo-detected saturation recovery and electron-electron double resonance (ELDOR) at X-band, and by continuous-wave saturation recovery at X-band and S-band. ELDOR reductions for malonic acid radical in polycrystalline and single-crystal samples indicate that nuclear spin relaxation is faster than both electron spin relaxation and cross relaxation between 93 and 233 K. Deuteration of the carboxylate protons caused the maximum ELDOR reduction to shift from about 110 to 150 K, consistent with the assignment of the rapid nuclear spin relaxation to hydrogen-bonded proton dynamics. ELDOR enhancements for both radicals formed in methyl malonic acid indicate that cross relaxation is faster than both electron spin relaxation and nuclear spin relaxation between 77 and 220 K. Enhanced cross relaxation and electron spin relaxation are attributed to the rotation of methyl groups at a rate comparable to the electron Larmor frequency. The temperature dependence of the enhancement of 1/T _1e was analyzed to determine the activation energies for methyl rotation. The same radical is formed in irradiated methyl malonic acid and L-alanine, but the barrier to rotation of the α-methyl is 500 K in the methyl malonic acid host and 1500 K in the L-alanine host, which indicates a large impact of the lattice on the barrier to rotation.     

Vibrational study of squaric acid

Infrared and Raman spectra of polycrystalline squaric acid and its deuterated derivative have been investigated at various temperatures in the 3600–30 cm^-1 range. Two infrared active lattice modes have been identified at 230 and 125 cm^?1 in the spectra at room temperature phase. A new assignment of some intramolecular vibrations involving OH and CO group is proposed. The behaviour of intramolecular and lattice bands as a function of temperature and phase transition is discussed.     

Torsional coupling in pyruvic acid

New assignments of rotational transitions in the first excited state of the skeletal torsion were made and showed an unexpected interchange in the sequence of energy levels for the internal rotation of the methyl group. This fact is traced back to a strong coupling between the skeletal torsion and the methyl torsion. A two dimensional flexible model for torsional motion was developed which could account for the observations. The model includes structural relaxation and torsional potential energy coupling and allowed successful prediction and further assignments of transitions in the second excited state of the skeletal torsion.     

Multi-bubble sonoluminescence of phosphoric acid

Multi-bubble sonoluminescence spectra of 85% H₃PO₄ and the dependences of sonoluminescence intensity on the acid concentration and temperature are obtained. The spectra contain a weakly structured 300–600-nm band formed by the superposition of radiation from several emitters (presumably, oxygencontaining products of acid sonolysis, viz., PO, HOPO, and PO₂). Weak luminescence at a wavelength exceeding 600 nm can be due to emission from excited O* and Ar* atoms. The shape of the fundamental band changes upon a transition from multi-bubble sonolysis to sonolysis in the setup for one-bubble sonoluminescence, in which several clusters of cavitation bubbles are formed in a spherical flask at ultrasonic frequencies multiple of the first acoustic resonance frequency (multi-cluster sonoluminescence). The form of the temperature dependence of the sonoluminescence intensity depends on the detection regime: for natural heating of 85% acid under the action of ultrasound, a curve with a luminescence peak at 40°C is observed, while in detection with preliminary thermostating “over points,” only an inflection exists on a monotonic curve describing a decrease of intensity upon heating. An analogous curve for acids with a lower viscosity (hydrochloric and nitric acids) has neither a peak nor inflection irrespective of the detection regime. It is concluded that the viscosity of phosphoric acid plays a decisive role in the evolution of cavitation and in obtaining intense sonoluminescence.     

Electron-impact fragmentation of ascorbic acid

The processes of ascorbic acid total and dissociative ionization by 6 to 100 eV electrons in the temperature interval 360–460 K are studied with an MX-7304A monopole mass spectrometer. A scheme of ascorbic acid fragmentation due to electron-impact-induced ionization is suggested, and possible channels of producing the most intense fragment ions in the mass spectrum are indicated. The energy dependences and thresholds of fragment ion formation are determined for the first time in the incident electron energy range 7–30 eV.     

Sonophotocatalysis of oxalic acid solution

Sonophotocatalysis of oxalic acid was performed in various atmospheric conditions. Sonophotocatalysis means a coupled reaction of sonolysis and photocatalysis. CO(2), CO and H(2) were obtained. The yield of CO(2) was twice larger than the sum of yields of photocatalysis and sonolysis in an Ar atmosphere. Namely, synergistic effect was observed. Further improvement was observed after pre-sonication. Hydrogen peroxide produced during sonication is a key material for the synergistic effect. In surroundings including O(2), however, synergistic effect could not be observed. The role of ultrasonic waves on the sonophotocatalysis of organic compounds was investigated.     

硝酸溶液的超声研究

用自动化脉冲回波声速测量仪测量了重量百分比浓度范围为20%~99%的硝酸在不同温度时的超声波速度。计算得诸如摩尔声速、声阻抗、绝热压缩系数、分子间自由程以及纯HNO₃液体的声速等参数,另外还推算出超额声速、超额摩尔体积、超额绝热系数、超额分子间自由程等参数。结果显示,随着硝酸浓度的增加,溶液中的离子间相互作用可能存在着先增加尔后又减小的现象。     

Conversion of a weak organic acid to a super acid in the gas phase

The effects of selected metal ions on the gas‐phase acidity of weak organic acids have been explored using the DFT and Moller–Plesset Perturbation Theory (MP2) calculations. The three organic acids selected for this study were acetic acid (aliphatic), benzoic acid (aromatic), and glycine (amino acid). The acidities of these compounds are compared with the acidity of their Li⁺‐, Na⁺‐, and K⁺‐complexed species. The results indicate that upon complexation with Li⁺, Na⁺, and K⁺ at 298 K, the gas‐phase acidity of acetic acid, for example, varies from 345.3 to 218.8, 230.2, and 240.1 kcal/mol, respectively (i.e., its dissociation becomes much less endothermic). These values indicate that a weak organic acid can be converted to a super acid when it is complexed with an ionic metal. Copyright © 2007 John Wiley & Sons, Ltd.     

Mössbauer study of some metal chelates of salicylhydroxamic acid and benzohydroxamic acid

Mössbauer study of Fe(II) chelates of Benzohydroxamic (BHA)-, Salicylhydroxamic (SHA)-, and 5-Nitrosalicylhydroxamic (5NSHA)-acids has been carried out. The observed quadrupole splitting in the three complexes indicate that distortion from octahedral symmetry is maximum in case of Fe(II)-SHA, thus, suggesting the involvement of phenolic-OH of SHA moiety in the formation of chelate. The isomer shift was found to vary in sequence SHA>5NSHA >BHA, indicating that σ and or π bonding is stronger in Fe(II)-BHA.     

Raman study of squaric acid

Raman spectra of squaric acid have been measured at various temperatures below and above the transition temperature. Six low frequency bands below 300 cm^?1 are assigned to translational and librational modes of the squaric molecule on the basis of the recent crystal determination by X-ray diffraction. A discussion is given of the striking temperature dependence of these external modes in the ordered phase in connection with the phase transition.     

Ultrasonic study of nitric acid

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