Reaction Pathways of

The conclusion is that there are no known examples of behaviour of type (a) for pyrazoles. The same negative conclusion could have been extended to the other reaction pathways of Figure 25 until very recently when an example of type (e) was described (Scheme 31 (82PC40400). Other dienophiles do not take part in this reaction. 

The reaction pathway of 0-, N-, and S-containing l, 2-bifunctional benzenes with fluoroolefins depended on the relative abilities of the heteroatom to stabilize an adjacent anionic center, e.g., (17) and (18) [87-JCS(P1)763]. 

The reaction of alkoxyarylcarbene complexes with alkynes mainly affords Dotz benzannulated [3C+2S+1C0] cycloadducts. However, uncommon reaction pathways of some alkoxyarylcarbene complexes in their reaction with alkynes leading to indene derivatives in a formal [3C+2S] cycloaddition process have been reported. For example, the reaction of methoxy(2,6-dimethylphenyl)chromium carbene complex with 1,2-diphenylacetylene at 100 °C gives rise to an unusual indene derivative where a sigmatropic 1,5-methyl shift is observed [60]. Moreover, a related (4-hydroxy-2,6-dimethylphenyl)carbene complex reacts in benzene at 100 °C with 3-hexyne to produce an indene derivative. However, the expected Dotz cycloadduct is obtained when the solvent is changed to acetonitrile [61] (Scheme 19). Also, Dotz et al. have shown that the introduction of an isocyanide ligand into the coordination sphere of the metal induces the preferential formation of indene derivatives [62]. 

No attempt was made to measure CO2 in these experiments. By increasing the temperature to 320°C, catalyst deactivation was prevented, and no carbon residue could be detected on the spent catalyst. Thus, temperature can be expected to significantly shift the reaction pathways of organic contaminants. In this study, and in all other studies, excellent corrosion resistance was observed for the corrosion coupons. 

This method (sec Table 1, method C, 8.2.2.2) yields Au clusters in high yield e.g. (AuyfPPh,) ] as prepared by the Au evaporation or the borohydride route is an attractive starting material for the synthesis of most Au clusters. Scheme I shows the reaction pathways of [AUgfPPh,) ] with electron-pair donor bases. 

DFT-GGA calculations are very useful for investigating plausible reaction pathways of various molecules on surfaces. The method provides detailed information on the bonding geometry, on bond energies as well on activation barriers, and transition states which are otherwise not accessible. Typical accuracies in such numbers amount to a few tenths of an eV, making the method particularly useful to investigate trends. 

Scheme 1. Reaction pathway of EA synthesis from EDA and NH3 over H-EDTA-MOR.

SURFACE-STRUCTURE-DEPENDENT REACTION PATHWAYS OF METHYL GROUPS ON NI(IOO) and NI(111) SURFACES... 

Nakabayashi, S., Yagi, 1., Sugiyama, N., Tamura, K. and Uosaki, K. (1997) Reaction pathway of four-electron oxidation of formaldehyde on platinum electrode as observed by in situ optical spectroscopy. Surf. Sci., 386, 82-88. 

Wolter O, Willsau J, Heitbaum J. 1985. Reaction pathways of the anodic oxidation of formic acid on platinum evidenced by oxygen-18 labeling—A DEMS study. J Electrochem Soc 132 1635-1638. 

Scheme 6.19 Reaction pathways of the Simmons-Smith reaction.

Figure 2.1 Free energy diagram for the reaction pathway of a chemical reaction, and the same reaction catalyzed by an enzyme. Note the significant reduction in activation energy (the vertical distance between the reactant state and the transition state) achieved by the enzyme-catalyzed reaction.

Figure 2.2 Key reaction intermediates in the reaction pathway of serine proteases.

Brosius, R., Bazin, P., Thibault-Starzyk, F. et al., (2005) Operando FTIR study of reaction pathways of selective catalytic reduction of NOx with decane in the presence of water on iron-exchanged MFI-type zeolite, J. Catal., 234, 191. 

Fig. 20. A possible polymerisation mechanism for five-membered heterocyles showing the two alternative reaction pathways of radical-radical coupling and radical-monomer coupling.

CC7 sykes, p. Some Reaction Pathways of Carboxylic Acid Derivatives (1979). 

Emerson, J.P., Farquhar, E.R. and Que, L. Jr. (2007) Structural snapshots along reaction pathways of non-heme iron enzymes. Angewandte Chemie, International Edition, 46, 8553-8556. 

Oxidation intermediates and reaction pathways of wet hydrogen peroxide oxidation of p-coumaric acid over (Al-Fe)PILC catalyst... 

The pyrene-like aromatic chromophore of BaPDE is characterized by a prominent and characteristic absorption spectrum in the A 310-360 nm spectral region, and a fluorescence emission in the X 370-460 nm range. These properties are sensitive to the local microenvironment of the pyrenyl chromophore, and spectroscopic techniques are thus useful in studies of the structures of the DNA adducts and in monitoring the reaction pathways of BaPDE and its hydrolysis products in DNA solutions. 

---