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Penta-atomic radicals

It has proved convenient to classify centers other than trapped electrons as monatomic, diatomic, triatomic, tetra-atomic and penta-atomic (9), these classes being expanded to include more complex species having similar basic structures. Thus, the radicals R2NO and (S03)2N02 were classed with the corresponding simple AB3 tetra-atomic radicals. [Pg.8]

Protonated pyridazine is attacked by nucleophilic acyl radicals at positions 4 and 5 to give 4,5-diacylpyridazines. When acyl radicals with a hydrogen atom at the a-position to the carbonyl group are used, the diacylpyridazines are mainly converted into cyclo-penta[ f]pyridazines by intramolecular aldol reactions (Scheme 43). [Pg.30]

As we showed previously in this chapter, silicon easily expands its valence shell to become a penta-coordinated species. Therefore, it is expected that an intramolecular transfer of organosilicon group from X to Y may occur via a radical mechanism, provided that the R substituents on the silicon atom are not good leaving groups (Reaction 6.20). [Pg.137]

In the reaction of the penta-O-acetylglucopyranos-l-yl radical with tributyltin deutcride, the axial trapping product is formed in far higher yield compared to other radicals with equatorial -substituents44. This is attributed to stereoelectronic effects between the ring oxygen atom and the radical center. [Pg.637]

Rate data have been obtained from a detailed analysis of the previously reported 1420 maximum and fall off in the photodimerization of acenaphthylene with increasing concentrations of dissolved ethyl iodide.1420 The heavy-atom solvent dibromomethane facilitates the cross cycloaddition of acenaphthylene to trans- and cw-penta-1,3-diene by inducing intersystem crossing to the triplet state of the aromatic hydrocarbon. The intermediacy of a biradical is proposed and the stereospecificity can be understood in terms of the maintenance of the stereochemical integrity of the allylic radical units.143... [Pg.72]

Other Reactions of Allenes.— Radical-chain additions to allenes are presumed to involve radical intermediates of allylic structure by initial attack at the central carbon atom or of vinylic structure by attack at the terminal carbons. The extent to which these structures are preferred depends upon structure of starting allene, nature of attacking radicals, and reaction conditions. Addition of toluene-/ -sulphonyl iodide to chiral allenes (cyclonona-1,2-diene and penta-2,3-diene) results in racemic products (376), and hence attack on... [Pg.74]

Such tetrathedral sorbtion complex can be formed only in the intersections of two types of channels in the structure of penta-sile zeolites. The first alcohol molecule displaces Ha cation from equilibrium position in a lattice (this is supported by linear drop of heat on the whole section of filling from 0 to 0.5 mmol/g) and localizes it on favourable positioned oxigeii atoms of a lattice in the points of channels intersection. In this case methyl and especially ethyl groups partially enter straight channel of zeolite. The second alcohol molecule is added to localized complex from the opposite side as well as with alkyl radical partially in a straight channel. To form such a... [Pg.531]


See other pages where Penta-atomic radicals is mentioned: [Pg.9]    [Pg.9]    [Pg.25]    [Pg.896]    [Pg.159]    [Pg.702]    [Pg.40]    [Pg.60]    [Pg.3]    [Pg.313]    [Pg.229]    [Pg.159]    [Pg.44]    [Pg.330]    [Pg.339]    [Pg.136]    [Pg.455]    [Pg.448]    [Pg.368]    [Pg.381]    [Pg.126]    [Pg.152]    [Pg.444]    [Pg.70]    [Pg.37]    [Pg.68]    [Pg.45]    [Pg.92]    [Pg.290]    [Pg.46]    [Pg.3]   
See also in sourсe #XX -- [ Pg.18 ]




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