Reactions with organic molecules

Photochemical reaction with organic molecules within the tumour cells, where hydrogen abstraction occurs. This initiates a number of radical reactions, resulting in destruction of the tumour. 

The hydrated electron behaves as a nucleophile in its reactions with organic molecules and its reactivity is greatly enhanced by electron-withdrawing substituents attached to aromatic rings or adjacent to double bonds. Some of the features of the reactivity of are illustrated by the data in Table 3. 

Although OH behaves mechanistically like H in its reactions with organic molecules, it is less selective and more reactive than H in H-abstraction reactions because the formation of the H—OH bond is 57 kJ mol more exothermic than that of H—H. Examples of the reactivities of H , OH, and 0 are listed in Table 4. 

Evidence for the potential dependence of the transfer coefficient predicted by eqn. (155) is not very clear. However, variations beyond experimental error have recently been observed by Saveant and Tessier for a series of simple electron transfer reactions with organic molecules in different non-aqueous solvents [70a]. 

The reactivity of the surface such as the generation of radical species and reaction with organic molecules. 

The surface can also be modified via a reaction with organic molecules or intermediates to introduce specific functional groups. 

Hydrogen is important as a reactant in heterogeneously catalyzed process. In exchange reactions with organic molecules, hydrogen and deuterium have been extensively investigated in relation to catalysis. 

As already discussed, reactions at extended electrodes and particles differ only insofar as, at particles, both an oxidation and a reduction process always occur simultaneously. There is, however, one further aspect which may be of importance for using big or small particles. Taking two solutions containing semiconductor particles of different sizes, i.e. for instance of 3 nm and 4 /im, then many more particles are present in the solution containing the 3 nm-particles than in that of 4 /im-particles, provided that the concentration of the semiconductor material is identical in both solutions. As it can easily be calculated, a time interval of 5.4 ms exists between the absorption of two photons in one individual 3 nm-particle for a photon-flux of 4 x 10 cm s assuming that all photons are absorbed in the colloidal solution [114]. In the case of the 4 pm-particles, the time interval is about 20 ps for the same photon flux, i.e. it is shorter by a factor of 10 , compared to the time interval estimated for the 3 nm-particles. This can be important for reactions where two or more electrons are involved, typical in many oxidation- and reduction reactions with organic molecules [114]. 

In its reactions with organic molecules, OH behaves as an electrophile whereas 0 is a nucleophile. Thus, like H (see above), OH readily adds to double bonds but 0 does not however, both forms of the radical abstract H from C-H bonds. In the case of an aromatic molecule carrying an aliphatic side chain, OH adds preferentially to the aromatic ring and 0 abstracts H from the side chain this can result in a change of reaction mechanism when the pH is raised so that 0 replaces OH as the oxidant. 

An important property of EPR spectroscopy is the detailed information provided by the structure of the spectra so that there is higher degree of certainty of correctly identifying the radicals than is the case with optical spectroscopy. Thus, chemically similar radicals that would be expected to have similar UV absorption spectra have completely different EPR spectra. For example, in its reactions with organic molecules, OH can attack at a number of different sites, either to abstract a hydrogen atom from a saturated molecule (see Table 5) or to add to an aromatic ring. Each of the product radicals has a distinctive EPR spectrum, and the relative efficiency with which reaction occurs at each site on the target molecule can be determined from the intensities of the spectra of the various radical products. 

In its reactions with organic molecules, OH is an electrophile whereas O " is a nucleophile. Forexample, in their reaction with aromatic compounds containing an aliphatic side chain, OH adds preferentially to the aromatic ring but O" abstracts H from the side chain ... 

B. Ranby and J. F. Rabek, Eds., Singlet Oxygen Reactions with Organic Molecules and Polymers, Wiley, New York, 1978. 

In reactions with organic molecules e q reacts as nucleophilic reagent it attacks molecules with low-lying molecular orbital, like aromatic hydrocarbons, conjugated olefinic molecules, carboxyl compounds, and halogenated hydrocarbons (Swallow 1982 Buxton 1982, 1987 Buxton et al. 1988). In the latter case, addition is usually followed by halide ion elimination, so the reaction can be considered as a dissociative electron capture. For instance, the reaction with chlorobenzene yields phenyl radical and chloride ion... 

Rush JD, Koppenol WH (1986) Oxidizing intermediates in the reaction of ferrous EDTA with hydrogen peroxide. Reactions with organic molecules and fer-rocytochrome c. J Biol Chem 261 6730-6733 Saran M, Bors W (1990) Radical reactions in vivo - an overview. Radiat Environ Biophys 29 249-262... 

To be able to probe sites with basic character in a zeolite it is necessary to completely avoid the presence of Bronsted acid sites. For most reactions with organic molecules a basic and an acidic reaction pathway is possible and. 

Reactions of one particular radical are listed in the order which is given by application of the above criteria to the substrate molecule. The reactions with organic molecules are however preceded by the reactions with inorganic compounds. Only in a few cases with rather complex substrates it seemed appropriate to list the substrates in alphabetical order. 

---