Enthalpy of formation of thiophene derivatives

The enthalpy of formation in the gas phase has been calculated for 21 carbonyl compounds of the thiophene series with the aid of the PM3, MINDO, AM1, and MNDO semiempirical quantum-chemical methods. Comparison of them with experimental data showed that the best linear correlation was achieved with the PM3 method. The latter in conjunction with a developed linear regression equation has been used to predict the enthalpy of formation of 22 carboxylic acids and ketones of the thiophene series.     

Anion-radical mechanism of bromine exchange by iodine in furan derivatives

The kinetics of bromine exchange by iodine in furan derivatives were studied; it is shown that the reaction is reversible and inhibited by oxidizing agents. Chloro derivatives of furan do not undergo this reaction. A cryptoreductive mechanism is proposed; the first stepof this mechanism consists of electron transfer to the halofuran molecule with subsequent reversible dissociation of the anion radical — inclusion of the iodide anion in the dissociation equilibrium leads to the substitution product.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1601–1606, December, 1976.     

Rydberg bands in the UV spectrum of thiophene and its derivatives

The ultraviolet spectra of twelve halogenothiphenes have been recorded in the vapour phase. New transitions were observed in the region 45 000 to 50 000 cm⁻¹ which are absent in solution spectra and are assigned to Rydberg transitions. There is a good agreement of the band positions with those calculated from adiabatic ionization potential, using the quantum defect of thiphene. A study of the vibronic structure does not rule out the possible existence of two Rydberg-transitions. The vibrational frequencies of the fine structure are close to the observed values in the UP spectrum. The other members of the Rydberg series can be found in the far ultraviolet spectrum of thiophene.     

Functional derivatives of thiophene

5-Tosylamino-2,3-dialkylthiophenes, which are alkylated to the corresponding 5-alkyl (tosyl)-amino derivatives, were synthesized from 2-amino-3-carbethoxy-4,5-dialkylthiophenes by tosylation and subsequent decarboxylation.See [1] for communication XV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 204–206, February, 1977.     

Functional derivatives of thiophene

A method is proposed for the synthesis of isatin analogs — 4,5-dioxothieno[2,3-b] pyrroles and 5,6-dioxothieno[3,2-b]pyrroles — by reaction of oxalyl chloride with amino-substituted α-amino- and Β-aminothiophene. The thiosemicarbazones of 4-ary1-5,6-dioxothieno[3,2-b]pyrroles were synthesized. n]mis|See [1] for communication X.     

Functional derivatives of thiophene

2-Aryl-4-oxothieno[2,3-d]oxazine derivatives were synthesized. Opening of the oxazine ring to give 2-benzamidothiophene-3-carboxylic acid hydrazide derivatives is observed when these compounds are treated with hydrazine hydrate.See [1] for Communication 17.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 45–46, January, 1980.     

Organodimagnesium derivatives of thiophene

It was established that 2,5-dibromo-3-R-4-arylthiophenes form organodimagnesium compounds in ether with the accompaniment of dibromoethane. It is shown that because of steric hindrance, only 2-ethoxalyl-3-R-4-arylthiophenes are formed in the reaction of the organodimagnesium compounds with diethyl oxalate. It was established that the bromomagnesiumethoxycarbinolates obtained from the indicated thiophenes and bromomagnesium ethoxide have high thermal stabilities. The IR and PMR Spectra of the synthesized compounds were studied.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 754–757, June, 1982.     

Functional derivatives of thiophene

A method is proposed for the synthesis of 5-acylamino-2,3-dimethylthiophene-4-carbaldehydes and 5-acylamino-2,3-tetramethylenethiophene-4-carbaldehydes by the formylation of the corresponding thiophenes using the Vilsmeier reaction. From the formyl derivatives obtained, previously unaccessible derivatives of thieno[2,3-b]pyridine, thieno[2,3-d]pyrimidine, and thieno[3′,2′∶5,6]pyrido[2,3-d]-pyrimidine have been synthesized.     

Functional derivatives of thiophene

The nitration of 3-ethoxycarbonyl-4-hydroxy-2-methyl- and 4-chloro-3-ethoxycarbonyl-2-methylthiophenes has given the corresponding 5-nitro derivatives of thiophene. The 4-chloro-3-ethoxycarbonyl-2-methylthiophene was synthesized by the decarboxylation of 3-chloro-4-ethoxycarbonyl-5-methylthiophene-2-carboxylic acid, which is formed by the oxidation of 3-chloro-4-ethoxycarbonyl-5-methylthiophene-2-carbaldehyde.For Communication IV, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1024–1025, August, 1973.     

Functional derivatives of thiophene

Acyl derivatives of substituted β-thienylhydrazines were obtained by reaction of 2-methyl-3-carbethoxy-4-hydroxythiophene with acyl hydrazines. Hydrolysis of the products gave a thienylhydrazine derivative and its hydrochloride.     

Functional derivatives of thiophene

A preparative method for the synthesis of thienobenzothiazines — phenothiazine analogs-was worked out on the basis of 2-methyl-3-carbethoxythiophene derivatives and nitroarenesulfenyl chlorides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 741–745, June, 1973.     

Functional derivatives of thiophene

The derivatives obtained by reaction of o-halonitrothiophenes with cyanoacetic and acetoacetic esters were converted to thieno[2,3-b]- and thieno[3,2-b]pyrroles by reductive cyclization.See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1628–1630, December, 1973.     

Estimation of adsorption parameters from temperature-programmed-desorption thermograms: application to the adsorption of carbon dioxide onto Na- and H-mordenite

In this work, a model is proposed for the estimation of the adsorption parameters from TPD thermograms when the adsorption cell can be modeled as a well-mixed reactor, evaluating the adsorption and desorption rate constants from statistical thermodynamics. The estimation procedure consists of fitting the model to the experimental TPD thermograms using numerical methods. The study of the effect of readsorption in this system reveals that this effect must be taken into account in most cases. Only with high activation energies of adsorption may this effect be negligible. The model is used to estimate the adsorption parameters of the systems CO(2)-Na-mordenite and CO(2)-H-mordenite, including an analysis about the degrees of freedom of the adsorbed phase. The estimated values of the adsorption enthalpy have been compared with the ones obtained from adsorption equilibrium data.     

Synthesis of some thiophene derivatives

The synthesis of thiopene derivatives from diacetylenic hydrocarbons has been described [1]. We have examined for the first time the reaction of diacetylenic diesters with hydrogen sulfide and with NaHS. The diacetylenic diesters react readily with hydrogen sulfide or NaHS in acetone at pH 9–10 to give 2,5-disubstituted thiopheries (see Table 1).Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 713–714, May, 1970.     

A study of radicals arising in the low-temperature radiolysis of thiophene and some of its derivatives

EPR was used to investigate the radicals formed by radiolysis of furan, thiophene, and some of their substitution products having the general formula C₄H₃RS, where R = Cl, Br, COOH, C(CH₃)₃, and of di-tert-butylthiophene. By analyzing the EPR spectra it is shown that radicals formed by radiolysis of furan, thiophene, their alkyl substitution products, and 2-thiophene carboxylic acid arise in primary radiation-chemical events with splitting of the C-H bond in both ring and side chain. Characteristic of the radiolysis of these compounds is formation of secondary radicals by addition of hydrogen atoms at the double bond of the heteroaromatic ring. The values of the hyperfine splittings in the spectra of the secondary radicals are, for protons of methylene group 32 e [positions 2(5)] or 40 e [positions 3(4)], and 13 e for protons of the thiophene ring. In radiolysis of 2-chlorothiophene and 3-bromothiophene the main products are radicals with the unpaired electron localized on the sulfur atom.     

Nitro derivatives of the thiophene series. 4. Nitration of thiophene derivatives with metal nitrates in acetic anhydride

The nitration of 2-formylthiophene, 2-acetothienone, and unsaturated ketones of the thiophene series with copper and aluminum nitrates in acetic anhydride at various temperatures was studied. At low temperatures 2-acetothienone gives a mixture of 4- and 5-nitro isomers, while 2-formylthipphene gives only a 5-nitro-substituted compound in the diacetate form; ,-unsaturated ketones are not nitrated under these conditions. When the reaction is carried out at 70–90 °C, one can obtain mixtures of nitro ketones in the case of unsaturated ketones; 2-formylthiophene is oxidized to thiophene-2-carboxylic acid, while 2-acetothienone gives a substance, the structure of which could not be established. The reaction of copper and aluminum nitrates with acetic anhydride was investigated by means of thermal and x-ray diffraction analysis. It is shown that the reaction is accompanied by the formation of free nitric acid, and the nitrating agent in these mixtures is consequently the nitronium cation.See [1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 913–916, July, 1981.