Radicals, derived from

Such reactions can be initiated by free radicals, derived from compounds (initiators) such as benzoyl peroxide, ammonium persulphate or azobis-isobutyronitrile or by ionic mechanisms... 

The radical cation and neutral radical derived from triethylamine are shown below. 

Anion-radicals derived from the reduction of nitrothiazoles were studied by Tordo et al. (285). The reaction scheme is the following ... 

Univalent radicals derived from saturated unbranched alkanes by removal of hydrogen from a terminal carbon atom are named by adding -yl in place of -ane to the stem name. Thus the alkane... 

Bivalent radicals derived from saturated unbranched alkanes by removal of two hydrogen atoms are named as follows (1) If both free bonds are on the same carbon atom, the ending -ane of the hydrocarbon is replaced with -ylidene. However, for the first member of the alkanes it is methylene... 

Bivalent radicals derived from unbranched alkenes, alkadienes, and alkynes by removing a hydrogen atom from each of the terminal carbon atoms are named by replacing the endings -ene, -diene, and -yne by -enylene, -dienylene, and -ynylene, respectively. Positions of double and triple bonds are indicated by numbers when necessary. The name vinylene instead of ethenylene is retained for —CH=CH—. 

Radicals derived from monocyclic substituted aromatic hydrocarbons and having the free valence at a ring atom (numbered 1) are named phenyl (for benzene as parent, since benzyl is used for the radical C5H5CH2—), cumenyl, mesityl, tolyl, and xylyl. All other radicals are named as substituted phenyl radicals. For radicals having a single free valence in the side chain, these trivial names are retained ... 

Radicals derived from heterocyclic compounds by removal of hydrogen from a ring are named by adding -yl to the names of the parent compounds (with elision of the final e, if present). These exceptions are retained ... 

Radicals derived from furan are named similarly to analogous radicals in the ben2ene series. Typical radicals are 2 (or a)-furyl (5), 2-furfuryl (6), 2-furoyl (7), and 2-furfur5hdene (8) ... 

Phospholipids. Phospholipids, components of every cell membrane, are active determinants of membrane permeabiUty. They are sources of energy, components of certain enzyme systems, and involved in Hpid transport in plasma. Because of their polar nature, phosphoUpids can act as emulsifying agents (42). The stmcture of most phosphoUpids resembles that of triglycerides except that one fatty acid radical has been replaced by a radical derived from phosphoric acid and a nitrogen base, eg, choline or serine. 

Some heterocyclic compounds are at the same time cyclic examples of common functional groups. In such cases, they may be so named, and radicals derived from them may be derived accordingly, as in (164). 

Another quite general source of free radicals is the decomposition of azo compounds. The products are molecular nitrogen and the radicals derived from the substituent groups ... 

Two classes of charged radicals derived from ketones have been well studied. Ketyls are radical anions formed by one-electron reduction of carbonyl compounds. The formation of the benzophenone radical anion by reduction with sodium metal is an example. This radical anion is deep blue in color and is veiy reactive toward both oxygen and protons. Many detailed studies on the structure and spectral properties of this and related radical anions have been carried out. A common chemical reaction of the ketyl radicals is coupling to form a diamagnetic dianion. This occurs reversibly for simple aromatic ketyls. The dimerization is promoted by protonation of one or both of the ketyls because the electrostatic repulsion is then removed. The coupling process leads to reductive dimerization of carbonyl compounds, a reaction that will be discussed in detail in Section 5.5.3 of Part B. 

By using various trapping reagents, it has been deduced that the transannular fragmentation is rapidly reversible. The cyclization of the fragmented radical C is less favorable, and it is trapped at rates which exceed that for recyclization under most circumstances. " Radicals derived from ethers and acetals by hydrogen abstraction are subject to fragmentation, with formation of a ketone or ester, respectively. 

H2 and H2O2 [64]. The three primary radical species react with monomers to give radicals derived from monomers [63]. All these generated radicals are available to contribute to the chain initiation. This increases the exponent of the monomer concentration in these systems. 

Isocyanides can be reduced to the corresponding hydrocarbons by (TMS)3SiH. The reaction can be considered as a smooth route for the deamination of primary amines. An example is given in Reaction (20). The key step for these chain reactions is expected to be the fragmentation of the intermediate radical derived from the fast addition of (TMSlsSi radical to the terminal carbon atom. 

The number of reported reactions in which the radical derived from the decomposition of AIBN plays a role in the termination process has increased considerably. Often these reactions are not radical chain reactions, since the initiator is used in stoichiometric amounts. A few examples of rearomatization of cyclohexadienyl radicals by disproportionation have been reported herein. Below are some other examples, where the phenyl selenide 61 reacts with (TMSfsSiH (3 equiv), AIBN (1.2 equiv) in refluxing benzene for 24 h to give the coupling product of radicals 63 and 64 in good yields (Scheme 9).i24,i25 these cases,... 

In another procedure, acyl radicals derived from phenyl selenoesters ArCOSePh I by treatment of them with Bu3SnH) add to a,P-unsaturated esters and nitriles to give y-keto esters and y-keto nitriles, respectively. ... 

Regrettably, Q and e values are imprecise and tend to vary with the reactivity ratios used in their calculation (115). An attempt has been made to improve the Price-Alfrey equation by the assignment of different values of e to the monomer and to the radical derived from it (116). Schwan and Price (117) have reexamined the Price-Alfrey equation, and they write it in the form ... 

Alkali metal reduction is a widely employed method for the preparation of radicals derived from various classes of conjugated compounds such as hydrocarbons, heterocycles, nitro compounds, quinones, and nitriles. For... 

By pulse radiolysis of nitrous oxide-saturated aqueous solutions of ferricyanide (2 X 10 " M) and various alcohols (0.1 M), Adams and Willson " were able to obtain absolute rate coefficients for the ferricyanide oxidation of the radicals derived from the alcohols by attack of the solvent irradiation product, OH-. 

Carotenoid radicals — Many of the important oxidations are free-radical reactions, so a consideration of the generation and properties of carotenoid radicals and of carbon-centered radicals derived from carotenoids by addition of other species is relevant. The carotenoid radicals are very short-lived species. Some information has been obtained about them by the application of radiation techniques, particularly pulse radiolysis. Carotenoid radicals can be generated in different ways. "... 

Matsuo, M. Matsumoto, S. Electron spin resonance spectra of the chromanoxyl radicals derived from tocopherols (vitaminE) and theirrelated compounds. Lipids 1983,18, 81-86. 

Mukai, K. Tsuzuki, N. Ouchi, S. Fukuzawa, K. Electron spin resonance studies of chromanoxyl radicals derived from tocopherols. Chem. Phys. Lipids 1982, 30, 337-345. 

Since alkoxy radicals are known precursors to chain scission in autoxidation (24), the "hot" alkoxy radicals formed as shown should undergo facile chain scission or fragmentation. The chain scission is illustrated for the alkoxy radical derived from either the ethylene or propylene monomer unit in EPM ... 

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