scholarly journals LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions

ChemPhotoChem ◽  
2019 ◽  
Vol 3 (10) ◽  
pp. 984-992 ◽  
Author(s):  
Yining Ji ◽  
Daniel A. DiRocco ◽  
Jonas Kind ◽  
Christina M. Thiele ◽  
Ruth M. Gschwind ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Photochemical Reactions ◽  
Mechanistic Studies ◽  
Practical Tool

Synthesis, characterization, and enzymic conversion of nonhydrolysable analogues of propionylcoenzyme A

1994 ◽  
Vol 72 (1) ◽  
pp. 164-169 ◽  
Author(s):  
Yimin Zhao ◽  
Martina Michenfelder ◽  
János Rétey
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Coenzyme A ◽  
The Novel ◽  
Mechanistic Studies ◽  
Preparative Scale ◽  
Propionibacterium Shermanii ◽  
Fab Mass Spectrometry ◽  
Michaelis Constants ◽  
Coenzyme B

We describe the synthesis of three novel analogues of propionyl-coenzyme A, in which the sulfur atom has been replaced by methylene, ethylene, and thiomethylene, respectively. All three analogues, propionyl-dethia(carba)-CoA (1), propionyl-dethia(dicarba)-CoA (2), and S-(2-oxobutanyl)-CoA (3) were characterized by 1H and 31P NMR spectroscopy and FAB mass spectrometry. Propionyl-CoA–oxaloacetate transcarboxylase from Propionibacterium shermanii accepted the novel analogues as substrates and carboxylated them to the corresponding methylmalonyl-CoA analogues (4–6). The latter were further converted into the succinyl-CoA analogues by the coenzyme-B12-dependent methylmalonyl-CoA mutase from the same organism. The succinyl-CoA analogues, succinyl-dethia(carba)-CoA (7), succinyl-dethia(dicarba)-CoA (8), and 4-carboxy(2-oxobutanyl)-CoA (9) were obtained on a preparative scale and their Michaelis constants (Km) with methylmalonyl-CoA mutase were determined to be 0.136, 2.20, and 0.132 mM, respectively (Km for succinyl-CoA is 0.025 mM). The Vmax values for 7, 8, and 9 are 1.1, 0.013, and 0.0047 µmol min−1 U−1, respectively (Vmax for succinyl CoA is 1.0). The utility of the novel coenzyme A analogues in enzyme mechanistic studies is discussed.

scholarly journals Photochemische Reaktionen von Übergangsmetall-Olefin-Komplexen, V [1]. Die Umsetzung von Tricarbonyl-η-6.6-dimethylfulven-chrom(0) mit 7-Methyl- und 7-Methoxycycloheptatrien / Photochemical Reactions of Transition Metal Olefin Complexes, V [1]. The Reactions of Tricarbonyl-η-6,6-dimethylfulvene-chromium(0) with 7-Methyl- and 7-Methoxycycloheptatriene

1982 ◽  
Vol 37 (10) ◽  
pp. 1322-1326 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Hans Kurz
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Column Chromatography ◽  
Room Temperature ◽  
Photochemical Reactions ◽  
Membered Ring ◽  
Reaction Products ◽  
Methyl Group

Abstract The stereochemistry of the photo reaction products of tricarbonyl-η-6,6-dimethyl-fulvene-chromium(O) (1) with 7-methyl-and 7-methoxycycloheptatriene was studied by NMR-spectroscopy. Both trienes add to 1, displace a CO ligand, and form substituted dicarbonyl-η3-2-cycloheptadienylene-η5-2-cyclopentadienylidene-propane-chromium(0) complexes. With C7H7CH3 only one isomer (3) is formed with the methyl-group in endo-position and the enyl system encompassing C(1′)-C(3′) of the seven membered ring. C7H7OCH3 yields 3 isomers which were separated by column chromatography. 5 has the same constitution as 3. The isomers 4 and 5 bear the OCH3-group in e^o-position. The enyl system of 4 is located on C(1′)-C(3′), that of 6 on C(3′)-C(5′). 6 rearranges at room temperature to 4.

Activation of Oxidation Catalysts by Solvation

1996 ◽  
Vol 454 ◽  
Author(s):  
Annette D. Eddowes ◽  
Dana Stallings ◽  
Caprice L. Hightower ◽  
Susan A. Jansen
Keyword(s):  
Photochemical Reactions ◽  
Oxidation Reactions ◽  
Mechanistic Studies ◽  
Oxidation Catalysts ◽  
Keggin Ion ◽  
Solution State ◽  
Keggin Type ◽  
Activation Of Oxidation

AbstractThe versatility of heteropolyanions implies many different uses for Keggin type catalysts. However, new roles for these catalysts must first be preceeded by further understanding of the mechanisms by which they operate. It has been observed that the solvation and/or complexation of heteropolyanions promotes or limits activity in homogeneous chemistry. For this reason the solution state and the solvation characteristics of the catalyst were studied in oxidation and photochemical reactions. Simple oxidation reactions provide a system by which the solution state of the catalyst can be studied. The catalyst used for these mechanistic studies is the Keggin ion (PMo10V2O40)−5.

Mechanistic studies on oxide catalysts. I. Reactions of propene and cyclopentene on calcium oxide

1986 ◽  
Vol 406 (1831) ◽  
pp. 183-204 ◽  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Nmr Spectroscopy ◽  
Calcium Oxide ◽  
Oxide Catalysts ◽  
Catalytic Reactions ◽  
Deuterium Nmr ◽  
Addition Reactions ◽  
Mechanistic Studies ◽  
Dominant Mechanism

Mass spectrometry, gas chromatography and deuterium NMR spectroscopy have been used to examine the products from the reactions of propene or cyclopentene with deuterium on calcium oxide. The information so gained on the number, location and grouping of the deuterium atoms in the products provides evidence about the nature and reactivity of the adsorbed intermediates involved in the catalytic reactions. The dominant mechanism of exchange, which occurs readily on calcium oxide even at 240 K with either propene or cyclopentene, is interconversion between adsorbed alkene and adsorbed π-allyl species. Catalysis of addition reactions also occurs, but at rates which are about 10 2 to 10 4 times slower than exchange. Different mechanisms of exchange mainly involving vinylic intermediates are found on γ-alumina.

Sign in / Sign up

Export Citation Format

Share Document