- Retention Characteristics and Sorption Enthalpies of Esters of Natural Hydroxycarboxylic Acids on DB-1 Stationary Phase
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Abstract: Sorption characteristics and retention of esters of glycolic, lactic, malic, and tartaric acids with C1?C8 alcohols of linear structure are studied by gas-liquid chromatography in the temperature range of 90?260°C on DB-1 nonpolar phase. The values of the retention indices of the compounds studied are obtained. On the basis of experimentally determined retention times, the thermodynamic characteristics of sorption under the conditions of limiting dilution are estimated. The dependences of the change in sorption enthalpies on the length of the linear alkyl substituent and on the value of the logarithmic retention index are found. The possibility of estimating the energy of intermolecular interactions of lactic acid esters in the liquid phase is shown on the basis of the obtained values of sorption enthalpies and vaporization enthalpies.
- Portnova,Yamshchikova, Yu. F.,Krasnykh
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p. 577 - 583
(2019/06/03)
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- Natural preservatives
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In the present invention, provided is a compound, which has good antibacterial effects and is denoted by general formula (I), or a pharmaceutical acceptable salt thereof where R1 is saturated or unsaturated straight chains or branch chains of an alkyl group in general formula (I); R2 is hydrogen, methyl or is selected from a general formula (2); and R3 is hydrogen, saturated or unsaturated straight chains or branch chains of an alkyl group, and X is hydrogen or is selected from a hydroxyl group in general formula (2).COPYRIGHT KIPO 2015
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Paragraph 0085; 0086
(2016/12/26)
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- Development of lactic ester as bifunctional additive of methanol-gasoline
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In this paper, lactic esters were synthesized and used as phase stabilizer and saturation vapor pressure depressor of methanol-gasoline. The results show that the stabilities of the methanol-gasoline depend on the length of the lactic esters' alkoxy group. Several lactic esters were found to be effective in various gasoline-methanol blends, and the lactic esters display high capacity to depress the saturation vapor pressure of methanol-gasoline. According to the results, it can be concluded that the lactic esters have the great potential to be bifunctional gasoline-methanol additives.
- Zhang, Jie,Yang, Changchun,Tang, Ying,Xu, Lianghong,Wang, Xiaoting
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p. 4827 - 4829
(2014/12/10)
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- Lipase-catalyzed oligomerization and hydrolysis of alkyl lactates: Direct evidence in the catalysis mechanism that enantioselection is governed by a deacylation step
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Lipase-catalyzed oligomerization of alkyl d-and l-lactate monomers (RDLa and RLLa, respectively) was studied for the first time. It has been found that the oligomerization occurs enantioselectively only for d-lactates to give oligomers up to heptamers of lactic acid (LA) in good to high yields by using primary C1 to C8 alkyl groups and sec-butyl group for d-lactate monomers. No reaction happened for all l-lactates in similar conditions. Lipase-catalyzed hydrolysis of alkyl d-and l-lactates was also examined, revealing that the hydrolysis took place for both d-and l-lactates, although l-lactates proceeded a couple of times slower. The hydrolysis results clearly demonstrate that the lipase catalysis mechanism involves an acyl-enzyme intermediate (EM) formation via the acylation step from both d-and l-lactates as a rate-determining step, and the subsequent deacylation step, a nucleophilic attack of water to the EM, takes place to produce free LA. On the other hand, in the oligomerization of d-lactates, the deacylation step, in which a sec-alcohol group of the monomer or of the propagating chain-end attacks to the EM, is only allowed for the sec-d-alcohol group to give a one-LA-unit-elongated oligomer. l-Lactates form the EM; however, the subsequent deacylation reaction with both the sec-l-and sec-d-alcohol groups does not take place, failing in the oligomerization to occur. These results provide with the first direct evidence in the lipase catalysis that the enantioselection is governed by the deacylation step. In the co-oligomerization between l-and d-lactates, the l-isomer retarded the reaction rate of the d-isomer, which was found due to the function of the former as a competitive inhibitor in the acylation step toward the latter.
- Ohara, Hitomi,Onogi, Akihisa,Yamamoto, Masafumi,Kobayashi, Shiro
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experimental part
p. 2008 - 2015
(2011/03/22)
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- Ultrasound-assisted solvent-free synthesis of lactic acid esters in novel SO3H-functionalized Br?nsted acidic ionic liquids
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Mild and efficient Fischer esterification reactions of lactic acid with a variety of straight chain aliphatic alcohols, cyclohexanol and benzyl alcohol were successfully performed using two novel Br?nsted acidic ionic liquids that bear an aromatic sulfonic acid group on the imidazolium or pyridinium cation under ultrasound irradiation. These reactions carried out smoothly with good to excellent conversion rate (78-96%) and satisfactory yields (73-92%) in shorter reaction time (4-6 h) at room temperature when the amount of ionic liquids was 20 mol%. These ionic liquids could be recovered readily and recycled five times without any significant loss in their catalytic activity.
- Li, Xinzhong,Lin, Qi,Ma, Liang
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experimental part
p. 752 - 755
(2011/10/08)
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