Electronic Structure and Reactivities of Monoölefins

Sato, Seiichiro; Cvetanović, R. J.

doi:10.1021/ja01522a016

Cited by 41 publications

(12 citation statements)

References 4 publications

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“…The rate constant of the reaction of oxygen atonls with butadiene is very close to that of isobutene ancl other two-substituted ethylene clerivatives as may be expected in view of the electrophilic character of oxygeil atoms in their reactions with olefins (2,9). The temperature coefficient of the rate constant will be discussed elsewhere together with the data obtained for a number of monoolefins (10).…”

Section: Discussionsupporting

confidence: 52%

Reaction of Oxygen Atoms With Butadiene

Cvetanović¹,

Doyle²

1960

Can. J. Chem.

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Reaction of oxygen atoms with 1,3-butadiene has been investigated a t rooin temperature. It is found that it conforms to the general rnechanisil~ established previously for the analogous reactions of rnonoolef~ls. 0111y 1,2-addition occurs, and the addition products, butadiene moi~oxide and 3-butenal, possess excess energy when formed as a result of high heats of reaction. The pressure dependence of the forlnation of the addition products yields the values of the "lifetimes" of the initially produced "hot" tliolecules.~The relative rate cotlstants have been determined a t 25 and 127" C and froin these the relatlve values of the A r r h e n i~~s parail~eters have been calculated.The general mechanism of reaction of oxygen atoms with allcenes has recently been established in this laboratory (1) and the trends in the relative rate constants (2) demonstrated the electrophilic character of the ground-state oxygen atoms in these reactions. As an extension of this work the present study of the analogous reaction with 1,3-butadiene, as the simplest representative of conjugated diolefins was carried out.The particular questions which the present investigation was hoped to ails\\-er are: first, whether conjugated diolefins in their reactions with oxygen atoms follo~v the general mechanisn~ established for monoolefins; secondly, whether only 1,2-or also l,4-addition products are formed; and lastly, ivllether the value of the rate constant of the reaction of oxygen atoms with 1,3-butadiene is such as inight be expected in view of the trends and relations established in the case of monoolefins (2). Affirmative answers to these questions have been obtained and only the tmo 1, 2-addition products predicted on the basis of the rules forinulated for the monolefins (I), butadiene monoxide and 3-butenal, the latter readily isomerizing to the more stable crotonaldehydc, have been observed. The 1,4-addition product, 2,s-dihydrofuran, is not formed.The pronounced pressure effect observed in the present work illustrates particularly \ d l initial formation of "hot" addition products and the consequent "pressure-dependent frngmentation" (1) in the reactions of oxygen atoms with olefins. As a result, in some of these reactions, including 1,s-butadiene itself, the addition products are essentially completely decomposed a t pressures of a few millin~eters and are then not observable experimentally. This feature and some other difficulties inherent in the electrical discharge method for production of oxygen atoms, as discussed recentl>. else\\~here (3), are believed to be responsible for the entirely different conclusions from the present ones arrived a t by Avralnenko and I

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Section: Discussionsupporting

confidence: 52%

Reaction of Oxygen Atoms With Butadiene

Cvetanović¹,

Doyle²

1960

Can. J. Chem.

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“…Also approximate linear free energy plots were obtained with some other series of electrophilic reactions (12), as well as approxin~ate linear correlations with the theoretically derived excitation energies and bond orders (17). In view of the more con~plete and more accurate list of the relative rate constants for this reaction series now available (Table 111), and additional literature information for some of the other reaction series considered, it is necessary to examine these correlations in somewhat greater detail.…”

Section: Resultsmentioning

confidence: 96%

“…2 relative rate constants are plottecl against the excitation energies obtained by ~llolecular orbital calculatioils (17). Excellent linear correlation is shown by the peracetic acid series.…”

Section: Resultsmentioning

confidence: 97%

Electrophilic Character of Oxygen Atoms

Cvetanović¹

1960

Can. J. Chem.

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The relative rates of reactions of oxygen atoms with a n~~r n b c r of olefins in the vapor phase deter~nined in previous nrorl; are s~ummarized and supplenlented by some additional results. The uncertainty in the values of the relative rate constants is no\\; believed to be reduced to only a few per cent. A n~~m b e r of simple correlations observed previously have been re-exa~~~inecl on the basis of the more complete and more accurate list of values available a t present. These correlations show a distinct electrophilic character of oxygen atoms in their reactions with olefins and their potential significance for the understanding of the finer details of these addition processes is discussed. INTRODUCTIONPossibilities of finding simple correlations between reaction rates and physical properties of the reactants have been extensively explored a t various times in the past wit11 the object of establishing the factors which contribute to chemical reactivity. Thus, for example, considerations of the lilcely potential energy changes when two molecules interact have suggested linear dependeilce of activation energies on such quantities as heats of reaction or singlet-triplet excitation energies (1-6). In the case of metathetical reactions such views have found little experimental support. Some additioil reactions, o n the other hand, a t least those involving a number of aromatic hydrocarbons (5, 6) and a somewhat restricted group of olefns (T), appear to show simple relations of this kind.Reactions of atoms v~ith serias of structurally related c o m p o u~~d s are particularly attractive for this type of investigation, especially if they can be studied under conditions where complications from solvei~t effects of variable magnitude can be eliminated. Solvent effects are of course absent in vapor phase reactions, but until very recentl~; there were essentially no rate clata for series of adclitioil reactions in the vapor phase. A11 exception to this represented the reactions of H-atom adclitio~ls to olefins, i~lvestigated by Robb and i\/Ielville (8). However, the work now in progress in this laboratory oil these reactions a t higher pressures and with the use of a clifferent technique (9) reveals some differences in the values of the rate constaiits from those obtaiiled by these authors. A discussion of the trends in reactivity in this reaction series has, therefore, to be delajwl until the current ivork is completecl.Although free atoins as a rule possess unpaired electroils and thus have free radical character, they nlay be expected to react in particular reactions as either electrophilic, nucleophilic, or radical reagents. ' he type of the reactant character exhibited mill be largely cleternlined by the relative values of the electron affinities ancl ioi~ization potentials of the atoins ancl their reaction partners.In the past several years extensive information on the vapor phase reactions of oxygen atoms with olefins has been accumulated in this laboratory. Both the mechanisn~ (10, 11) and the relative rates (1...

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“…Oxene, one of the active oxygen species produced by the decomposition of hydrogen peroxide, can easily add to carbon-carbon double bonds including conjugated ones such as benzene. This type of addition is 10 3 times faster in rate than the hydrogen abstraction from the methyl group [20,[23][24][25]. In order to further confirm the oxene character of the active oxygen species, cyclohexene and styrene were selected as substrates.…”

Section: Resultsmentioning

confidence: 99%