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Journal articles on the topic 'Hammett equation'

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Published: 4 June 2021

Last updated: 17 February 2022

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1

Liu, Lei, Yao Fu, Rui Liu, Rui-Qiong Li, and Qing-Xiang Guo. "Hammett Equation and Generalized Pauling's Electronegativity Equation." Journal of Chemical Information and Computer Sciences 44, no. 2 (March 2004): 652–57. http://dx.doi.org/10.1021/ci0342122.

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2

Reis, Jo�o Carlos R., Manuel A. P. Segurado, and Jaime D. Gomes De Oliveira. "Plurilinear improvement of the Hammett equation." Journal of Physical Organic Chemistry 8, no. 10 (October 1995): 671–88. http://dx.doi.org/10.1002/poc.610081006.

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3

Bartoletti, Antonella, Simona Bartolini, Raimondo Germani, Gianfranco Savelli, and Clifford A. Bunton. "Hammett equation and micellar effects upon deacylation." Journal of the Chemical Society, Perkin Transactions 2, no. 4 (1994): 723. http://dx.doi.org/10.1039/p29940000723.

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4

Linert, W., R. Schmid, and AB Kudrjawtsev. "Concerning the Problem of the Isokinetic Relationship. III. The Temperature-Dependance of the hammett Equation." Australian Journal of Chemistry 38, no. 5 (1985): 677. http://dx.doi.org/10.1071/ch9850677.

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It is shown that the temperature-dependence of the Hammett equation is, in contrast to tradition, both physically and experimentally better described by means of temperature-dependent σ and temperature- independent ρ (termed ρo). The relationship between ρo and the customary (temperature dependent) ρ is ρT = ρo(1/T-1/Tbiso)/(1/T-1/Tbiso) where Tbiso , is the isoequilibrium temperature of the benzoic acid ionization, for which the present analysis suggests a value of -255 K, and T is 298 K. In these terms, the temperature variation of the Hammett equation can be evaluated by supplying merely E(u)a (the activation energy for the reaction of the unsubstituted reactant) and ρo, in that the σ value for the isokinetic substituent , i.e., the abscissa of the common point of intersection in the Hammett plot, is σiso = (1/T-1/Tbiso)E(u)a/(2.303Rρo) = E(u)a/(2630po) Further, ρo I related to energies ρo = E(u)a/(ΔH°u-ΔH°s(iso))where ΔH°u and ΔH°s(iso) are the ionization enthalpies of the parent benzoic acid and that bearing the isokinetic substituent , respectively. Analogous equations apply to thermodynamic reaction series when substituting E(u)a for ΔH°u(series). Along these lines the interpretation of the customary Hammett plot is advanced.

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5

Vandanapu, Jagannadham, and Sanjeev Rachuru. "Effect of Hetero Atom on the Hammett’s Reaction Constant (ρ) from the Physical Basis of Dissociation Equilibriums of (Dithio) Benzoic Acids and (Thio) Phenols and Its Application to Solvolysis Reactions and Some Free Radical Reactions." Advances in Physical Chemistry 2012 (July 3, 2012): 1–4. http://dx.doi.org/10.1155/2012/598243.

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The emergence of putative Hammett equation in mid 1930s was a boon to physical-organic chemists to elucidate the reaction mechanisms of several organic reactions. Based on the concept of this equation several hundreds of papers have emerged in chemical literature in the last century on the effect of structure, on reactivity, and very few on thermodynamic stability and kinetic reactivity of intermediates. In this article an attempt is made to explain the effect of hetero atom on Hammett’s reaction constant (ρ) taking the dissociation equilibriums of benzoic acids, dithiobenzoic acids, phenols, and thiophenols.

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6

Schwan, Adrian L. "Do our students really understand the Hammett equation?" Journal of Chemical Education 70, no. 12 (December 1993): 1001. http://dx.doi.org/10.1021/ed070p1001.

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7

Alunni, Sergio, Sergio Clementi, Cynthia Ebert, Paolo Linda, Giuseppe Musumarra, Michael Sjöström, and Svante Wold. "Use of the Hammett equation in substituted thiophenes." J. Chem. Soc., Perkin Trans. 2, no. 4 (1985): 485–90. http://dx.doi.org/10.1039/p29850000485.

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8

Shorter, John. "ChemInform Abstract: The Prehistory of the Hammett Equation." ChemInform 31, no. 33 (June 3, 2010): no. http://dx.doi.org/10.1002/chin.200033287.

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9

Pytela, Oldřich, Jiří Kulhánek, Miroslav Ludwig, and Václav Říha. "Chemometrical Analysis of Substituent Effects. III. Additivity of Substituent Effects in Dissociation of 3,4-Disubstituted Benzoic Acids in Organic Solvents." Collection of Czechoslovak Chemical Communications 59, no. 3 (1994): 627–38. http://dx.doi.org/10.1135/cccc19940627.

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Sixteen 3,4-disubstituted benzoic acids (with all combinations of CH3O, CH3, Cl/Br, and NO2 substituents) have been synthesized and their dissociation constants measured in seven organic solvents (methanol, acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, 1,2-dichloroethane). The effect of disubstitution and the validity of additive correlation relationships based on the Hammett equation have been analyzed by means of the analysis of variance, comparison of overall residual standard deviations of correlation equations of additive and additive multiplicative type, and application of the Hammett equation with internal (latent, defined in various ways) parameters and external (taken from literature) parameters describing the substituent effects. The effect of disubstitution has been found to be additive and describable within the validity range of the substituent constants adopted - by applying the additivity principle without any additional correction for interactions between the two substituents. The same conclusion has been drawn from the comparison of overall residual deviations in correlation equations for mono- and disubstituted derivatives. The analysis of differences between the reaction constants of the Hammett equation applied to mono- and disubstituted benzoic acids has shown that in organic solvents the solvation of substituents makes various contributions. The substituent influence is stronger in polar aprotic solvents (acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile) than that in the protic, basic, and less polar ones in which the stabilization by hydrogen bond becomes important, the role of proton donor being played either by the solvent itself (methanol) or by its conjugated acid (pyridine) or by a molecule of the dissociating acid as a consequence of homoconjugation (1,2-dichloroethane).

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10

Marrs, Peter S. "Class Projects in Physical Organic Chemistry: The Hammett Equation." Journal of Chemical Education 78, no. 4 (April 2001): 527. http://dx.doi.org/10.1021/ed078p527.

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11

Domingo, Luis R., Patricia Pérez, and Renato Contreras. "Electronic Contributions to the σpParameter of the Hammett Equation." Journal of Organic Chemistry 68, no. 15 (July 2003): 6060–62. http://dx.doi.org/10.1021/jo030072j.

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12

Bragato, Marco, Guido Falk von Rudorff, and O. Anatole von Lilienfeld. "Data enhanced Hammett-equation: reaction barriers in chemical space." Chemical Science 11, no. 43 (2020): 11859–68. http://dx.doi.org/10.1039/d0sc04235h.

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13

van Beek, L. K. H. "A relationship between dipole moments and the Hammett equation." Recueil des Travaux Chimiques des Pays-Bas 76, no. 9 (September 2, 2010): 729–32. http://dx.doi.org/10.1002/recl.19570760908.

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14

Schoustra, Sybren K., Joshua A. Dijksman, Han Zuilhof, and Maarten M. J. Smulders. "Molecular control over vitrimer-like mechanics – tuneable dynamic motifs based on the Hammett equation in polyimine materials." Chemical Science 12, no. 1 (2021): 293–302. http://dx.doi.org/10.1039/d0sc05458e.

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15

Du, Juan, Changwei Wang, Shiwei Yin, Wenliang Wang, and Yirong Mo. "Resonance-assisted/impaired anion–π interaction: towards the design of novel anion receptors." RSC Advances 10, no. 59 (2020): 36181–91. http://dx.doi.org/10.1039/d0ra07877h.

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16

Waisser, Karel, Miloš Macháček, Jean Lebvoua, Jiří Hrbata, and Jaroslav Dršata. "Quantitative relations between chemical structure and hepatotoxicity of thiobenzamides." Collection of Czechoslovak Chemical Communications 53, no. 11 (1988): 2957–61. http://dx.doi.org/10.1135/cccc19882957.

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1H NMR chemical shifts of thioamide protons have been determined for a group of thiobenzamides, and the values obtained have been correlated with the Hammett constants. From the relations found the σm and σp values of thioamide group and some other σ constants describing the total effect of two substituents in the phenyl group have been calculated. The relation between the hepatotoxicity for rats (expressed as log ALT) and the Hammett constants is described by equation of parabola.

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17

Ikeda, Glenn K., Karen Jang, Scott O. C. Mundle, and Andrew P. Dicks. "The Hammett Equation: Probing the Mechanism of Aromatic Semicarbazone Formation." Journal of Chemical Education 83, no. 9 (September 2006): 1341. http://dx.doi.org/10.1021/ed083p1341.

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18

Huang, Jin, and H. Brian Dunford. "Oxidation of substituted anilines by horseradish peroxidase compound II." Canadian Journal of Chemistry 68, no. 12 (December 1, 1990): 2159–63. http://dx.doi.org/10.1139/v90-331.

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The kinetics of oxidation of eight monosubstituted anilines catalyzed by horseradish peroxidase compound II has been studied at pH 7.00 and 7.60. With p-toluidine the rates of oxidation by compound II have been measured at 21 pH values between 3.60 and 10.25. The rate–pH profile indicates that an acidic form of compound II and the electrically neutral, unprotonated form of p-toluidine are reactive. The correlation of rate constants for the substituted anilines with the substituent constant σ in the Hammett equation suggests that the aromatic amine donates an electron to compound II in the rate-controlling step and loses a proton simultaneously. The value of ρ, the susceptibility factor in the Hammett equation, is −6.0 ± 0.7. The reactivity of anilines with HRP-II observed in this study is lower than that of anilines with HRP-I observed previously, although the value of ρ is the same within experimental error (D. Job and H. B. Dunford. Eur. J. Biochem. 66, 607 (1976)). The difference in reactivity is explained by the relative complexities of the reactions of compounds I and II. Keywords: horseradish peroxidase, peroxidase compound II, aniline oxidation, Hammett correlation, enzymatic oxidation.

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19

Urosevic, Jovica, Sasa Drmanic, Jasmina Nikolic, Ivan Juranic, and Bratislav Jovanovic. "Structure-reactivity correlation for the kinetics of the reaction of substituted 4-phenyl-1,4-dihydropyridines formation." Journal of the Serbian Chemical Society 78, no. 12 (2013): 1963–73. http://dx.doi.org/10.2298/jsc131120139u.

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Quantitative structure-reactivity correlations for the kinetics of the Hantzsch's synthesis of substituted 4-phenyl-1,4-dihydropyridines in the reaction between ethyl m- and p-substituted benzylidene acetoacetate and enamine has been studied. The reaction kinetics was followed using spectrophotometric measurements. It was found that the reaction correspond to the second-order kinetics. Quantitative structure-reactivity correlations of log k with the corresponding substituent constants (s,s+,sI and sR+) using Hammett and extended Hammett equation (DSP equation). They show linear relationship with positive values of reaction constants (r). The obtained data were processed by the linear regression analysis. It is confirmed that Michael's addition of enamine to benzylidene represents the slow step of the reaction with high positive charge at the benzylidene molecule. MO calculations were performed and they were also in agreement with the conclusions derived from structure-reactivity correlations.

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20

Dargó, Gergő, Adrienn Bölcskei, Alajos Grün, Szabolcs Béni, Zoltán Szántó, Antal Lopata, György Keglevich, and György T. Balogh. "Proton dissociation properties of arylphosphonates: Determination of accurate Hammett equation parameters." Journal of Pharmaceutical and Biomedical Analysis 143 (September 2017): 101–9. http://dx.doi.org/10.1016/j.jpba.2017.05.038.

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21

Böhm, Stanislav, Patrik Paŕík, and Otto Exner. "Range of validity of the Hammett equation: acidity of substituted ethynylbenzenes." New Journal of Chemistry 30, no. 3 (2006): 384. http://dx.doi.org/10.1039/b512698c.

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22

Umarani, R., and G. Radhakrishnan. "Structure–reactivity correlations of substituted 2-phenylthiazolidines." Canadian Journal of Chemistry 70, no. 7 (July 1, 1992): 2009–14. http://dx.doi.org/10.1139/v92-252.

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Systematic investigations of the kinetics of the reactions of ethyl bromoacetate (EBA) and of picryl bromide (PB) with 2-phenylthiazolidines (PT) in 100% ethanol were undertaken at 30, 35, 40, and 45 °C. The most incisive information concerning the Hammett equation comes from the extensive studies on the substituted 2-phenylthiazolidines, establishing linear Hammett plots with negative ρ values. The kinetic data, plotted in a Brønsted fashion against pKa of the corresponding thiazolidinium ions, yield linear relationships. The activation parameters were computed. The linear relationships between ΔH≠ and ΔS≠ signify a consistent mechanism throughout the series.

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23

Sanjeev, Rachuru, Ramavath Ravi, Vandanapu Jagannadham, and Adam A. Skelton. "Experimental and Quantum Mechanical Study of Nucleophilic Substitution Reactions of meta- and para-Substituted Benzyl Bromides with Benzylamine in Methanol: Synergy Between Experiment and Theory." Australian Journal of Chemistry 70, no. 1 (2017): 90. http://dx.doi.org/10.1071/ch16061.

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This work involves the experimental and theoretical study of the nucleophilic substitution of meta- and para-substituted benzyl bromides with benzylamine. Conductometric rate experiments confirm the applicability of the Hammett linear free-energy relationship to this system. To gain a deep understanding of the physical chemistry at play, a quantum mechanical study of the reaction is also conducted. The quantum mechanical calculations not only reproduce the experimental free energy of activation, but also provide greater insights at the molecular and atomic level. Isolation of the calculated transition state structure and application of the Hammett equation to its electronic, structural, and energetic properties are studied.

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24

Shawali, Ahmad S., Mosselhi A. N. Mosselhi, and Thoraya A. Farghaly. "Synthesis and Tautomeric Structure of 2-arylazo-4H-imidazo[2,1-b][1,3,4]thiadiazines." Journal of Chemical Research 2007, no. 8 (August 2007): 479–83. http://dx.doi.org/10.3184/030823407x237885.

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Two series of the title compounds were prepared via reaction of N-aryl 2-oxohydrazonoyl halides with 1-amino-4-phenylimidazoline-2-thione. Their tautomeric structure was elucidated by spectral analysis, and the correlation of their acid dissociation constants with the Hammett equation, to be as the hydrazone form.

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25

Palát Jr., Karel, Stanislav Böhm, Gabriela Braunerová, Karel Waisser, and Otto Exner. "Reaction series not obeying the Hammett equation: conformational equilibria of substituted thiobenzanilides." New Journal of Chemistry 26, no. 7 (May 31, 2002): 861–66. http://dx.doi.org/10.1039/b111156f.

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26

Elguero, José, Manuel Gil, Nerea Iza, Carmen Pardo, and Mar Ramos. "FT-IR and 13C-NMR Correlations for Some N-Substituted Azoles and Benzazoles." Applied Spectroscopy 49, no. 8 (August 1995): 1111–19. http://dx.doi.org/10.1366/0003702953965029.

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The FT-IR (in carbon tetrachloride) and 13C-NMR (in deuterochloroform) spectra of six p-substituted aniline derivatives, as reference compounds, and nine 1- p-aminophenyl-azoles and benzazoles were recorded. The measured spectral parameters from FT-IR were symmetric, vs(NH2), and antisymmetric, vas(NH2), stretching fundamentals and their band intensity ratio, A( vas)/ A( vs), while the corresponding 13C-NMR parameters were C-1 to C-4 chemical shifts of 1- p-aminophenyl carbons. Different IR and 13C-NMR spectral parameters and Hammett constants σp (or σp-) were correlated, and statistic analysis of the results permitted an estimation of σp values of the nine (azol-1-yl) substituents. An empirical equation to calculate the Hammett constants of new azoles and benzazoles is proposed.

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27

Stankovičová, Mária, and Jozef Čižmárik. "Kinetics of alkaline hydrolysis and correlation studies of m- and p-substituted piperidinoethyl phenylcarbamates." Collection of Czechoslovak Chemical Communications 54, no. 7 (1989): 1846–53. http://dx.doi.org/10.1135/cccc19891846.

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Kinetics of alkaline hydrolysis have been studied with a series of 15 m- and p-substituted piperidinoethyl phenylcarbamates. The rate constants have been determined at 70, 60, 50, and 40 °C and the activation parameters have been calculated. These values have been correlated with the substituent constants σ, F, R, F, R, π. Validity of the Hammett equation and the Swain-Lupton equation has been confirmed in the series studied and for the p-derivatives, respectively. The lipophilicity parameter π does not correlate with the values found.

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28

Pytela, Oldřich. "Chemometric Analysis of Substituent Effects. II. Relation Between Hammett Substituent Constants σm and σp and a New Model for Quantitative Description of Substituent Effects." Collection of Czechoslovak Chemical Communications 59, no. 2 (1994): 381–90. http://dx.doi.org/10.1135/cccc19940381.

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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.

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29

Agrawal, Yadvendra K., and Nirmalya Sinha. "Thermodynamic proton-ligand stability constants of hydroxamic acids and applicability of Hammett equation." Journal of Chemical & Engineering Data 33, no. 2 (April 1988): 90–92. http://dx.doi.org/10.1021/je00052a007.

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30

Noto, Renato, Michelangelo Gruttadauria, Paolo Lo Meo, and Domenico Spinelli. "Protonation of Some 5-Substituted Di(2-thienyl) Ketones in Sulfuric Acid. A Comparison with Other 2-Thienyl and Phenyl Ketones." Collection of Czechoslovak Chemical Communications 64, no. 11 (1999): 1893–901. http://dx.doi.org/10.1135/cccc19991893.

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Protonation equilibria of some 5-substituted di(2-thienyl) ketones have been investigated spectrophotometrically in aqueous solutions of sulfuric acid at 298 K. The experimental pKBH+ values have been analyzed by means of the Hammett equation. The calculated ρ as well as the pKBH+ and m* values have been compared with those for substituted 2-acetyl- thiophenes and phenyl 2-thienyl ketones.

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31

Bartnicka, H., I. Bojanowska, and MK Kalinowski. "Solvent Effect on the Hammett Reaction Constant of Substituted Benzoic Acids." Australian Journal of Chemistry 46, no. 1 (1993): 31. http://dx.doi.org/10.1071/ch9930031.

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Potentiometric titration has been used to measure dissociation constants of 13 monosubstituted benzoic acids in nitromethane, benzonitrile , acetonitrile , propylene carbonate, acetone, N,N-dimethylformamide, dimethyl sulfoxide, methanol and formamide. The reaction constants of the Hammett equation were found to depend on the solvent acidity and basicity expressed by the α and β parameters of Kamlet and Taft. The p values determined earlier in water and ethanol also obey this rule.

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32

Zhang, Hongchang, and H. Brian Dunford. "Hammett pσ correlation for reactions of lactoperoxidase compound II with phenols." Canadian Journal of Chemistry 71, no. 12 (December 1, 1993): 1990–94. http://dx.doi.org/10.1139/v93-248.

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A stopped-flow kinetic study shows that the reaction rates of lactoperoxidase compound II with substituted phenols are greatly dependent upon the substituent on the benzene ring. Of the 15 phenols studied, it has been possible to relate the reaction rate constants with the ionization constants of 11 phenols by a linear Hammett free-energy relationship: (log (kX/kH) = ρσ) at pH 7.0 and 25.0 °C. The 11 m-and p-substituted phenols yield a ρ value of −2.7 ± 0.2. The data do not correlate with σ+ values using the Brown–Okamoto equation. These results can be explained by a mechanism in which the substrate simultaneously gives an electron and a proton to lactoperoxidase compound II, and they indicate that the active site is accessible to substrate. To explain the abnormal behavior of the four phenols that do not fit the Hammett plot we used Hansch hydrophobic factors π for all of the substituents. The resultant best-fit equation: log (kX/kH) = ρσ + rπ + c yielded the values ρ = −2.1 ± 0.5, r = 0.4 ± 0.1, and c = −0.2 ± 0.1. The rates of reduction of lactoperoxidase compound II by p-iodophenol have been studied from pH 6.5 to 11.2. The kinetics are influenced by an acid group of pKE 9.5 in the active site of lactoperoxidase compound II and by the ionization of the substrate (pKS 9.0). The acidic form of lactoperoxidase compound II and the electrically neutral, unionized form of phenol are the reactive species. A reanalysis of data on reactions of horseradish peroxidase compounds I and II with substituted phenols using more recent σ values yielded Hammett ρ values of −5.5 ± 0.3 and −4.5 ± 0.2.

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33

Ludwig, Miroslav, Oldřich Pytela, Helena Javůrková, and Miroslav Večeřa. "Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides." Collection of Czechoslovak Chemical Communications 52, no. 12 (1987): 2900–2908. http://dx.doi.org/10.1135/cccc19872900.

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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.

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34

Pytela, Oldřich, Martin Kaska, Miroslav Ludwig, and Miroslav Večeřa. "Solvolysis kinetics and mechanism of substituted 3-acetyl-1,3-diphenyltriazenes in acid medium; Kinetic acidity function." Collection of Czechoslovak Chemical Communications 52, no. 9 (1987): 2212–16. http://dx.doi.org/10.1135/cccc19872212.

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The decomposition kinetics has been measured of fourteen 3-acetyl-1,3-bis(subst. phenyl)triazenes in 40% (v/v) ethanol and sulphuric acid. The kinetic acidity function and catalytic rate constants have been determined from the rate constants observed. Mechanism has been suggested for the general acid-catalyzed solvolysis from comparison of the course of the kinetic acidity function and H0 function and from the reaction constant of the Hammett equation.

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35

Keenan, Sheue L., Karl P. Peterson, Kelly Peterson, and Kyle Jacobson. "Determination of Hammett Equation Rho Constant for the Hydrolysis of p-Nitrophenyl Benzoate Esters." Journal of Chemical Education 85, no. 4 (April 2008): 558. http://dx.doi.org/10.1021/ed085p558.

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36

Schultz, David, and Jonathan R. Nitschke. "Designing Multistep Transformations Using the Hammett Equation: Imine Exchange on a Copper(I) Template." Journal of the American Chemical Society 128, no. 30 (August 2006): 9887–92. http://dx.doi.org/10.1021/ja061841u.

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37

Makitra, R. G., and I. P. Polyuzhin. "Correlation Analysis of the Enthalpies of Vaporization of Isomers with the Hammett-Taft Equation." Russian Journal of General Chemistry 75, no. 5 (May 2005): 739–44. http://dx.doi.org/10.1007/s11176-005-0310-2.

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38

Sipilä, Julius, Harri Nurmi, Ann Marie Kaukonen, Jouni Hirvonen, Jyrki Taskinen, and Jari Yli-Kauhaluoma. "A modification of the Hammett equation for predicting ionisation constants of p-vinyl phenols." European Journal of Pharmaceutical Sciences 25, no. 4-5 (July 2005): 417–25. http://dx.doi.org/10.1016/j.ejps.2005.04.002.

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39

Dyall, LK, and GJ Karpa. "Pyrolysis of Aryl Azides. VIII. Hammett Correlations of Rates of Pyrolysis of Substituted 2-Azidobenzophenones." Australian Journal of Chemistry 41, no. 8 (1988): 1231. http://dx.doi.org/10.1071/ch9881231.

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Eight 2-azidobenzophenones with 4- or 5-substituents have been pyrolysed in decalin solution to yield 3-phenyl-2,1-benzisoxazoles. Rate values at 100° are correlated with the Hammett substituent constants, with respect to both the azido (A) and benzoyl (B) reaction centres , and yield the equation log k = -4.38 + 2.08σ-/A -1.52σB. There is a similar equation for rates measured at 120°. Although nitro and benzoyl differ considerably in their neighbouring group abilities in azide pyrolyses, it is concluded that they exert their effects through the same mechanism. The results are consistent with both published variants of an electrocyclic mechanism (Dyall; Smith, Budde and Chou).

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40

Ludwig, Miroslav, Václav Baron, Karel Kalfus, Oldřich Pytela, and Miroslav Večeřa. "Dissociation constants of substituted benzoic acids in water and in organic solvents." Collection of Czechoslovak Chemical Communications 51, no. 10 (1986): 2135–42. http://dx.doi.org/10.1135/cccc19862135.

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Potentiometric titration has been used to measure dissociation constants of 38 monosubstituted benzoic acids in water and in 6 organic solvents (methanol, ethanol, dimethylformamide, acetonitrile, sulfolane, acetone). The results have been analyzed and interpreted from the point of view of substituent and solvent effects on the dissociation of the title substrates. It has been proved that solvents affect not only the reaction constant but also the substituent constant of the Hammett equation.

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41

Kulič, Jiří, and Aleš Ptáček. "Catalyzed Alkaline Hydrolysis of Substituted Phenyl Acetates." Collection of Czechoslovak Chemical Communications 58, no. 8 (1993): 1798–802. http://dx.doi.org/10.1135/cccc19931798.

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2-Iodosobenzoic acid forming strong nucleophile in alkaline medium - 1-oxido-1,2-benziodoxol-3(1H)-one, was used as a catalyst of alkaline hydrolysis of substituted phenyl acetates (4-NO2, 3-NO2, 3-Cl, 4-Br, H, 4-CH3, 3-CH3, 4-OCH3, 3-OCH3) in the presence of hexadecyltrimethylammonium bromide as a micellar agent. It was found that the observed first-order rate constants kobs can be correlated by the Hammett equation: log kobs = (-3.29 ± 0.03) + (1.77 ± 0.001) σ.

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42

Kulič, Jiří, Jiří Sussenbek, and Aleš Ptáček. "Alkaline Hydrolysis of Substituted Phenyl Acetates Catalyzed by Quaternary Ammonium Salts." Collection of Czechoslovak Chemical Communications 58, no. 12 (1993): 2891–95. http://dx.doi.org/10.1135/cccc19932891.

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Alkaline hydrolysis if the phenyl acetates CH3COOC6H4X (X = 4-NO2, 3-NO2, 3-Cl, H, 4-CH3, 3-CH3, and 4-OCH3) in the presence of hexadecyltris(2-hydroxyethyl)ammonium chloride, bis(2-hydroxyethyl)hexadecyl(methyl)ammonium bromide, and hexadecyltrimethylammonium bromide has been studied. Comparison of the rates of the hydrolysis for the above tenzides showed that the most efficient catalyst is the hexadecyltris(2-hydroxyethyl)ammonium chloride. In all cases, the rate data correlated well with structure effects by the Hammett equation.

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43

Milart, Piotr, and Tadeusz M. Krygowski. "Analysis of solvent and substituent effects on uv and visible spectra of N-(α-methylarylidene)-p-(N′,N′-dimethylamino)-anilines." Canadian Journal of Chemistry 63, no. 11 (November 1, 1985): 3256–57. http://dx.doi.org/10.1139/v85-538.

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Substituent effect on the long wave band in uv/vis spectra of p-substituted N-(α-methylarylidene)-p-(N′,N′-dimethylamino)-anilines (X = CH3O, CH3, H, Cl, and NO2) measured in eight solvents follows well the Hammett equation. Solvent effect on this band depends well on ET only for Cl- and NO2-substituted species. Both these findings support the conclusion that the long-wave band is in fact intramolecular charge transfer form the basicity center [Formula: see text] towards substituents.

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44

Darugar, Vahidreza, Mohammad Vakili, Sayyed Faramarz Tayyari, Fadhil Suleiman Kamounah, and Raheleh Afzali. "Application of Hammett equation to intramolecular hydrogen bond strength in para-substituted phenyl ring of trifluorobenzoylacetone and 1-aryl-1,3-diketone malonates." European Journal of Chemistry 9, no. 3 (September 30, 2018): 213–21. http://dx.doi.org/10.5155/eurjchem.9.3.213-221.1713.

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The stability of two stable cis-enol forms in two categories of β-diketones, including para-substituted of trifluorobenzoylacetone (X-TFBA) and 1-aryl-1,3-diketone malonates (X-ADM, X: H, NO2, OCH3, CH3, OH, CF3, F, Cl, and NH2) has been obtained by different theoretical methods. According to our results, the energy difference between the mentioned stable chelated enol forms for the titled compounds is negligible. The theoretical equilibrium constants between the two stable cis-enol of the mentioned molecules are in excellent agreement with the reported experimental equilibrium constant. In addition, the effect of different substitutions on the intramolecular hydrogen bond strength has been evaluated. The correlation between Hammett para-substituent constants, σp. with the theoretical and experimental parameters related to the strength of hydrogen bond in p-X-TFBA and p-X-ADM molecules also investigated by means of density functional theory calculations. The electronic effects of para-substitutions on the intramolecular hydrogen bond strength were determined by NMR and IR data related to intramolecular hydrogen bond strength, geometry, natural bond orbital results, and topological parameters. These parameters were correlated with the Hammett para-substituent constants, σp. Good linear correlations between σp and the several parameters related to the hydrogen bond strength, in this study were obtained.

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45

Exner, Otto, and Stanislav Böhm. "Validity of the Hammett equation for isolated molecules: basicity of 3- and 4-substituted benzonitriles." Phys. Chem. Chem. Phys. 6, no. 14 (2004): 3864–71. http://dx.doi.org/10.1039/b404556d.

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46

Sanjeev, R. "Dipole Moments and Melting Points and Their Unsolved Miracles on the Application of Hammett Equation." Education Journal 1, no. 1 (2012): 1. http://dx.doi.org/10.11648/j.edu.20120101.11.

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47

Simón-Manso, Yamil. "Linear Free-Energy Relationships and the Density Functional Theory: An Analog of the Hammett Equation." Journal of Physical Chemistry A 109, no. 9 (March 2005): 2006–11. http://dx.doi.org/10.1021/jp0454467.

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48

Wojaczyńska, M., and B. N. Kolarz. "Application of the Hammett equation for sorption of aromatic compounds on polymeric sorbents. Part II." Reactive Polymers, Ion Exchangers, Sorbents 4, no. 1 (December 1985): 55–60. http://dx.doi.org/10.1016/0167-6989(85)90034-0.

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49

Wagnerczauderna, E., and MK Kalinowski. "Hammett-Streitwieser Reaction Constants for the Electroreduction of Diaryl Ketones in Aprotic Media." Australian Journal of Chemistry 49, no. 8 (1996): 901. http://dx.doi.org/10.1071/ch9960901.

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Cyclic voltammetry has been used to measure formal potentials of seven aromatic ketone/ketyl radical anion systems in benzonitrile, acetonitrile , propylene carbonate, acetone, N,N- dimethylformamide, N-methylpyrrolidin-2-one, dimethyl sulfoxide and hexamethylphosphoric triamide. The values measured in each solvent obey the Hammett- Streitwieser equation; the reaction constants were found to depend on the solvent acidity and basicity expressed by acceptor and donor numbers, respectively. The results are discussed in terms of the solvation of the products and reactants of the electrode reaction.

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50

Sanjeev, R., David Geelan, and V. Jagannadham. "Non-associative Behavior of Thiophenols: Trouton’s Rule, Ramsey-Shields- Eötvös Equation and Application of Hammett Equation to the Surface Tension Data." Educación Química 30, no. 4 (October 11, 2019): 83. http://dx.doi.org/10.22201/fq.18708404e.2019.4.69633.

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