Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. I, 4-Substituted Styrenes

Hamer, Gordon K.; Peat, I. R.; Reynolds, William F.

doi:10.1139/v73-135

Cited by 178 publications

(64 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, u, is applicable to measurements in both aromatic and aliphatic systems. Finally, in view of the precise correlations against u, for data from various aprotic polar substituent is greater along C(P)-H(C) than along C(P)-H(B) (3). Thus the prediction is p,H(C) > p,H(B) and pRH(C) -pRH(B).…”

mentioning

confidence: 95%

See 1 more Smart Citation

Substituent-induced chemical shifts in 3- and 4-substituted styrenes: definition of substituent constants and determination of mechanisms of transmission of substituent effects by iterative multiple linear regression

Reynolds¹,

Gomes²,

Maron³

et al. 1983

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

Iterative multiple linear regression analysis of substituent-induced chemical shifts in 3- and 4-substituted styrene derivatives is used to redefine σF and [Formula: see text] substituent constants (with respective standard errors of ca. 0.01 and 0.005). Correlations with the data for various model systems indicate that these substituent constants are applicable to data sets involving both chemical shift and acidity measurements in aprotic media. The approach we have used involving a homogeneous data set with a large number of variables is particularly suited for providing well-defined dual substituent parameter constants for the more common neutral substituents.Correlations for individual nuclei are entirely consistent with a previously proposed model of substituent effects involving field, resonance, and polarization effects. From these results and the results for other model systems, it is concluded that σF and [Formula: see text] are respectively pure field and resonance substituent constants. It is pointed out that a combination of detailed statistical testing and chemical modelling is essential for a thorough understanding of aromatic substituent effects.Parameters for predicting non-electronic contributions to ortho and meta chemical shifts are derived, thus allowing the patterns of electronic substituent effects for these carbons to be determined. However, only an approximate ipso factor can be deduced.

show abstract

mentioning

confidence: 95%

“…A specific model was also proposed for I3C chemical shifts in 4H, 4M, and 4B derivatives (3,4). It was assumed that resonance effects in 4H should mainly affect the conjugated ortlzo, para, and p carbons (see 4).…”

mentioning

confidence: 99%

Substituent-induced chemical shifts in 3- and 4-substituted styrenes: definition of substituent constants and determination of mechanisms of transmission of substituent effects by iterative multiple linear regression

Reynolds¹,

Gomes²,

Maron³

et al. 1983

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Specifically, we have noted excellent agreement between 13C s.c.s. and carbon charge densities for C(1) and C(P) of 4-substituted styrenes (4,16). However, the agreement is much worse for C(2,6) and C(a), apparently because the C N D 0 / 2 calculations significantly over-estimated the -R dependence for these carbons.…”

mentioning

confidence: 99%

“…This parameter is largest for + R groups (NO,, CF,, CN) and smallest for -R groups (CH,, F, OCH,, NH,, N(CH,),), indicating respective enhancement and inhibition of hyperconjugative donation of electrons by the methyl group. The variation o f f with 4 probably arises from n charge density changes at C(l) due to n polarization effects (4,31).…”

mentioning

confidence: 99%

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

Dawson¹,

Hamer²,

Reynolds³

1974

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

Comparisons of 'H chemical shifts and charge densities (determined by C N D 0 / 2 MO calculations) for 4-substituted derivatives of styrene, toluene, benzylchloride, and N,N,N-trimethylphenylammonium ion indicate that the chemical shifts primarily reflect intramolecular electronic effects. These effects are reflected by correlations of 'H chemical shifts with the F and R reactivity parameters of Swain and Lupton. It is concluded that it is valid to correlate substituent-induced chemical shifts for aromatic derivatives with divided reactivity parameters provided that ( I ) chemical shifts are measured at infinite dilution in a non-polar medium and'(2) at least ten derivatives of each family are investigated.Calculations for 4-substituted toluenes indicate that there will be a small conformational dependence for substituent-induced benzylic proton chemical shifts.La comparaison des deplacements chimiques ' H et des densites de charge (dktermintes par la mkthode CNDO/2 MO) pour des derives substitues en position 4 du styrene, du toluene, du chlorure de benzyle et de I'ion N,N,N-trimkthylphinyl ammonium indiquent que les deplacements chimiques refletent principalement les effets Clectroniques intramolCculaires. Ces effets apparaissent sous forme de correlation entre les deplacements chimiques 'H avec les parametres de rkactivite F e t R de Swain et Lupton. On en conclut qu'il est valide de faire une correlation entre le substituant et les diplacements chimiques induits dans les derives aromatiques possedant des parametres de reactivite divises pourvu (I) q u e les deplacements chimiques soient mesurks dilution infinie dans un solvant non-polaire et (2) qu'au moins dix derives de la famille soient etudits.Les calculs pour les toluenes substituCs en position 4 indiquent qu'il y a une petite dependance conformationnelle pour les dkplacements chi~niques des protons benzyliques qui ont ett induits p a r les substituants.[ (1) derivatives) should reflect resonance effects since R = 0 for the N(CH,),+ group (3). They also [I]

show abstract

“…Table 1. These chemical shift values (ppm) are correlated with different Hammett substituent constants and F & R parameters using single and multi-linear regression analyses according to the approach of Reynolds [32,33]. In this correlation, the structureparameter equation employed is shown in equation (7).…”

Section: Uv-visible Spectral Correlationsmentioning

confidence: 99%

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

Senbagam¹,

Rajarajan²,

Vijayakumar³

et al. 2015

ILCPA

View full text Add to dashboard Cite

ABSTRACT. 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 λ max (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. 1.INTRODUCTION Schiff's bases are an important class of organic compounds possessing biological activities and structural significance. It has been proved that the incorporation of this molecule into the biologically active azomethine linkage (-CH=N-) produces compounds with high pharmacological activity [1]. Schiff's bases are represented by the general formula RCH=NR' where >C=N is the azomethine group [2]. The colour of the Schiff's bases is due to the presence of this azomethine (>C=N) linkage and can vary by introducing other auxochromic groups. When functional groups, such as -OH, -SH, -COOH are present in these ligands in suitably tailored positions, they enable them to be powerful chelating, biological and analytical reagents. On this basis of such groups present, the Schiff's bases may be di, tri, tetra or polydentate in nature. Compounds containing azomethine group are basic in nature, as N atom of this group has a lone pare of electrons and the double bond has electron donating character. Schiff's bases displayed the phenomenon of tautomeris[3], thermochromy and photochromy[4] and geometrical isomerism [5]. They possess both types of hydrogen bonding i.e. intra-molecular as well as inter-molecular [6]. Schiff's bases are widely studied and used in the fields of organic synthesis and metal ion complexation [7] for a number of reasons: their physiological and pharmacological activities [8] their use in ionselective electrodes [9] in the determination of heavy metals ions in environmental samples [10] and in the extraction of metals ions [11,12] and their many catalytic applications (e.g. for epoxidation of olefins, alkene cyclopropanation [13,14] trimethylsilylcyanation of ketones [15] asymmetric oxidation of methyl phenyl sulfide enantioselective epoxidation of silylenol [16] and ring-opening polymerization of lactide [17]. In recent years, correlation analysis has been applied by chemists for solving the effect of substituents on Schiff's bases through spectral data. Literature survey shows that there is no information available regarding the study of UV, IR and NMR spectral correlation and antimicrobial activities of substituted (E)-N-benzylidene-2-aminopyrimidine compounds. Hence the authors have taken efforts fo...

show abstract

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. I, 4-Substituted Styrenes

Cited by 178 publications

References 20 publications

Substituent-induced chemical shifts in 3- and 4-substituted styrenes: definition of substituent constants and determination of mechanisms of transmission of substituent effects by iterative multiple linear regression

Substituent-induced chemical shifts in 3- and 4-substituted styrenes: definition of substituent constants and determination of mechanisms of transmission of substituent effects by iterative multiple linear regression

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

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

Contact Info

Product

Resources

About