Reactivity of phenylsulfonyl isothiocyanates and transfer of substituent effects through the sulfonyl group

1991 ◽  
Vol 56 (12) ◽  
pp. 2872-2878 ◽  
Author(s):  
Gejza Suchár ◽  
Oľga Hritzová ◽  
Ján Imrich ◽  
Antónia Jasovská
Keyword(s):  
Spectroscopic Method ◽  
Substituent Effects ◽  
Stopped Flow ◽  
Nucleophilic Additions ◽  
Reaction Centre ◽  
Electronic Effects ◽  
Sulfonyl Group ◽  
Electronic Effects Of Substituents ◽  
Kinetics Of

Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigated by the stopped-flow UV spectroscopic method and the transfer of electronic effects of substituents on the reaction centre through the SO2 group was examined. The structure and the polar character of SO2NCS, NCS and SO2 groups is discussed.

Gas-phase elimination kinetics of ethyl esters of chloroacetate, 3-chloropropionate, and 4-chlorobutyrate. The electronic effects of substituents at the acyl carbon

1981 ◽  
Vol 85 (9) ◽  
pp. 1243-1245 ◽  
Author(s):  
Gabriel Chuchani ◽  
Juana L. Triana ◽  
Alexandra Rotinov ◽  
Dario F. Caraballo
Keyword(s):  
Gas Phase ◽  
Ethyl Esters ◽  
Electronic Effects ◽  
Elimination Kinetics ◽  
Acyl Carbon ◽  
Electronic Effects Of Substituents ◽  
Kinetics Of ◽  
Phase Elimination

Kinetics of reactions of para-substituted phenyl isocyanates with amines and alcohols

1991 ◽  
Vol 56 (8) ◽  
pp. 1662-1670 ◽  
Author(s):  
Ivan Danihel ◽  
Falk Barnikol ◽  
Pavol Kristian
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Rate Constants ◽  
Substituent Effects ◽  
Steric Effects ◽  
Stopped Flow ◽  
Partial Charges ◽  
Hammett Correlation ◽  
One Step ◽  
Kinetics Of

The reaction of para-substituted phenyl isocyanates with amines and alcohols was studied by stopped-flow method. The Hammett correlation obtained showed that the sensitivity of the above mentioned reactions toward substituent effects is the same as that of analogous reactions of phenyl isothiocyanates (ρ ~ 2). The rate constants of these reactions were found to be affected more by steric effects than by solvent effects. An one step multicentre mechanism with partial charges in transition state has been proposed for the title reactions.

Substituent Effects on the Base-Catalysed Hydrolysis of Phenyl Esters of ortho-Substituted Benzoic Acids

2001 ◽  
Vol 66 (5) ◽  
pp. 770-784 ◽  
Author(s):  
Ingrid Bauerová ◽  
Miroslav Ludwig
Keyword(s):  
Substituent Effects ◽  
Uv Spectrophotometry ◽  
Reaction Centre ◽  
Benzoic Acids ◽  
Model Compounds ◽  
Pseudo First Order Reaction ◽  
Reaction Conditions ◽  
Substituted Benzoic Acids ◽  
Kinetics Of ◽  
Hydrolysis Of

Fourteen model phenyl esters of 2-substituted benzoic acids were synthesised. Structures and purity of model compounds were confirmed by 1H and 13C NMR spectroscopy, as well as by HPLC and elemental analysis. Kinetics of base-catalysed hydrolysis of model phenyl esters occurring by the BAc2 mechanism were measured by UV spectrophotometry in 50% (v/v) aqueous dimethyl sulfoxide solutions at 25 °C under pseudo-first-order reaction conditions (c(NaOH) = 0.001-1.0 mol l-1). Linear relation between J-E and log kobs with the slope close to unity was found for all model compounds. Neither one-parameter nor multiparameter Hammett-type description of variability of experimental data obtained for phenyl esters of 2-substituted benzoic acids was found. Two groups (conjugating and non-conjugating) were created by division of ortho-substituents in ortho-position using the AISE theory, based on their interaction with the 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.

scholarly journals Substituent Effects on the Radical Scavenging Activity of Isoflavonoid

2019 ◽  
Vol 20 (2) ◽  
pp. 397 ◽  
Author(s):  
Yan-Zhen Zheng ◽  
Geng Deng ◽  
Rui Guo ◽  
Da-Fu Chen ◽  
Zhong-Min Fu
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Antioxidative Activity ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Electronic Effects ◽  
Antioxidative Properties ◽  
Electronic Effects Of Substituents

Understanding the role of substituents is of great importance for the preparation of novel phenolic compounds with enhanced antioxidative properties. In this work, the antioxidative activity of isoflavonoid derivatives with different substituents placed at the C2 position was determined by density functional theory (DFT) calculations. The bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA) related to hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were calculated. The strongest antioxidative group of isoflavonoid is not altered by the substituents. Excellent correlations were found between the BDE/IP/PA and Hammett sigma constants. Equations obtained from linear regression can be useful in the selection of suitable candidates for the synthesis of novel isoflavonoids derivatives with enhanced antioxidative properties. In the gas and benzene phases, the electron-donating substituents would enhance the antioxidative activity of isoflavonoids via weakening the BDE of 4′−OH. In water phase, they will reduce the antioxidative by strengthening the PA of 7−OH. Contrary results occur for the electron-withdrawing groups. In addition, the electronic effects of substituents on the BDE/IP/PA have also been analyzed.

Transmission of substituent effects in N-(p-substituted phenyl)-phthalimides

1990 ◽  
Vol 55 (1) ◽  
pp. 261-272 ◽  
Author(s):  
Miroslav Holík ◽  
Božena Matějková
Keyword(s):  
Conformational Changes ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Principal Component ◽  
Electronic Effects ◽  
Diamagnetic Anisotropy ◽  
Electronic Effects Of Substituents ◽  
C Nmr

Chemical shifts of benzene part of the title compounds have been correlated with substituent chemical shifts (SCS) increments a for 1H and z for 13C NMR spectra. These correlations gave pieces of information not only about the through-conjugation of substituents but also about the change of the twist about the central N-C bond with the change of substituent in the para-position. In such a way the electronic effects of substituents have been studied together with the effects due to conformational changes which manifest themselves with the change in the van der Waals repulsion and/or diamagnetic anisotropy of double bond. Chemical shifts in phthalimide part of molecule have been related to the electronic effect of distant substituent after separation of the main source of variation from random error by principal component analysis.

Electronic Effects of Aryl and Heteroaryl Groups on the Rate of Quaternization of 5-Aryl(or Heteroaryl)pyrimidines

1980 ◽  
Vol 35 (4) ◽  
pp. 468-470 ◽  
Author(s):  
David W. Allen ◽  
David J. Buckland ◽  
Barrie G. Hutley
Keyword(s):  
Substituent Effects ◽  
Phenacyl Bromide ◽  
Rate Data ◽  
Electronic Effects ◽  
Kinetics Of

The kinetics of quaternization of a series of 5-aryl- and 5-heteroarylpyrimidines with phenacyl bromide in acetonitrile have been studied in order to assess the electronic effects of the 5-substituent. The observed order of reactivity is 5-(1-methylpyrrol-2-yl) > 5-panisyl >5-(2-furyl) >5-p-tolyl > 5-(2-thienyl) >phenyl > 5-(m-chlorophenyl). The reactions are enthalpy controlled and the rate data can be accounted for in terms of the electronwithdrawing or donating ability of the 5-substituent. The substituent effects of the 2-fury 1- and 2-thienyl groups in the above reaction are significantly different from those observed in the piperidinolysis of 2-chloro-5(2-heteroaryl)pyrimidines.

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.

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