ChemInform Abstract: SUBSTITUENT EFFECTS ON CARBON-13 CHEMICAL SHIFTS IN 4-SUBSTITUTED BIPHENYLS AND BENZENES, A SUBSTITUENT EFFECT TRANSMITTED THROUGH EIGHT COVALENT BONDS

1H, 13C and 15N NMR spectra of twenty substituted N-phenoxyethylanilines 1-20 were completely and unambiguously assigned using a combination of both homo- and heteronuclear (gs-COSY), 1H detected heteronuclear one-bond (gs-HMQC) and long-range (gs- HMBC) gradient-selected correlation experiments. Correlations between chemical shifts and substituent constants are analyzed separately for both phenyl rings using variable substituents para to the fixed substituent -OCH2CH2NHC6H5 (series I) and -NHCH2CH2OC6H5 (series II), respectively. The correlation coefficient for chemical shifts vs. a linear combination of inductive and resonance substituent constants is high and improves when only the six values, corresponding to each para-monosubstituted series, were used. For nitrogen chemical shifts excellent linear dependences were obtained. The results show that the ethylene chain is not able to transmit the substituent effect from one aromatic ring to the other.

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Substituent effects on the 13C chemical shifts of monosubstituted twistanes

Canadian Journal of Chemistry ◽

10.1139/v77-443 ◽

1977 ◽

Vol 55 (17) ◽

pp. 3161-3165 ◽

Cited By ~ 15

Author(s):

Helmut Beierbeck ◽

John K. Saunders

Keyword(s):

Chemical Shift ◽

Substituent Effect ◽

Chemical Shifts ◽

Substituent Effects ◽

13C Chemical Shifts ◽

Bond Interaction ◽

Chemical Shift Data ◽

Shift Data ◽

Deshielding Effect

The 13C chemical shift data for some hydroxy, chloro, bromo, and oxo twistane derivatives are presented and compared to the shifts observed in corresponding adamantanes. The substituent effect at the α and β carbons is more pronounced in twistanes than in adamantanes. The substituent shift induced at an antiperiplanar γ carbon is shown to depend on the presence or absence of 1,3-diaxial hydrogen–hydrogen interactions between the substituted and γ carbons. If such an interaction is present the effect is of shielding whereas if it is absent, the effect is of deshielding. The deshielding effect appears to occur via a through bond interaction.

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

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19951316 ◽

1995 ◽

Vol 60 (8) ◽

pp. 1316-1332 ◽

Cited By ~ 5

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.

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Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20061557 ◽

2006 ◽

Vol 71 (11-12) ◽

pp. 1557-1570 ◽

Cited By ~ 10

Author(s):

Vilve Nummert ◽

Mare Piirsalu ◽

Ilmar A. Koppel

Keyword(s):

Kinetic Study ◽

Alkaline Hydrolysis ◽

Rate Constants ◽

Substituent Effect ◽

Substituent Effects ◽

Alkyl Substituent ◽

Solvent Parameters ◽

Substituent Constants ◽

Hydrolysis Of ◽

Main Factor

The second-order rate constants k2 (dm3 mol-1 s-1) for the alkaline hydrolysis of substituted alkyl benzoates C6H5CO2R have been measured spectrophotometrically in aqueous 0.5 M Bu4NBr at 50 and 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH, CH2C6H5, CH2CH2Cl, CH2CH2OCH3, CH2CH3) and in aqueous 5.3 M NaClO4 at 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations: ∆ log k = c0 + c1σI + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆EσI + c7∆YσI + c8∆PσI ∆ log k = c0 + c1σ* + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆Eσ* + c7∆Yσ* + c8∆Pσ* . ∆ log k = log kR - log kCH3. σI and σ* are the Taft inductive and polar substituent constants. E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆E = ES - EH2O , ∆Y = YS - YH2O , ∆P = PS - PH2O were used. The solvent electrophilicity, E, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σI constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity E was found to be similar to that observed earlier for meta and para substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters.

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Nuclear Magnetic Resonance Chemical Shifts of some Monosubstituted Isothiazoles

Canadian Journal of Chemistry ◽

10.1139/v75-083 ◽

1975 ◽

Vol 53 (4) ◽

pp. 596-603 ◽

Cited By ~ 10

Author(s):

Roderick E. Wasylishen ◽

Thomas R. Clem ◽

Edwin D. Becker

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Chemical Shifts ◽

Substituent Effects ◽

Charge Densities ◽

Monosubstituted Benzenes ◽

Proton Chemical Shifts ◽

Nuclear Magnetic

Carbon-13 and proton chemical shifts have been measured for several monosubstituted isothiazoles. Substituent effects upon these chemical shifts are compared with those observed for monosubstituted benzenes, pyridines, and thiophenes. In general the observed substituent effects in the isothiazoles and thiophenes closely parallel one another. Correlations between the observed carbon-13 Chemical shifts and CNDO/2 calculated charge densities are examined.

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