Polar Substituent Effects Research Articles

Reactivity of substituted styrenes in the catalytic addition reaction with the trichloromethyl radical

Relative reactivities have been investigated in the catalytic addition of tetrachloromethane to substituted styrenes by the competitive method. The polar effects of substituents on benzene ring were correlated with Hammett equation for a copper and ruthenium catalyst, giving ρ values equal to -0.39 and -0.18 respectively. The results indicate that in contrast to classical additions the catalytic addition of tetrachloromethane is not a free radical chain process but that the trichloromethyl radical, presumably coordinated, reacts with the carbon-carbon double bond via innersphere pathways.

Substituent Rate Effects in Sigmatropic Homodienyl [1,5]-Hydrogen Migrations

The small but systematic polar substituent effect on the rates of [1,5]- homodienyl hydrogen migrations previously observed for the series of alkenylcyclopropane substrates (1) has been further explored through two additional substrate series (4) and (6) bearing the aryl probe at C4 and at the migration origin C1 respectively. However, negligible substituent effects were apparent at these positions. It now seems that the substituent effect originally observed at C5 reflects electronic perturbation by the substituent, rather than an inherent charge separation in the transition state for homodienyl rearrangement. The aryl group at C1 of the series (6) does, however, afford a substantial rate enhancement relative to the parent cis-1-methyl-2-vinylcyclopropane. In addition, exclusive formation of (1E,4Z)-1-arylhexa-1,4-diene rearrangement products is observed. These kinetic and stereochemical observations are interpreted in terms of a stereoelectronically favoured equatorial conformation for the aryl group in the transition state for rearrangement.

Polar and Dipolar Substituent Effects and Transition State in the Reaction between Substituted Anilines and Nitrosobenzene. An Evaluation of Ortho and Electrostatic Effects

Abstract The rate constants of the hydronium catalyzed attack of substituted anilines on nitrosobenzene, to give azobenzene, exhibit a large dependence on the substituent constant σ− (ρ−=−1.92). The relatively high value of ρ− compared to that obtained from the equilibrium of protonation of anilines (ρ−=−2.77) and the solvent effect on the rate constants support the idea that the transition state involves a large amount of nitrogen–nitrogen bond formation and therefore a strong charge development on the nitrogen and oxygen of the amino and nitroso groups, respectively. A good correlation between basicity and nucleophilic reactivity is obtained by the Brönsted equation (β=0.65, r=0.988) for the para and meta dipolar substituents. Aminobenzoates show a significantly higher reactivity than that calculated from the Brönsted line and this is attributed to an electrostatic participation of the carboxylato group. Nevertheless, this effect is somewhat compensated by repulsion between the carboxylato and the negatively charged oxygen of the nitroso group.

Chain-substituted lipids in monomolecular films. The effect of polar substituents on molecular packing

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChain-substituted lipids in monomolecular films. The effect of polar substituents on molecular packingF. M. Menger, S. D. Richardson, M. G. Wood Jr., and M. J. SherrodCite this: Langmuir 1989, 5, 3, 833–838Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 May 1989https://doi.org/10.1021/la00087a043RIGHTS & PERMISSIONSArticle Views125Altmetric-Citations49LEARN 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 (666 KB) Get e-Alerts Get e-Alerts

Substituent effects on partition coefficients of barbituric acids.

Precise partition coefficients in 1-octanol-water at 25 degrees C were determined for three 2-thiobarbituric acids and 14 barbituric acids with a wider range of substituents. The experimental log P values (log Pexp) of barbituric acids were correlated with the carbon number and the branching effect of the C5 substituent(s) by linear regression analysis. The carbon number term makes a major contribution to the partition coefficients. The contribution of the polar effect of the C5 substituents was insignificant in contrast to a previous report. Hydrophobic constants (pi) were determined for allyl, phenyl, and chloro-substituents, and these empirical pi values gave much closer predicted calculated log P (log Pcalc) values when applied to the reported log Pexp values.

Transmission of polar substituent effects through the bicyclo[2.2.2]octane ring system as monitored by fluorine-19 NMR shifts: 19F NMR study of 10-substituted 9-fluorotriptycenes and 4-substituted-4'-fluorobibicyclo[2.2.2]octanes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransmission of polar substituent effects through the bicyclo[2.2.2]octane ring system as monitored by fluorine-19 NMR shifts: 19F NMR study of 10-substituted 9-fluorotriptycenes and 4-substituted-4'-fluorobibicyclo[2.2.2]octanesWilliam Adcock and V. Sankar IyerCite this: J. Org. Chem. 1988, 53, 22, 5259–5266Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://doi.org/10.1021/jo00257a011RIGHTS & PERMISSIONSArticle Views751Altmetric-Citations23LEARN 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 (1 MB) Get e-Alerts Get e-Alerts

PHOSPHORYL TO CARBONYL MIGRATION OF AMINO GROUPS IN MIXED ANHYDRIDES. THE EFFECT OF N-SUBSTITUENTS

Abstract The rates of fragmentation of mixed anhydrides (MeO)(p-X-C6H4NMe)P(O)OC(O)Ph (1) (X=MeO, H, Cl, CF3) giving carboxyamides PhC(O)NMe(C6H4-X-p) were measured in CDCl3 at 70°C. The reaction constant ρ=+0.85 was obtained. The magnitude of ρ is taken as an indication of low sensitivity of rate to polar effects of substituents (in agreement with the concerted mechanism postulated), and its positive sign suggests that the cleavage of the P‒N bond is more advanced in the transition state than is the formation of the N‒C bond.

Polar substituent effects in the bicyclo[2.2.2]octane ring system: A 19F NMR study of some 4‐substituted bicyclo[2.2.2]octane‐1‐carbonyl fluorides

AbstractFluorine‐19 substituent chemical shifts (SCS) are reported for a series of 4‐substituted bicyclo[2.2.2]octane‐1‐carbonyl fluorides containing a limited but a representative number of dipolar substituents. The 19F SCS, which cover a very narrow range (<0.5 ppm), are found to correlate poorly against polar field parameters (σF). Polar field susceptibility parameters (ρF) for the fluorine probe were determined indirectly and their origin is briefly discussed in the light of the carbonyl 13C SCS which reflect π polarization of the COF group.

The methanolysis kinetics and dissociation constants of 1-(subst. benzoyl)-3-phenylthioureas

A series of seven 1-(subst. benzoyl)-3-phenylthioureas have been prepared and their dissociation constants and solvolysis rate constants have been measured in methanol at 25 °C. The reaction constants found show that the solvolysis rate is limited by the attack of methoxide ion on the benzoyl carbonyl group of the non-dissociated substrate. The polar effect of substituents in benzoyl group is extensively transferred also by the intramolecular hydrogen bond.

ChemInform Abstract: Transmission of Polar Substituent Effects in Saturated Systems: Synthesis and 19F‐NMR Study of 3‐Substituted Adamant‐1‐yl Fluorides.

ChemInform Abstract: Transmission of Polar Substituent Effects in Saturated Systems: Synthesis and 19F‐NMR Study of 3‐Substituted Adamant‐1‐yl Fluorides.

Stable simple enols. Polar and resonance substituent effects of .alpha.-aryl groups on keto .dblharw. enol equilibria of stable enols

Stable simple enols. Polar and resonance substituent effects of .alpha.-aryl groups on keto .dblharw. enol equilibria of stable enols

Transmission of polar substituent effects in saturated systems: synthesis and fluorine-19 NMR study of 3-substituted adamant-1-yl fluorides

Transmission of polar substituent effects in saturated systems: synthesis and fluorine-19 NMR study of 3-substituted adamant-1-yl fluorides

Amidines. Part 24. Influences of alkyl substituents at the amidino carbon atom on the sensitivity to substitution at the imino nitrogen atom. pK a Values of N 1 N 1-dimethylamidines

Three series of N1N1-dimethylamidines, propionamidines, isobutyramidines, and pivalamidines, each containing the same set of 25 substituents Rx at the imino nitrogen atom have been synthesized and their pKa values in 95.6% ethanol (azeotrope) measured. The pKa values were correlated with σ and σ0 constants as well as with the pKa values of the corresponding primary amines RxNH2. Regression parameters for the series studied were compared with those for N1N1-dimethyl-formamidines and -acetamidines. It is shown that the sensitivity of the amidine group to substitution at the imino nitrogen atom depends on the polar effects of substituents at the amidino carbon atom. A good linear correlation between the slope of the correlation line and the σ* value of the substituent at the amidino carbon atom is found.

Polar substituent effects on NMR chemical shifts of group 14 elements: synthesis and NMR (carbon-13, silicon-29, tin-119, and lead-207) substituent chemical shifts (SCS) of 4-substituted bicyclo[2.2.2]oct-1-ylbutanes, -trimethylsilanes, -trimethylstannanes, and -trimethyl plumbanes (M(CH3)3, M = carbon, silicon, tin, and lead) and 4-substituted bicyclo[2.2.1]hept-1-yltrimethylstannanes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolar substituent effects on NMR chemical shifts of group 14 elements: synthesis and NMR (carbon-13, silicon-29, tin-119, and lead-207) substituent chemical shifts (SCS) of 4-substituted bicyclo[2.2.2]oct-1-ylbutanes, -trimethylsilanes, -trimethylstannanes, and -trimethyl plumbanes (M(CH3)3, M = carbon, silicon, tin, and lead) and 4-substituted bicyclo[2.2.1]hept-1-yltrimethylstannanesWilliam. Adcock, Hemakanthi. Gangodawila, Gaik B. Kok, V. Sankar. Iyer, William. Kitching, Gregory M. Drew, and David. YoungCite this: Organometallics 1987, 6, 1, 156–166Publication Date (Print):January 1, 1987Publication History Published online1 May 2002Published inissue 1 January 1987https://doi.org/10.1021/om00144a029RIGHTS & PERMISSIONSArticle Views241Altmetric-Citations19LEARN 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 (1 MB) Get e-Alerts Get e-Alerts

The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone

The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone have been studied kinetically as a function of temperature and substrate concentration. The absolute rate constants for these reactions in the gas phase, in the units M−1 s−1, obey the following relations.[Formula: see text]The activation energies for these reactions are comparable to those for the reactions of O(3P) with alcohols, but the preexponential factors for the reactions of O(3P) with these ketones are significantly smaller than those for the analogous reactions with alcohols. The available data indicate that the reactivity of O(3P) toward ketones shows a variation with polar effects of substituents which is similar to that found for the reactions of OH with ketones.

Effect of polar substituents on the position of metal-proton and metal-metal exchange equilibria involving substituted acetylenes and their Ph3Sn, Ph3Pb, and RHg derivatives

The electron effects of substituents in an acetylenic residue and in organometallic radicals on the position of metal-metal and metal-proton exchange equilibria in toluene were studied by /sup 19/F-//sup 1/H/ NMR for systems containing substituted acetylenes and/or their organometallic derivatives. An increase in electron-acceptor properties of the substituent destabilizes the less polar hydrogen-carbon or metal-carbon bonds to a greater extent than the more polar metal-carbon bonds; the differences increase with increasing difference in the polarity of the corresponding bonds in the sequence cyclo-C/sub 6/H/sub 11/Hg < PhHg < Ph/sub 3/Pb < Ph/sub 3/Sn.

Liquid crystal polymers 23. Steric and polar effects of large substituents in thermotropic aromatic polyesters with decamethylene spacers

AbstractA series of thermotropic aromatic polyesters based on a triad ester mesogenic unit containing an arylsulfonyl substituted hydroquinone group and a decamethylene spacer group was prepared. The large arylsulfonyl substituent was substituted in the para‐position with either electron donating or accepting groups to study the effect of steric and polar interactions on the thermal transitions of these polymers and on the thermodynamic parameters of their isotropization transitions. All polymers formed nematic melts, and a regular decrease in T1, ΔH1 and ΔS1 was observed with increasing molecular radius of the substituted hydroquinone group. However, a polarity or polarizability effect was superimposed on these relationships. Model compounds containing the same aromatic ester triad were prepared and their thermotropic properties were compared to those of the polymers. Essentially identical effects were observed for both.

Transmission of polar substituent effects through the bicyclo[2.2.2]octane ring system as monitored by NMR shifts: A 13C NMR study of 4‐substituted‐1‐methylbicyclo[2.2.2]octanes

AbstractCarbon‐13 substituent chemical shifts (SCS) are reported for the methyl group of a series of 4‐substituted 1‐methylbicyclo[2.2.2]octanes covering a wide range of electronic substituent effects. Unlike the 13C SCS of the α‐carbon centre in various unsaturated side‐chain probes attached to the bicyclo[2.2.2]octane ring, which are mainly proportional to substituent field effects (σF), the 13CH3, SCS are found to display a definitive statistical dependence on substituent electronegativity effects as well as the field parameter. Compelling support for the validity of the statistical dissection by multivariate analysis is provided by an independent measure of polar susceptibility parameters (ρF; CDCl3, and CCl4). The coefficient (A) of the Buckingham equation for linear electric field effects on the CH3, group is calculated for CCl4 as the solvent. The origin of the reverse substituent electronegativity effect is discussed, and compared with the similar phenomenon displayed by the resonance contribution to the 13C SCS of the β‐carbon of p‐substituted ethylbenzenes.

Retention of aliphatic anionic surfactants in ion chromatography

Mobile-phase ion chromatography with suppressed conductivity detection provides an efficient technique for the analysis of aliphatic and olefinic anion Retention parameters, such as hydrophobicity, solvophobic surface area and the effect of polar substituents, are discussed to explain the different ret

Polar substituent effects in the bicyclo[2.2.2]octane ring system: polarography of 4-substituted bicyclo[2.2.2]oct-1-yl iodides

Polar substituent effects in the bicyclo[2.2.2]octane ring system: polarography of 4-substituted bicyclo[2.2.2]oct-1-yl iodides