Correlation Of Substituent Effects Research Articles

Correlation of substituent effects on carbon-13 NMR chemical shifts of side-chain carbons in 5-aryl-2£,4£-pentadienoic acid derivatives by Taft DSP equation

Correlation of substituent effects on carbon-13 NMR chemical shifts of side-chain carbons in 5-aryl-2£,4£-pentadienoic acid derivatives by Taft DSP equation

Correlation of substituent effects on carbon-13 NMR chemical shifts of side-chain carbons in 5-aryl-2E,4E-pentadienoic acid derivatives by Taft DSP equation

Correlation of substituent effects on carbon-13 NMR chemical shifts of side-chain carbons in 5-aryl-2E,4E-pentadienoic acid derivatives by Taft DSP equation

Correlation of substituent effects and energy levels of the two lowest excited states of the azulenic chromophore

[structure: see text] Experimental and calculated data show that the relative energy levels of the two lowest excited states of azulene are sensitive to the nature and position of substituents on the nonalternant hydrocarbon. Extending such investigations led to a rational explanation for some of the baffling data on azulenic bacteriorhodopsin analogues in the literature.

Preparation and nuclear magnetic resonance studies of diaryloxytriphenylphosphoranes. Correlation of substituent effects with 31P N.M.R. chemical shifts

Triphenylphosphine and diisopropyl azodicarboxylate react with phenols in tetrahydrofuran or chloroform at 0° to give diaryloxytriphenylphosphoranes. A linear free-energy relationship has been found between the 31P n.m.r. chemical shifts of many of these phosphoranes and the acid dissociation constants of the corresponding phenols. In general, electron-withdrawing groups on the phenol result in downfield 31P n.m.r. chemical shifts, while electron donating groups result in up-field shifts.

Solvolytic reactivity of 1-trifluoromethyl-1-phenylethyl tosylate. Correlation of substituent effects in the formation of highly destabilized carbonium ions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolvolytic reactivity of 1-trifluoromethyl-1-phenylethyl tosylate. Correlation of substituent effects in the formation of highly destabilized carbonium ionsAnnette D. Allen, Michael P. Jansen, Kalavelil M. Koshy, Nevindra N. Mangru, and Thomas T. TidwellCite this: J. Am. Chem. Soc. 1982, 104, 1, 207–211Publication Date (Print):January 1, 1982Publication History Published online1 May 2002Published inissue 1 January 1982https://doi.org/10.1021/ja00365a037RIGHTS & PERMISSIONSArticle Views204Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (632 KB) Get e-Alerts Get e-Alerts

A correlation of substituent effects with proton chemical shifts in aromatic tetrazolic acids

AbstractThe effect of substituents on the proton chemical shifts and spin–spin coupling constants in ortho‐, meta‐ and para‐substituted 5‐phenyltetrazoles (tetrazolic acids) in DMSO–CH3CN (1:1, v/v) was studied. With the meta‐ and para‐ substituted compounds the additivity rule of chemical shifts was obeyed, thereby enabling increments characterizing the effects of individual substituents in monosubstituted benzenes to be determined. By employing the Smith and Proulx equation, the chemical shifts of the aromatic protons were correlated with the F, R and Q substituent constants. The values of these constants are 1.02, −0.004 and 5.49, respectively, for the tetrazolyl substituent.

A correlation of substituent effects with the acidity of aromatic tetrazolic acids

The values of thermodynamic dissociation constants, Ka, have been determined for ortho-, meta-, and para-substituted 5-phenyltetrazoles (referred to as tetrazolic acids) and the effect of the nature of the substituent on the strength of the acids are discussed. The pKa values, determined in 50%(v/v) ethanol–water and in 75%(v/v) dimethyl sulphoxide–water are correlated with the substituent constants σm and σp, which are equal to 0.64 and 0.56 respectively for the tetrazolyl substituent. To evaluate the contribution of the field and resonance effects, the Ka values were correlated with the i…� and constants based on the Swain–Lupton equation. The correlation, accomplished by using a two-parameter linear regression, gave i…�= 1.17 and =–0.13.

Carbon‐13 magnetic resonance spectra of cocaine metabolites and derivatives

AbstractThe carbon‐13 nmr spectral assignments oi cocaine, O‐benzoylecgonine, ecgonine, norcocaine, O‐benzylnorecgonine, norecgonine, and N‐allylnorcocaine were made. The assignments were primarily based on the correlation of substituent effects within series and selective proton irradiation studies.

Photoelectron spectra of substituted benzenes

Photoelectron spectra of several substituted dimethylanilines, nitrobenzenes, acetophenones and nitrosobenzenes have been studied with a view to examine the electronic effects of substituents on the various φ and n levels. The results are discussed in the light of molecular orbital calculations and electronic absorption spectra. Correlation of substituent effects on the IE's with π-electron densities and Hammett substituent constants has enabled rationalization of all available data on mono- and disubstituted benzenes. The IE's generally increase with the electron-withdrawing power of the substituents.

Acidity of hydrocarbons. Ionisation constants for some substituted 9-phenylfluorenes

The pKa values of a series of substituted 9-phenylfluorenes have been measured. In conjunction with earlier studies, the results enable the establishment of an H– acidity function for 25–97% aqueous dimethyl sulphoxide containing tetramethylammonium hydroxide. It is indicated that this scale does not parallel the acidity function based on the ionisation of aniline indicators in the more aqueous solutions. Substituents in the fluorene ring exert a greater influence on hydrocarbon acidity than those in the 9-phenyl nucleus. The correlation of substituent effects on hydrocarbon acidity, by use of a modified Hammett equation, suggests that the 9-phenyl ring is displaced from planarity with the fluorene nucleus by ca. 39°, close to the value predicted earlier by molecular orbital calculations.

Field and charge-transfer theory for the quantitative correlation of substituent effects in aromatic molecules. Part I. The field and charge-transfer (FCT) theory

The principles of the previously suggested title theory of substituent electronic effects on aromatic molecules are clarified and the question of how best to apply the theory is discussed. It is shown how FCT theory may be regarded as an extension of Swain and Lupton's version of that theory of substituent effects normally used by organic chemists. The potential advantages of the FCT treatment over Swain and Lupton's treatment are stated.

Field and charge-transfer theory for the quantitative correlation of substituent effects in aromatic molecules. Part III. Thermal heterolytic addition and elimination reactions of substituted benzenes

Expressions, based on simple reaction models, for the effects of substituents on the equilibrium constants and rate constants of the reactions mentioned in the title are derived. Conditions under which ρσ relationships should be valid are established. Various theoretical σ and ρ scales are evaluated and are shown to be in good agreement with empirical scales when they ought to be. The calculations of all of the theoretical scales involve only one measured value of a substituent effect on a reaction.

Field and charge-transfer theory for the quantitative correlation of substituent effects in aromatic molecules. Part IV. Non-additivity in electrophilic substitution reactions

By the theoretical model described in Part III the additivity principle for substituent effects should fail in aromatic electrophilic substitutions. The non-additivity is predicted to arise because the charge-transfer effect of each substituent depends on the inductive power of all the substituents. Here the non-additivity is calculated for several series of polyhomosubstituted benzenes and heterodisubstituted benzenes. The results indicate that, although it should provide a good approximation when applied to polyalkylbenzenes, the additivity principle should lead to considerable errors when applied in the general case. From the calculations a number of predictions are made concerning the pattern of non-additivity. The outcome of empirical checks on the theoretical predictions gives confidence that the FCT theory of non-additivity may provide a much better theoretical tool than the additivity principle.

Field and charge-transfer theory for the quantitative correlation of substituent effects in aromatic molecules. Part II. Photoelectron spectra of substituted benzenes

FCT theory is shown to provide a better basis than Swain–Lupton theory for the extraction of information on substituent electronic effects from photoelectron spectra. With the aid of an FCT-based analysis, photoelectron spectroscopy yields information on –CT and FCP effects which cannot be obtained by other methods. It is concluded that the vertical ionization potential of the most tightly bound π-electron in benzene is 12·24 eV.

The proton resonance spectra of heterocycles—VI: The correlation of substituent effects on chemical shifts in bicyclic compounds

AbstractThe proton chemical shifts are reported for monosubstituted naphthalenes, quinolines and quinoxalines. Together with literature data, these chemical shifts are compared with the parent compounds and substituent effects evaluated statistically. The effect of substituents parallels that in benzenes, but is modified by bond fixation, steric hindrance and other effects which can, at least qualitatively be understood. The treatment enables estimation of likely chemical shifts for ABC spectra in fused aromatic systems which should facilitate the solution of such spectra.

The acidity of weak carbon acids. Part II. A correlation of substituent effects

Correlations of the acidities of weak carbon acids in the fluorene and related series with simple molecular orbital calculations and appropriate linear free-energy relationships are reported. An explanation of the effects of the alkyl groups on the acidities of 9-alkylfluorenes is presented.

Substituent effects in the fragmentation of acetanilides

The mass spectra of a series of meta- and para-substituted acetanilides have been examined. Substituent effects have been used to provide information about the mechanism of the competing fragmentations and of the structures of the ions involved. The correlation of substituent effects with ionization potential and appearance potential measurements and with Δ(A.P. – I.P.) values suggests that the fragmentation of meta-substituted acetanilides proceeds through an excited state.

Kinetics of reactions of Schiff base complexes of iron(II). Part II. Reactions of substituted tris-[N-(2-pyridylmethylene)aniline]complexes with bases and with hydrogen peroxide

Kinetics of reactions of substituted tris-[N-(2-pyridylmethylene)aniline]iron(II) complexes with hydrogen peroxide, with 2,2′-bipyridyl and related compounds, and with hydroxide ion are reported. Reaction with hydrogen peroxide proceeds by rate-determining loss of one ligand molecule, as in acid fission, followed by rapid reaction of intermediates with hydrogen peroxide. Reaction with 2,2′-bipyridyl also proceeds by rate-determining loss of one ligand molecule followed by complete conversion into the tris-(2,2′-bipyridyl)iron(II) complex. Reaction with hydroxide ion occurs partly by dissociation and partly by direct nucleophilic attack. Correlation of substituent effects on the rates for hydroxide attack with Hammett σ-values is described. Finally, reactions of nitro- and related substituent complexes, which behave anomalously in acid fission, are discussed.