Substituent effects on the chemical shifts of the bridge protons of benzonorbornenes

1967 ◽  
Vol 45 (11) ◽  
pp. 1185-1193 ◽  
Author(s):  
Naoki Inamoto ◽  
Shozo Masuda ◽  
Kazuo Tori ◽  
Katsutoshi Aono ◽  
Hiroshi Tanida
Keyword(s):  
Benzene Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron System ◽  
Electronic Interaction ◽  
Orbital System ◽  
Significant Difference ◽  
Bridge Carbon ◽  
Hammett Relationship ◽  
Good Agreement

The substituent effects on the chemical shifts of the C9 bridge protons in a series of 6-substituted benzonorbornenes and benzonorbornadienes, and on those of the C2 protons in 5-substituted 2-indanols, were investigated. They were linearly correlated with the modified Hammett relationship τR − τH = ρ (σm + σp)/2. The ρ values obtained from the anti-C9 protons in the bornenes and bornadienes were slightly but significantly larger than those from the corresponding syn protons, whereas no significant difference was observed between the ρ values obtained from syn-9-benzonorbornenols and the indanols. The larger ρanti values were explained in terms of a stereospecific electronic interaction between the π-electron system of the benzene ring and the orbital system of the bridge carbon. In addition, it was shown that the above modified Hammett relationship gives generally a good agreement with the substituent effects on the aliphatic constituents of benzocyclenes and analogous compounds.

N.M.R. STUDIES OF BRIDGED RING SYSTEMS: II. UNUSUAL MAGNETIC DESHIELDING EFFECT ON THE BRIDGE METHYLENES OF NORBORNADIENE AND BENZONORBORNADIENE

1964 ◽  
Vol 42 (4) ◽  
pp. 926-933 ◽  
Author(s):  
K. Tori ◽  
Y. Hata ◽  
R. Muneyuki ◽  
Y. Takano ◽  
T. Tsuji ◽  
...  
Keyword(s):  
Double Bond ◽  
Benzene Ring ◽  
Chemical Shifts ◽  
Electron System ◽  
Electron Systems ◽  
Double Bonds ◽  
Diamagnetic Anisotropy ◽  
Anisotropy Effect ◽  
Transannular Interaction ◽  
Olefinic Double Bond

Proton magnetic resonance spectra of some norbornane derivatives having double bonds and (or) a benzene ring in the skeleton were studied. Differences in the chemical shifts between the bridge methylenes of norbornene and benzonorbornene and that of norbornane result from the diamagnetic anisotropy effect of a double bond or a benzene ring being in good agreement with the values calculated theoretically. However, in the norbornadiene derivatives which have two double bonds or one olefinic double bond with a benzene ring in a part of the skeleton, the signals of their bridge methylenes show extraordinarily larger downfield shifts by about 0.8 p.p.m. than those expected from the additive shielding due to each π-electron system. This anomaly is not observed in bicyclo[2.2.2]octane ring series. A large transannular interaction between two π-electron systems in that system would be a major contribution to the above anomaly.

scholarly journals 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

1973 ◽  
Vol 51 (6) ◽  
pp. 915-926 ◽  
Author(s):  
Gordon K. Hamer ◽  
Ian R. Peat ◽  
W. F. Reynolds
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron System ◽  
Resonance Spectroscopy ◽  
Molecular Orbital Calculations ◽  
Electronic Effects ◽  
Partial Explanation ◽  
Charge Densities ◽  
Related Compounds ◽  
Molecular Framework

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.

Torsional angles and substituent effects in phenyl-substituted azoles by carbon-13 N.M.R. chemical shifts

1980 ◽  
Vol 33 (8) ◽  
pp. 1763 ◽  
Author(s):  
CW Fong
Keyword(s):  
Benzene Ring ◽  
Inductive Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Structural Deformation ◽  
Steric Interaction ◽  
Hydrogen Atoms ◽  
Ortho Hydrogen ◽  
Azole Ring ◽  
Torsional Angles

The torsional angles in 31 N-phenyl-substituted azole derivatives have been estimated by use of the 13C substituent chemical shifts of the meta and para carbon atoms. Steric interaction between the C 5 substituent on the azole rings and the ortho hydrogen atoms of the benzene ring is the major cause of non-planarity in these compounds. The azole rings undergo structural deformation with varying substituents on the azole ring. The inductive effect of a number of azole and azolium rings is discussed.

Ab initio calculations on 4-substituted benzoic acids; a further theoretical investigation into the nature of substituent effects in aromatic derivatives

1977 ◽  
Vol 55 (9) ◽  
pp. 1567-1574 ◽  
Author(s):  
Paul G. Mezey ◽  
William F. Reynolds
Keyword(s):  
Ab Initio ◽  
Field Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron System ◽  
Acid Dissociation ◽  
Molecular Orbital Calculations ◽  
Atomic Charges ◽  
Benzoic Acids ◽  
Substituted Benzoic Acids

Ab initio (STO-3G) molecular orbital calculations for 4-substituted benzoic acids and XCH3–HCO2H pairs are used to derive a theoretical field, TF and resonance, TR(BA), substituent scale. Comparison with previous calculations for 4-substituted styrenes shows that a common field scale can be used for different systems but that different resonance scales are necessary, depending upon the electronic nature of the probe group. The field effect primarily reflects the direct electrostatic interaction between the substituent and the carboxylic acid. However, there are also significant contributions due to field-induced polarization of the intervening phenyl π electron system. By contrast, the π polarization effect seems to be the dominant field effect in the case of non-interacting probes (such as carbon atomic charges or chemical shifts). A very close parallel is noted between substituent effects upon atomic charges and acid dissociation energies.

Infrared, 1H and 13C NMR Spectral Studies on Di- and Tri-substituted N-Aryl Amides, 2,6-X2C6H3NHCOCH3 – IXi and 2,4,6-X3C6H2NHCOCH3 – IXi (X = Cl or CH3 and I = 0, 1, 2 or 3)

2004 ◽  
Vol 59 (1-2) ◽  
pp. 69-76 ◽  
Author(s):  
B. Thimme Gowda ◽  
K. M. Usha ◽  
K. Jyothi
Keyword(s):  
General Formula ◽  
Benzene Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Spectral Studies ◽  
Side Chain ◽  
1H And 13C Nmr ◽  
Stretching Vibrations ◽  
Absorption Frequencies ◽  
C Nmr

Several di- and tri-substituted amides of the general formula, 2,6-X2C6H3NHCOCH3−iXi and 2,4,6-X3C6H2NHCOCH3−iXi (X = Cl or CH3 and i = 0, 1, 2, or 3) are prepared, characterised, and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution are studied. The C=O stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong absorptions in the ranges 1707 - 1658 cm−1 and 1700 - 1647 cm−1, respectively, while the N-H stretching vibrations of N-(2,6-dichlorophenyl)- and N-(2,6-dimethylphenyl)-amides appear as strong vibrations in the ranges 3271 - 3209 cm−1 and 3285 - 3214 cm−1, respectively. The N-H stretching vibrations of N-(2,4,6-trichlorophenyl)- and N-(2,4,6-trimethylphenyl)- amides also appear as strong absorptions in the ranges 3370 - 3212 and 3283 - 3225 cm−1, respectively, while those of the C=O vibrations appear in the ranges 1688 - 1617 and 1704 - 1647 cm−1. The analysis of the C=O and N-H absorption frequencies of all amides of the general formula XiC6H5−iNHCOCH3−iXi (where X = Cl or CH3, and i = 0, 1, 2 or 3) indicates that their variations do not show regular trends with substitution either in the phenyl ring or in the side chain. The chemical shifts of both the aromatic protons and the aromatic carbons of all the amides are calculated in two ways, either by adding the incremental shifts due to -COCH3−iXi groups and the substituents in the benzene ring to the chemical shifts of the corresponding aromatic protons or carbons of the parent aniline, or by adding the incremental shifts due to -NHCOCH3−iXi groups and the substituents in the benzene ring to the chemical shift of the benzene proton or carbon. The calculated chemical shifts of the aromatic protons and carbons of all the substituted amides by both methods lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating that the principle of additivity of the substituent effects is valid in these compounds.

Electrophilic and nucleophilic substitution in the Benzene ring and the Hammett Equation

1956 ◽  
Vol 9 (1) ◽  
pp. 61 ◽  
Author(s):  
J Miller
Keyword(s):  
Large Deviations ◽  
Nucleophilic Substitution ◽  
Benzene Ring ◽  
Electrophilic Substitution ◽  
Substituent Effects ◽  
Hammett Equation ◽  
Wide Range ◽  
Good Agreement

The Hammett equation as applied to aromatic nuclear electrophilic and nucleophilic substitution is tested for a wide range of substituents. For nucleophilic substitution quite good agreement is obtained for electron-attracting substituents using σ* values, but large deviations occur with substituents releasing electrons by the conjugative mechanism. In electrophilic substitution, in so far as results are available, a fair measure of agreement obtains for electron-attracting substituents, but very large and to some extent irregular deviations occur for the conjugative electron- releasing substituents. The deviations occur whether σ or σ* values are used, and new sets of σN** and σE** values are defined and the values recorded. A comparison is made of substituent effects in nuclear electrophilic and nucleophilic substitution.

Electronic effects of halogen-substituted methyl groups

1980 ◽  
Vol 33 (6) ◽  
pp. 1291 ◽  
Author(s):  
CW Fong
Keyword(s):  
Benzene Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Methyl Groups ◽  
Electronic Effects ◽  
Substituted Toluenes ◽  
Molecular Deformations

The electronic effects of the halogen-substituted methyl groups, CHnX3-n, where X is F, Cl, Br or I, have been examined by 13C n.m.r, spectroscopy in a series of α-halogen-substituted toluenes. The substituent chemical shifts of all carbon atoms, as well as the σI and σR0 substituent parameters derived from a dual substituent parameter (DSP) analysis, are examined in terms of hyperconjugative and π-inductive substituent effects. Bulky CHnX3-n substituents cause molecular deformations of the benzene ring, consequently invalidating the derivation of substituent parameters from a DSP analysis.

Proximity and conformation effects in 29Si and 13C NMR spectra of di-ortho substituted trimethylsiloxybenzenes

1990 ◽  
Vol 55 (8) ◽  
pp. 2027-2032 ◽  
Author(s):  
Jan Schraml ◽  
Robert Brežný ◽  
Jan Čermák
Keyword(s):  
Benzene Ring ◽  
13C Nmr ◽  
Proximity Effect ◽  
Nmr Spectra ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Proximity Effects ◽  
13C Nmr Spectra ◽  
Methoxy Groups ◽  
C Nmr

29Si and 13C NMR spectra of five 4-substituted 2,6-dimethoxytrimethylsiloxybenzenes were studied with the aim to elucidate the nature of the deshielding proximity effects observed in the spectra of ortho substituted trimethylsiloxybenzenes. The sensitivity of 29Si chemical shifts to para substitution is in the studied compounds essentially the same as in mono ortho methoxytrimethylsiloxybenzenes. The deshielding proximity effect of the ìsecondî methoxy group is somewhat smaller than that of the ìfirstî group. The present results indicate that the two methoxy groups assume coplanar conformations with the benzene ring and are turned away from the trimethylsiloxy group which is not in the benzene plane. It is argued that in mono ortho methoxytrimethylsiloxybenzenes the two substituent groups adopt the same conformations as in the compounds studied here.

Chemometric Analysis of Substituent Effects. VII. Inductive Effect as a Basic Substituent Effect. Isoeffect Substituent Constant

1995 ◽  
Vol 60 (8) ◽  
pp. 1316-1332 ◽  
Author(s):  
Oldřich Pytela ◽  
Aleš Halama
Keyword(s):  
Inductive Effect ◽  
Chemical Shifts ◽  
Quantitative Description ◽  
Substituent Effects ◽  
Intersection Point ◽  
Chemometric Analysis ◽  
Reaction Centre ◽  
Substituent Constant ◽  
Modified Method ◽  
Substituted Benzoic Acids

The paper deals with chemometric analysis of the inductive effect. The notion of inductive effect is discussed, and unambiguous definitions are given for the notions of triad: reaction centre-basic skeleton-substituent, and the therewith connected definitions of inductive effect. For a quantitative description of inductive effect 7 types of chemical models were selected including noncyclic compounds, cyclic, and bicyclic compounds, derivatives of quinuclidine, 3-substituted benzoic acids, sulfonamides and pyridines. Altogether 139 sets of experimental data from literature have been used including altogether 1 294 points (9.3 points per set, 5 points at least) reflecting substituent effects of 34 substituents. It has been found that for a standard model the dissociation of substituted bicycloalkanecarboxylic acids only is satisfactory, all the other models reflecting also the mesomeric effects to variable extent (up to 10%). A distinctly different substitution behaviour was observed with 19F and 13C NMR chemical shifts of 4-substituted 1-fluoro- or 1-methylbicyclo[2.2.2]octanes. The earlier suggested model of substituent effects based on different way of transmission of substituent effects (3 classes) has been used for separating the inductive and mesomeric effects: it is mathematically presented as a set of straight lines with the intersection point at the so-called isoeffect substituent constant. Using the modified method of conjugated deviations a chemometric scale has been created for the inductive effect which agrees very well with the conventional scales given in literature; the only differences were observed for F and CH=O substituents (which are overestimated and underestimated, respectively, in literature). In the context given the inductive effect appears as a fundamental quantity forming a basis for quantitative description of other effects transferred by electrons.

Standardisation of von Willebrand Factor in Therapeutic Concentrates: Calibration of the 1st International Standard for von Willebrand Factor Concentrate (00/514)

2002 ◽  
Vol 88 (09) ◽  
pp. 380-386 ◽  
Author(s):  
Dawn Sands ◽  
Andrew Chang ◽  
Claudine Mazurier ◽  
Anthony Hubbard
Keyword(s):  
Von Willebrand Factor ◽  
International Study ◽  
Expert Committee ◽  
International Standard ◽  
A Value ◽  
Significant Difference ◽  
Factor Concentrate ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Good Agreement

SummaryAn international study involving 26 laboratories assayed two candidate von Willebrand Factor (VWF) concentrates (B and C) for VWF:Antigen (VWF:Ag), VWF:Ristocetin Cofactor (VWF:RCo) and VWF:Collagen binding (VWF:CB) relative to the 4th International Standard Factor VIII/VWF Plasma (4th IS Plasma) (97/586). Estimates of VWF:Ag showed good agreement between different methods, for both candidates, and the overall combined means were 11.01 IU/ml with inter-laboratory variability (GCV) of 10.9% for candidate B and 14.01 IU/ml (GCV 11.8%) for candidate C. Estimates of VWF:RCo showed no significant difference between methods for both candidates and gave overall means of 9.38 IU/ml (GCV 23.7%) for candidate B and 10.19 IU/ml (GCV 24.4%) for candidate C. Prior to the calibration of the candidates for VWF:CB it was necessary to calibrate the 4th IS Plasma relative to local frozen normal plasma pools; there was good agreement between different collagen reagents and an overall mean of 0.83 IU per ampoule (GCV 11.8%) was assigned. In contrast, estimates of VWF:CB in both candidates showed large differences between collagen reagents with inter-laboratory GCV’s of 40%. Candidate B (00/514) was established as the 1st International Standard von Willebrand Factor Concentrate by the WHO Expert Committee on Biological Standardisation in November 2001 with assigned values for VWF:Ag (11.0 IU/ampoule) and VWF:RCo (9.4 IU/ampoule). Large inter-laboratory variability of estimates precluded the assignment of a value for VWF:CB.

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