[19] Photochemistry and isomer determination of 13-cis-and trans-bacteriorhodopsin

1982 ◽  
pp. 167-174
Author(s):  
Norbert A. Dencher ◽  
Charles N. Rafferty ◽  
Walter Sperling
Keyword(s):  
Cis And Trans ◽  
Isomer Determination

Catalytic processing of organochlorine wastes into valuable monomers

2021 ◽  
pp. 41-47
Author(s):  
B. Stepasiuk ◽  
◽  
T. Haievska ◽  
O. Spaska ◽  
Yu. Bilokopytov ◽  
...  
Keyword(s):  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Radical Mechanism ◽  
Ethylene Dichloride ◽  
Experimental Development ◽  
Laboratory Activity ◽  
Catalytic Processing ◽  
Chlorinated Organic ◽  
Cis And Trans

The paper is devoted to experimental development of method for 1,1,2-trichlorethane (TCE) dehydrochlorination (DHC). The economic and environmental issues of organic chlorinated compounds processing are described. The basic principle and possible products of TCE processing are presented. The DHC of TCE, which is one of the chlorinated organic wastes produced in the ethylene dichloride process, to vinylidene chloride (VDC) was carried out over over CaO, MgO supported on SiO2 and modified with CsCl catalysts. This process was carried out in a continuous flow fixed-bed reactor. The prepared catalysts were characterized by surface area and base properties before/after reaction. The methodology for determining properties of catalyst is described. Laboratory activity test apparatus was developed, and the schematic diagram is presented in the paper. The method of determination of TCE concentration of was calculated from its partial saturation vapor pressure at a given temperature is presented. Encouraging results were obtained on the catalyst containing 10 % CsCl/CaO·SiO2. The direction of the DHC reaction changed radically under described conditions: VDC was not formed at all and the major products were cis- and trans-1,2-dichloroethene. Interesting results were obtained with the catalytic system comprising 10 % (MgO-CsCl) (1:1) supported on SiO2. DHC of 2 % TCE/Ar at 302 °C proceeds quantitatively over 20 h with selectivity for VDC of more than 80%. These systems are suitable to study the factors providing the binding and removal of HCl from the reaction zone. A possible way to increase the selectivity for VDC is the creation of the conditions favoring the DHC of TCE into VDC by the radical mechanism, which was observed in experiments with 10% CsCl/CaSiO3. The directions for future researches are formulated and described.

Reactivities of Piperazine-2,5-diones in Radical Bromination Reactions

1996 ◽  
Vol 49 (11) ◽  
pp. 1229 ◽  
Author(s):  
CLL Chai ◽  
DCR Hockless ◽  
AR King
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Chemical Reactivity ◽  
Trans Isomers ◽  
Radical Bromination ◽  
Conformational Effects ◽  
Cis And Trans Isomers ◽  
The Difference ◽  
Cis And Trans

The reactivities of various N,N'- diacetylated piperazine-2,5-diones towards radical bromination reactions are reported. The studies show that glycyl centres of piperazine-2,5-diones are more reactive towards radical bromination reactions compared to α-substituted amino acid centres. In addition, large differences in reactivities were observed for the cis and trans isomers of N,N'-diacetylated alanine anhydride. Single-crystal structure determination of each isomer revealed that conformational effects may account for the difference in chemical reactivity.

Gas-Liquid Chromatographic Determination of TYans-Unsaturation in Fats and Oils on Packed Columns: Effect of Positional Isomers

1978 ◽  
Vol 61 (3) ◽  
pp. 702-708
Author(s):  
Henry B S Conacher ◽  
Jagannath R Iyengar
Keyword(s):  
Fats And Oils ◽  
Chromatographic Determination ◽  
Packed Columns ◽  
Gas Liquid Chromatography ◽  
Positional Isomers ◽  
Tubular Columns ◽  
Acid Isomerization ◽  
Cis And Trans ◽  
Liquid Chromatographic

Abstract Studies in our laboratories indicated that the trans contents of a number of commercial margarines, determined by gas-liquid chromatography (GLC) on a 15 ft column packed with 10% Silar IOC, were approximately 80-85% of those determined by infrared spectroscopy. This is mainly due to overlap of some of the trans positional isomers with the cis positional isomers in the octadecenoate fraction, shown by studies involving determination of the transoctadecenoate content of the margarines by silver ion thin layer chromatography/GLC, and by preparation and study of the GLC behavior of the cis and trans positional isomers of Δ6-, Δ9-, Δ12-, and Δl5-octadecenoates. The last 3 isomers were prepared by hydrazine reduction and nitrous acid isomerization of linoleic and linolenic acids. Since it is possible that longer, more efficient columns might result in better separation of the cis- and traru-octadecenoate isomers, it is recommended that studies be continued on longer packed columns (20 ft) and possibly on support-coated open tubular columns.

Quantitative Determination and Confirmation of Low Levels of Diethylstilbestrol in Feeds

1972 ◽  
Vol 55 (6) ◽  
pp. 1345-1353
Author(s):  
Marshall T Jeffus ◽  
Charles T Kenner
Keyword(s):  
Thin Layer ◽  
Quantitative Determination ◽  
Official Method ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Before And After ◽  
Chromatographic Procedure ◽  
Low Levels ◽  
Cis And Trans

Abstract A method for the determination of diethylstibestrol in feeds, which is based on official first action method 38.048–38.051, is proposed. Interfering feed extractives are removed by using a tripotassium phosphate-Celite column prior to measurement at 415 nm before and after irradiation. Recoveries of equilibrated standards added to Soxhlet extracts of several samples averaged 94.3% compared to 86.3% by the official method. The background absorbance at 415 nm obtained by using the proposed method was approximately 6% of the background by the official method for solutions containing equivalent amounts of sample. A thin layer chromatographic method is also included for the confirmation and identification of the cis and trans isomers of the drug. The proposed method has been found satisfactory for the quantitative determination of 0.55–44 ppm diethylstilbestrol and the thin layer chromatographic procedure can detect as little as 0.07 ppm.

Some Aspects of the Determination of the Microstructures of Polymers

1969 ◽  
Vol 23 (1) ◽  
pp. 17-22 ◽  
Author(s):  
John L. Binder
Keyword(s):  
Cis And Trans

The importance of the correct polymer absorptivities for determining the microstructures of polybutadienes and polyisoprenes, particularly when one component is present in large amount, is shown. A method is described for determining both the major and minor polymer absorptivities and an application to the analyses of butadiene—isoprene copolymers is given. The absorptivities of cis- and trans-C(CH3)=CH at 890 cm−1, cis- and trans-C(CH3)=CH at 1155 cm−1 and 1130 cm−1, and of cis-CH=CH at 967 cm−1 are discussed.

Sign in / Sign up

Export Citation Format

Share Document