The Kinetics and Mechanism of the Reversible Chain Reaction of Quinone Imine with Hydroquinone

The kinetics of the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-di-tert-butyl-1,4-hydroquinone in chlorobenzene was studied at 298.2 and 340 K. The previously proposed chain mechanism was confirmed and discussed. The rate constants and Arrhenius parameters of all elementary steps were determined or reliably estimated. Data on the possibility of radical formation by a termolecular reaction of quinone imine with two 4-hydroxydiphenylamine molecules were obtained, and the rate constant of this reaction was evaluated: k= 0.22 l²mol^–2s^–1at 298 K. The reversibility of all of the most important steps of this chain reaction (chain initiation, propagation, and termination) was demonstrated.     

Kinetic parameters of radical reactions of 2-mercaptobenzothiazole with quinone imines

The chain reaction of N,N′-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole was studied by two methods developed earlier for the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole. In the methods used, the kinetic scheme of the reaction is simplified by creating conditions under which the rates of all stages except radical generation and decay can be neglected. One of the methods was updated. For the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole, both methods gave close results; for the chain reaction of N,N′-diphenyl-1,4-phenylenediamine with 2-mercaptobenzothiazole, the results differed by approximately one order of magnitude.     

Molecular-Radical Catalysis of the Chain Reaction of Quinone Imine with Hydroquinone under the Action of Aromatic Amines

Secondary aromatic amines are catalysts of the chain reaction (v = 10³ units) of N-phenyl-1,4-benzoquinone monoimine with 2,5-di-tert-butyl-1,4-hydroquinone. A complex mechanism of amine catalysis reveals that the rate of the chain reaction may increase, decrease, or remain unchanged in the presence of these compounds. In that case the product composition does not change, and amines are not consumed. The effects of temperature and the nature of para substituents (six species) on the activity of aromatic amines as catalysts were studied. A mechanism was proposed for the catalytic reaction; it implies the coupled occurrence of chain and catalytic processes. An expression for the rate of the catalytic reaction was obtained. The rate constants of individual steps with the participation of a catalyst and its radicals were calculated using the method of crossing parabolas. With the use of these data, a theoretical calculation of the dependence of the reaction rate on catalyst concentration was performed; the results were in good agreement with experimental data. The mechanism of the catalytic reaction was discussed; the similarities and distinctions between this mechanism and the mechanisms of other coupled chain reactions were demonstrated.     

The features of the kinetics of radical reactions of quinone imines with 2-mercaptobenzothiazole

Kinetics of the reactions of N-phenyl-1,4-benzoquinone monoimine and N,N′-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole in chlorobenzene at T = 343 K has been studied by using kinetical spectrophotometry method (periodic spectral measurements and/or monitoring the wavelengths of the absorption band of quinone imines in the visible region). Two general features of the reactions, namely, radical mechanism and the existence of two steps were found. Kinetic features depend on the structure of a quinone imine. A reaction between N,N′-diphenyl-1,4-benzoquinone diimine and 2-mercaptobenzothiazole at first (initial) steps proceeds in an autoinhibition mode and has two independent channels, one of which being radical-chain. The addition of an initiator strongly accelerates the reaction only at the initial step, on completion of which the reaction rate decreases significantly and do not depend on the presence of the initiator. This testifies to the proceeding of the reaction by a non-chain mechanism subsequently to the initial step. The interaction involving N-phenyl-1,4-benzoquinone monoimine proceeds by a radical non-chain mechanism from the very beginning up to the end, and at the initial steps it proceeds in the autoaccelerating mode. The initiator has no influence on the reaction rate. For the process of the interaction of N,N′-diphenyl-1,4-benzoquinone monoimine and 2-mercaptobenzothiazole in the presence of 4-hydroxydiphenylamine, a radical mechanism was proposed, that serves to describe the kinetic features of the reaction and to obtain a quantitative estimation of some of its kinetic parameters.     

Kinetics and mechanism of the chain reaction between <Emphasis Type="Italic">N</Emphasis>-phenyl-1,4-benzoquinone monoimine and thiophenol

The kinetics of the reaction between N-phenyl-1,4-benzoquinone monoimine (quinone monoimine) and thiophenol is studied in chlorobenzene at 343 K. The reaction has the same mechanism proposed earlier for a similar reaction involving N,N'-diphenyl-1,4-benzoquinone diimine (quinone diimine). This mechanism has two paths: chain and nonchain. An important difference between the kinetics of the two reactions is the apparent reversible nature of the chain reaction in the quinone monoimine + thiophenol system. This nature reveals itself when the concentrations of thiophenol are comparable to or slightly higher than the concentrations of quinone imine. In light of this, kinetic research is conducted under conditions where the concentrations of thiophenol are significantly higher than those of quinone monoimine, allowing us to simplify the kinetic features and obtain interpretable data. The rate constants of the reaction’s elementary steps are estimated and found to be three to five times lower for the reaction involving quinone monoamine than for the one involving quinone diimine. Both reactions have relatively short chains whose lengths do not exceed several tens of units.     

New approaches to studying the kinetics of the radical reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole

The kinetics of the reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole in chlorobenzene at 298 and 343 K under argon has been studied by kinetic spectrophotometry. The reaction orders have been determined. The influence of tetraphenylhydrazine and azobisisobutyronitrile initiators has been investigated. An accelerating effect of one of the reaction products, 4-hydroxydiphenylamine, has been discovered. The accelerating effect strenthens with an increasing 2-mercaptobenzothiazole concentration. Two methods are proposed for determination of the kinetic parameters of the reaction. The first method uses data on the consumption rate of quinoneimine in the noninitiated reaction in the presence of 4-hydroxydiphenylamine. In the second method, the accumulation of quinone monoimine is studied during initiator decomposition in the presence of mixtures of 4-hydroxydiphenylamine and 2-mercaptobenzothiazole and parameters are estimated from the dependences of the limiting concentration of accumulated quinone monoimine on the initiation rate and on the concentrations of the reactants Using the proposed approaches, the numerical values of a number of kinetic parameters of the radical reactions of the quinone compounds with thiols have been determined for the first time for the reaction studied.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-sulfonyl derivatives of 1,4-benzoquinone monoimine with substituted hydrazines

Reaction direction of N-sulfonyl derivatives of 1,4-benzoquinone monoimine with substituted hydrazines depends on the redox potential of the quinone imine and on the basicity of the hydrazine. Aryl (alkyl)hydrazines of high basicity favor the reduction of quinone monoimine. In reactions with less basic aroylhydrazones N'-(4-oxocyclohexa-2,5-dienylidene)aroylhydrazides were obtained only from the alkylsubstituted in the quinoid ring N-sulfonyl derivatives possessing a lower redox potential.     

Reversible chain reaction between <Emphasis Type="Italic">N,N</Emphasis>′-diphenyl-1,4-benzoquinonediimine and 2,5-dichlorohydroquinone: Kinetics,mechanism, and the rate constants of elementary steps

The kinetics of the reversible chain reaction between N,N′-diphenyl-1,4-benzoquinonediimine and 2,5-dichlorohydroquinone was studied in chlorobenzene at 298 and 343 K. Experiments in the presence of an initiator proved that the reaction proceeds via a chain mechanism with a chain length of ～10⁴ to 10⁵ units, depending on the reactant and initiator concentrations and temperature. The reaction rate first increases and then decreases with increasing concentrations of the reaction products (N,N′-diphenyl-1,4-phenylenediamine and 2,5-dichloroquinone) due to the pronounced reversibility of the chain termination and propagation steps involving the reaction products. The reaction orders with respect to the components were determined. The rate constants and activation energies of most of the elementary steps of the forward and backward chain reactions were determined or reliably estimated. Induction periods were observed for the first time in the reversible chain reactions in the quinoneimine + hydroquinone systems. The induction periods are due to the long time required for the establishment of the steady-state radical concentrations in the system.     

Thiocyanation of N-aryl,N-acetyl,and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine

N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine with alkyl substituents in the quinoid ring have been synthesized and their spectral characteristics were determined. The thiocyanation of N-aryl, N-acetyl, and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine depending on the LUMO energy of the initial quinone monoamine affords derivatives of benzo[d][1,3]oxathiol-2-ones and benzo[d]oxazole-2(3H)-thiones.     

Iron pentacarbonyl assisted photochemical route to 2,5- and 2,6-divinyl-substituted 1,4-benzoquinones from 1-ene-3-ynes

Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)₅ yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η²,η²:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η²,η²:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%).     

Time-resolved ESR study of the lowest excited triplet states of para-quinones in glassy matrices at 77 k

The lowest excited nπ* triplet of 9.10-anthraquinone, 1.4-naphthoquinone and 1,4-benzoquinone were studied in glassy matrices at 77 K using a time-resolved ESR method. The D value of the triplet state of 9,10-anthraquinone varied from ?0.351 cm^?1 in a polar solvent to ?0.318 cm^?1 in a non-polar solvent. Both 1,4-naphthoquinone and 1,4-benzoquinone in polar solvents showed triplet state spectra with a D value of ?0.330 cm^?1. A computer simulation revealed the existence of widely distributed zero-field splitting parameters in the glassy condition. These data are compared with an analysis of CIDEP results of para-quinones.     

Synthesis of benzoquinone derivatives containing benzotriazole fragments

2,3,5,6-Tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone was synthesized in 85% yield by reaction of 2,3,5,6-tetrachloro-1,4-benzoquinone with 1H-benzotriazole in pyridine at room temperature. Treatment of 2,3,5,6-tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone with piperidine, ω-amino acids, and aromatic amines gave the corresponding 2,5-diamino-3,6-bis(1H-benzotriazol-1-yl)-1,4-benzoquinones.     

The reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide

Reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide in aprotic solvents leads to the generation of semiquinone (SQ^.H), alkylperoxy (ROO^.), and alkyloxy radicals. The reaction of SQ^.H and ROO^. produces 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone, 3,6-di-tert-butyl-1-oxacyclohepta-3,5-diene-2,7-dione, and 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinone. The radical generated from solvent attacks SQ^.H at position 4 with C−C bond formation. 4-Benzyl-2,5-di-tert-butyl-6-hydroxycyclohexa-2,5-diene-1-dione produced in this way is transformed into 4-benzyl-3,6-di-tert-butyl-1,2-benzoquinone under the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1999.     

Spectroscopic and structural aspects of the reactions of 1,4-quinones with sulfur and nitrogen nucleophiles

A series of 1,4-benzoquinone derivatives from 2,5-dichloro-3,6-diethoxy-1,4-benzoquinone and 2,6-dichloro-3,5-diethoxy-1,4-benzoquinone were prepared by nucleophilic substitution reactions of sulfur and nitrogen nucleophiles. Spectral techniques (¹H NMR, ¹³C NMR, FT–IR, and LC–MS) were employed to structurally characterize the reaction products of alkoxy, chloro substituted-1,4-benzoquinones with thiols and amines in the presence of sodium carbonate in ethanol at room temperature. The orientations and the regioselectivity of the reactions of alkoxy, chloro substituted-1,4-benzoquinones with various thiol and amine nucleophiles are discussed.     

Investigation of electrochemically induced Michael addition reactions. Oxidation of some dihydroxybenzene derivatives in the presence of azide ion

In aqueous solution containing azide ion as a nucleophile, electrochemical oxidation of hydroquinone and some dihydroxybenzoic acids have been studied using cyclic voltammetry and controlled-potential coulometry. The voltammetric data show that electrochemically generated para and ortho-benzoquinones participate in Michael addition reactions with azide ions to form the corresponding diazido or diaminobenzoquinones. In this work, we have proposed various mechanisms for the electrode process and we report an efficient and one-pot method for the synthesis of 2,5-diazido-1,4-benzoquinone, 2,5-diamino-1,4-benzoquinone, 4,5-diamino-1,2-benzoquinone, and 2,3-diamino-5,6-dioxocyclohexa-1,3-dienecarboxylic acid based on the Michael reaction of electrochemically generated ortho and para-benzoquinones with azide ion in an undivided cell using an environmentally friendly reagent-less method in ambient conditions. An estimation of the observed homogeneous rate constant (k_obs) of the reaction of electrochemically generated para-benzoquinone with azide ion by the digital simulation method is also presented.     

Oxidative Ionization Under Certain Negative-Ion Mass Spectrometric Conditions

1,4-Hydroquinone and several other phenolic compounds generate (M – 2) ^–? radical-anions, rather than deprotonated molecules, under certain negative-ion mass spectrometric conditions. In fact, spectra generated under helium-plasma ionization (HePI) conditions from 1,4-hydroquinone and 1,4-benzoquinone (by electron capture) were practically indistinguishable. Because this process involves a net loss of H^? and H⁺, it can be termed oxidative ionization. The superoxide radical-anion (O₂ ^–?), known to be present in many atmospheric-pressure plasma ion sources operated in the negative mode, plays a critical role in the oxidative ionization process. The presence of a small peak at m/z 142 in the spectrum of 1,4-hydroquinone, but not in that of 1,4-benzoquinone, indicated that the initial step in the oxidative ionization process is the formation of an O₂ ^–? adduct. On the other hand, under bona fide electrospray ionization (ESI) conditions, 1,4-hydroquinone generates predominantly an (M – 1) ^– ion. It is known that at sufficiently high capillary voltages, corona discharges begin to occur even in an ESI source. At lower ESI capillary voltages, deprotonation predominates; as the capillary voltage is raised, the abundance of O₂ ^–? present in the plasma increases, and the source in turn increasingly behaves as a composite ESI/APCI source. While maintaining post-ionization ion activation to a minimum (to prevent fragmentation), and monitoring the relative intensities of the m/z 109 (due to deprotonation) and 108 (oxidative ionization) peaks recorded from 1,4-hydroquinone, a semiquantitative estimation of the APCI contribution to the overall ion-generation process can be obtained.

Open image in new window

Graphical Abstract ?

     

Halogenation of N-substituted <Emphasis Type="Italic">p</Emphasis>-quinone monoimines and <Emphasis Type="Italic">p</Emphasis>-quinonemonooxime ethers: XII. Halogenation of <Emphasis Type="Italic">N</Emphasis>-aroyl-2(3)-methyl-1,4-benzoquinone monoimines and their reduced forms

A strong acceptor substituent at the nitrogen atom of the N-substituted p-quinone monoimine decreases the stability of the halogen-containing cyclohexene structures formed at the addition of a halogen molecule to the C=C bond of the quinoid ring. As a result of the bromination of N-benzoyl-2-methyl-1,4-benzoquinone monoimine alongside the usual products of addition and substitution the 5-benzoyloxy-2,3,6-tribromo-6-methylcyclohex-2-ene-1,4-dione was isolated.     

Conducting materials prepared by the oxidation of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-benzoquinone

p-Phenylenediamine was oxidized with p-benzoquinone in the aqueous solutions of methanesulfonic acid (MSA). The conductivity of the products increased with increasing concentration of MSA from 1.5?×?10^?12 S cm^?1 in 0.1 M MSA up to 3.4?×?10^?4 S cm^?1 in 5 M MSA. The low-molecular-weight products are basically composed of one p-benzoquinone and two p-phenylenediamine molecules. Their molecular structure is discussed on the basis of mass, Fourier-transform infrared, Raman, NMR and electron paramagnetic resonance (EPR) spectroscopies. The formation of 2,5-di(p-phenylenediamine)-p-benzoquinone protonated with methanesulfonic acid best complies with the information provided by spectroscopic techniques. Its conversion to hydroquinone tautomer explains the formation of unpaired spins observed by EPR and their potential contribution to the conduction.     

An improved synthesis and some reactions of diethyl 4-oxo-4H-pyran-2,5-dicarboxylate

The reaction of ethyl 2-(dimethylamino)methylene-3-oxobutanoate with diethyl oxalate in the presence of sodium hydride in THF gave diethyl 4-oxo-4H-pyran-2,5-dicarboxylate, from which 4-oxo-4H-pyran-2,5-dicarboxylic and 4-oxo-1-phenyl-1,4-dihydropyridine-2,5-dicarboxylic acids and their derivatives were obtained in good yields.     

Synthesis and investigation of poly(p-phenylenediamine)–poly(1,4-benzoquinonediimine-<Emphasis Type="Italic">N,N</Emphasis>-diyl-1,4-phenylene)

Poly(1,4-benzoquinonediimine-N,N-diyl-1,4-phenylene) having similar structure to pernigraniline was synthesized by chemical oxidative polymerization of p-phenylenediamine and its salt using potassium peroxydisulfate as an oxidant in molar ratio 1:0.8, in acetic acid, at 278 K. Acetylation of amino end groups of polymers were carried out aiming to prevent self-condensation of amino groups with 1,4-benzoquinone diimine groups by 1,4-addition. Attempting to carry out the reduction of obtained polymer with hydrazine hydrate, it was shown that 1,4-addition of hydrazine to quinonediimine groups occurs instead of expected reduction reaction. When doping obtained polymers with iodine, the electrical conductivity increases up to 10^?4 S/cm.