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1

Zjawiska dysocjacji i asocjacji towarzyszące reakcjom przeniesienia protonu między C-kwasami i zasadami organicznymi w rozpuszczalnikach aprotonowych

Nowak I., Binkowska I., Stańczyk-Dunaj M., Jarczewski A.

Wiadomości Chemiczne

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2008

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[Z] 62, 1-2

67-95

EN

The proton transfer reactions in solutions have attracted the attention of a number of laboratories for many years. These processes seem to be quite simple as they proceed without perturbation of bounding electrons and have low steric demands what enables study of their mechanism. However, many factors influences the mechanisms of these reactions. Among them and not the trifling ones, are dissociation-association effects accompanying them. The definition, behavior and reactivity of carbon acids (C-acids) depending on the type of electron withdrawing group are given [1-57]. Also the values of dissociation constants of C-acids in protic and aprotic solvents are collated in Tables 4, 5 and 7 [11, 38, 49]. The nature of products, free ions and ion pairs, of proton transfer reactions of various C-acids and strong organic bases are carefully discussed. Also their spectral characteristics are given. The equilibria and the possible routes between the substrates and the products of these reactions are also shown [58-66]. The reasons of the homoconjugation effects as a result of an association of the ionic products of the proton transfer reactions in different solvents are discussed in the context of their solvation abilities [67-86]. The formation constants of the homoconjugation complexes of amidine and guanidine bases in relation to their pK? values are quoted in Table 6 [87-95]. The nature of heteroconjugation complexes formed as the result of hydrogen bonding of different entities in the system of proton transfer reactions is discussed [96-116]. The pK? values of a number of C-acids, derivatives of nitromethane, measured in acetonitrile by potentiometric method, are given in Table 7. The pK? values of these derivatives measured in DMSO/H2O systems are compared with those obtained in acetonitrile [18, 38]. The general view of these problems is discussed and carefully reviewed.

2

tert-Butylimino-tris(dimethylamino)phosphorane as a Proton Acceptor in the System of Reaction of 1-Nitro-1-(4-nitrophenyl)alkanes in THF

Wisłocka I., Nowak I., Jarczewski A.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 12

2017-2029

EN

Unexpectedly the reaction of deprotonation of carbon acids with phosphazene bases occurred very slowly. The kinetic study of the proton transfer reactions between C-acids of the series of nitroalkanes with increasing bulk of R = H, Me, Et, i-Pr substituents as 4-nitrophenylnitromethane (1), 1-nitro-1-(4-nitrophenyl)ethane (2), 1-nitro-1-(4-nitrophenyl) propane (3), 2-methyl-1-nitro-1-(4-nitrophenyl)propane (4) and the tert-butylimino-tris(dimethylamino)phosphorane (5) named P1-t-Bu phosphazene is elaborated. The reactions have been studied in THF under pseudo-first-order conditions. The product of the proton transfer reactionwith P1-t-Bu in THF appeared to be associated into ion pairs. The equilibrium constants range from >100000 to 11.8 decreasing along with growing bulk of alkyl substituent in the reacting C-acid. The second order rate constants (k2H) are rapidly declining: 9360, 2.31, 0.66, 0.09 dm3 mol–1 s–1for 1, 2, 3, and4 respectively, and could not be accounted for the small values of the enthalpies of activation HH = 6.1, 18.0, 20.7 and 11.1 kJ mol–1. The reactions show negative and relatively large values of the entropies of activation SH = –149.7, –176.5, –178.7, –227.8 J mol–1 deg–1. The primary deuterium kinetic isotope effects are large showing tendency of reverse relation towards steric hindrance of the reacting C-acids, kH/kD = 15.8, 13.6, 13.2 for 1,2, and 3, respectively. The results have been discussed in terms of the influence of steric effects brought by the bulk of alkyl substituents in the C-acid and the base on formation of the transition state. Also the influence of traces of residual water present in the reaction system has been taken into consideration.

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Influence of fatty acid methyl esters' additive to diesel engine on ecology, fuel consumption and vehicle's performance

Chłopek Z., Jarczewski A., Bardziński W., Sar H.

Journal of KONES

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2006

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Vol. 13, No. 1

261-268

EN

The paper presents results of researching a vehicle equipped with diesel engine, fueled by diesel fuel with fatty acid methyl esters' additive. Research was conducted on chassis dynamometer in static conditions (load characteristics) and dynamic road test cycles according to 83 ECE Regulation. On the basis of results the characteristics of average pollutants' emission, fuel consumption and exhaust opacity as a function of fatty acid methyl esters' additive to diesel fuel were made. Characteristics of engine's power and torque as a function of acid methyl esters' additive were also made. Research showed that together with increasing share of esters in diesel oil to 100% with reference to clean diesel oil there was taken place by the decreasing level of HC emission of 28 %, CO emission decreasing of 21%, increasing NOx emission of 8%, the smokiness decreasing of exhaust gases of 57%. Measurement of the fuel consumption with the method of the carbon balance showed increasing of the fuel consumption with the increasing of FAME share in the mixture. Growth volumetric fuel consumption clean esters with relation to the clean diesel oil carried out of 16%. There also was observed the essential decreasing of the smokiness of exhaust gases with increasing of FAME share. At to supply of the engine clean esters there was observed decreasing of the maximum power of 5. 1% with relation to supply clean diesel oil For the fuel of 10 % FAME decreasing of the engine power carries out about 0, 5 %.

PL

Artykuł prezentuje badania pojazdu zaopatrzonego w silnik diesla, zasilany olejem napędowym z c estrów metylowych kwasu tluszczowego(FAME). Badania były prowadzone na hamowni warunkach statycznych (charakterystyka obciążeniowa) i dynamicznych cyklach testu drogowego s Przepisów 83 ECE. Na bazie wyników charakterystyka średnich wartości składników toksycznych zużycie paliwa i wyglądu spalin zostały opracowane charakterystyki mocy silnika i momentu obrotowego w funkcji dodatku estrów metylowych do oleju napędowego. Badania wykazały, że wraz ze wzrostem udziału estrów w oleju napędowym do 100% w odniesieniu do czystego oleju napędowego nastąpił spadek poziomu emisji HC o 28 %, spadek emisji CO o 21%, wzrosłe NOX o 8%, spadek zadymienia spalin o 57%. Pomiary zużycia paliwa metodą bilansu węgla wykazały ł zużycia paliwa ze wzrostem udziałów FAMĘ w mieszaninie. Wzrost objętościowego zużycia czystych estrów w stosunku do czystego oleju napędowego wyniósł ok. 16%. Zaobserwowano też istotne zmniejszenie; spalin ze wzrostem udziału FAME. Przy zasilaniu silnika czystymi estrami zaobserwowano spadek i maksymalnej o 5,1% w stosunku do zasilania czystym olejem napędowym, dla paliwa z 10% dodatkiem FAME spadek mocy silnika wynosi około 0,5 %.

4

Homoconjugation of Some Organic Bases in Acetonitrile

Stańczyk-Dunaj M., Jarczewski A.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 6

1025-1032

EN

The largest value of the homoconjugation constant in acetonitrile has been found for tribenzylamine KHOMO = 7.73 and the lower for N-methylpiperidine KHOMO = 3.44. For triethylamine, tri-n-propylamine, tributylamine, 1,3-diphenylguanidine, 2-tert-butyl- 1,1',3,3'-tetramethylguanidine, 1,1',2,2',3-pentamethylguanidine, 1,8-bis(dimethylamino) naphthalene, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene bases no homoconjugated complexes BH+B were formed. Additionally the basicity of tribenzylamine pKa = 16.13, 1,3-diphenylguanidine pKa = 18.79, 1,1',2,2',3-pentamethylguanidine pKa = 23.12, and 2-tert-butyl-1,1',3,3'-tetramethylguanidine pKa = 23.56 in acetonitrile are given.

5

Structure of Pyridine-2-azo-p-phenyltetramethylguanidine

Borowiak T., Dutkiewicz G., Binkowska I., Jarczewski A.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 11

1427-1435

EN

Replacement of dimethylamino group in pyridine-2-azo-p-dimethylaniline (PADA) by a stronger electron - releasing tetramethylguanidil (TMG) group forms a new complexing agent, pyridine-2-azo-p-phenyltetramethylguanidine (PAPT). The substitution does not enhance the expected complexing ability of PAPT in comparison with that of PADA. For steric reasons the tetramethylguanidil substituent CN3 and phenyl ring are not coplanar, which makes the resonance between them limited. This manifests in small contribution of quinoid form in the canonical structure distribution. The additivity of angular parameters in the phenyl ring is preserved.

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Proton Abstraction from 4-Nitrophenyl[bis(ethylsulphonyl)]methane with TMG, TBD and MTBD Bases in Acetonitrile

Jarczewski A., Binkowska I.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 12

1895-1903

EN

4-Nitrophenyl[bis(ethylsulphonyl)]methane has been synthesized and used in kinetic studies of proton abstraction induced by 1,1,3,3-tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 7-methyI-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) bases in acetonitrile. The pK, values of this carbon acid in water and in acetonitrile solvents are 10.08 and 22.8 respectively. The electronic spectra of 4-nitrophenyl[bis(ethylsulphonyl)]methane and its anion ar well defined and temperaturę dependent. The rates of proton abstraction are large as the reaction occurs in the range of microseconds. The relaxation times were studied by spectrophotometric temperature-jump technique. The rate constants for proton transfer reaction promoted by TMG, TBD and MTBD bases in acetonitrile are: 1.39x10 5-2.1 Ix10 5; 8.8x10 6-19.2x10 6; 0.84x105-2.43x 10S [dm3 mol-1 s-1] respectively between 20-40°C. The enthalpies of activation are: deltaH# = 18.1, 28.7 and 40.0 [kJ mol-1] for TMG, TBD and MTBD respectively. The entropies of activation are all negative: deltaS# = -84.9, -13.6, -14.3 [J mol-1 deg-1] for the same sequence of bases reacting with 4-nitrophenyl[bis(ethylsulphonyl)]methane in acetonitrile solvent. The general discussion of the results obtained and their comparison with those for proton transfer reaction carried out with "normal" C-acids is given.

7

Anion Radical Formation in the Reaction of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) with Tribenzylamine in Acetonitrile

Dworniczak M., Jarczewski A.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 11

1739-1743

EN

Kinetics of the reaction of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) with tribenzylamine in acetonitrile has been measured spectrophotometrically. The product of this reaction is a stable anion radical of DDQ. The reaction is relatively slow, due to a considerable steric hindrance in both quinone and amine molecule. Activation parameters indicate a charge separation in the transition state. The mechanism of the reaction has been proposed.

8

Reakcje przeniesienia protonu od C-kwasów do zasad organicznych w rozpuszczalnikach aprotonowych

Jarczewski A.

Wiadomości Chemiczne

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2000

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[Z] 54, 3-4

203-226

EN

The proton transfer reactions in solutions seem to be simple, yet a number of consecutive steps can be distinguished. The useful tool in determining the mechanisms of these reactions was, and still is the primary deuterium kinetic isotope effect]. Therefore the factors influencing the rate constants and then KIE of these reactions as: steric hindrance of reactants, polarity of solvents and symmetry of transition state were widely discussed. The commonly acepted view on the deuterium kinetic isotope effects is that they are large when bulky substituents are crowded around the reaction site], and also the reactions are carried out in low polarity solvent]. However, there was found that even in polar aprotic solvents as acetonitrile large KIE values take place]. The KIE values are not very sensitive on the steric hindrance, showing in some extreme cases reduced KIE values, what is incompatible with previous papers. Likewise some other effects as "scrambling effect" simulating very large KIE are considered . The products of proton transfer reactions between C-acids and strong organic bases in polar aprotic solvents in contrary to previous findings appeared to be highly dissociated into free ions. The reason and consequences of erroneous fulfillment of Benesi-Hildebrand equation are discussed. It was essential to carry out the kinetic study of the proton transfer reactions, in particular those of low equilibrium constants in a BH+/B buffer. Then the association effect should be considered. Also a number of homoconjugation constants for selected organic bases and equilibrium acidities of some C-acids in acetonitrile solvent are given. The study of proton transfer reactions in mixed H2O-Me2SO solution prevented the homoconjugation effects and gave the thermodynamic and kinetic acidity, what enabled to evaluate the intrinsic barriers or intrinsic reactivity. To assess the aci-nitro behavior of C-acids the protonation reaction of 4-nitrophenylnitromethane carbanion at different pH values were performed. The influence of residual water which cannot be removed completely from the reaction systems of C-acids and strong organic bases in aprotic solvent was a subject of interest for many years. After careful examination it appeared that the traces of water in reaction medium, in aprotic solvents, caused a marked decrease of reaction rate instead of its acceleration [97]. It was clamed that the reactivity of ion pairs is negligible compared to free ions. However, in some cases the reactions are going via ion pair reagents with distinct differentiation of reactivity between loose and tight ion pairs . Using literature values of the fractionation of cesium n-propoxide for ions and ion pairs, 2.5 times larger reactivity has been found for ion pairs than free ions in proton abstraction from 1-(4-nitrophenyl)-1-nitroethane. The recent progress in the study of proton transfer reactions indicates new aspects in understanding the mechanism and theory of these processes.

9

Kinetics and Mechanism of the reaction Between 2,3,5,6-Tetrabromo-1,4-benzoquinone and Tetramethylguanidine in Benzene

Dworniczak M., Jarczewski A.

Polish Journal of Chemistry

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1999

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Vol. 73, nr 10

1739-1744

EN

The reaction of bromanil (2,3,5,6-tetrabromobenzoquinone)with 1,1,3,3-tetramethylguanidine in benzene has been studied spectrophotometrically. The reaction proceeds according to the mechanism of vinylic substitution with a charge-transfer complex as the intermediate compound. the final product is a disubstituted quinone. The reaction mechanism is discussed.

10

Kinetics of the reaction of 2,3,5,6-tetrachloro-1,4-benzoquinone with imidazole in acetonitrile and benzene

Dworniczak M., Przybyszewska M., Jarczewski A.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 1

108-112

EN

Nucleophilic vinylic substitution of 2,3,5,6-tetrachloro-1,4-benzoquinone by imidazole in acetonitrile and benzene has been studied spectrophotometrically. The reaction product is the diaminodichlorosubstituted quinone. The values of the activation parameters indicate that there is a considerable charge separation in the transition state. The reaction mechanism is discussed.