Dual mechanism for

The laser flash photolysis of aromatic diisocyanate based polyurethanes in solution provides evidence for a dual mechanism for photodegradation. One of the processes, an N-C bond cleavage, is common to both TDI (toluene diisocyanate) and MDI (methylene 4,4 -diphenyldiisocyanate) based polyurethanes. The second process, exclusive to MDI based polyurethanes, involves formation of a substituted diphenylmethyl radical. The diphenylmethyl radical, which readily reacts with oxygen, is generated either by direct excitation (248 nm) or indirectly by reaction with a tert-butoxy radical produced upon excitation of tert-butyl peroxide at 351 nm. 

Comprehensive N-labelling studies by Clusius, Huisgen and co-workers have led to the elucidation of the detailed mechanism which is shown in Scheme 4. A dual mechanism for this reaction was... 

Shaw, P.A. Nash, D.J. (1998) Dual mechanisms for the formation of fluvial sil-cretes in the distal reaches of the Okavango Delta Fan, Botswana. Earth Surface Processes and Landforms 23, 705-714. 

Scheme 13 Dual mechanisms for the aryl to imidoyl palladium migration in the synthesis of fluoren-9-ones [top dual C-H activation bottom single C-H activation]...

Weisz, A., Oguchi, S., Cicatiello, L., and Esumi, H. (1994). Dual mechanism for the control of inducible-type NO synthase gene expression in macrophages during activation by interferon-y and bacterial lipopolysaccharide. Transcriptional and post-transcriptional regulation. J. Biol. Chem. 269, 8324-8333. 

Grundon MF, Surgenor SA (1978) Asymmetric synthesis and absolute stereochemistry of the alkaloies araliopsine, isoplatydesmine, and ribalinine. Dual mechanism for a dihydrofuro-quinolone-dihydropyranoquinolone rearrangement J Chtan Soc Chem Commun 14 624-626... 

The dual mechanism for paraffin hydrocracking includes the steps shown in Figure 9. Dual means that catalyst has two kinds of active sites -acid-based and metal-based. Section 3.7 lists the acids and metals that are used to make these catalysts. 

Figure 9. Metal/acid ( dual ) mechanism for paraffin hydrocracking.

Liu, RS.H. and Hammond, G.S., The case of medium-dependent dual mechanisms for photoisomerization one-bond-fhp and hula-twist, Proc. Natl. Acad. Sci. USA, 97, 11153, 2000. 

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