Reactive species generation

All the examples of reactivity in acidic medium (Scheme 40) involve a reagent with a sp C hybridized electrophilic center, but the actual reactive species generated bears a sp C electrophilic center. In this case, exocyclic N-alkylation is not surprising (see Section III.2). 

Chemical vapor deposition (CVD) is a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction. It is this reactive process that distinguishes CVD from physical deposition processes, such as evaporation, sputtering, and sublimation.8 This process is well known and is used to generate inorganic thin films of high purity and quality as well as form polyimides by a step-polymerization process.9-11 Vapor deposition polymerization (VDP) is the method in which the chemical reaction in question is the polymerization of a reactive species generated in the gas phase by thermal (or radiative) activation. 

Interesting hydrocarbon oxidations have been observed with Fe(II) catalysts with oxygen as the oxidant. These catalytic systems have become known as Gif chemistry after the location of their discovery in France.228 An improved system involving Fe(III), picolinic acid, and H202, has been developed. The reactive species generated in these systems is believed to be at the Fe(V)=0 oxidation level229... 

Depending on the type of reactive species generated upon exposure to UV light, photoinitiators are classified as free radical, cationic, and anionic. 

The reactive species generated by the photoexcitation of organic molecules in the electron-donor-acceptor systems are well established in last three decades as shown in Scheme 1. The reactivity of an exciplex and radical ion species is discussed in the following sections. The structure-reactivity relationship for the exciplexes, which possess infinite lifetimes and often emit their own fluorescence, has been shown in some selected regioselective and stereoselective photocycloadditions. However, the exciplex emission is often absent or too weak to be identified although the exciplexes are postulated in many photocycloadditions [11,12], The different reactivities among the contact radical ion pairs (polar exciplexes), solvent-separated radical ion pairs, and free-radical ions as ionic species... 

A conclusion must be drawn from these experiments, The concentration of reactive species generated at dose rates as high as 3000 krad/h is sufficiently high so that they recombine with one another and do not have the time to diffuse and react with die surrounding lignin matrix. This is not the case when the dose rate is lower, the concentration of these reactive species is such that they have the time to diffuse and react with the lignin matrix. The result is an increase in the pulp ISO brightness. To compare our results with those used in literature (8-10-12), a 2.S Mrad dose was chosen. 

Miyashita M, Hoshino M, Yoshikoshi A (1988) Sodium Phenylseleno(triethoxy)borate, Na [PhSeB(OEt)3]7 the Reactive Species Generated from (PhSe)2 with NaBlT) in Ethanol. Tetrahedron Lett 29 347... 

The main reactions taking place when chloromethylated polystyrene (CMS) and chloromethylated poly(diphenylsiloxane) (SNR) are irradiated with high energy electrons or deep UV (KrF excimer laser, 248 nm) radiation have been studied. The results are discussed in terms of short-lived reactive species generated using pulse radiolysis and laser (248 nm) photolysis techniques. 

Tungsten(I) complexes are rare but are found as dimeric compounds or as reactive species generated by one-electron oxidation of 18-electron compounds. 

Related to copper-containing enzymes such as laccase and tyrosinase, recent studies have been conducted on the structural characterization of the reactive species generated from molecular oxygen and copper complexes. A continuous effort has also been directed toward the efficient utilization of such oxygen-copper complexes as oxidants, in industrial processes, which will hopefully replace metal compounds such as chromate, manganate and others. 

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