Xn:Harmful;
141-82-2Relevant articles and documents
Investigation of Radical Reactions Important in the Gyoergyi-Turanyi-Field Model of the Belousov-Zhabotinskii Reaction
Foersterling, Horst-Dieter,Stuk, Linda
, p. 7320 - 7325 (1991)
In the Gyoergyi-Turanyi-Field (GTF) model of the Belousov-Zhabotinskii (BZ) reaction, malonyl radicals (MA.) and bromomalonyl radicals (BrMA.) are assumed to be important intermediates.The hydrogen abstraction reactions MA. + BrMA -> MA + BrMA. (a) and BrMA. + MA -> BrMA + MA. (b) (MA, malonic acid; BrMa, bromomalonic acid) transfer from free-radical nature of the malonyl species to the bromomalonyl species and vice versa.The rates of these two reactions determine in part the relative importance of these radical intermediates.Another key radical reaction is BrMA. + Ce4+ + H2O -> BrTTa + Ce3+ (c) (BrTTA, bromotartronic acid), which is a source of Br- through decomposition of BrTTA in the model.It has been deduced from ESR and spectrophotometric experiments that reactions a-c do not contribute to the chemistry of the BZ reaction.Numerical integration of the GTF rate equations, omitting reactions a-c, shows no oscillation in BZ systems with high initial concentrations of BrMA.Experimentally, these systems exhibit oscillations with no induction period.
An unusual acylated malvidin 3-glucoside from flowers of Impatiens textori Miq. (Balsaminaceae)
Tatsuzawa, Fumi,Saito, Norio,Mikanagi, Yuki,Shinoda, Koichi,Toki, Kenjiro,Shigihara, Atsushi,Honda, Toshio
, p. 672 - 674 (2009)
Acylated malvidin 3-glucoside was isolated from the purple flowers of Impatiens textori Miq. as a major anthocyanin component along with malvidin 3-(6″-malonyl-glucoside). Its structure was elucidated to be malvidin 3-O-[6-O-(3-hydroxy-3-methylglutaryl)-β
Exploring the Promiscuous Enzymatic Activation of Unnatural Polyketide Extender Units in Vitro and in Vivo for Monensin Biosynthesis
Grote, Marius,Schulz, Frank
, p. 1183 - 1189 (2019)
The incorporation of new-to-nature extender units into polyketide synthesis is an important source for diversity yet is restricted by limited availability of suitably activated building blocks in vivo. We here describe a straightforward workflow for the biogenic activation of commercially available new-to-nature extender units. Firstly, the substrate scope of a highly flexible malonyl co-enzyme A synthetase from Streptomyces cinnamonensis was characterized. The results were matched by in vivo experiments in which the said extender units were accepted by both the polyketide synthase and the accessory enzymes of the monensin biosynthetic pathway. The experiments gave rise to a series of predictable monensin derivatives by the exploitation of the innate substrate promiscuity of an acyltransferase and downstream enzyme functions.
Diverse structural assemblies of a series of ninhydrin derivatives: Quantitative analyses from experimental and theoretical studies
Hundal, Geeta,Kapoor, Kamal K.,Mahajan, Sheena,Saini, Yeshwinder,Seth, Saikat Kumar
, (2021)
Three ninhydrin derivatives (2–4) have been synthesized where the reaction of ninhydrin with Meldrum's acid yielded [3.3.3] propellanoid (2) and ethyl 2,2-bis (1,3-dioxo-2,3-dihydro-1H-inden-2-yl)acetate (3) while with malononitrile yielded a spiroindenopyran (4). The products being crystalline in nature and are characterized by single crystal X-ray diffraction in addition to other spectroscopic studies. X-ray crystallography reveals that solid-state structure of the title compounds exhibits C?H···π, π?π and lone-pair(l.p)···π interactions in building supramolecular assemblies. Indeed, compound (2) was stabilized through extended supramolecular C?H···π/π?π/π···H?C network whereas compounds (3) and (4) are stabilized through lone-pair (l.p)···π and π?π interaction respectively. The diverse intermolecular interactions via Hirshfeld surface analysis enables quantitative contributions to the crystal packing that exposes the similarities and differences in the interactions experienced by each compound. The distinctive energy frameworks have been calculated for individual molecules and the interaction energies suggest that the contacts are largely dispersive in nature. The binding energies associated with the non-covalent interactions observed in the crystal structures have been calculated using theoretical DFT calculations. Finally, the interplay between the interactions have been characterized by Bader's theory of “atoms-in-molecules” (AIM).
Kinetic modeling of malonylgenistin and malonyldaidzin conversions under alkaline conditions and elevated temperatures
Vaidya, Nirupama A.,Mathias, Kevin,Ismail, Baraem,Hayes, Kirby D.,Corvalan, Carlos M.
, p. 3408 - 3413 (2007)
The conversion and degradation of malonylglucosides were kinetically characterized under elevated pH/heat conditions. Malonylgenistin and malonyldaidzin were heated at 60, 80, and 100°C and pH values of 8.5, 9, and 9.5. A simple kinetic model was developed, which adequately predicted the conversion and degradation reactions. The conversion and degradation rates increased as temperature and pH increased. The rates of conversion of both malonylglucosides into their respective β-glucosides were comparable under all pH/heat treatments. However, at 100°C, the rates of degradation of malonyldaidzin were approximately double those of malonylgenistin, under all pH treatments. When malonlydaidzin was heated at 100°C and pH 9.5, degradation of the produced daidzin occurred. Therefore, an alternative kinetic model was developed to better predict the conversion and degradation of malonyldaidzin occurring at 100°C and pH 9.5. The models developed provide soy food manufacturers with guidelines for better control of the profile and level of isoflavones.
Design of bisquinolinyl malonamides as Zn2+ ion-selective fluoroionophores based on the substituent effect
Moriuchi-Kawakami, Takayo,Kawata, Keita,Nakamura, Sho,Koyama, Yoshiaki,Shibutani, Yasuhiko
, p. 9805 - 9813 (2014)
A series of malonamides possessing two quinoline moieties were synthesized and characterized as fluoroionophores for the Zn2+ ion. We focused on the relationship between the substituents introduced to the C2-position of the malonamides and their Zn2+ ion-selectivity, exploiting the structural effect of the substituents in the design of the fluoroionophores with high selectivity. The substituents introduced to the malonamides were the methyl, benzyl and naphthalenylmethyl groups. In dimethyl sulfoxide solvent, all substituted bisquinolinyl malonamides showed excellent fluorescence sensing for the Zn2+ ion, while unsubstituted bisquinolinyl malonamide 1 displayed ratiometric sensing for the Co2+ ion. N,N′-Bis(8-quinolyl)-2-methyl-2-naphthalenylmethyl malonamide 4 exhibited the highest Zn2+ ion-selectivity against the Cd2+ ion. Although the substituents introduced into the C2-position are spatially distant from the quinoline recognition moiety, this study indicated that they greatly influenced the ion selectivities of the bisquinolinyl malonamides. Furthermore, it was demonstrated that visible fluorescence analyses could be performed on malonamide 4.
Sengupta
, p. 298 (1969)
Degradation of 2,5-dihydroxy-1,4-benzoquinone by hydrogen peroxide under moderately alkaline conditions resembling pulp bleaching: A combined kinetic and computational study
Hosoya, Takashi,Rosenau, Thomas
, p. 11194 - 11203 (2013)
2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the mechanism of H2O2 degradation of DHBQ under conditions relevant to pulp bleaching (3.0% H2O2, NaOH, pH 10), to obtain insights useful for improved pulp processing. DHBQ is degraded quantitatively into malonic acid with an activation energy (Ea) of 16.1 kcal/mol and activation entropy (ΔaS) of ～28 cal/mol·K. Higher concentrations of sodium cations increase the reaction rate. Theoretical computations indicate the formation of an intermediate IO having an O-O bridge between C-2 and C-5 of the 1,4-cyclohexadione structure. IO undergoes O-O homolysis to form a biradical Bt, which is fragmented into malonate anions. The calculated Ea (17.8 kcal/mol) agrees well with the experimental one. Coordination of Na+ to IO and Bt decreases their energies and enhances the O-O homolysis rate, which is consistent with the acceleration by sodium cation and the negative ΔaS. The homolysis of IO is much favored over that of the neutral counterpart, with the unpaired electrons of Bt being stabilized by the geminal anionic oxygen. This difference in the stability of the intermediates translates into significant variations in the reaction rate and the product distribution between pH 10 and neutral/acidic conditions.
Single particle analysis of secondary organic aerosols formed from 1,4-cyclohexadiene ozonolysis using a laser-ionization single-particle aerosol mass spectrometer
Narukawa, Masahiro,Matsumi, Yutaka,Matsumoto, Jun,Takahashi, Kenshi,Yabushita, Akihiro,Sato, Kei,Imamura, Takashi
, p. 120 - 126 (2008)
Real-time analysis of secondary organic aerosol (SOA) particles formed from 1,4-cyclohexadiene (CHD) ozonolysis in a smog chamber was performed using a laser-ionization single-particle aerosol mass spectrometer (LISPA-MS). The instrument can be used to obtain both the size and chemical compositions of individual aerosol particles with a high time-resolution (≈2 s at the maximum). Both positive- and negative-ion mass spectra can be obtained by changing the voltage polarity of the instrument. The negative-ion spectra of the SOA particles provided important information about the chemical compositions of the SOA particles. In the negative-ion spectra, intense mass peaks were determined to correspond to ions with carboxyl and aldehyde groups. The signal intensities of the intense mass peaks from compounds with carboxyl groups were higher than those from compounds with aldehyde groups as a function of the particle size. The peaks suggest that the SOA particles contain more oxygenated organic compounds as the particle size increases, namely, the chemical compositions of the SOA particles vary as a function of the particle size. We demonstrated that the real-time single-particle analysis of SOA particles by using the LISPA-MS technique can be used to clarify the formation and transformation processes of SOA particles in smog chambers.
Hydrolysis of amides to carboxylic acids catalyzed by Nb2O5
Siddiki,Rashed, Md. Nurnobi,Touchy, Abeda Sultana,Jamil, Md. A. R.,Jing, Yuan,Toyao, Takashi,Maeno, Zen,Shimizu, Ken-Ichi
, p. 1949 - 1960 (2021/03/26)
Hydrolysis of amides to carboxylic acids is an industrially important reaction but is challenging due to the difficulty of cleaving the resonance stabilized amidic C-N bond. Twenty-three heterogeneous and homogenous catalysts were examined in the hydrolysis of acetamide. Results showed that Nb2O5was the most effective heterogeneous catalyst with the greatest yield of acetic acid. A series of Nb2O5catalysts calcined at various temperatures were characterized and tested in the hydrolysis of acetamide to determine the effects of crystal phase and surface properties of Nb2O5on catalytic performance. The high catalytic performance observed was attributed mainly to the facile activation of the carbonyl bond by Lewis acid sites that function even in the presence of basic inhibitors (NH3and H2O). The catalytic studies showed the synthetic advantages of the present method, such as simple operation, catalyst recyclability, additive free, solvent free, and wide substrate scope (>40 examples; up to 95% isolated yield).
Ozonolysis of α-angelica lactone: a renewable route to malonates
Dell’Acqua, Andrea,Stadler, Bernhard M.,Tin, Sergey,Wille, Lukas,de Vries, Johannes G.
supporting information, p. 10524 - 10527 (2021/10/19)
Industrially relevant intermediates such as malonic acid, malonates and 3-oxopropionates can be easily accessed by ozonolysis of α-angelica lactone, derived from the platform chemical levulinic acid. The roles of the solvent and of the quenching conditions are of key importance for the outcome of the reaction.
