F:Flammable;
78-84-2Relevant articles and documents
Marine natural products: highly functionalized steroids (12β-hydroxy-24-norcholesta-1,4,22-trien-3-one and 12β-acetoxy-24-norcholesta-1,4,22-trien-3-one) from sea raspberry, Gersemia rubiformis
Kingston, John F.,Fallis, Alex G.
, p. 820 - 824 (1982)
Two new C26 steroid Δ1,4-dien-3-ones 5 and 6 wit 12β oxygen functions have been isolated from the soft coral Gersemia rubiformis and their structures elucidated from their spectral data and chemical transformations.
Kinetic and mechanistic study of the oxidative deamination and decarboxylation of L-valine by alkaline permanganate
Harihar, Abdulazizkhan L.,Kembhavi, Mohammadsaleem R.,Nandibewoor, Sharanappa T.
, p. 739 - 748 (2000)
The kinetics of the oxidation of L-valine, (L-Val) by permanganate in aqueous alkaline medium at a constant ionic strength of 0.50 mol · dm-3 was studied spectrophotometrically. The reaction is of first order in [permanganate ion] and of fractional order in both [L-Val] and [alkali]. Addition of products has no significant effect on the reaction rate. However, increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation process in alkaline medium has been shown to proceed via two paths, one involving the interaction of L-valine with permanganate ion in a slow step to yield the products, and the other path the interaction of alkali with permanganate ion to give manganate. Some reaction constants involved in the mechanism were determined; calculated and observed rate constants agree excellently. The activation parameters were computed with respect to the slow step of the mechanism.
Catalytic dehydration of 2,3-butanediol over P/HZSM-5: Effect of catalyst, reaction temperature and reactant configuration on rearrangement products
Zhao, Jinbo,Yu, Dinghua,Zhang, Wengui,Hu, Yi,Jiang, Ting,Fu, Jie,Huang, He
, p. 16988 - 16995 (2016)
As a type of important bio-based vicinal diol, 2,3-butanediol could be transformed into methyl ethyl ketone and 2-methyl propanal through a pinacol rearrangement mechanism under acid catalysis conditions. In this paper, a series of P/HZSM-5 (Si/Al = 360) samples with various phosphate contents were prepared and tested via the catalytic transformation of 2,3-butanediol, with particular focus on the effect of phosphate content on the ratio of methyl ethyl ketone to 2-methyl propanal. The catalyst structures were studied using several physico-chemical methods such as XRD, N2 sorption, NH3-TPD and FT-IR. At 180 °C, the ratio of methyl ethyl ketone to 2-methyl propanal increased from 5.1 to 37.5 when the content of phosphate increased from 0.5 to 8.0. When the reaction temperature increased from 180 °C to 300 °C over 4% P2O5/HZSM-5, the ratio of methyl ethyl ketone to 2-methyl propanal decreased from 15.6 to 2.5. The configuration of 2,3-butanediol would affect the conversion but not the selectivity. The characterization results demonstrated that the phosphate modification of HZSM-5 could not only reduce the strong and medium acid sites but also produce new weak acid sites. Strong acid sites and high reaction temperatures could promote the formation of 2-methyl propanal through methyl migration via carboniums. Based on these results, a possible surface reaction model was proposed.
Efficient dehydration of bio-based 2,3-butanediol to butanone over boric acid modified HZSM-5 zeolites
Zhang, Wengui,Yu, Dinghua,Ji, Xiaojun,Huang, He
, p. 3441 - 3450 (2012)
The dehydration of bio-based 2,3-butanediol provides an alternative green way to produce butanone, which is mainly produced through the dehydrogenation of butanol in industry. In this research, the effect of the framework Si/Al ratio on 2,3-butanediol dehydration over HZSM-5 zeolites (Si/Al = 38-360) was investigated. HZSM-5(360) was further modified with boric acid, and the influence of the loading amount of boric acid on the dehydration performance was studied. The results showed that high Si/Al ratio was beneficial to low-temperature activation of 2,3-butanediol and the methyl migration to 2-methyl propanal. 1.0%B/HZSM-5(360) not only showed best performance at 180°C but also kept stable activities between 180-300°C with a high LHSV 2.4 h-1. According to the characterization results, excellent performance over HZSM-5(360) was due to the highest amount of strong acidic sites (1.1674 mmol g-1) attributed to H-bonded hydroxyl groups, normally silanols. Coexistence of more effective extraframework B-OH species and retained silanols were responsible for the promotion of catalytic performance over 1.0%B/HZSM-5(360).
Generation of Simple Enols in Aqueous Solution from Alkali Metal Enolates. Some Chemistry of Isobutyraldehyde Enol
Chiang, Y.,Kresge, A. J.,Walsh, P. A.
, p. 6314 - 6320 (1986)
The enol isomer of isobutyraldehyde was generated in aqueous solution by reaction of its lithium and potassium enolates with water and of the trimethylsilyl enol ether with fluoride ion, and rates of ketonization of the enol were measured in HCl, DCl (in D2O), and NaOH solutions and in CNCH2CO2H, HCO2H, CH3CO2H, CH2ClPO3H-, and H2PO4- buffers.Rates of enolization of isobutyraldehyde were also determined, by iodine scavenging, in HClO4 and NaOH solutions.The reaction rates in HCl and NaOH give two independent estimates of the keto-enol equilibrium constant for isobutyraldehyde in aqueous solution at 25 deg C, which are in good agreement with each other and whose average is KE = (1.37 +/- 0.09)*1E-4, pKE = 3.86 +/- 0.03.The ketonization rates in NaOH solution also provide an estimate of the acidity constant of isobutyraldehyde enol ionazing as an oxygen acid, KaE = (2.37 +/- 0.14)*1E-12 M, pKaE = 11.63 +/- 0.03, which, when combined with KE, gives the acidity constant of the keto form of isobutyraldehyde ionizing as a carbon acid, KaK = (3.23 +/- 0.29)*1E-16 M, pKaK = 15.49 +/- 0.04.The ketonization reaction in buffer solutions shows both general-acid and general-base catalysis, consistent with two parallel reaction paths involving rate-determing β-carbon protonation of both enol and enolate ion.Analysis of the data in terms of this scheme shows enolate to be 1E8 times more reactive than enol.Arguments are advanced to the effect that all of the present data are consistent with stepwise reaction mechanisms and do not require a concerted reaction path.
Ti-SBA-15 supported Cu-MgO catalyst for synthesis of isobutyraldehyde from methanol and ethanol
Zhang, Junfeng,Wu, Yingquan,Li, Li,Wang, Xiaoxing,Zhang, Qingde,Zhang, Tao,Tan, Yisheng,Han, Yizhuo
, p. 85940 - 85950 (2016)
Ti-SBA-15 supported Cu and MgO catalysts were prepared and used for the first time in the one-step conversion of methanol and ethanol to isobutyraldehyde (IBA). The results show that the loadings of Cu and MgO, and catalyst calcination temperature have strong effects on the catalyst activity. A high yield of IBA, 32.7%, and high ethanol conversion, 96.6%, were achieved at 360 °C with WHSV of 3.0 mL (g-1 h-1) on the catalyst calcined at 400 °C when the loadings of Cu and Mg were 20.0 wt% and 6.5 wt%, respectively. The physicochemical properties of the catalysts were analyzed by various techniques including XRD, N2 adsorption and desorption, FT-IR, H2-TPR, CO2-TPD and XPS. The ordered mesoporous structure of the catalysts was retained with the introduction of CuO and MgO. The size of CuO particles on the catalysts was retained though they suffered from a varied calcination temperature. H2-TPR measurements revealed that the increase of calcination temperature from 400 °C to 700 °C resulted in the decrease of basicity of the catalysts, and enhanced the interaction between the Cu and Mg species and the support. The results from XPS analysis indicated that the binding energy of Cu 2p was increased with the introduction of MgO, while the increased calcination temperature easily resulted in the decrease of Cu content on the catalyst surface due to probable migration of Cu species into internal pores or their incorporation into the framework of the Ti-SBA-15 support.
Os(VIII)/Ru(III) catalysed oxidation of l-valine by Ag(III) periodate complex in aqueous alkaline medium: A comparative kinetic study
Malode, Shweta J.,Shetti, Nagaraj P.,Nandibewoor, Sharanappa T.
, p. 1526 - 1540 (2011)
The kinetics of osmium(VIII) (Os(VIII)) and ruthenium(III) (Ru(III)) catalysed oxidation of l-valine (l-val) by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at 25 °C and a constant ionic strength of 0.006 mol dm-3 was studied spectrophotometrically. The stoichiometry is the same in both the catalysed reactions, i.e., [l-val]:[DPA] = 1:1. The reaction is of first order in [Os(VIII)], [Ru(III)], and [DPA] and has less than unit order in [l-val] and negative fractional order in [OH-]. Added periodate had no effect on rate of reaction. The products were identified by spot test and characterized by spectral studies. The catalytic constant (K C) was also calculated for both catalysed reactions at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed and thermodynamic quantities were also determined. It has been observed that the catalytic efficiency for the present reaction is in the order of Os(VIII) > Ru(III). The probable active species of catalyst and oxidant have been identified. Graphical Abstract: The kinetics of osmium(VIII) (Os(VIII)) and ruthenium(III) (Ru(III)) catalysed oxidation of l-valine (l-val) by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at 25 °C and a constant ionic strength of 0.006 mol dm-3 was studied spectrophotometrically. Suitable mechanisms were proposed and active species of DPA, Os(VIII) and Ru(III) were identified. The main products were identified and characterized by spectral studies.
Kinetics of oxidation of L-valine by a copper(III) periodate complex in alkaline medium
Sharanabasamma,Angadi, Mahantesh A.,Salunke, Manjalee S.,Tuwar, Suresh M.
, p. 187 - 199 (2012)
The kinetics of oxidation of L-valine by a copper(III) periodate complex was studied spectrophotometrically. The inverse second-order dependency on [OH-] was due to the formation of the protonated diperiodatocuprate(III) complex ([Cu(H3IO6) 2]-) from [Cu(H2IO6) 2]3-. The retarding effect of initially added periodate suggests that the dissociation of copper(III) periodate complex occurs in a pre-equilibrium step in which it loses one periodate ligand. Among the various forms of copper(III) periodate complex occurring in alkaline solutions, the monoperiodatocuprate(III) appears to be the active form of copper(III) periodate complex. The observed second-order dependency of [L-valine] on the rate of reaction appears to result from formation of a complex with monoperiodatocuprate(III) followed by oxidation in a slow step. A suitable mechanism consistent with experimental results was proposed. The rate law was derived as: (Equation presented) The temperature effect on the rate of reaction was also studied. The activation parameters of the reaction Ea, ΔH#, ΔS#, ΔG#, and log 10 A are 49 ± 2 kJ·mol-1, 47.5 ± 2 kJ·mol-1, -49 ± 2 J·K -1·mol-1, 62 ± 3 kJ·mol-1 and 6.0 ± 0.1, respectively. Springer Science+Business Media, LLC 2012.
Detailed structure-function correlations of bacillus subtilis acetolactate synthase
Sommer, Bettina,Von Moeller, Holger,Haack, Martina,Qoura, Farah,Langner, Clemens,Bourenkov, Gleb,Garbe, Daniel,Loll, Bernhard,Brück, Thomas
, p. 110 - 118 (2015)
Isobutanol is deemed to be a next-generation biofuel and a renewable platform chemical.[1] Non-natural biosynthetic pathways for isobutanol production have been implemented in cell-based and in vitro systems with Bacillus subtilis acetolactate synthase (AlsS) as key biocatalyst.[2-6] AlsS catalyzes the condensation of two pyruvate molecules to acetolactate with thiamine diphosphate and Mg2+ as cofactors. AlsS also catalyzes the conversion of 2-ketoisovalerate into isobutyraldehyde, the immediate precursor of isobutanol. Our phylogenetic analysis suggests that the ALS enzyme family forms a distinct subgroup of ThDP-dependent enzymes. To unravel catalytically relevant structure-function relationships, we solved the AlsS crystal structure at 2.3 ? in the presence of ThDP, Mg2+ in a transition state with a 2-lactyl moiety bound to ThDP. We supplemented our structural data by point mutations in the active site to identify catalytically important residues.
Oxidation of propylene and isobutylene in a reactor with barrier discharge
Kudryashov,Ryabov,Sirotkina,Shchegoleva
, p. 1904 - 1906 (2004)
The oxidation of propylene and isobutylene in barrier-discharge plasma in the presence of octane was studied. The possible reaction mechanism was considered.
