Group transfers definition

Coenzyme in the narrow sense, the dissociable, low-molecular-mass active group of an enzyme which transfers chemical groups (see Group transfer) or hydrogen or electrons. C. in this sense couple two otherwise independent reactions, and can thus be regarded as transport metabolites. In a wider sense, a C. can be regarded as any catalytically active, low-molecular-mass component of an enzyme. This definition includes C. that are covalently bound to enzymes as prosthetic groups. A holoenzyme consists of a C. in combination with an apoenzyme (enzyme protein). 

The first demonstration of living polymerization and the current definition of the process can be attributed to Swarc. Living polymerization mechanisms offer polymers of controlled composition, architecture, and molecular weight distribution. They provide routes to low-dispersity end-functional polymers, to high-purity block copolymers, and to stars and other more complex architectures. Traditional methods of living polymerization are based on ionic, coordination, or group transfer mechanisms. 

Pericyclic reactions were defined in 1969 by R. B. Woodward and R. Hoffmann as reactions in which all first-order change.s in bonding relationships take place in concert on a closed curve that is, as concerted reactions in which all bonds are formed or brokeasimultaneously around a circle. This definition arose from the systematic study of the conservation of orbital symmetry in a series of reactions electrocyclic reactions, cycloadditions, sigmatropic shifts, cheletropic reactions, and group transfer and elimination reactions. Excellent reviews on the historical evolution of pericyclic reactions have been published. ... 

Compounds containing the iV-thiosulfinylamino group (R—N=S=S) have been reported recently.85 "88 The aryl compounds are rather unstable purple oils which show promise as sulfur transfer agents, although few definitive examples have yet been reported.87... 

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