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Bacterial Polyesters and Their Models Obtained by Ring-Opening Polymerization of β-Lactones
Published in Stanislaw Penczek, H. R. Kricheldorf, A. Le Borgne, N. Spassky, T. Uryu, P. Klosinski, Models of Biopolymers by Ring-Opening Polymerization, 2018
Alain Le Borgne, Nicolas Spassky
All catalysts used are dried prior to use. Solvents used (toluene, CHC13) are dried and distilled over P2O5 and stored over molecular sieves. Chloral is distilled (b.p. 96°C/765 mmHg) under N2 and stored at – 25°C. Ketene is prepared by pyrolysis of acetone vapors in an apparatus described by Williams and Hurd.86 Residual acetone vapors are removed as thoroughly as possible by cooling the vapors to — 40°C (ketene b.p. — 42°C). No further purification of the ketene is performed. With the equipment used, after 45 to 60 min, about 0.01 mol of ketene is formed, as established by leading ketene through an aniline solution and isolating acetanilide formed. All chloral-ketene addition reactions are performed under an inert atmosphere of dried nitrogen.
A facile one-pot, solvent-free synthesis of new pyrazolone-1,3-dithiolan hybrids through the reaction between 2-pyrazoline-5-ones, CS2, and α-chloroacetaldehyde
Published in Journal of Sulfur Chemistry, 2022
Leila Sabahi-Agabager, Saeideh Akhavan, Farough Nasiri
Pyrazolones have a broad spectrum of biological activities such as antitumor, antibacterial, antifungal, and anti-inflammatory activities [1–3]. Aryl pyrazoles have inhibition activity against mushroom tyrosinase [4] and pyrazoles bearing C = O group have antitumor activity on bone marrow and cervix cells [5]. These heterocyclic systems are also applied in the industrial preparation of herbicides and dyes [1,2]. A literature survey shows that the biological activities of bioactive compounds are usually improved if two or more biologically active units are collected together in a single molecule [1]. Therefore, pyrazolones hybrids with different heterocycles are known to contain various chemotherapeutic effects and have found use as antimicrobial, antifungal, and antiviral agents [6,7]. In addition, sulfur-containing heterocycles that serve as biologically active molecules are in various natural compounds and drugs [8]. An efficient method for synthesis of sulfur-containing heterocyclic rings is to use ketene dithioacetals. The reaction between a carbon nucleophile and carbon disulfide form ketene dithioacetals as an important synthon in organic chemistry [9]. Lanconazole (I) and its thienyl-analog (II) with ketene dithioacetal shows significant antifungal activity [10,11]. Besides that, dithiafulvene (III) acts as a strong electron donor, and it was used [10] in dye-sensitized solar cells (Scheme 1).
Particle size distribution and chemical composition of aerosolized vitamin E acetate
Published in Aerosol Science and Technology, 2020
Vladimir B. Mikheev, Theodore P. Klupinski, Alexander Ivanov, Eric A. Lucas, Erich D. Strozier, Cory Fix
The three highly reactive posited intermediates—ATMMC, DQM, and ketene—may also be of pulmonary toxicity concern. ATMMC and DQM are quinone methides, a reactive compound class that can alkylate amino acids (Bolton, Turnipseed, and Thompson 1997) and DNA nucleosides (Lewis et al. 1996). For example, the metabolic formation of a quinone methide may be important in the pulmonary toxicity of butylated hydroxytoluene (Mizutani, Yamamoto, and Tajima 1983). Ketene is a powerful acetylating reagent (Eck 1973) that is highly toxic when inhaled (Wooster, Lushbaugh, and Redemann 1947). The putative reaction scheme in Figure 1 shows ketene formation directly as a product of ATMMC, consistent with one suggested pathway proposed by Wu and O’Shea (2020). While ketene may also be formed directly from the aryl acetates VEA (Wu and O'Shea 2020) or DHQMA, we have no evidence to support those pathways because no signals consistent with the expected concurrently generated products (vitamin E and durohydroquinone, respectively) were observed.
An Experimental and Detailed Chemical Kinetic Investigation of the Addition of C2 Oxygenated Species in Rich Ethylene Premixed Flames
Published in Combustion Science and Technology, 2019
Zisis Malliotakis, Nicolas Leplat, George Vourliotakis, Christos Keramiotis, George Skevis, Maria A Founti, Jacques Vandooren
Ketene is then consumed to the methyl radical (R23) and the ketenyl radical (R24), after being attacked by a hydrogen atom. The branching ratio of the two reactions is 3:2. Ketene levels in Flame C are substantially higher than the corresponding levels in Flames A and B due to the acetic acid decomposition path. However, ketenyl radical levels are almost equal in all three flames. This is attributed to the fact that ketenyl fast attains steady state values which are independent of its formation kinetics. Leplat and Vandooren (2012) have shown that once formed, ketene will most likely follow two decomposition paths. Either the formation of CH3 after reactions with H atoms (R23) or the formation of ketenyl. The authors showed that increasing the equivalence ratio increases the importance of reaction (R23), due to the increased availability of H atoms, causing thus an increase in the CH3 formation. This was observed in the reaction path analysis carried out showing that 30% of ketene formed CH3. In the current study the equivalence ratio is significantly higher than that of Leplat and Vandooren (2012) justifying that 60% of ketene (see Figure 6) is consumed to form CH3.Despite this augmented reaction path, the formation of methyl radical in the acetic acid flame remains at lower levels compared to the other flames where methyl is formed directly from acetaldehyde.