Conjugated diene system, type

Table 5 Base peaks in the El-mass spectra of Type I compounds including a conjugated diene system [163,164]a... 

Conjugated diene System of the type C=C—C=C, in which two pairs of doubly bonded carbons are joined by a single bond. The TT electrons are delocalized over the unit of four consecutive sp -hybridized carbons. 

Type I Pheromones with a Conjugated Diene System... 

Vitamin D, like other sterols containing conjugated diene systems, enters into Diels-Alder type reactions. On this basis Windaus and Thiele (1936) prepared the adduct of ergocalciferol with maleic anhydride and presumed the reaction to be quantitative. 

Allylic carbocations and allylic radicals are conjugated systems involved as reactive intermediates m chemical reactions The third type of conjugated system that we will examine conjugated dienes, consists of stable molecules... 

Addition (Section 10 10) Addition of reagents of the type X—Y to conjugated dienes in which X and Y add to the ter mini of the diene system... 

Conjugated diene (Section 10 5) System of the type C=C—C=C in which two pairs of doubly bonded carbons are joined by a single bond The tt electrons are delocalized over the unit of four consecutive sp hybridized carbons Connectivity (Section 1 6) Order in which a molecule s atoms are connected Synonymous with constitution Constitution (Section 1 6) Order of atomic connections that defines a molecule... 

To explain the formation of non-crosslinked polymers from the diallyl quaternary ammonium system, Butler and Angelo proposed a chain growth mechanism which involved a series of intra- and inter-molecular propagation steps (15). This type of polymerization was subsequently shown to occur in a wide variety of symmetrical diene systems which cyclize to form five or six-membered ring structures. This mode of propagation of a non-conjugated diene with subsequent ring formation was later called cyclopolymerization. 

The polymerization of conjugated dienes with transition metal catalytic systems is an insertion polymerization, as is that of monoalkenes with the same systems. Moreover, it is nearly generally accepted that for diene polymerization the monomer insertion reaction occurs in the same two steps established for olefin polymerization by transition metal catalytic systems (i) coordination of the monomer to the metal and (ii) monomer insertion into a metal-carbon bond. However, polymerization of dienes presents several peculiar aspects mainly related to the nature of the bond between the transition metal of the catalytic system and the growing chain, which is of o type for the monoalkene polymerizations, while it is of the allylic type in the conjugated diene polymerizations.174-183... 

A mild triple catalytic system consisting of Pd(OAc)2, hydroquinone, and a transition metal macrocycle (for example, iron phthalocyanine) was reported [243]. The catalytic effect is carried out by the interaction of Pd(II) with the substrate and the acquisition of two electrons, which are further transferred to the benzoquinone that is reduced to hydroquinone. The hydroquinone is then reorganized to benzoquinone by the 02/metal macrocycle system. The following types of transformations were carried out in mild conditions using the developed system 1,4-oxidation of conjugated dienes, oxidation of terminal olefins to methyl ketones, and allylic oxidation. 

Spontaneous transfer reactions in conjugated diene polymerisation systems are more complex than those in monoalkene polymerisation systems. Two types of chain termination reaction can occur in principle in polymerisation systems containing conjugated diene. The first type, mononuclear termination, consists in a hydrogen abstraction from the growing chain with the formation of an Mt H bond [scheme (7)] which reforms an Mt [ /3-(All)] bond on reaction with the monomer ... 

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