Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides

1987 ◽  
Vol 52 (12) ◽  
pp. 2900-2908 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Helena Javůrková ◽  
Miroslav Večeřa
Keyword(s):  
Factor Analysis ◽  
Hydrogen Bonds ◽  
Model Equation ◽  
Substituent Effects ◽  
Regression Function ◽  
Reaction Centre ◽  
Solvent Dependence ◽  
Substituent Constants ◽  
Reaction Constants

The potentiometric titration in water, methanol, dimethyl sulphoxide, dimethylformamide, and acetonitrile has been used for determination of pK values of 13 N-arylbenzenesulphonamides. The validity of the Hammett and Yukawa-Tsuno models using several sets of substituent constants has been evaluated by the test to check adequacy of the regression function and by the factor analysis. It has been found that the substituent effects in solvents must be interpreted with regard to the experimental method used, solvent, set of the substituent constants, as well as the model equation ETR. The dependence of the Hammett reaction constants on the solvent has been analyzed and reveals a preferred stabilization of the conjugated base through hydrogen bonds. Direct conjugation of the reaction centre with the substituent and with different extent of the solvent-dependence with the 4-CN and 4-NO2 derivatives have been observed.

Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (21) ◽  
pp. 3681-3685 ◽  
Author(s):  
Tomasz A. Modro
Keyword(s):  
Substituent Effects ◽  
Resonance Spectroscopy ◽  
Benzene Derivatives ◽  
13C Nuclear Magnetic Resonance ◽  
Phosphorus Containing ◽  
Substituent Constants ◽  
Parameter Approach ◽  
Reactivity Determination ◽  
C Nmr

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

Chemometric Analysis of Substituent Effects. II. Relation Between Hammett Substituent Constants σm and σp and a New Model for Quantitative Description of Substituent Effects

1994 ◽  
Vol 59 (2) ◽  
pp. 381-390 ◽  
Author(s):  
Oldřich Pytela
Keyword(s):  
Dissociation Constants ◽  
General Relation ◽  
Quantitative Description ◽  
Substituent Effects ◽  
Data Series ◽  
Reaction Centre ◽  
Substituent Constant ◽  
New Model ◽  
Resonance Effects ◽  
Substituent Constants

The paper presents values of 25 substituent constants σi obtained by optimizing 46 data series of dissociation constants of substituted benzoic acids in various media. The constants σi fulfil the general relation between the substituent constants of the Hammett type in meta and para positions enabling the description of substituent effects from both positions at the same time by a single constant. The Hammett substituent constants are interpreted by means of the σi constants with an accuracy better than 0.03 units. In addition to it, the validity of general relationship between σp and σm was verified on a set of 56 substituents with the prediction accuracy of 0.06 units for σp, and after excluding the probably incorrectly parametrized substituents NHCOC6H5, CH3S, and F the accuracy has improved to 0.05 units (98% of interpreted variability). The given relationship has served as a basis for suggesting a new model of transfer of substituent effects to a reaction centre: the model involves both the Hammett equation and the Yukawa-Tsuno equation and explains their background. The suggested model uses generalized transmission coefficients to separately describe the transformation of a single primary substituent effect - depending on its structure - into one inductive and two resonance effects which are transmitted through two independent channels to the reaction centre and here transformed into the resulting observable effect. From the model it follows that the substituent constant σp is not a substituent constant in the true sense of the word since it involves the characteristics of skeleton and of reaction centre.

Chemometrical Analysis of Substituent Effects. V. ortho Effect

1994 ◽  
Vol 59 (9) ◽  
pp. 2005-2021 ◽  
Author(s):  
Oldřich Pytela ◽  
Josef Liška
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects ◽  
Reaction Centre ◽  
Benzoic Acids ◽  
Electronic Effects ◽  
Substituent Constant ◽  
Zero Values ◽  
Substituent Constants ◽  
Substituted Benzoic Acids ◽  
Intramolecular Hydrogen

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 σI, σR, 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, σoi, describes the electronic effects and was adjusted with the application of the isoparameter relation (σoi as a function of σmi) suggested in previous communications. This constant (after excluding the substituents NHCOCH3 and OCOCH3) correlates very well (R = 0.993) with the σI and σR constants. The second substituent constant, σHGi, 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, NH2, NHCH3, NHCOCH3, COOH, CONH2, and SO2NH2. The third substituent constant, σSi, 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 σI, σR, 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 σI, σR, and u constants. Moreover, the tests have shown that the σoi constant is not suitable for interpretations of processes involving direct conjugation between the reaction centre and substituent.

Reactivity of p-Substituted Benzaldoximes in the Cleavage of p-Nitrophenyl Acetate: Kinetics and Mechanism

2004 ◽  
Vol 69 (2) ◽  
pp. 397-413 ◽  
Author(s):  
Jan Pícha ◽  
Radek Cibulka ◽  
František Hampl ◽  
František Liška ◽  
Patrik Pařík ◽  
...  
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects ◽  
Statistical Modelling ◽  
Reaction Centre ◽  
Deprotonated Form ◽  
Rate Limiting Step ◽  
Reaction Constant ◽  
Reaction Constants ◽  
Intramolecular Hydrogen ◽  
The Given

Eleven p-substituted benzaldoximes (p-XC6H4CH=NOH, where X = H, CH3, CF3, F, Cl, Br, OCH3, N(CH3)2, COOCH3, CN, NO2) have been synthesized and their dissociation constants determined in 10% (v/v) aqueous dioxane at 35 °C. Under the same conditions, the pseudo-first order rate constants kobs of their reactions with p-nitrophenyl acetate (PNPA) were measured at pH values from 7.8 to 10.8 and at concentrations coxime ranging from 0 to 4.00 × 10-3 mol l-1. The kinetic model and mechanism of the said reaction was proposed by means of mathematical statistical modelling of the dependences of kobs on pH and coxime. The mechanism involves a pre-equilibrium (k-1/k1) in which PNPA forms a tetrahedral intermediate (THI) with the deprotonated form of oxime. In the given medium, THI is in equilibrium with the non-reactive conjugated acid THIH (dissociation constant Ka,THIH) which is stabilized by intramolecular hydrogen bond. Depending on pH, the rate-limiting step consists either in formation of THI from educts (pH < pKa,oxime) or in its spontaneous (k2) and oxime-catalyzed (k3, general acid catalysis) decomposition to products (pH > pKa,oxime). Evaluation of substituent effects on dissociation constants (Ka,oxime) of the oximes showed that there is no direct conjugation between the substituent and the reaction centre (the found reaction constant ρ(Ka,oxime) = 0.91). The transmission coefficient of the transfer of these effects through C=N-O grouping corresponds approximately to one bond. The reaction constants in the Hammett equation obtained from the regression model are: ρ(k-1Ka,THIH/k1) = 1.29, ρ(k2Ka,THIH) = 0.20 and ρ(k3Ka,THIH) = 0.67. These reaction constants have been discussed with the regard to the reaction mechanism suggested.

Chemometric Analysis of Substituent Effects. IX. Alternative Interpretation of Substituent Effects (AISE) - Orthogonal Model

1996 ◽  
Vol 61 (5) ◽  
pp. 704-712 ◽  
Author(s):  
Oldřich Pytela
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Alternative Interpretation ◽  
Reaction Centre ◽  
Class Iii ◽  
Coordinate Axis ◽  
The Family ◽  
Reaction Constants ◽  
The Individual ◽  
Point Of Intersection

Continuing the previous communications, the present paper suggests an orthogonal model of alternative interpretation of substituent effects (AISE). Following this approach, substituents are classified into three classes. Those of class II are defined as substituents whose atom bound to the basic skeleton bears a character of nucleophile, i.e. it is able of an intramolecular nucleophilic interaction with the reaction centre. The class III includes substituents whose atom bound to the basic skeleton is electrophilic in nature and can correspondingly interact with the reaction centre too. The class I includes the substituents possessing none of the above-mentioned characteristics. Within the model suggested the substituent effects can be described by a family of three lines corresponding to the substituent classes described with a single substituent constant at the coordinate axis. The validity of the model suggested has successfully been tested by comparison with other correlation equations using 318 reaction series taken from literature. It has been found that the value of the point of intersection at the coordinate axis (the isosubstituent constant) is smaller in processes with electron deficit and grater in those with electron excess in the reaction centre. The slopes of the individual lines in the family of lines (the reaction constants) decrease in the order II > I > III in most cases, the only exception being the processes with direct conjugation between a negatively charged reaction centre and the substituent and some gas phase processes.

Substituent effects in 1,3-indanediones

1982 ◽  
Vol 47 (5) ◽  
pp. 1486-1493 ◽  
Author(s):  
Alexander Perjéssy
Keyword(s):  
Substituent Effects ◽  
Empirical Equations ◽  
Substituent Constants ◽  
Complex Structural

The carbonyl stretching frequencies correlate well with substituent constants in a series of 166 1,3-indanediones using improved and extended Seth-Paul-Van Duyse equation. Transmissive factors and group electronegativities have been used to find empirical equations for calculation of substituent constants of more complex structural fragments.

The protonation of the ethylenediphosphinetetraacetate anion and the crystal structure of the bis (hydrogen bromide) of ethylenediphosphinetetraacetic acid

1981 ◽  
Vol 46 (12) ◽  
pp. 3063-3073 ◽  
Author(s):  
Jana Podlahová ◽  
Bohumil Kratochvíl ◽  
Vratislav Langer ◽  
Josef Šilha ◽  
Jaroslav Podlaha
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Determination ◽  
Free Acid ◽  
Hydrogen Bromide ◽  
Carboxyl Groups ◽  
Spectroscopic Methods ◽  
X Ray ◽  
Partial Formation

The equilibria and mechanism of addition of protons to the ethylenediphosphinetetraacetate anion (L4-) were studied in solution by the UV, IR, 1H and 31P NMR spectroscopic methods. A total of six protons can be bonded to the anion. They are added stepwise, first with partial formation of zwitterions containing P-H bonds, which then dissociate with formation of the free acid, H4L, where all four protons are bonded in carboxyl groups. The formation of zwitterions is strongly dependent on the concentration. In the final stage, the acid bonds two additional protons to form the bis-phosphonium cation, H6L2+. A number of isostructural salts containing this cation, H4L.2 HX (X = Cl, Br, I), have been prepared. The X-ray crystal structure determination of the bromide confirmed the expected arrangement. The bromide crystals are monoclinic, a = 578.2, b = 1 425.0, c = 1 046.7 pm, β = 103.07° with a space group of P21/c, Z = 2. The final R factor was 0.059 based on 1 109 observed reflections. The structure consists of H6L2+ cations containing protons bonded to phosphorus atoms (P-H distance 134 pm) and of bromide anions, located in gaps which are also sufficiently large for I- anions in the isostructural iodide. The interbonding of phosphonium cations proceeds through hydrogen bonds, C-OH...O=C, in which the O...O distance is 275.3 pm.

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

Chemometric Analysis of Substituent Effects. VIII. Alternative Interpretation of Substituent Effects (AISE)

1995 ◽  
Vol 60 (9) ◽  
pp. 1502-1528 ◽  
Author(s):  
Oldřich Pytela
Keyword(s):  
Multiple Bond ◽  
Substituent Effects ◽  
Alternative Interpretation ◽  
Class I ◽  
Reaction Centre ◽  
Correlation Equations ◽  
Class Iii ◽  
Substituent Constant ◽  
Chemical Models ◽  
The Individual

Alternative interpretation of substituent effects (AISE) starts from the presumption that a substituent only possesses a single property described by a single substituent constant. This property is transmitted to the reaction centre by three different ways depending on the interaction type in the triad reaction centre - basic skeleton - substituent. For interpretation it is substantial whether or not the substituent has p electrons at the atom adjacent to the basic skeleton. If it has none, the substituent belongs to class I and operates only by its basic effect described by the mentioned single substituent constant. Substituents of class II possess a free electron pair at the atom adjacent to the basic skeleton, and those of class III have a multiple bond between the first and the second atoms which is polarized in the direction from the basic skeleton. Substituent effects in class I are described by a substituent constant identical with σI constant. Substituents in classes II and III show additional effects proportional to the same constant. Hence, a separate treatment of substituent effects in the individual classes provides three straight lines intersecting in a common point. Mathematically, the description of substituent effects in this approach is expressed by a family of lines with a single explaining variable. The point of intersection, which is referred to as the iso-effect point, is not identical with the classic standard substituent - hydrogen - but is near to CN substituent. The approach given has the advantage of adopting a single substituent constant whose scale can be adjusted relatively precisely. Its drawback (like in the case of the correlation equations derived from the principle of separation of substituent effects) lies in a more extensive set of substituents needed for a correlation. The AISE principle has been applied to 318 series of experimental data describing effects of 32 substituents in a large variety of chemical models (aliphatic, alicyclic, aromatic, heteroaromatic, with or without direct conjugation between reaction centre and substituent) in both chemical reactions and equilibria. A comparison with two other correlation relations with two and three substituent constants for interpretation of substituent effects based on the principle of separation of the individual substituent effects showed that the closeness of AISE based correlations is comparable with that of the correlation equations currently used. It was somewhat less successful in the models with direct conjugation between reaction centre and substituent but the AISE principle can be used even in these cases.

Sign in / Sign up

Export Citation Format

Share Document