Hammett Substituent Constants Research Articles

Synthesis, Spectral Studies, Pharmacological and Insect Antifeedant Activities of some (<i>E</i>)-1-(2-(2-Benzyloxy-3-Methacrylate))-1-Naphthyl Enones

Totally twelve title compounds have been synthesized by Claisen-Schmidt condensation of (E)-methyl 2-(2-(((1-acetylnaphthalen-2-yl) oxy) methyl) phenyl)-3-methoxy acrylate and substituted benzaldehydes in presence of catalytic quantity of LiOH.H2O catalyst under stirring in room temperature. The yields of the compounds are more than 92%. The synthesized titled compounds were characterized by their physical constants, IR, NMR and Mass spectral data. The spectral data such as infrared ν COs-cis, s-trans, COester, NMR chemical shifts (δ, ppm) of Hα, Hβ, Cα, Cβ, CO of enone moiety, Hβʹ and CO of acrylate moieties have been correlated with Hammett substituent constants, F and R parameters. The antimicrobial, antioxidant and insect antifeedant activities of all synthesized compounds have been evaluated using corresponding bacterial and fungal strains, DPPH radical scavenging and Disc diffusion bio-assay of 4th instar larvae Achoea Janata L with castor-leaf discs.

Synthesis and Assessment of Substituent Effect on (<i>E</i>)-1-(4-Fluoro-3-Methylphenyl)-3-Phenylprop-2-en-1-One Compounds

In the present investigation, a series of substituted (E)-1-(4-fluoro-3-methylphenyl)-3-phenylprop-2-en-1-one compounds were synthesized by condensation reaction of 4-fluoro-3-methyl acetophenone with substituted benzaldehydes in the presence of alkali. The yields of synthesized compounds are more than 80%. The structures of all the synthesized compounds were confirmed by their physical constants, UV, IR and NMR spectral data. All the observed spectral data of substituted (E)-1-(4-fluoro-3-methylphenyl)-3-phenylprop-2-en-1-one compounds have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analyses. From the results of statistical analysis the effects of substituents have been discussed.

Synthesis, Spectral Studies, Pharmacological and Insect Antifeedant Activities of some (<i>E</i>)-1-(2-(2-Benzyloxy-3-Methacrylate))-1-Naphthyl Enones

Totally twelve title compounds have been synthesized by Claisen-Schmidt condensation of (E)-methyl 2-(2-(((1-acetylnaphthalen-2-yl) oxy) methyl) phenyl)-3-methoxy acrylate and substituted benzaldehydes in presence of catalytic quantity of LiOH.H2O catalyst under stirring in room temperature. The yields of the compounds are more than 92%. The synthesized titled compounds were characterized by their physical constants, IR, NMR and Mass spectral data. The spectral data such as infrared ν COs-cis, s-trans, COester, NMR chemical shifts (δ, ppm) of Hα, Hβ, Cα, Cβ, CO of enone moiety, Hβʹ and CO of acrylate moieties have been correlated with Hammett substituent constants, F and R parameters. The antimicrobial, antioxidant and insect antifeedant activities of all synthesized compounds have been evaluated using corresponding bacterial and fungal strains, DPPH radical scavenging and Disc diffusion bio-assay of 4th instar larvae Achoea Janata L with castor-leaf discs.

Solvent-free synthesis of azomethines, spectral correlations and antimicrobial activities of some E-benzylidene-4-chlorobenzenamines

Some azomethines including substituted benzylidene-4-chlorobenzenamines (E-imines) have been synthesized by fly-ash: PTS catalyzed microwave assisted condensation of 4-chloroaniline and substituted benzaldehydes under solvent-free conditions. The yield of the imines has been found to be more than 85%. The purity of all imines has been checked using their physical constants and UV, IR and NMR spectral data. These spectral data have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. The antimicrobial activities of all imines have been studied using standard methods. KEY WORDS: Solvent-free synthesis, Fly-ash: PTS, Aryl imines, Spectral correlations, Antimicrobial activities Bull. Chem. Soc. Ethiop. 2015, 29(2), 275-290DOI: http://dx.doi.org/10.4314/bcse.v29i2.10

Investigation of the effect of π–π stacking interaction on the properties of –CONH2 functional group of benzamide

The effect of π–π stacking between substituted benzene and benzamide on the properties of –CONH2 functional group, as an important unit in the drugs activities, was studied at the M06-2X/6-311++G(d,p) level of theory. All substituents enhanced the π–π interaction energies, where a reasonably good correlation was found between the interaction energies and Hammett constants of substituents. A linear correlation is observed between the sum of electron charge density at the cage critical point ∑ρ ccp obtained from the atoms in molecules (AIM) analysis and the interaction energies, where both values grow up with electron-withdrawing substituents (EWSs). The electrostatic potential around the O and N atoms, the natural charges, and the dipole moment of C=O bond have been calculated to predict the ability of functional group on the electrophilic and nucleophilic attacks. The charge transfer increases the electrostatic potential around the benzamide functional group in the presence of electron-donating substituents (EDSs). EWSs increase the acidity of the N atom of the –NH2 group; a linear relationship is observed between the acidity calculated with the molecular electrostatic potential around the N atom and the natural valence orbital energies.

Substituent effect study on experimental 13C NMR chemical shifts of (3-(substituted phenyl)-cis-4,5-dihydroisoxazole-4,5-diyl)bis(methylene)diacetate derivatives

Eleven novel (3-(substituted phenyl)-cis-4,5-dihydroisoxazole-4,5-diyl)bis(methylene) diacetate derivatives were synthesized in the present study. These dihydroisoxazole derivatives were characterized by IR, 1H NMR, 13C NMR and elemental analyses. Their 13C NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constant (σ), inductive substituent constant (σI), different of resonance substituent constants (σR, σRo) and Swain–Lupton substituent parameters (F, R) were performed using SSP (single substituent parameter), and DSP (dual substituent parameter) methods, as well as single and multiple regression analysis. From the result of regression analysis, the effect of substituent on the 13C NMR chemical shifts was explained.

Synthesis, Spectral Correlations and Antimicrobial Activities of 2-Pyrimidine Schiff’s Bases

In the present study, a series of substituted (E)-N-benzylidene-2-aminopyrimidine compounds have been synthesized by condensation reaction with 2-aminopyrimidine and meta- and para- substituted benzaldehydes. These synthesized Schiff’s base compounds are confirmed by their physical constants, UV, IR and NMR spectral data. All the observed UV absorption maximum λmax(nm), IR frequencies νC=N(cm-1), NMR δ(ppm) of C-H & C=N chemical shifts have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analyses in order to study the effect of substituents on these spectral data has been studied. The antimicrobial activities of all the synthesized Schiff’s base compounds have been studied using Bauer-Kirby disc diffusion method

Spectral LFER Studies on Some Sydnone Chalcones

A series containing ten (E)-4-(N-(4-cinnamoylphenyl)sulfamoyl)-3-(p-tolyl)-1,2,3-oxadiazol-3-ium-5-olates were prepared and examined their purities by literature method. The infrared and NMR spectral data were assigned and correlated with Hammett substituent constants and Swain-Lupton’s constants using single and multi-regression analysis. From the results of statistical analyses the effects of substituents on the spectral data have been discussed.

Synthesis, Spectral Correlations and Antimicrobial Activities of 2-Pyrimidine Schiff’s Bases

In the present study, a series of substituted (E)-N-benzylidene-2-aminopyrimidine compounds have been synthesized by condensation reaction with 2-aminopyrimidine and meta- and para- substituted benzaldehydes. These synthesized Schiff’s base compounds are confirmed by their physical constants, UV, IR and NMR spectral data. All the observed UV absorption maximum λmax(nm), IR frequencies νC=N(cm-1), NMR δ(ppm) of C-H & C=N chemical shifts have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analyses in order to study the effect of substituents on these spectral data has been studied. The antimicrobial activities of all the synthesized Schiff’s base compounds have been studied using Bauer-Kirby disc diffusion method

Spectral LFER Studies on Some Sydnone Chalcones

A series containing ten (E)-4-(N-(4-cinnamoylphenyl)sulfamoyl)-3-(p-tolyl)-1,2,3-oxadiazol-3-ium-5-olates were prepared and examined their purities by literature method. The infrared and NMR spectral data were assigned and correlated with Hammett substituent constants and Swain-Lupton’s constants using single and multi-regression analysis. From the results of statistical analyses the effects of substituents on the spectral data have been discussed.

Infrared, <sup>1</sup>H and <sup>13</sup>C NMR Spectral Studies of some 4-([1,1′-Biphenyl]-4-yl)-6-(Substituted Phenyl)-5,6-Dihydro-4H-1,3-Oxazine-2-Amines: Assessment of Substituent Effects

About ten titled compounds were prepared by microwave assisted silica-phosphoric acid catalysed cyclization of substituted styryl 4-biphenyl ketones and urea under solvent-free conditions. The infrared frequencies (ν, cm-1) of NH2, C=N, COC stretches, NMR spectral chemical shifts (δ, ppm) of NH2, H4-6, C=N, and C4-6 were assigned and correlated with Hammett substituent constants, F and R parameters using single and multi-regression analysis. From the results of statistical analysis, the effect of substituents on the infrared frequencies (ν, cm-1) and NMR chemical shifts (δ, ppm) has been studied.

Infrared, <sup>1</sup>H and <sup>13</sup>C NMR Spectral Studies of some 4-([1,1′-Biphenyl]-4-yl)-6-(Substituted Phenyl)-5,6-Dihydro-4H-1,3-Oxazine-2-Amines: Assessment of Substituent Effects

About ten titled compounds were prepared by microwave assisted silica-phosphoric acid catalysed cyclization of substituted styryl 4-biphenyl ketones and urea under solvent-free conditions. The infrared frequencies (ν, cm-1) of NH2, C=N, COC stretches, NMR spectral chemical shifts (δ, ppm) of NH2, H4-6, C=N, and C4-6 were assigned and correlated with Hammett substituent constants, F and R parameters using single and multi-regression analysis. From the results of statistical analysis, the effect of substituents on the infrared frequencies (ν, cm-1) and NMR chemical shifts (δ, ppm) has been studied.

13C NMR substituent-induced chemical shifts in 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones (thiones)

In the present, study mostly novel ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones and ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-thiones were synthesized. These oxadiazole derivatives were characterized by IR, 1H NMR, 13C NMR and elemental analyses. Their 13C NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constants (σ), Brown Okamoto substituent constants (σ+, σ−), inductive substituent constants (σI) and different of resonance substituent constants (σR, σRo) were performed using SSP (single substituent parameter), DSP (dual substituent parameter) and DSP-NLR (dual substituent parameter-non-linear resonance) methods, as well as single and multiple regression analysis. Negative ρ values were found for all correlations (reverse substituent effect). The results of all statistical analyses, 13C NMR chemical shift of CN, CO and CS carbon of oxadiazole rings have shown satisfactory correlation.

Substituent effects on selectivity of coupled oxidation of iron tetraphenylporphyrins

Coupled oxidation of iron tetraphenylporphyrins bearing either a OMe , Me , F , Cl , COOMe , CF 3 or CN group in the para-position of the phenyl groups gave tetraarylbiladien-ab-1-one and triarylbilindione. The ratios of the yields of the former to those of the latter were linearly correlated with the Hammett substituent constants σp+, with a positive slope (Δρ = 0.64). The Hammett plot of the oxidation rate vs. the substituent constant σp also showed a positive slope (ρ = 0.30). These substituent effects suggest that a nucleophilic step is included in the formation of bilindione. Coupled oxidation of an A3B type tetraarylporphyrin having an electron withdrawing nitro group in one of the phenyl groups indicated that the oxidation leading to biladienone occurred rather statistically in any of the meso-positions, while the oxidation leading to bilindione occurred preferentially in the meso-position bearing the 4-nitrophenyl group.

Effect of Substituents on Phenazine Derivatives by Spectral Studies

A series of eleven substituted dipyrido[3,2-a; 2′,3′-c]phenazine derivatives have been synthesized and examined their purities by literature method. The infrared and 13C NMR spectral data of prepared phenazines were correlated with Hammett substituent constants, F and R parameters using single and multi-regression analysis. From the results of statistical analysis, the effect of substituents on the infrared frequencies (ν, cm-1) and 13C nmr chemical shifts(δ, ppm) has been studied.

Regio- and stereoselective synthesis of functionalized allylic fluorides via palladium-catalyzed three-component tandem carbofluorination of allenes

We developed a highly efficient palladium-catalyzed three-component tandem carbofluorination of allenes with ArI and AgF. Nucleophilic trapping of π-allyl palladium intermediates generated from carbopalladation of allenes with AgF delivers functionalized allylic fluorides with highly branched selectivity. This transformation features simultaneous construction of C–C and C–F bond in one step, allowing for the facile synthesis of functionalized allylic fluorides, valuable synthetic building blocks. Moreover, a good correlation between regioselectivity and substituent Hammett constants was observed in the reactions of mono-alkyl substituted allene substrates, corroborating with the proposed outer-sphere fluorination pathway. This study uncovered the regioselectivity trends being controlled by both electronic and steric factors, which paved the way for further developments in selective synthesis of branched functionalized allylic fluorides difficult to access from established methodologies.

Effect of Substituents on Phenazine Derivatives by Spectral Studies

A series of eleven substituted dipyrido[3,2-a; 2′,3′-c]phenazine derivatives have been synthesized and examined their purities by literature method. The infrared and 13C NMR spectral data of prepared phenazines were correlated with Hammett substituent constants, F and R parameters using single and multi-regression analysis. From the results of statistical analysis, the effect of substituents on the infrared frequencies (ν, cm-1) and 13C nmr chemical shifts(δ, ppm) has been studied.

Discovery, understanding, and bioapplication of organic fluorophore: a case study with an indolizine-based novel fluorophore, Seoul-Fluor.

Owing to its high sensitivity and great applicability, the fluorescence phenomenon has been considered as an inevitable research tool in the modern scientific fields of chemistry, biology, materials science, biomedical science, and their interfaces. Many strategies have been pursued to understand and manipulate the photophysical properties of fluorescent materials, but the scientific community has been focused on the repeated application of existing organic fluorophores or the identification of unique fluorescence properties in a trial-and-error basis without systematic studies. Moreover, recent studies are emphasizing the necessity of deeper understanding about the structure-photophysical property relationship of organic fluorophores for the development of better fluorescent probes. Herein, we provide an overview of a novel fluorescent molecular framework, Seoul-Fluor, which can be rationally engineered to furnish a wide variety of fluorophores in terms of the photophysical properties. Seoul-Fluor is built on an indolizine-based fluorescent platform with three different positions to introduce various substituents: R(1) and R(2) substituents for electronic perturbation; R(3) substituent as a functional handle for bioconjugation. Over the past decade, we have demonstrated that the Seoul-Fluor system has (i) tunable and predictable emission wavelength covering a full visible-color range; (ii) controllable quantum yield via photoinduced electron transfer phenomenon; and (iii) environment-sensitive fluorogenic properties that can be modified through intramolecular charge transfer processes. We convincingly demonstrated the prediction of photophysical properties, that is, emission wavelength and quantum yield, through the construction of a systematic set of analogues and the subsequent analysis of their photophysical properties without the highly sophisticated theoretical support. Guided by quantifiable parameters such as the Hammett substituent constants or energy levels of the molecular orbitals, this unique organic fluorophore can serve as a versatile molecular platform for the development of novel fluorescent switchable biosensors and fluorogenic bioprobes. In this Account, we will discuss the discovery and recent progress made on Seoul-Fluor, the rational design of Seoul-Fluor-based bioprobes, and their practical applications to specific biological processes that are facilitated by systematic studies of the structure-photophysical property relationships.

Homogeneous synthesis of partially substituted cellulose phenylcarbamates aiming at chiral recognition

AbstractHomogeneous carbanilation of cellulose with nine kinds of substituted phenyl isocyanates, in which the substituents were varied from electron‐donating to electron‐withdrawing groups, was carried out in 1‐allyl‐3‐methylimidazolium chloride (AmimCl) without any catalyst. The degree of substitution (DS) of cellulose phenylcarbamates in a range from 0 to 3 was readily controlled by altering reaction temperature, reaction time and molar ratio of phenyl isocyanate/anhydroglucose unit. Furthermore, the electronic effect of the substituents on the aromatic ring had a prominent impact on the reactivity of phenyl isocyanates. The phenyl isocyanates with stronger electron‐withdrawing substituents exhibited a higher reactivity. A plot of DS and Hammett substituent constants exhibited linearity with a positive slope. Subsequently, four kinds of partially substituted cellulose phenylcarbamates with DS of 2.0 were synthesized successfully in AmimCl, and then employed as coated‐type chiral stationary phases (CSPs) for high‐performance liquid chromatography. The enantioseparation results demonstrated that these CSPs exhibited high chiral recognition abilities for some racemates. The substituents on the phenyl moieties had a considerable effect on the chiral recognition ability of cellulose phenylcarbamate‐based CSPs. © 2015 Society of Chemical Industry

Structural study of various substituted biphenyls and their radical anions based on time-resolved resonance Raman spectroscopy combined with pulse radiolysis.

The structures of various para-substituted biphenyls (Bp-X; X = -OH, -OCH3, -CH3, -H, -CONH2, -COOH, and -CN) and their radical anions (Bp-X(•-)) were investigated by time-resolved resonance Raman spectroscopy combined with pulse radiolysis. The inter-ring C1-C1' stretching modes (ν6) of Bp-X were observed at ∼1285 cm(-1), whereas the ν6 modes of Bp-X(•-) with an electron-donating or -withdrawing substituent were significantly up-shifted. The difference (Δf) between the ν6 frequencies of Bp-X and Bp-X(•-) showed a significant dependence on the electron affinity of the substituent and exhibited a correlation with the Hammett substituent constants (σp). In contrast to Bp-H(•-) with a planar geometry, the theoretical and experimental results reveal that all Bp-X(•-) with an electron-donating or -withdrawing substituent have a slightly twisted structure. The twisted structure of Bp-X(•-) is due to the localization of the unpaired electron and negative charge density on one phenyl moiety in Bp-X(•-).