Alkoxy radicals ethoxy

The first step in the pyrolysis of the alkyl nitrates has been supposed to be O N bond fission to give NO2 and an alkoxy radical. The activation energy is 39-5 kcal for methyl nitrate and 39-9 or 34-6 kcaP <> for ethyl nitrate. If the latter value for ethyl nitrate is taken, and assumed to be i)(EtO -NO2) a value for the heat of formation of the ethoxy radical in good agreement with that given by Rebbert and Laidler is obtained, so apparently we may put D(MeO -NO2) =40 kcal, and i)(EtO -NO2) =34 kcal. In the opinion of the present author, however, the mechanism of the reaction is not sufficiently well established to allow this to be done. The discrepancy between the result of Adams and Bawn and that of Phillips 390 is large and may well be because of the different pressure ranges in which these authors worked. A further examination of the effect of pressure on rate constant is necessary before it can be taken as established that the reaction is of the first order. 

Fig. 8 Schematic representation of the geometries of the alkoxy radicals, methoxy, ethoxy, vinoxy, and i-propoxy. The highest occupied 7r-orbitals, approximately localized on the 0 atom, are indicated for each molecule.

Even though the radical attacking ethyl alcohol in the above reaction generated a-hydroxyethyl rather then ethoxy free radical, there seems to be little or no tendency for alkoxy free radicals to rearrange to a-hydroxyalkyl radicals. Thus in the reaction... 

The use of iV-alkoxy pyridinium salts is not limited to cationic polymerization. Since, in addition to cationic species, ethoxy radicals are also formed upon direct and sensitized irradiation of pyridinium salts (see above), pyridinium salt based photoinitiating systems may be used to initiate the polymerization of vinyl monomers that are prone to free radical polymerization. Kayaman et al. [71] recently polymerized mono- and bi-functional acrylate monomers by photosensitization of pyridinium salts. It therefore appears that pyridinium salts can promote both cationic and free radical polymerization and are, thus, eminently suitable for use in hybrid systems. 

Both 102 and 108 were confirmed as (macro)alkyl radical scavengers in an oxygen deficient environment. 102 traps 1-cyano-l-methylethyl used in excess [107]. The respective thermolabile JV-alkylate 110 (R = EtO, 20% yield) and a stable 8-alkylate 111 (R = EtO, 50% yield) are formed. 6-Ethoxy-8-alkoxy-2,2,4-trimethyl-l,2-dihydroquinoline 112 (R=EtO, R1 = 1-cyano-l-methylethyl) is formed as the main product from 108, probably by isomerization of the O-substituted hydroxylamine generated in the first stage from 108. 

The dominance of the apical ligands in the LCAO description of the semi-occupied orbital of these radicals is emphasised not only by the invariance of aj q gqj to apical substitution, but also by the relatively minor changes ina.3] and ajq p) on equatorial substitution. Alkoxy groups, as opposed to fluoro alkoxy groups, appear preferentially in equatorial positions in phosphoranylradicals. A comparison of the data for PF4 with those for its ethoxy-substituted derivatives (Table IV) shows that apical substitution of OEt for F has a far greater effect on the Pand ypej-fineinterac-... 

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