Phenyl radical preparation

An alternative method of preparation of the cyclohexyl radical which has been used is by the reaction of the phenyl radical (prepared from phenyl iodide and sodium) with a matrix of cyclohexane. Clearly the amount of cyclohexane formed by the disproportionation reaction cannot be measured. However, the amount of benzene, formed in the initial abstraction reaction, is equal to that of the cyclohexyl radicals and thus also to the total amount of products formed by the cyclohexyl termination reactions. Thus a mass balance can be made and values of k jkc (Table 9) calculated on the same basis as before (Fig. 20). An upper limit of the value of k jk can be obtained from these experiments on the assumption that no side reactions occur. The material balance gives... 

Phenyl radicals attack azoles unselectively to form a mixture of phenylated products. Relative rates and partial rate factors are given in Table 7. The phenyl radicals may be prepared from the usual precursors PhN(NO)COMe, Pb(OCOPh)4, (PhC02)2 or PhI(OCOPh)2. Substituted phenyl radicals react similarly. 

Arylations have been used to prepare pentafluorophenylbenzene, but the overall reliabihty of these methods is quesQoiiable In particular, if phenyl radicals... 

The trapping of alkyl, alkoxyl and alkylthiyl radicals by trivalent phosphorus compounds, followed by either a-scission or p-scission of the ensuing phosphoranyl radical, is a powerful tool for preparation of new trivalent or pen-tavalent phosphorus compounds [59]. However, the products of these reactions strongly depend on the BDE of the bonds, which are either formed or cleaved. For example, the addition of phenyl radicals on a three-coordinate phosphorus molecule occurs irreversibly, while that of dimethylaminyl (Me2N ) or methyl radicals is reversible, the amount of subsequent P-scission (formation of compound C) depending on the nature of Z and R (Scheme 25). For tertiary alkyl radicals and stabilized alkyl radicals no addition is observed (Scheme 25) [63]. 

Reduction of phenyldiazonium chloride in acetonitrile containing a high concentration of an aromatic substrate, which can act as a free-radical trap, leads to phenylation of the substrate in 14 - 33% yields together with 50 - 50% of benzene formed by phenyl radical attack on the acetonitrile [132], Intramolecular capture of the phenyl radical, in an electrochemical equivalent of the Pschorr reaction, is much more successful and phenanthrene derivatives can be prepared in 90 - 96% yield [133],... 

To confirm the structures of the products formed in the reaction between thienothiophenes 1 and 2 and phenyl radicals, the corresponding 2-phenyl- and 3-phenyl-substituted thienothiophenes 1 and 2 were synthesized by independent methods (see Section II,B). In addition, 2-phenyl-substituted thienothiophenes 1 and 2 were prepared by photolysis of the corresponding 2-iodo compounds, under conditions previously used with the iodothiophenes [Eqs. (86), (87)]. 

The hydantoins (116 and 117) have been prepared from DL-j8-ferrocenyl-a-alanine and N - ferrocenyl methyl-AT-(a-carbethoxy-benzyl)urea, respectively.68 The Friedel Crafts reaction of ferrocene and 2-pyrroylchloride gave the ketone (118).112,113 The polarographic half-wave potentials of 118 and other related ferrocenes were measured113 and it was concluded that the ferrocene radical was more electropositive than the phenyl radical. 

Our initial experiments to prepare the radical by the reaction of sodium atoms with phenyl iodide were inconclusive because the resolution was very poor when the parent halide was used as the matrix. Attempts to increase the resolution by using camphane or adamantane as a matrix were unsuccessful as immediately after formation the phenyl radical abstracted hydrogen from the matrix to form benzene and a radical from the matrix. Complete reaction also occurred with matrices of other saturated hydrocarbons which possessed only secondary hydrogens... 

An example of the first type of reaction is provided by the preparation of the cyclohexyl radical by the reaction of phenyl radicals with cyclohexane. The preparation of the cyclohexyl radical without the use of a... 

Tri-phenyl amine is prepared by treating a boiling solution of sodium in di-phenyl amine with brom benzene. The acid influence of the phenyl radicals gives to di-phenyl amine the property of forming a sodium compound which then reacts with the brom benzene. 

Secondary thioamides react with dimethylcyanomethyl radicals to give thioimidic acid anhydrides (288 Scheme 44), in poor yields,whereas with phenyl radicals phenylthioimidates (289) are obtained in fairly good yields. Thiolactim ethers (290 equation 154) (ring size 6-9) have been prepared by rearrangement of l-azido-l-methylmercaptocycloalkanes. ... 

Radicals 9 and lOJj were prepared with the hope of increasing phenyl radical persistence by increasing the distance the H-atom must jump in a 5-center intramolecular H-atom abstraction in comparison with the distances involved for IJj and 4fj e.g., 2.25 A for 9Jj. This approach was unsuccessful (in solution) because of intermolecular H-atom abstraction by the more exposed radical centers. However, these experiments did serve to define the requirements necessary to most readily observe unequivocal examples of QMT in intermolecular H-atom abstractions, viz., relatively fixed and relatively close spatial coordinates for the H-atom donor and the H-atom receiver, see final section in this chapter. 

Acetic aldehyde can be formed in a similar way from ethylidene chloride, CH3.CHCI2, but its preparation by this reaction lacks practical value. There is marked difference between the ease with which benzal chloride and ethylidene chloride react with water the presence of the phenyl radical in the former brings about an activity not shown by the aliphatic halide. The choice of the compounds used in the preparation of the two classes of aldehydes is determined, to some extent, by the substances which can be obtained conveniently and at a low price. The alcohols are, in general, the starting point for the preparation of many aliphatic compounds, on account of their reactivity and the fact that they are prepared commercially on a large scale. In the aromatic series, on the other hand, the hydrocarbons are of the greatest importance as a source of other compounds. 

Derivatives of pyridine, quinoline or woqiiinolme may be prepared by causing the diazotised ammo-compounds of such substances to react with antimonites or the corresponding free acids. The parent material may contain substituents, e.g. hydroxy-, ammo-, carboxy- or phenyl- radicals or halogens. The most advantageous proportions appear to be 2 to 3 molecular equivalents of antimomte to each equivalent of heterocyclic compound. Reduction with suitable agents produces stibino-compoimds. ... 

Graft epoxy-acrylic copolymer prepared with a free radical initiator is an example of the "grafting from" process. In the case where benzoyl peroxide was used as the free radical initiator, it is determined that about 77% of the free radical initiator instead of causing initiation of monomers, chain transfers with the epoxy resin backbone, followed by the "grafting from" of22onomers onto the epoxy resin. Benzoyl peroxide is known to decompose mostly (90 ) to the benzoyloxy radical and the (10 ) phenyl radical. Mechanisms of grafting can be demonstrated in the following two schemes. (Schemes A and B). 

The phenyl radicals then abstract hydrogens from the methyl groups that are present when the polysulfone is prepared from bisphenol A ... 

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