GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Effects of Substituents and Medium on Acidity of α,α-Bis(butylsulfonyl)toluenes
    Institute of Organic Chemistry & Biochemistry ; 1994
    In:  Collection of Czechoslovak Chemical Communications Vol. 59, No. 2 ( 1994), p. 391-400
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 59, No. 2 ( 1994), p. 391-400
    Abstract: Seven substituted α,α-bis(butylsulfonyl)toluenes and three 2-aryl-1,1,3,3-tetraoxo-1,3-dithiolanes have been prepared and their 1 H NMR, IR, and MS spectra measured. The p K HA values of the substituted α,α-bis(butylsulfonyl)toluenes have been determined by potentiometric titration in dimethyl sulfoxide, dimethylformamide, and 80% (v/v) mixture of dimethyl sulfoxide and water. The results are interpreted by the Yukawa-Tsuno relationship (parameter r = 0.43 - 0.49) and classified in relation to analogous N - and O -acids by the methods with latent variables (the method of conjugated deviations).
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19940391
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1994
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Chemometric Analysis of Substituent Effects. I. Substituent Effects on the Dissociation of Monosubstituted Benzoic Acids
    Institute of Organic Chemistry & Biochemistry ; 1994
    In:  Collection of Czechoslovak Chemical Communications Vol. 59, No. 1 ( 1994), p. 159-174
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 59, No. 1 ( 1994), p. 159-174
    Abstract: Forty-six representative sets of data relating to the dissociation of monosubstituted benzoic acids in various solvents were extracted from the literature. The set of substituents included 25 common substituents in the meta position and the same number of substituents in the para position. Hydrogen served as the reference standard. The sets were subjected to regression analysis using conventional empirical models. The Hammett model was found to be valid within the limits of experimental error. The Taft model with the σ R 0, σ R + and σ R - parameters is the best model to account for the substituent effects from the meta or para position solely. The inductive and mesomeric effects of the substituent are also best separated on this parametric scale. By applying the method of conjugated deviations (analysis of latent variables), a single latent variable was found to be sufficient to describe the data variability in all the three data sets analyzed ( meta + para in the Hammett model and sets of meta and para substituted derivatives separately). The relationship between the first latent variables from the meta and para positions is isoparametric, the substituents lie on three straight lines intersecting in one point. The first straight line corresponds to substituents with the I effect (CH 3 , C 2 H 5 , tert -C 4 H 9 , C 6 H 5 , SO 2 NH 2 , CN, NO 2 and hydrogen as the reference standard), the second straight line corresponds to substituents with I and +M effects (NH 2 , N(CH 3 ) 2 , NHCOCH 3 , CH 3 O, SH, F, Cl, Br), and the third straight line corresponds to substituents with I and -M effects (CHO, CH 3 CO, COOR, SO 2 CH 3 , CF 3 ). The +M mesomeric effect is twice as strong as the -M effect. These facts were used to propose a new empirical model for the description of substituent effects by means of one substituent constant and one ( meta ) or two ( para ) reaction constants. The PLS method revealed that the additional effects contribute about 8% to the data variability in the interpretation of the para substitution through meta substitution.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19940159
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1994
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Chemometrical Analysis of Substituent Effects. V. ortho Effect
    Institute of Organic Chemistry & Biochemistry ; 1994
    In:  Collection of Czechoslovak Chemical Communications Vol. 59, No. 9 ( 1994), p. 2005-2021
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 59, No. 9 ( 1994), p. 2005-2021
    Abstract: The dissociation constants of nineteen ortho substituted benzoic acids have been determined in eight organic solvents (methanol, ethanol, acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, 1,2-dichloroethane). The correlation between the σ I , σ R , and υ constants were unsuccessful due to neglecting the description of intramolecular hydrogen bond effect. The method of conjugated deviations has been applied to the results obtained and to those given in literature for ortho substituted benzoic acids (the dissociation constants, the reaction with diphenyldiazomethane, 33 sets), and values of three types of substituent constants have been determined for 29 substituents. The first of these substituent constants, σ o i , describes the electronic effects and was adjusted with the application of the isoparameter relation (σ o i as a function of σ m i ) suggested in previous communications. This constant (after excluding the substituents NHCOCH 3 and OCOCH 3 ) correlates very well ( R = 0.993) with the σ I and σ R constants. The second substituent constant, σ HG i , describes the interaction of the reaction centre (the oxygen atom of carboxylate anion) with the substituent, and it has non-zero values for the substituents OH, SH, NH 2 , NHCH 3 , NHCOCH 3 , COOH, CONH 2 , and SO 2 NH 2 . The third substituent constant, σ S i , describes the steric effects and is not significantly related to any of the known quantities of this type. The set given was tested together with the triad of σ I , σ R , and υ on the definition set and on a set extended by other 28 sets of processes with ortho substituted compounds. On the whole, the set of substituent constants suggested explains 94.6% of variability of data, whereas only 66.0% are explained with the use of σ I , σ R , and u constants. Moreover, the tests have shown that the σ o i constant is not suitable for interpretations of processes involving direct conjugation between the reaction centre and substituent.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19942005
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1994
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Solvent effects on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)-triazene II. Reactions in aprotic solvents
    Institute of Organic Chemistry & Biochemistry ; 1990
    In:  Collection of Czechoslovak Chemical Communications Vol. 55, No. 1 ( 1990), p. 156-164
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 55, No. 1 ( 1990), p. 156-164
    Abstract: The effect of aprotic solvents (hexane, cyclohexane, dichloromethane, 1,2-dichloroethane, benzene, acetonitrile, acetone, 1,2-dimethoxyethane, ethyl acetate, dioxane) on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene has been studied with trichloroacetic acid as the acid catalyst. It has been found that beside the non-dissociated monomer of the acid also its dimer acts as the catalytic species. With regard to the results obtained in protic solvents (the catalysis by proton and general acid) three cases can be encountered of the dependence of observed rate constant on analytical concentration of the acid. The effect of solvents (inclusive of the protic ones) on the catalytic rate constant of the reaction with the non-dissociated monomer of acid is best interpreted by the equation suggested by Koppel and Palm and by the solvent scale suggested by us earlier. The solvent acidity and polarity have positive effect, whereas its basicity has negative effect. The catalytic rate constant of the reaction with the acid dimer decreases with increasing solvent basicity and polarity, due predominantly to the decrease in the equilibrium constant of dimerization.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19900156
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1990
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    Additive-multiplicative description of extrathermodynamic relations: Application to solvent effect
    Institute of Organic Chemistry & Biochemistry ; 1990
    In:  Collection of Czechoslovak Chemical Communications Vol. 55, No. 3 ( 1990), p. 634-643
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 55, No. 3 ( 1990), p. 634-643
    Abstract: The paper is focused on evaluation of significance of the additive-multiplicative model of extrathermodynamic relations (linear free energy relationships) as compared with the additive model. Application of the method of conjugated deviations to a data matrix describing manifestations of solvent effects in 367 processes in solutions (6 334 data) has shown that introduction of cross-terms into the additive model is statistically significant for a model with two and particularly three parameters. At the same time the calculation has provided a new set of statistical parameters for description of solvent effect with application of the additive-multiplicative model. Compared with an analogous set designated for the additive model, the new parameters show a lower mutual correlation, retaining the same nature of the properties described, i.e. polarity-acidity (PAC parameter), polarity-basicity (PBC), and polarity-polarizability (PPC).
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19900634
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1990
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    Relative ionization cross-sections of oxygenated C(4) molecules
    Elsevier BV ; 1990
    In:  International Journal of Mass Spectrometry and Ion Processes Vol. 97, No. 2 ( 1990-5), p. 117-124
    Details
    In: International Journal of Mass Spectrometry and Ion Processes, Elsevier BV, Vol. 97, No. 2 ( 1990-5), p. 117-124
    Type of Medium: Online Resource
    ISSN: 0168-1176
    URL: Article
    DOI: 10.1016/0168-1176(90)85052-4
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1990
    detail.hit.zdb_id: 1484635-4
    detail.hit.zdb_id: 218269-5
    SSG: 11
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?
    Institute of Organic Chemistry & Biochemistry ; 1994
    In:  Collection of Czechoslovak Chemical Communications Vol. 59, No. 9 ( 1994), p. 2029-2041
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 59, No. 9 ( 1994), p. 2029-2041
    Abstract: The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19942029
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1994
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 8
    Online Resource
    Online Resource
    Synthesis, kinetics and mechanism of cyclization of 1-(2-aryloxycarbonylphenyl)-3-phenyltriazenes
    Institute of Organic Chemistry & Biochemistry ; 1990
    In:  Collection of Czechoslovak Chemical Communications Vol. 55, No. 11 ( 1990), p. 2692-2700
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 55, No. 11 ( 1990), p. 2692-2700
    Abstract: Twelve substituted 1-(2-aryloxycarbonylphenyl)-3-phenyltriazenes have been synthetized and kinetics of their reactions have been measured in 52.1% (by mass) aqueous methanol at pH 3 to 11. Plots of k obs vs pH show three regions: noncatalyzed cyclization (pH 4 to 7), acid-catalyzed splitting of the triazene chain, and base-catalyzed cyclization. The non-catalyzed cyclization exhibits a kinetic isotope effect, the reaction constant ρ = 2.69 (σ - p ), and β 1g = 1.02, which indicates a mechanism of E1cB type with intramolecular proton transfer and a transient formation of a ketene intermediate. The base-catalyzed cyclization, on the other hand, exhibits the reaction constant ρ = 1.05 (σ - p ), β 1g = 0.4, and distinct steric effects, which indicates a cyclization by B Ac 2 mechanism with rate-limiting formation of the tetrahedral intermediate.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19902692
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1990
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 9
    Online Resource
    Online Resource
    Kinetics and Mechanism of Acid Catalyzed Decomposition of 1-Phenyl-3,3-dialkyltriazenes
    Institute of Organic Chemistry & Biochemistry ; 1994
    In:  Collection of Czechoslovak Chemical Communications Vol. 59, No. 2 ( 1994), p. 401-411
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 59, No. 2 ( 1994), p. 401-411
    Abstract: Five model 1-phenyl-3,3-dialkyltriazenes (methyl, ethyl, 2-propyl, butyl, cyclohexyl) have been synthesized and their acid-catalyzed decomposition kinetics have been investigated spectrophotometrically in aqueous ethanol (40 vol.%) with pivalic acid as the catalyst. The results show that the rate-determining step is catalyzed by the proton. The decrease in the observed rate constant at higher concentrations of pivalic acid is explained by the formation of an unreactive complex of the nondissociated acid and respective triazene. The steric effect of alkyl groups on the catalytic rate constants is discussed.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19940401
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1994
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 10
    Online Resource
    Online Resource
    Reactivity of proton and general acid with 1,3-bis-(4-methylphenyl)triazene in aqueous methanol
    Institute of Organic Chemistry & Biochemistry ; 1990
    In:  Collection of Czechoslovak Chemical Communications Vol. 55, No. 11 ( 1990), p. 2701-2706
    Details
    In: Collection of Czechoslovak Chemical Communications, Institute of Organic Chemistry & Biochemistry, Vol. 55, No. 11 ( 1990), p. 2701-2706
    Abstract: The effect of concentration of benzoic acid and composition of the binary solvent water-methanol on the rate of decomposition of 1,3-bis(4-methylphenyl)triazene has been studied. It has been found that both general acid catalysis by undissociated benzoic acid and catalysis by the proton are significant. The rate constant k HA of general acid catalysis decreases monotonously with decreasing amount of water in the mixture due to preferred solvation of the activated complex as compared with the educts. The rate constant k H of the catalysis by proton in its dependence on methanol concentration exhibits a minimum for 80% (by wt.) of methanol in the mixture. This phenomenon is caused by formation of the conjugated acid from more basic methanol and proton with simultaneous solvation by water and methanol; the particle thus formed is a weaker acid as compared with the complexes existing in water or in methanol. The k H value is higher in methanol than in water due to preferred solvation of the educts as compared with that of the transition state.
    Type of Medium: Online Resource
    ISSN: 0010-0765 , 1212-6950
    URL: Article
    DOI: 10.1135/cccc19902701
    Language: English
    Publisher: Institute of Organic Chemistry & Biochemistry
    Publication Date: 1990
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...