Rotational isomerism in fluorene derivatives. XX. Conformational equilibria of 9-substituted 9-(o-methylthiomethylphenyl)- and 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes

1991 ◽  
Vol 69 (4) ◽  
pp. 615-619 ◽  
Author(s):  
Akiko Nishida ◽  
Yoshifumi Akagawa ◽  
Shinsuke Shirakawa ◽  
Shizuo Fujisaki ◽  
Shoji Kajigaeshi
Keyword(s):  
Low Temperature ◽  
Key Words ◽  
Equilibrium Constant ◽  
Internal Rotation ◽  
Kinetic Data ◽  
Room Temperature ◽  
Rotational Isomerism ◽  
Oxidation Products ◽  
Conformational Isomerism ◽  
Conformational Equilibria

Several 9-substituted 9-(o-methylthiomethylphenyl)fluorenes and their oxidation products, 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes, were prepared. Each equilibrium constant at room temperature or at low temperature was investigated and the conformational equilibria [Formula: see text] of these compounds are discussed by comparing them with those of the corresponding 9-substituted 9-(o-methylthiophenyl)fluorenes and 9-substituted 9-(o-methylsulfinylphenyl)fluorenes in which the o-substituents were one CH2 unit shorter than those of the title compounds. Kinetic data for the internal rotation of several compounds are also given. Key words: conformational isomerism, restricted rotation, 9-arylfluorenes.

THE APPLICATION OF NATURAL AND SYNTHETIC ANTIOXIDANTS TO INCREASE THE OXIDATION RESISTANCE OF LINSeED OIL

2020 ◽  
Vol 13 (4(50)) ◽  
pp. 41-51
Author(s):  
I. P. Edimecheva ◽  
A. A. Sosnovskaya ◽  
O. I. Shadyro
Keyword(s):  
Ascorbic Acid ◽  
Kinetic Data ◽  
Room Temperature ◽  
Linseed Oil ◽  
Ascorbyl Palmitate ◽  
Natural Antioxidants ◽  
Oxidation Products ◽  
Free Access ◽  
Synthetic Antioxidants ◽  
Acid Esters

The effectiveness of several synthetic and natural antioxidants (AO) in inhibiting the oxidation of linseed oil has been studied. Under the conditions of accelerated oxidation at 100 °С, the values of the induction period of oxidation and stabilization factors of linseed oil in the presence of additives of known phenolic AOs, tocopherols, fat-soluble ascorbic acid esters and compositions based on them were determined. The data obtained indicate that ascorbic acid esters effectively inhibit the oxidation of linseed oil. The stabilizing effect of ascorbyl palmitate (AP) increases with an elevation in the content of α-linolenic acid in the oil and a decrease in the oxidative stability of the oil. One AP provided better stabilization efficiency than some known compositions based on it. Kinetic data on the accumulation of oxidation products in linseed oil with AP additives during the storage at room temperature and with free access of the air were obtained, demonstrating high inhibiting activity of AP under these conditions, which provides a possibility to increase the shelf life of the stabilized oil up to 18 months or more.

A molecular mechanics study of conformational isomerism in 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins

1991 ◽  
Vol 69 (12) ◽  
pp. 1957-1963 ◽  
Author(s):  
Lawrence D. Colebrook
Keyword(s):  
Force Field ◽  
Key Words ◽  
Molecular Mechanics ◽  
Internal Rotation ◽  
Transition States ◽  
Rotational Energy ◽  
Conformational Isomerism ◽  
Hindered Rotation ◽  
Energy Profiles ◽  
Conformational Preferences

Energy profiles for internal rotation about the C—N pivot bond in a series of 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins have been computed using the MMX molecular mechanics force field. Rotational ground and transition states have been identified and their energies calculated. Conformational preferences of diastereomeric rotamers have been investigated. Computed rotational energy barriers generally are within ± 2 kcal/mol of the experimentally determined values. Key words: conformational isomerism, hindered rotation, hydantoins, thiohydantoins, molecular mechanics.

Survival of mouse blastocysts after low-temperature preservation under high pressure

2004 ◽  
Vol 52 (4) ◽  
pp. 479-487 ◽  
Author(s):  
Cs. Pribenszky ◽  
M. Molnár ◽  
S. Cseh ◽  
L. Solti
Keyword(s):  
Phase Transition ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
High Hydrostatic Pressure ◽  
Room Temperature ◽  
Freezing Point ◽  
Significant Loss ◽  
Embryo Cryopreservation ◽  
Subzero Temperatures ◽  
Survival Capacity

Cryoinjuries are almost inevitable during the freezing of embryos. The present study examines the possibility of using high hydrostatic pressure to reduce substantially the freezing point of the embryo-holding solution, in order to preserve embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The pressure of 210 MPa lowers the phase transition temperature of water to -21°C. According to the results of this study, embryos can survive in high hydrostatic pressure environment at room temperature; the time embryos spend under pressure without significant loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C significantly reduced the survival capacity of the embryos; gradual decompression had no beneficial effect on survival at that stage. Based on the findings, the use of the phenomena is not applicable in this form, since pressure and low temperature together proved to be lethal to the embryos in these experiments. The application of hydrostatic pressure in embryo cryopreservation requires more detailed research, although the experience gained in this study can be applied usefully in different circumstances.

Changes in color characteristics of culinary products from turkey meat produced with the use of low-temperature heat treatment

Vsyo o myase ◽  
2020 ◽  
pp. 22-24
Author(s):  
Nasonova V.V. ◽  
◽  
Tunieva E.K. ◽  
Motovilina A.A. ◽  
Mileenkova E.V. ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Production Technology ◽  
Meat Products ◽  
Oxidation Products ◽  
Turkey Meat ◽  
Color Characteristics ◽  
Low Temperature Processing ◽  
Temperature Heat ◽  
Temperature Heat Treatment

The paper presents the results of the study on the effect of low-temperature heat treatment on color characteristics and protein oxidation products depending on the method, temperature and duration of heat treatment of culinary products from turkey meat. At present, the use of low-temperature processing in the production technology for meat products with improved organoleptic indices is a topical direction.

Kinetics of catalytic conversion of methanol at higher pressures

1980 ◽  
Vol 45 (12) ◽  
pp. 3402-3407 ◽  
Author(s):  
Jaroslav Bartoň ◽  
Vladimír Pour
Keyword(s):  
Low Temperature ◽  
Reaction Kinetics ◽  
Water Vapour ◽  
Kinetic Data ◽  
Catalytic Conversion ◽  
The Given ◽  
Kinetics Of

The course of the conversion of methanol with water vapour was followed on a low-temperature Cu-Zn-Cr-Al catalyst at pressures of 0.2 and 0.6 MPa. The kinetic data were evaluated together with those obtained at 0.1 MPa and the following equation for the reaction kinetics at the given conditions was derived: r = [p(CH3OH)p(H2O)]0.5[p(H2)]-1.3.

scholarly journals Synthesis, antibiotic structure–activity relationships, and cellulose dissolution studies of new room-temperature ionic liquids derived from lignin

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Shihong Liu ◽  
Michael Gonzalez ◽  
Celine Kong ◽  
Scott Weir ◽  
Aaron M. Socha
Keyword(s):  
Antibacterial Activity ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Oxidation Products ◽  
Cellulose Dissolution ◽  
Melting Points ◽  
E Coli ◽  
Alkyl Chains ◽  
Renewable Feedstocks ◽  
Commodity Chemicals

Abstract Background Ionic liquids (ILs) are promising pretreatment solvents for lignocellulosic biomass, but are largely prepared from petroleum precursors. Benzaldehydes from depolymerized lignin, such as vanillin, syringaldehyde, and 4-methoxy benzaldehyde, represent renewable feedstocks for the synthesis of ionic liquids. We herein report syntheses of novel lignin-derived ionic liquids, with extended N-alkyl chains, and examine their melting points, cellulose dissolution capacities, and toxicity profiles against Daphnia magna and E. coli strain 1A1. The latter organism has been engineered to produce isoprenol, a drop-in biofuel and precursor for commodity chemicals. Results The new N,N-diethyl and N,N-dipropyl methyl benzylammonium ILs were liquids at room temperature, showing 75–100 °C decreased melting points as compared to their N,N,N-trimethyl benzylammonium analog. Extension of N-alkyl chains also increased antibacterial activity threefold, while ionic liquids prepared from vanillin showed 2- to 4-fold lower toxicity as compared to those prepared from syringaldehyde and 4-methoxybenzaldehyde. The trend of antibacterial activity for anions of lignin-derived ILs was found to be methanesulfonate < acetate < hydroxide. Microcrystalline cellulose dissolution, from 2 to 4 wt% after 20 min at 100 °C, was observed in all new ILs using light microscopy and IR spectroscopy. Conclusions Ionic liquids prepared from H-, S- and G-lignin oxidation products provided differential cytotoxic activity against E. coli and D. magna, suggesting these compounds could be tailored for application specificity within a biorefinery.

Photophysical properties of N719 and Z907 dyes, benchmark sensitizers for dye-sensitized solar cells, at room and low temperature

2021 ◽  
Vol 23 (10) ◽  
pp. 6182-6189
Author(s):  
Dariusz M. Niedzwiedzki
Keyword(s):  
Solar Cells ◽  
Low Temperature ◽  
Optical Spectroscopy ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Dye Sensitized Solar Cells ◽  
Time Resolved ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Photophysical properties of N719 and Z907, benchmark Ru-dyes used as sensitizers in dye-sensitized solar cells, were studied by static and time-resolved optical spectroscopy at room temperature and 160 K.

Transition Insulator-Metal and Antiferromagnetic-Paramagnetic Cu Doped in La0.47Ca0.53MnO3

2015 ◽  
Vol 1123 ◽  
pp. 73-77 ◽  
Author(s):  
Yohanes Edi Gunanto ◽  
K. Sinaga ◽  
B. Kurniawan ◽  
S. Poertadji ◽  
H. Tanaka ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Magnetic Structure ◽  
Room Temperature ◽  
Paramagnetic Phase ◽  
Perovskite Manganites ◽  
Antiferromagnetic Phase ◽  
Temperature Transition ◽  
Cu Doping ◽  
Metal State

The study of the perovskite manganites La0.47Ca0.53Mn1-xCuxO3 with x = 0, 0.06, 0.09, and 0.13 has been done. The magnetic structure was determined using high-resolution neutron scattering at room temperature and low temperature. All samples were paramagnetic at room temperature and antiferromagnetic at low temperature. Using the SQUID Quantum Design, the samples showed that the doping of the insulating antiferromagnetic phase La0.47Ca0.53MnO3 with Cu doping resulted in the temperature transition from an insulator to metal state, and an antiferromagnetic to paramagnetic phase. The temperature transition from an insulator to metal state ranged from 23 to 100 K and from 200 to 230 K for the transition from an antiferromagnetic to paramagnetic phase.

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