THE APPLICATION OF THE HAMMETT EQUATION TO ORTHO-SUBSTITUTED BENZENE REACTION SERIES

1960 ◽  
Vol 38 (12) ◽  
pp. 2493-2499 ◽  
Author(s):  
Marvin Charton
Keyword(s):  
Benzene Ring ◽  
Substituent Effects ◽  
Para Position ◽  
Steric Effects ◽  
Side Chain ◽  
Ortho Position ◽  
Reaction Site ◽  
Hammett Equation ◽  
Reaction Series ◽  
Electrical Effect

The Hammett equation is directly applicable to ortho-substituted benzene reaction series in which reaction site and benzene ring are separated by some group Z, apparently due to the absence of steric effects in these series. The σp values are used in the correlations. Fourteen ortho-substituted benzene reaction series have been correlated. The electrical effect of a substituent in the ortho position is found to be about 0.75 times its effect in the para position. The effect of the side-chain Z in the transmission of substituent effects is OCH2 > SCH2 > CH = CH > SeCH2 > CH2CH2.

Substituent effects on the thermodynamic functions of ionization of metasubstituted anilinium ions

1968 ◽  
Vol 21 (4) ◽  
pp. 939 ◽  
Author(s):  
PD Bolton ◽  
FM Hall
Keyword(s):  
Linear Function ◽  
Thermodynamic Functions ◽  
Substituent Effects ◽  
Negative Slope ◽  
Hammett Equation ◽  
Reaction Parameter ◽  
Reaction Series ◽  
Acidity Constants ◽  
Temperature Range ◽  
Relationship Of

Thermodynamic acidity constants of the meta-methoxyanilinium, meta- chloroanilinium, meta-bromoanilinium, and meta-iodoanilinium ions have been measured spectrophotometrically over the temperature range 5-50� and those of the meta-nitroanilinium ion over the temperature range 5-60�. The thermodynamic functions of ionization, ΔG25, ΔH25, ΔS25, and ΔCp,25, have also been calculated for each ion. For a series of seven meta-substituted anilinium ions the acidity constants show close obedience to the Hammett equation over the temperature range 10-50� with the reaction parameter p being a precise linear function of 1/T. The same reaction series also shows a well-defined isoequilibrium relationship of negative slope.

Mutagenic effects of the herbicide 3′,4′-dichloropropionanilide and its degradation products

1970 ◽  
Vol 16 (5) ◽  
pp. 369-372 ◽  
Author(s):  
Ishwari Prasad
Keyword(s):  
Aspergillus Nidulans ◽  
Benzene Ring ◽  
Mutation Frequency ◽  
Degradation Products ◽  
Para Position ◽  
Ortho Position ◽  
Back Mutation ◽  
Mutagenic Effects

3′,4′-Dichloropropionanilide; its biodegradation products 3,4-dichloroaniline and 3,3′,4,4′-tetrachloroazobenzene; and related chloroaniline and chlorobenzenes were tested for effects on the back mutation frequency of the meth3 locus in Aspergillus nidulans. 3,4-Dichloroaniline was more mutagenic than 3,3′,4,4′-tetrachloroazobenzene and 3′,4′-dichloropropionanilide. Chlorine in the para position on benzene ring increased mutagenicity more than chlorine in the meta or ortho position. Chloroaniline was more mutagenic than the corresponding dichlorobenzene.

Substituent Effects of Phosphorus and Arsenic Containing Groups in Aromatic Substitution. IV. Nitration of Aromatic Phosphine Oxides

1975 ◽  
Vol 53 (10) ◽  
pp. 1468-1474 ◽  
Author(s):  
Edmund Malinski ◽  
Antonina Piekos ◽  
Tomasz A. Modro
Keyword(s):  
Sulfuric Acid ◽  
Benzene Ring ◽  
Phosphorus Atom ◽  
Substituent Effects ◽  
Ortho Position ◽  
Phosphine Oxides ◽  
Aromatic Substitution ◽  
Tertiary Phosphine ◽  
Aqueous Sulfuric Acid

The nitration of some tertiary phosphine oxides ArP(O)R2 in aqueous sulfuric acid has been investigated. All compounds studied react as conjugate acids. When the phosphinyl group is bonded directly to the benzene ring, high deactivation and meta-orientation is found, accompanied in most cases by some substitution at the ortho position. The substituent effects of the "quasiphosphonium" group P(OH)R2+are compared with those of structurally related systems and are discussed in terms of pπ–dπ, interactions of the oxygen and the phosphorus atom.

Field and Resonance Components of Substituent Effects in Relation to the Hammett Equation

1972 ◽  
Vol 50 (7) ◽  
pp. 1030-1035 ◽  
Author(s):  
L. D. Hansen ◽  
L. G. Hepler
Keyword(s):  
Substituent Effects ◽  
Similar Reaction ◽  
Hammett Equation ◽  
Reaction Series ◽  
Field Interaction ◽  
Isokinetic Relationship ◽  
Resonance Effects ◽  
Transmission Coefficients ◽  
Substituent Constants ◽  
Specific Reactions

Following Swain and Lupton's analysis of substituent effects, we have taken ΔG0 = aete + artr for a typical substituent effect reaction. In this equation ae and ar are substituent constants for electrostatic field and resonance effects while te and tr are corresponding transmission coefficients. Both substituent constants and tr are taken to be independent of solvent and temperature, while te is taken to depend on both solvent and temperature. General conclusions based on analysis of this model are the following. (i) A Hammett ρσ equation with constant σ values that are valid over a range of temperatures for a variety of reactions in several solvents can be obtained only when either the field or the resonance interaction is negligible compared with the other. (ii) A Hammett ρσ equation can be expected to hold for "similar" reaction series in a given solvent at one temperature even when both the field and resonance interactions are important, (iii) An isoequilibrium or isokinetic relationship can be expected only when the field interaction is dominant.The general equations leading to these and other conclusions are presented so that one can later insert appropriate mathematical descriptions of detailed models and thereby obtain information about specific reactions.

Chemometric Analysis of Substituent Effects. VI. A Study of ortho Effect in Dissociation of 2,6-Disubstituted Benzoic Acids

1995 ◽  
Vol 60 (5) ◽  
pp. 829-840 ◽  
Author(s):  
Jiří Kulhánek ◽  
Oldřich Pytela
Keyword(s):  
Latent Variables ◽  
Dissociation Constants ◽  
Additive Model ◽  
Substituent Effects ◽  
Point Of View ◽  
Steric Effects ◽  
Benzoic Acids ◽  
Hammett Equation ◽  
Substituent Constants ◽  
Substituted Benzoic Acids

Ten 2,6-disubstituted benzoic acids have been synthesized containing all possible combinations of the following substituents: CH3, OCH3, Cl, and NO2. The dissociation constants of these acids have been measured by potentiometric titration in methanol, acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, and 1,2-dichloroethane. The experimental data obtained together with the pK values of 2-substituted benzoic acids in the same solvents have been analyzed from the point of view of ortho effect and additivity of disubstitution. The mutual interaction between substituents was found to represent only 0.12% of the variability due to substitution and to contribute to the overall variability of data less than the interaction between the substituent and solvent by a factor of about 13. The analysis of data by the method of multiple linear regression revealed a contribution of steric effects beside the effects transmitted through the aromatic skeleton. The 2- and 6-substituents effects are additive within the validity of the Hammett equation, and an addition of a multiplicative term describing interactions between the substituents is statistically insignificant. Nonlinear regression has been adopted in the additive model with multiplicative term to find the inner substituent constants including all the effects of substituents from ortho position: the term describing the interaction between 2- and 6-substituents is statistically insignificant in this model. An application of the method of conjugated deviations revealed two statistically significant latent variables. The first one explains 91.5% of the variability of data and is connected with the substituent effects transmitted through the aromatic skeleton. The second one explains 7.5% of variability of data and predominantly reflects the steric effects of substituents.

Infrared, 1H and 13C NMR Spectral Studies on Di- and Tri-substituted N-Aryl Amides, 2,6-X2C6H3NHCOCH3 – IXi and 2,4,6-X3C6H2NHCOCH3 – IXi (X = Cl or CH3 and I = 0, 1, 2 or 3)

2004 ◽  
Vol 59 (1-2) ◽  
pp. 69-76 ◽  
Author(s):  
B. Thimme Gowda ◽  
K. M. Usha ◽  
K. Jyothi
Keyword(s):  
General Formula ◽  
Benzene Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Spectral Studies ◽  
Side Chain ◽  
1H And 13C Nmr ◽  
Stretching Vibrations ◽  
Absorption Frequencies ◽  
C Nmr

Several di- and tri-substituted amides of the general formula, 2,6-X2C6H3NHCOCH3−iXi and 2,4,6-X3C6H2NHCOCH3−iXi (X = Cl or CH3 and i = 0, 1, 2, or 3) are prepared, characterised, and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution are studied. The C=O stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong absorptions in the ranges 1707 - 1658 cm−1 and 1700 - 1647 cm−1, respectively, while the N-H stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong vibrations in the ranges 3271 - 3209 cm−1 and 3285 - 3214 cm−1, respectively. The N-H stretching vibrations of N-(2,4,6-trichlorophenyl)- and N-(2,4,6-trimethylphenyl)- amides also appear as strong absorptions in the ranges 3370 - 3212 and 3283 - 3225 cm−1, respectively, while those of the C=O vibrations appear in the ranges 1688 - 1617 and 1704 - 1647 cm−1. The analysis of the C=O and N-H absorption frequencies of all amides of the general formula XiC6H5−iNHCOCH3−iXi (where X = Cl or CH3, and i = 0, 1, 2 or 3) indicates that their variations do not show regular trends with substitution either in the phenyl ring or in the side chain. The chemical shifts of both the aromatic protons and the aromatic carbons of all the amides are calculated in two ways, either by adding the incremental shifts due to -COCH3−iXi groups and the substituents in the benzene ring to the chemical shifts of the corresponding aromatic protons or carbons of the parent aniline, or by adding the incremental shifts due to -NHCOCH3−iXi groups and the substituents in the benzene ring to the chemical shift of the benzene proton or carbon. The calculated chemical shifts of the aromatic protons and carbons of all the substituted amides by both methods lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating that the principle of additivity of the substituent effects is valid in these compounds.

Electrophilic and nucleophilic substitution in the Benzene ring and the Hammett Equation

1956 ◽  
Vol 9 (1) ◽  
pp. 61 ◽  
Author(s):  
J Miller
Keyword(s):  
Large Deviations ◽  
Nucleophilic Substitution ◽  
Benzene Ring ◽  
Electrophilic Substitution ◽  
Substituent Effects ◽  
Hammett Equation ◽  
Wide Range ◽  
Good Agreement

The Hammett equation as applied to aromatic nuclear electrophilic and nucleophilic substitution is tested for a wide range of substituents. For nucleophilic substitution quite good agreement is obtained for electron-attracting substituents using σ* values, but large deviations occur with substituents releasing electrons by the conjugative mechanism. In electrophilic substitution, in so far as results are available, a fair measure of agreement obtains for electron-attracting substituents, but very large and to some extent irregular deviations occur for the conjugative electron- releasing substituents. The deviations occur whether σ or σ* values are used, and new sets of σN** and σE** values are defined and the values recorded. A comparison is made of substituent effects in nuclear electrophilic and nucleophilic substitution.

The Nature and Transmission of Substituent Electrical Effects in Alicyclic Solvolysis

1999 ◽  
Vol 64 (11) ◽  
pp. 1849-1876 ◽  
Author(s):  
Marvin Charton
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Field Effect ◽  
Resonance Effect ◽  
Steric Effects ◽  
Reaction Site ◽  
Reliable Indication ◽  
Leaving Group ◽  
Electrical Effect ◽  
Substituted 1

The correlation of rate constants taken from the literature for 2-exo- and 2-endo-norbornyl derivatives substituted in positions 1, 4, 5-exo, 6-exo, 6-endo, and 7-anti with the triparametric LDR equation and relationships derived from it has been carried out. A delocalized (resonance) electrical effect has been found in all but the 4-substituted derivatives. The resonance effect may be somewhat greater when the leaving group is exo than when it is endo. Steric effects occur in the 6-endo-substituted derivatives. The transition state resembles a classical carbocation rather than the nonclassical norbornyl carbocation. The correlation of solvolysis rate constants for 2- and 3-substituted 1- and 4-exo-substituted 2-exo-adamantyl derivatives gave no reliable indication that a delocalized electrical effect existed in these systems. A study of solvolysis rate constants for 4-substituted 1-[2.2.2]bicyclooctanyl, 6-exo-substituted [2.2.2]bicyclooctan-2-exo-yl and 6-exo-substituted [2.2.2]bicyclo- octan-2-endo-yl derivatives showed a delocalized electrical effect only in the latter of these systems. Such an effect was also observed in 4-substituted 2-chloro-2-methylbutane solvolyses. The transmission of electrical effects is by a modified field effect. It is dependent on 1/n where n is the number of bonds intervening between substituent and reaction site.

scholarly journals Computational study of the substituent effects on the gas-phase stabilities of phenylboranylmethyl anions

2017 ◽  
Vol 89 (11) ◽  
pp. 1685-1694
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio
Keyword(s):  
Gas Phase ◽  
Benzene Ring ◽  
Computational Study ◽  
Resonance Effect ◽  
Substituent Effects ◽  
Nbo Analysis ◽  
Side Chain ◽  
Isodesmic Reactions ◽  
Effect Analysis ◽  
Orbital Interactions

AbstractThe relative gas-phase stabilities of ring-substituted phenylboranylmethyl anions were computationally determined using isodesmic reactions. The energies of species included in the reactions were calculated at the B3LYP/6-311+G(2d,p) level of theory. The obtained substituent effects were analyzed by the extended Yukawa-Tsuno equation, and unexpectedly substantial r− (0.59) and s (0.65) values were found for the fully-optimized planar anion. The substantial through-resonance effect quantified by the r− value was observed, although it is not possible to draw a canonical form in which the negative charge is delocalized on the benzene ring. Substituent effects were also analyzed for the anions in which the dihedral angle (φ) between the side chain plane and the benzene ring was fixed. The r− value decreased significantly by changing the φ from 0° to 90°, while the s value changed little. NBO analyses revealed that the r− value is proportional to the sum of the π–π* and σ–π* orbital interactions between the side chain and the benzene ring. This fact shows that the through-resonance effect quantified by the r− value is present at all φ, and therefore, the anion cannot become an ideal σ0-reference system. The constant saturation effect quantified by the s value can be explained by the constant charge distributed to the benzene ring. The combination of substituent-effect analysis and NBO analysis successfully revealed the nature of the anion.

Reaction series not obeying the Hammett equation: conformational equilibria of substituted thiobenzanilides

2002 ◽  
Vol 26 (7) ◽  
pp. 861-866 ◽  
Author(s):  
Karel Palát Jr. ◽  
Stanislav Böhm ◽  
Gabriela Braunerová ◽  
Karel Waisser ◽  
Otto Exner
Keyword(s):  
Hammett Equation ◽  
Reaction Series ◽  
Conformational Equilibria
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