Secondary radicals definition

Modified from the definition in [1,2]. secondary radical (in a chain polymerization)... 

When characterizing polymer networks, the following definitions are typically applied [150] and are illustrated in Fig. 7. When a radical on a polymer chain propagates through a pendant double (i.e. a double bond from a monomer with one double bond already reacted), a crosslink, secondary cycle, or primary cycle can be formed. A crosslink forms when the radical reacts with a pendant... 

Deoxygenation of ROH. Acetates, primary, secondary, or tertiary, are deox-> genated when heated with 1 in the presence of a radical initiator, di-r-butyl peroxide (DTBP). Yields using (C6H5)3SiH in place of 1 are definitely lower. The presence of a double bond in the substrate can lower yields owing possibly to hydrosilylation. 

It appears to be established that, at low temperatures, the reaction order is close to i and that the experimental results can be interpreted by a simple Rice-Herzfeld mechanism. At higher temperatures, the decomposition of the C2H5 radical becomes significant and the mechanism discussed above describes the kinetic data (at small conversions). There are, however, definite indications that at higher conversions and temperatures several secondary reactions occur resulting in the formation of a number of minor products. The kinetics of the reaction is rather complex under such circumstances. If these reactions can be neglected (small conversions), the mechanism is resonably described by steps (3)-(9). The steady-state treatment leads to... 

Regarding the possible mechanism, notably, toluene, ethylbenzene and terf-butylbenzene are less reactive than benzene, which is not consistent with the expected order for an electrophilic aromatic substitutions, such as that found with the classic Fenton reagent. There are also other differences with respect to the Fenton chemistry. In particular, under biphase conditions the reaction is definitely more selective although comparisons are difficult due to the huge amount of data, sometimes inconsistent, on the Fenton system (for which most of the data have been obtained with the iron used in stoichiometric amounts) it seems that selectivities dose to those observed under biphase conditions are only attained at a conversion around of 1%. Furthermore, in the biphase system, only a negligible amount (<1%) of biphenyl was detected among secondary products, whereas in the classic Fenton oxidation this compound is formed by radical dimerization of hydroxycydohexadienyl radicals in typical yields ranging from 8 to 39%. 

The well-known oxidations of primary and secondary alcohols with Cr species proceed through chromate esters. The definitive mechanistic expeii-ments " demonstrating that previously observed chromate esters were indeed on the reaction pathway showed that either formation or decomposition of the ester could be rate-determining. The rates of oxidation of cyclohexanol and the secondary hydroxyl group of a very steiically hindered steroid in aqueous acetic acid were measured as a function of the solvent composition. The former increased radically as the acetic add concentration increased whereas the latter remained invariant. The former exhibited a primary deuterium kinetic isotope effect of 5, whereas there was no KIE on the oxidation of the crowded steroid. Therefore, the rate-determining step in the oxidation of the cyclohexanol was decomposition of the chromate ester and in the oxidation of the steroid it was its formation, with the ester an obligate intermediate in both reactions. 

The great variation in the types of active centres generated in the irradiated monomer makes it possible to initiate polymerization by different mechanisms. In each specific case, the nature of the monomer determining the formation of a certain type of active centre which ensures effective initiation and the polymerization conditions, mainly the temperature and the medium (solvents), are of the greatest importance. Hence, the polymerization process usually occurs by a certain definite mechanism. Since in the course of secondary radiation-chemical transformations, in practice, particles with a longer lifetime form free radicals, the free-radical mechanism is the simplest process of radiation-induced initiation. 

The conversion of the green primary complex into the pale red secondary complex appears to be a reduction process even though it occurs in the absence of any added hydrogen donors. The most definite evidence for this is the case of peroxidase where the speed of the conversion is increased in the presence of all compounds with which the peroxide system reacts (Chance, 55). For catalase, where the conversion can only be obtained with alkyl hydroperoxides, the evidence is not so clear-cut, but at least the velocity of formation of the secondary complexes increases as the hydroperoxide concentration is increased. An alternative explanation for these effects would be that the primary and secondary complexes are in some sort of equilibrium where removal of the latter would have the effect of increasing the rate of conversion. There is no indication of any such equilibrium, however, and direct reduction of the primary complex appears to be the most likely explanation. One possible formulation for this change involves the production of a ferryl ion type of compound by the removal of an OH radical by the hydrogen donor from the 02H anion bound to the iron atom ... 

In 1958, Geiseler and Nagel31 reported the energetics of the chlorosulphonation reaction of n-dodecane (31) with a mixture of S02 and Cl2 (equation 14.) They reported that a mixture of primary and secondary sulphonyl chlorides were formed accompanied by liberation of 39.0 + 0.5 kcal mol-1. The ratio of primary (19) to (the other wise undefined mixture of isomeric) secondary products (32) was determined to be ca 1 11. However, in the absence of further study, we cannot determine how much this reaction is thermodynamically driven (e.g. sulphonyl chloride and free radical stabilities) versus kinetically driven (e.g. free radical reactivities). We will assume that the difference in heats of formation of all of the secondary sulphonyl chlorides are the same. That the difference of the heats of formation of the primary and secondary products is about 2 kcal mol-1 may be derived from values for a set of isomeric primary (n-) and secondary (i-) propyl derivatives shown in Table 8. From the long known and highly accurate heats of formation of liquid n-dodecane (31, — 83.9 kcal mol-1, Reference 3) and of gaseous S02 and HC1 (—70.9 and — 22.1 kcal mol-1, Cl2 equalling 0 by definition, all from Reference 12), we derive the heat of formation of any of the five different secondary n-dodecanesulphonyl chlorides (32) to be —171.9 kcal mol-1 and for the primary n-dodecane-1-sulphonyl chloride (19) a value of —169.9 kcal mol-1. 

CAS 61789-76-2 EINECS/ELINCS 263-086-0 Synonyms Amines, dicoco alkyl Dicoco alkyl amine Definition Secondary aliphatic amine derived from coconut acid Formula RjNH, R represents the coconut radical Properties Solid m.p. 40-47 C cationic Toxicology TSCA listed... 

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