Experimental proof that the Diels-Alder reaction of tetracyanoethylene with 9,10-dimethylanthracene passes through formation of a complex between the reactants

Kiselev, V. D.; Miller, John G.

doi:10.1021/ja00847a028

Cited by 123 publications

(104 citation statements)

References 4 publications

(4 reference statements)

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“…The enthalpy and entropy of formation (AH" = -3.20 f 0.4 and -2.70 f 0.3 kcal mol-', ASo = -8. 6 1.2 and -8.7 & 0.8 cal K-' mol-' in CC14 and CH2C12, respectively) are in agreement with those for CT complexes between chloranil and anthracene derivatives ''). Kochi and co-~orkers',~) were also influenced by Kiselev and Miller.…”

Section: Discussionsupporting

confidence: 81%

Are Charge‐Transfer Complexes Intermediates in Diels‐Alder Reactions? A Case Study of the Reaction of 1,2‐Dimethylenecyclopentane with Tetracyanoethylene

et al. 1991

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The Diels-Alder reaction of 1,2-dimethylenecyclopentane (1) and tetracyanoethylene (TCNE) is kinetically studied by conventional and stopped-flow UV/Vis absorption-spectroscopic techniques. A transient charge-transfer (CT) absorption band with h, , , = 490 nm (half-life at 20°C ca. 3.4 x lo-' s) is detected in dichloromethane solution. For the molar extinction coefficient a value of E~~~ = 310 M -I cm-I has been determined from measurements of the optical densitity at zero time as a function of excess diene concentration. With the aid of computer simulation the combined kinetic analysis of the disappearance of reactants and CT complex reveals that the data obtained from experiments at equimolar concentration and at a single temperature (20°C) can be interpreted equally well by both the model where the CT complex is an intermediate on the reaction path and where it is in a nonreactive side equilibrium with the reactants. Activation parameters have been determined for the disappearance of the starting compounds and of the CT complex. Contrary to what is expected for a CT complex being an intermediate in a concerted Diels-Alder reaction a more negative activation entropy for the decay of the CT complex than for the disappearance of the reactants is found. This suggests that the CT complex is unlikely to exhibit a transition-state-like structure as is required for a concerted cycloaddition. Experiments under pseudo-first-order conditions have led to an extension of the reaction scheme by a second-order reaction of the CT complex with the excess diene, the rate constant of which is virtually identical to that for the direct bimolecular cycloaddition. The conclusion is drawn for our case that there are more arguments against than arguments for the CT complex being a preorientation complex in the [4 + 21 cycloaddition.Soon after the discovery of the general principle of the Diels-Alder cycloaddition in 1928 I), Kuhn and WagnerJauregg') reported the observation of transient colors during the course of these reactions. This phenomenon has been observed many times in later years and its significance for the mechanism of the Diels-Alder reaction has been under discussion ever since'). Mulliken's theory of charge-transfer (CT) complexes4) provided an explanation for the origin of the new absorption band which occurred on mixing solutions of an electron donor diene and an electron acceptor olefin. It did not, however, provide any information about the role of these species in the cycloaddition. from rate measurements for the disappearance of the starting compounds at a single temperature. On the other hand, activation parameters may provide more definite information. Kiselev and Miller6) postulated that the negative activation enthalpy they determined for the cycloaddition reaction of 9,lO-dimethylanthracene with tetracyanoethylene (TCNE) in some solvents is evidence for a CT complex as an intermediate. However, a negative activation enthalpy only demonstrates that an intermediate is involved in the reaction. The nature of th...

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Section: Discussionsupporting

confidence: 81%

Are Charge‐Transfer Complexes Intermediates in Diels‐Alder Reactions? A Case Study of the Reaction of 1,2‐Dimethylenecyclopentane with Tetracyanoethylene

et al. 1991

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“…This has been attributed to the formation of a charge -transfer complex during the course of the reaction and seems, therefore, to provide evidence for a concerted mechanism. 1,3,4 Studies carried out with 1,4-dithiins 1 and anthracene 2 and its derivatives 3 -5 (Scheme 1) have shown that the formation of the Diels -Alder adducts 6 can in fact occur either via a charge -transfer complex or by direct addition, depending on the properties of the anthracene derivative used. 5 The first pathway proceeding via the formation of a chargetransfer complex was dominant when using anthracene 2 and the electron-rich derivatives 3 and 4.…”

Section: Thermal Mechanismmentioning

confidence: 99%

Diels–Alder reactions of anthracene, 9-substituted anthracenes and 9,10-disubstituted anthracenes

2003

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“…Charge transfer transitions in electron donor-acceptor complexes of substituted anthracenes with tetracyanoethylene When a methylene chloride solution of anthracene is mixed with tetracyanoethylene or TCNE, a transient blue coloration is observed immediately (1 l), and it persists for slightly longer times if the reactants are cooled prior to mixing (14). Analogously, 9-cyanoanthracene and tetracyanoethylene afford a green solution which lasts for a prolonged period.…”

Section: Photoelectron Spectra Of Anthracene and Its Derivativesmentioning

confidence: 99%

Electron transfer from anthracenes. Comparison of photoionization, charge-transfer excitation and electrochemical oxidation

Masnovi¹,

Seddon²,

Kochi³

1984

Can. J. Chem.

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, 2552 (1984). Quantitative measures of electron detachment from anthracene and various meso-substituted derivatives (D) are examined in the gas phase and in solution. The photoelectron spectra show well-resolved bands for El corresponding to the first ionization (i.e., D -+ Df + e) from a T-molecular orbital (HOMO) with maximum electron density at the 9,10-positions. The same series of anthracenes form 1: 1 electron donor-acceptor complexes with tetracyanoethylene [D,TCNE], which exhibit distinctive colors associated with charge transfer transitions hvcT to the ion pair [Df,TCNE7]. These measures of the gas phase energetics of electron transfer from the anthracenes are compared with their standard oxidation potentials E:, determined from the reversible cyclic voltammograms in methylene chloride and trifluoroacetic acid solutions. Although there are direct, linear free energy relationships between E l and hum as well as E l and E:,, the best correlation is observed between E:, and hvCT. The validity of the latter is discussed in terms of offsetting effects arising from differences in solvation energy and steric effects attendant upon 9,10-substitution in anthracenes. [Traduit par le journal]

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Experimental proof that the Diels-Alder reaction of tetracyanoethylene with 9,10-dimethylanthracene passes through formation of a complex between the reactants

Cited by 123 publications

References 4 publications

Are Charge‐Transfer Complexes Intermediates in Diels‐Alder Reactions? A Case Study of the Reaction of 1,2‐Dimethylenecyclopentane with Tetracyanoethylene

Are Charge‐Transfer Complexes Intermediates in Diels‐Alder Reactions? A Case Study of the Reaction of 1,2‐Dimethylenecyclopentane with Tetracyanoethylene

Diels–Alder reactions of anthracene, 9-substituted anthracenes and 9,10-disubstituted anthracenes

Electron transfer from anthracenes. Comparison of photoionization, charge-transfer excitation and electrochemical oxidation

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