Resonance Substituent Research Articles

The transmission of resonance effects through a methylene group—spectroscopic studies on some α-substituted-acetonitriles and p-toluonitriles

Frequencies and integrated intensities are recorded for the ν CN mode of a representative selection of α-substituted acetonitriles, α-substituted- p-toluonitriles and β-substituted propiononit-riles. The frequencies of the acetonitriles are confirmed to show an important substituent resonance effect. These results together with carbon-13 data on both series are used to consider the possibility of resonance effects being felt at a probe separated from the substituent by a methylene group.

ChemInform Abstract: THE VARIATION OF SUBSTITUENT RESONANCE EFFECTS WITH ELECTRON DEMAND

Chemischer InformationsdienstVolume 10, Issue 33 Physical Organic Chemistry ChemInform Abstract: THE VARIATION OF SUBSTITUENT RESONANCE EFFECTS WITH ELECTRON DEMAND D. A. R. HAPPER, D. A. R. HAPPERSearch for more papers by this authorG. J. WRIGHT, G. J. WRIGHTSearch for more papers by this author D. A. R. HAPPER, D. A. R. HAPPERSearch for more papers by this authorG. J. WRIGHT, G. J. WRIGHTSearch for more papers by this author First published: August 14, 1979 https://doi.org/10.1002/chin.197933037AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue33August 14, 1979 RelatedInformation

SUBSTITUENT EFFECTS OF PHOSPHORUS-CONTAINING GROUPS. THE ELECTRONIC EFFECTS IN ANILIDES AND PHENYL ESTERS

Abstract 13C NMR shielding parameters have been determined for the N-phosphorylated aniline and O-phosphorylated phenol derivatives, Ph–Y–P(O)Z2 (Y=NH, O), and for their complexes with titanium tetrachloride. Inductive and resonance substituent constants were calculated using the dsp approach for the neutral and charged substituents. The results are compared with those for the corresponding neutral and charged acetyl derivatives. Shielding effects and substituent constants are discussed in terms of the interactions of the lone pair at Y with the aromatic ring and with the acyl center. It is concluded that no significant p π-d π back-donation from Y to the phosphorus atom operates in the systems studied.

The variation of substituent resonance effects with electron demand

The Hammett substituent constants for a number of substituents have been resolved into constant inductive (σI) and variable resonance (σR) contributions. Variations in σR have been interpreted in terms of changes in the demand for π electrons made on substituents and an empirical scale of ‘electron demand’ has been set up. The relationship has been tested using reactivity data, and its applications discussed.

Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

Copolymerization Reactivities of α-Substituted Crotonyl Monomers

Abstract The radical copolymerizations of various α- substituted crotonyl monomers with styrene (St) and acrylonitrile (AN) were investigated, and the copolymerization parameters were determined by a least-squares procedure reported previously. The relative reactivities of the α-substituted crotonyl monomers toward polymer radicals of St and AN were found to correlate with the equation: log (relative reactivity of CH3CH[dbnd]CXY) = ρ (σ + σY) + A(Δlog Qx + Δlog QY), where Σ and Δlog Q are the polar Hammett and resonance substituent constants, respectively, and p and A are reaction constants. From the observed straight line relationships, the values of p and A were obtained to be as follows: ρ = 0.66, A = 0.75 for attack of poly-St radical, and ρ = -3.20, A = 1.3 for attack of poly-AN radical.

ChemInform Abstract: ON THE INTERPRETATION OF LINEAR CORRELATIONS BETWEEN NUCLEAR MAGNETIC RESONANCE SUBSTITUENT CHEMICAL SHIFTS AND SUBSTITUENT REACTIVITY PARAMETERS IN BENZENE DERIVATIVES

Chemischer InformationsdienstVolume 8, Issue 32 Physical Organic Chemistry ChemInform Abstract: ON THE INTERPRETATION OF LINEAR CORRELATIONS BETWEEN NUCLEAR MAGNETIC RESONANCE SUBSTITUENT CHEMICAL SHIFTS AND SUBSTITUENT REACTIVITY PARAMETERS IN BENZENE DERIVATIVES M. GODFREY, M. GODFREYSearch for more papers by this author M. GODFREY, M. GODFREYSearch for more papers by this author First published: August 9, 1977 https://doi.org/10.1002/chin.197732052AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue32August 9, 1977 RelatedInformation

On the interpretation of linear correlations between nuclear magnetic resonance substituent chemical shifts and substituent reactivity parameters in benzene derivatives

The currently poorly-understood relationships between n.m.r. substituent chemical shift (s.c.s) data and substituent reactivity parameters are reconsidered within the framework of a substantially modified version of the usual general theory for structure–property relationships, that has recently been proposed. Predictions concerning the circumstances under which quantitative linear correlations of two kinds should or should not occur are confirmed for compounds which are formally substituted benzenes. It is concluded that the theory merits consideration in the theoretical treatment of any case of a structure–property or an interproperty relationship. The implications for the use of n.m.r. s.c.s. data to obtain structural information about molecular systems are briefly discussed.

The two‐parameter taft equation in kinetics of free radical reactions

AbstractA new method was developed for the calculation of the resonance substituent constants of the two‐parameter Taft equation log ksub/k0=ρ*σ*+r*σr. It is based on a relationship between the spin density in free radicals and the rate constants of radical substitution reactions of CH3. Possibilities and limitations of the application of this correlation equation to the investigation of substitution and addition radical reactions are discussed.

A carbon-13 NMR study of phosphine, phosphite, arsine and stibine ligands and their LNi(CO) 3, LCr(CO) 5 and η-(C 5H 5)Mn-(CO) 2L complexes

13C NMR chemical shift and J( 13C 31P) coupling constant data are presented for PPh 3− n Me n ( n = 0, 1 and 2, P(OPh) 3, PEt 3, AsPh 3 and SbPh 3 ligands, and some corresponding LNi(CO) 3, LCr(CO) 5 and η-(C 5H 5)Mn(CO) 2L complexes. Analysis of the 13C NMR chemical shift data for the C(4) resonance in these C 6H 5X derivatives suggests: (1) a resonance substituent parameter R = 0.005 for X = PPh 2 and R = 0.09 for X = (CO) 5CrPPh 2, (2) a decrease in the resonance interaction of the Group VA atom with the phenyl ring in EPh 3 derivatives in the order E = P > As > Sb, and (3) an increase in the electron density at the phosphorus atom in PPh 3− n Me n derivatives in the order: PPh 3 < PPh 2Me < PPhMe 2. There appears tobe an anomalous shielding of the C(1) resonance in these derivatives upon complexation, and with increasing electronegativity of the Group Va atom. The electron-withdrawing character of the metal carbonyl moiety appears to increase in the order: η-(C 5H 5)Mn(CO) 2L < LNi(CO) 3 < LCr(CO) 5. The magnitude of the 1 J( 13C 31P) and 3 J( 13C 31P) coupling in trialkyl and triaryl phosphines increases upon complexation, while the magnitude of the 2 J( 13C 31P) coupling decreases. As a result, in (Me 2PhP)Ni(CO) 3, the 3 J( 13C 31P) coupling to the C(3,5) resonance of the phenyl group is larger than the 2 J( 13C 31P) coupling to the C(2,6) resonance. In contrast, complexation of triphenyl phosphite leads to an apparent increase in the magnitude of the 2 J( 13C 31P) coupling and a decrease in the magnitude of the 3 J( 13C 31P) coupling. The signs of the one-, two- and three-bond J( 13C 31P) coupling constants in Ph 3PMo(CO) 5 have been determined to be positive.

Theory of electron spin g-values for peroxy radicals

An SCF-MO calculation is performed to obtain principal components for the g-tensor of HOO and FOO. Results are then generalized to all peroxy radicals ROO through an equation which relates 〈 g〉 to Taft's inductive and resonance substituent parameters. The theory can be used to aid analysis of ESR spectra for chemical identification of peroxy radicals.

Infrared intensities as a quantitative measure of intramolecular interactions. Part XLIII. Quantitative estimation of electronic interactions in mono- and di-substituted ethylenes and the prediction of rotational barriers

Known rotational barriers in monosubstituted ethylenes are discussed in terms of substituent resonance and strain parameters. Related reasoning allows the rationalisation of known rotational barriers in 4-(dimethylamino)but-3-en-2-one in terms of substituent-ethylene and substituent–substituent interactions.

Infrared intensities as a quantitative measure of intramolecular interactions. Part XXXIV. Quantitative relations between conjugation and strain energies and σ°Rvalues: rotational barriers in monosubstituted benzenes

Known rotational barriers for substituents in monosubstituted benzenes are correlated with ring–substituent resonance interactions and strain energies. Rotational barriers are estimated for a variety of other substituents. σ Constants are related directly to the energy scale.

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Substituent-induced 1H chemical shifts (S.C.S.) for 19 4-substituted α-methyl- and α-t-butylstyrenes have been determined at infinite dilution in C6H12 and 13C S.C.S. have been determined for 0.4 M solutions in CCl4. S.C.S. are correlated with field and resonance substituent parameters and compared with charge densities determined by CNDO/2 MO calculations. The variation of S.C.S. with the dihedral angle, ρ, between phenyl and vinyl groups and the overall pattern of S.C.S. can be largely accounted for by a model of substituent effects based on field, resonance, and π polarization effects, with conjugative interactions varying as cos2ρ. Both 13C chemical shifts and charge densities indicate that the π polarization effect consists of two components: (1) a through-space polarization of the vinyl system by the polar C—X bond and (2) polarization of the entire conjugated styrene π electron system. However, significant deviations are noted for some of the 1H S.C.S. correlations. The CNDO/2 calculations indicate that these deviations are primarily due to electronic effects not predicted by the model outlined above. CNDO/2 calculations for related compounds provide a partial explanation by indicating that the magnitude of the field effect depends upon the nature of the molecular framework.

The Estimation of the Electronic Effects of Cyclopropyl and 2,2-Dichlorocyclopropyl Groups

Abstract The normal substituent constant, σ0, and the resonance substituent constant, Δ\barσR+, in the Yukawa and Tsuno treatment of cyclopropyl and 2,2-dichlorocyclopropyl were determined by the ionization of m-, p-substituted phenylacetic acids in 50% aqueous ethanol and by the solvolysis of α-(m-, p-substituted phenyl) ethyl chlorides in 80% aqueous acetone. For cyclopropyl, the obtained σ0 value indicates an inductive electron-attracting behavior, while the Δ\barσR+ value indicates a marked enhancement of the electron-releasing resonance effect on the electron deficient reaction center compared with alkyl groups. A minor resonance contribution was observed for the 2,2-dichlorocyclopropyl group.

The Substituent Effect. IV. Proton NMR Chemical Shifts of Phenols

Abstract NMR chemical shifts of the hydroxyl proton of m- and p-substituted phenols were determined in aprotic DMF and DMSO solutions. The effect of substituents on the hydroxy chemical shift was correlated much more excellently with our LArSR relationship, Δδ=ρ(σ0+rΔ\barσ\barR), than with simple Hammett equation, ρσ0 or ρσ−. The correlation resulted in ρ=1.655 and r=0.639 in DMF with correlation coefficient 0.9992 and ρ=1.530 and r=0.673 in DMSO with a correlation coefficient 0.9990. Anisotropy effect of any substituent was not significant. The deviations of particular substituents were ascribed to the modification of the electronic characters of substituents due to strong substituent-solvent interactions in DMF (or DMSO). The inductive and resonance substituent constants, (σi)DMF and (Δ\barσ\barR)DMF, were determined, on the basis of the assumption that the solvent-modification of a given substituent is practically the same at both meta and para positions.

Correlation of substituent resonance effects with free radical spin densities

Correlation of substituent resonance effects with free radical spin densities

The Reactivities of α -Substituted Acrylonitriles and Acrylic Esters in Radical Copolymerizations

Abstract In order to clarify the effect of the substituents in a-substituted acrylonitriles and acrylic esters on their relative reactivities toward a polystyryl radical, the radical copolymerizations of diethyl methylenemalonate, ethyl a-chloroacrylate, ethyl a-bromoacrylate, a-chloroacrylonitrile, methyl a-methoxyacrylate, and a-methoxyacrylonitrile with styrene (M2) were investigated at 60°C. From the copolymerization parameters obtained in this study and those reported in the literature, it was confirmed that the a substituents additively contributed to the values of log Q and e of the monomers. Hence, the reactivities of a-substituted acrylonitriles and acrylic esters relative to unsubstituted acrylonitrile and methyl acrylate toward polystyryl radical, respectively, were expressed by the following equation: log (rel. react.) = δlog QX + 0.83 σp where δ log Qx and σp are the resonance and polar substituent constants of α substituents, respectively. The values of δ log Qx were determined for CH30, CH3...

Configurational assignment of diastereomeric sulphoxides by nuclear magnetic resonance substituent and solvent effects

The first page of this article is displayed as the abstract.

The transmission of polar effects. Part VII. A proton magnetic resonance spectra study of substituted mesitylenes, durenes, anthracenes, and triptycenes

The chemical shifts of the ring protons in a series of monosubstituted mesitylenes and durenes, and of the 10-protons of a series of 9-substituted triptycenes and anthracenes have been measured in dimethyl sulfoxide, acetone, 2-methoxyethanol, and carbon tetrachloride. The solvent dependence of the substituent chemical shifts has been analyzed by linear free energy relations. The systems all show similar dependence which increases with increasing dielectric constant of the solvent. This does not result from the field effect being transmitted through the medium, but appears to arise from the formation of a hydrogen-bonded interaction between the solvent and the hydrogen of the solute. The substituent chemical shifts appear to arise from contributions from substituent field, resonance, magnetic anisotropy, and solvent effects.