Hydrocarbons toward

Table 12.10. Relative Reactivities of Some Aromatic Hydrocarbons toward Oxygen"...

The reactivity of a series of hydrocarbons toward oxygen measured under a standard set of conditions can give some indication of the susceptibility of various structural units to autoxidation. Table 12.10 gives the results for a series of hydrocarbons. These data indicate the activating effect of alkyl, vinyl, and phenyl substituents. 

Solubilizing activity are also used in enhanced oil recovery. Tar and extremely viscous hydrocarbons are recovered by the injection of an aqueous solution of an anionic orthophosphate ester surfactant into a petroleum formation, retaining the surfactant in the formation for about 24 h, and displacing the solubilized hydrocarbons toward a recovery well. The surfactant forms an oil microemulsion with the hydrocarbons in the formation. An anionic monoorthophosphate ester surfactant which is a free acid of an organic phosphate ester was dissolved in water. The input of surfactant solution was 2-25% of the pore volume of the formation [250]. To produce a concentrate for the manufacture... 

Bond-Stretch Isomerism and the Reactivity of some Highly Strained Tricyclic Hydrocarbons towards Acids and Bases... 

An indication of the nature of the transition state in aromatic substitution is provided by the existence of some extrathermodynamic relationships among rate and acid-base equilibrium constants. Thus a simple linear relationship exists between the logarithms of the relative rates of halogenation of the methylbenzenes and the logarithms of the relative basicities of the hydrocarbons toward HF-BFS (or-complex equilibrium).288 270 A similar relationship with the basicities toward HC1 ( -complex equilibrium) is much less precise. The jr-complex is therefore a poorer model for the substitution transition state than is the [Pg.150]

Table III. Relative Reactivities of Hydrocarbons Toward Various Radicals"...

Tphe original objectives of this work were to determine how much the relative reactivity of two hydrocarbons toward alkylperoxy radicals, R02, depends on the substituent R—, and whether there are any important abnormalities in co-oxidations of hydrocarbons other than the retardation effect first described by Russell (30). Two papers by Russell and Williamson (31, 32) have since answered the first objective qualitatively, but their work is unsatisfactory quantitatively. The several papers by Howard, Ingold, and co-workers (20, 21, 23, 24, 29) which appeared since this manuscript was first prepared have culminated (24) in a new and excellent method for a quantitative treatment of the first objective. The present paper has therefore been modified to compare, experimentally and theoretically, the different methods of measuring relative reactivities of hydrocarbons in autoxidations. It shows that large deviations from linear rate relations are unusual in oxidations of mixtures of hydrocarbons. 

A subsequent paper (23) gives propagation and termination constants for numerous additional hydrocarbons and deals mostly with relative reactivities of active hydrogen atoms and with effects of structure on termination constants. A comparison of relative reactivities of hydrocarbons toward alkylperoxy, tert-butoxy, and phenyl radicals uses a different alkyl in each alkylperoxy radical in spite of the differences in reactivity among different alkylperoxy (29) radicals. 

Reactivity Ratios and Relative Rates of Oxidation. Table VI summarizes reactivity ratios for all combinations of butadiene, styrene, Tetralin, and cumene reported here and by Hendry (12) for butadiene. The underscored r values in the table are calculated from the base point in the same column (1.00) and the reciprocals (because of the definition of r in Equation 2) of the relative reactivities of the hydrocarbons toward an average R02 radical, B S T C = 1.0 2.2 4.5 5 30 (all underscored values in the butadiene column). The calculated and experimental values always agree within 50%, and in seven out of 12 systems, within 15%. Thus, among these four hydrocarbons a change of R— in RC>2 affects relative reactivities by less (often much less) than 50%. 

Nielsen, T., Reactivity of Polycyclic Aromatic Hydrocarbons towards Nitrating Species, Environ. Sci, Technol., 18, 157-163 (1984). 

Reactivity of Strained Hydrocarbons Toward External Reagents. 733... 

REACTIVITY OF STRAINED HYDROCARBONS TOWARD EXTERNAL REAGENTS... 

H- (R). That is, the RH would be presenting a hydridic type of H atom to the CH2 group. This is very much in line with the types of reactivity displayed by hydrocarbons towards the isoelectron ic BII3 group. ... 

It is noteworthy that the reactivity of hydrocarbons towards CrOs(Ph3PO) parallels their reactivity toward R02- radicals for hydrogen abstraction. This suggests that Crvl-peroxo complexes almost exclusively act as hydrogen atom abstractors, in their homolytically dissociated form Crv—OO (equation 39).80... 

The complementary approach, activation of unsaturated hydrocarbons toward electrophilic attack by complexation with electron-rich metal fragments, has seen limited investigation. Although there are certainly opportunities in this area which have not been exploited, the electrophilic reactions present a more complex problem relative to nucleophilic addition. For example, consider the nucleophilic versus electrophilic addition to a terminal carbon of a saturated 18-electron metal-diene complex. Nucleophilic addition generates a stable 18-electron saturated ir-allyl complex. In contrast, electrophilic addition at carbon results in removal of two valence electrons from the metal and formation of an unstable ir-allyl unsaturated 16-electron complex (Scheme 1). 

III. The reactivities of hydrocarbons toward the styrene radical. Disc. Faraday Soc. 2, 328 (1947). 

Selectivity in the transformation of hydrocarbon towards a specific hydroperoxide is usually low which is due to the parallel decomposition of the latter and to side reactions of peroxyl radicals with oxidation products. In the case of polymers this is moreover enhanced by the presence of reactive defect structures in a polymer, which are the sites of the oxygen attack in the first stages of the reaction. 

Relative Reactivities of Hydrocarbons toward Cobalt Oxidation... 

As mentioned above, there is a scarcity of data on how variations in ketone structure affect CT quenching rates. A comparison of the interactions of substituted benzenes with triplet acetophenone and triplet a-trifluoroacetophenone is interesting 182,182). The relative reactivities of various hydrocarbons towards triplet acetophenone are suggestive of direct hydrogen atom abstraction by the triplet ketone. The low reduction potential of the trifluroketone enhances the rate of CT quenching so much that photoreduction proceeds almost entirely by a... 

Every teacher of the first course of organic chemistry, towards its beginning, emphasizes the different behavior of saturated and olefinic hydrocarbons towards halogens. The influence of ring strain is discussed rather later in the course. And a good thing too, for... 

The propensity of the parent hydrocarbon towards oxygen and sulfur nucleophiles (RO , RS ) has been noted earlier. 

Ihe reactivity of alkenes, alkynes, and aromatic hydrocarbons toward electrophiles in addition and substitution reactions is based on their jc-donor abihty. In any reaction involving the attack of an electrophile on a multiple bond, the initial interaction is between the electrophile and the electrons of the tc bond. 

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