Radicals hetero-substituted

Dialkyl peroxides have the stmctural formula R—OO—R/ where R and R are the same or different primary, secondary, or tertiary alkyl, cycloalkyl, and aralkyl hydrocarbon or hetero-substituted hydrocarbon radicals. Organomineral peroxides have the formulas R Q(OOR) and R QOOQR, where at least one of the peroxygens is bonded directly to the organo-substituted metal or metalloid, Q. Dialkyl peroxides include cyclic and bicycflc peroxides where the R and R groups are linked, eg, endoperoxides and derivatives of 1,2-dioxane. Also included are polymeric peroxides, which usually are called poly(alkylene peroxides) or alkylene—oxygen copolymers, and poly(organomineral peroxides) (44), where Q = As or Sb. 

Non- nucleophilic" radicals, e.g. alkyl radicals not substituted by a hetero atom at C do not... 

Carboxylates with different non-racemic chiral auxiliaries have been anodically de-carboxylated to explore the face-selective hetero- and homocoupling of the intermediate radicals. 2-Substituted malonamides were subjected to heterocoupling with different coacids. In the acids 30a-c, (2/ ,5.R)-2,5-dimethylpyrrolidine served as chiral amido group. 

The preparation of heteroarotinoids (9) and (10) Schemes 1.1 and 1.2) [29,31] began with the conversion of the known amines (18) [71] and (19) [72] to the respective fluoroborate diazonium salts (20) and (21), respectively, by standard techniques. Generation of the aromatic free radical was accomplished in acetone in the presence of the stable free radical TEMPO. Cyclization of hetero-substituted aromatic free radicals generally occurs in a regiospecific manner with the formation of an exocyclic primary radical which then couples with a second molar equivalent of TEMPO [73-75]. However, both exo- and endo-cyclic free radicals were generated from salt... 

Another heterochain polymer which has received a lot of attention recently is polyaniline. This material is produced by chemical or electrochemical oxidation of aniline, and it seems likely that it is very similar to, if not always identical with, aniline black , an ill-defined material of some antiquity. The propensity of hetero-substituted aromatics to undergo coupling via intermediate radical cations is well established and, since a monosubstituted benzene is effectively a trifunctional monomer in this context, it seems likely that this product is a network or highly branched material, which would account for its unattractive handling properties. 

Thus the activity of the methyl groups in this reaction decreases in the series C-4 > C-5 > C-3. This may be considered as evidence of the inhibiting effect of the nitrogen hetero atom on the radical substitution in methyl groups at C-3 and, to a lesser extent, at C-5 (compare the effect of the heterocyclic nitrogen in the pyridine and azole series ) and of a similar effect of the electron-accepting substituents in the 4-position on the methyl group at C-5. 

Oxidation of Carbon-Centered Radicals Substituted by a Hetero-Atom E at Ca... 

The examples so far described always involve a carbon-centered radical which is substituted at by a hetero atom such as O, S, or N. S is always a functional group that contains a double bond, usually an oxygen, i.e. the group =0. X then adds to S according to ... 

Depending on the nature of the attack on an aromatic nucleus, reagents are classified as electrophilic, nucleophilic, or radical. The fact that most chemists associate the term aromatic substitution with nitration, sulfonation, or azo coupling of the benzene ring demonstrates the predominance of the electrophilic substitution type in the carbocyclic series. However, the presence of a hetero atom in the ring changes the electron distribution in such a manner that nucleophilic substitutions gain more importance. That this situation is identical with the effect exercised by certain substituents attached to a carbocyclic system can... 

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