scholarly journals Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions

ACS Catalysis ◽  
2017 ◽  
Vol 7 (6) ◽  
pp. 4182-4188 ◽  
Author(s):  
Wei Liu ◽  
Mu-Jeng Cheng ◽  
Robert J. Nielsen ◽  
William A. Goddard ◽  
John T. Groves
Keyword(s):  
Bond Formation ◽  
Formation Step

Topography of the Free Energy Landscape on the Claisen-Schmidt Condensation: Solvent and Temperature Effect in the Rate-Controlling Step

2021 ◽  
Author(s):  
Nayara Dantas Coutinho ◽  
Hugo Gontijo Machado ◽  
Valter Henrique Carvalho-Silva ◽  
Wender A. Silva
Keyword(s):  
Free Energy ◽  
Temperature Effect ◽  
Strong Influence ◽  
Aldol Condensation ◽  
Energy Landscape ◽  
Bond Formation ◽  
Free Energy Landscape ◽  
Rate Controlling Step ◽  
Formation Step

Recent studies have assigned hydroxide elimination and C=C bond formation step in base-promoted aldol condensation the role of having a strong influence in the overall rate reaction, in contrast to...

Nitric oxide coupling mediated by iron porphyrins: the N–N bond formation step is facilitated by electrons and a proton

2012 ◽  
Vol 48 (72) ◽  
pp. 9041 ◽  
Author(s):  
Jun Yi ◽  
Brian H. Morrow ◽  
Adam L. O. C. Campbell ◽  
Jana K. Shen ◽  
George B. Richter-Addo
Keyword(s):  
Nitric Oxide ◽  
Bond Formation ◽  
Iron Porphyrins ◽  
Formation Step

scholarly journals Impact of the Ligand Flexibility and Solvent on the O–O Bond Formation Step in a Highly Active Ruthenium Water Oxidation Catalyst

2018 ◽  
Vol 57 (21) ◽  
pp. 13063-13066 ◽  
Author(s):  
Nitish Govindarajan ◽  
Ambuj Tiwari ◽  
Bernd Ensing ◽  
Evert Jan Meijer
Keyword(s):  
Water Oxidation ◽  
Bond Formation ◽  
Oxidation Catalyst ◽  
Highly Active ◽  
Formation Step

Tack and Green Strength of NR, SBR and NR/SBR Blends

1981 ◽  
Vol 54 (2) ◽  
pp. 403-414 ◽  
Author(s):  
G. R. Hamed
Keyword(s):  
Molecular Weight ◽  
Dominant Role ◽  
Bond Formation ◽  
Compressive Load ◽  
Pure Component ◽  
Green Strength ◽  
Low Viscosity ◽  
The Difference ◽  
Stock Flow ◽  
Formation Step

Abstract 1. A simple NR compound has superior tack compared to an SBR stock because of its greater ability to flow under compressive load and its higher green strength. The difference becomes greater as surface roughness is increased or test rate decreased. Tack differences between the two stocks can be quantitatively explained without assuming differences in the interdiffusion rate of SBR and NR molecules. NR is an “ideal” material for developing high tack. It can be processed to a low viscosity and still maintain high green strength. Furthermore, the mechanism responsible for the high green strength (strain crystallization) is not active in the bond formation step, hence does not interfere with contact and interdiffusion, but rather develops upon stressing. SBR, on the other hand, depends on entanglements, which tend to inhibit flow, to achieve green strength. Thus, if the molecular weight of the SBR is raised to enhance green strength to the level of NR, the stock will flow very poorly. Likewise, if SBR molecular weight is lowered, flow can be improved substantially, but green strength will decrease rapidly. Either of the above conditions result in poor tack. 2. For smooth, shiny surfaces brought together, contact occurs rapidly and nearly completely for both the NR and SBR stocks. This results in a relative tack near unity and hence, in this case, the tack strength is really a measure of stock green strength, i.e., tack is green strength limited. Obviously, when this condition exists, the addition to the stock of plasticizers, tackifiers, oils or other additives to facilitate stock flow (but decrease green strength) will nontheless reduce tack. Here, tack can only be increased by enhancing stock green strength, preferable without hindering flow ability. 3. The relative tack of SBR and SBR-dominated blends with moderately rough surfaces is less than unity and increases with contact pressure. Thus, tack is contact limited. In this instance, relative tack can be improved by decreasing stock viscosity, however, absolute tack will only be increased if good green strength is maintained. This may be the mechanism for the action of commencal tackifiers. 4. The tack of NR/SBR blends passes through a maximum with composition at about 80% NR. This is readily understood by noting that the green strength also reaches a maximum at this composition. For NR/SBR blends containing 60% or more of NR, green strength plays the dominant role in controlling tack. 5. Uncured adhesion of SBR to NR is less than the tack of either pure component. This suggests that interdiffusion is required to obtain high tack.

scholarly journals Biochemical mechanism of C-P bond formation of bialaphos: Use of gene manipulation for the analysis of the C-P bond formation step.

1990 ◽  
Vol 54 (8) ◽  
pp. 2121-2125 ◽  
Author(s):  
Tomomi HIDAKA ◽  
Osamu KARA ◽  
Satoshi IMAI ◽  
Hiroyuki ANZAI ◽  
Takeshi MURAKAMI ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biochemical Mechanism ◽  
Gene Manipulation ◽  
Formation Step

scholarly journals Nucleophilic water attack is not a possible mechanism for O–O bond formation in photosystem II

2017 ◽  
Vol 114 (19) ◽  
pp. 4966-4968 ◽  
Author(s):  
Per E. M. Siegbahn
Keyword(s):  
Photosystem Ii ◽  
Bond Formation ◽  
Short Paper ◽  
Different Types ◽  
Very High ◽  
Formation Step ◽  
Peroxide Product

Two different types of mechanisms are at present suggested for the O–O bond-formation step in photosystem II. The first one is a coupling between an oxyl radical and a bridging oxo. The second one is a nucleophilic water attack on a terminal oxo (or oxyl) group. In the present short paper, the six most reasonable versions of the latter mechanism have been studied and compared with the oxo-oxyl mechanism. The barriers are found to be much too high for the water attack, and that mechanism can therefore safely be ruled out. The reason is that the protonated peroxide product is always very high in energy.

Biochemical Mechanism of C–P Bond Formation of Bialaphos: Use of Gene Manipulation for the Analysis of the C–P Bond Formation Step

1990 ◽  
Vol 54 (8) ◽  
pp. 2121-2125 ◽  
Author(s):  
Tomomi Hidaka ◽  
Osamu Hara ◽  
Satoshi Imai ◽  
Hiroyuki Anzai ◽  
Takeshi Murakami ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biochemical Mechanism ◽  
Gene Manipulation ◽  
Formation Step
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