Reactions of aryl diazonium salts and arylazo alkyl ethers. III. Substituent effects in the ionization of anti-arylazo ethyl ethers in ethanol

1978 ◽  
Vol 31 (7) ◽  
pp. 1519 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Substituent Effects ◽  
Parameter Analysis ◽  
Diazonium Salts ◽  
Resonance Effects ◽  
Inductive Effects ◽  
Alkyl Ethers

A dual substituent parameter analysis of substituent effects on the ionization of anti-arylazo ethyl ethers in ethanol shows that the reaction is affected primarily by inductive effects. The reaction is insensitive to resonance effects and an explanation for this behaviour is offered.

Substituent effects in naphthalene. II. The strengths of the 4, 5, 6, 7, and 8-substituted 2-naphthoic acids

1965 ◽  
Vol 18 (9) ◽  
pp. 1365 ◽  
Author(s):  
PR Wells ◽  
W Adcock
Keyword(s):  
Electrostatic Interactions ◽  
Aqueous Ethanol ◽  
Substituent Effects ◽  
Simple Expression ◽  
Dipole Orientation ◽  
Aromatic Substituent ◽  
Resonance Effects ◽  
Naphthoic Acid ◽  
Inductive Effects ◽  
Substituted 1

The apparent pKa values of 44 substituted 2-naphthoic acids, six substituted 1-naphthoic acids, and the unsubstituted naphthoic acids have been determined for 50% v/v aqueous ethanol at 25�. The ΔpK values are examined in terms of Dewar and Grisdale's simple expression for aromatic substituent effects. This expression proves to be fairly satisfactory, but takes no account of substituent dipole orientation, secondary resonance effects, nor π-inductive effects. A survey of the naphthoic acid strengths demonstrates the importance of these factors. In particular, unambiguous evidence for the important role played by direct electrostatic interactions is obtained.

The application of the Hammett equation to 13C N.M.R. spectrometry. VI. Remote ring effects in azobenzenes and stilbenes

1983 ◽  
Vol 36 (10) ◽  
pp. 2083 ◽  
Author(s):  
D Christoforou ◽  
DAR Happer
Keyword(s):  
Chemical Shifts ◽  
Phenyl Group ◽  
Resonance Interaction ◽  
Parameter Analysis ◽  
The Other ◽  
Hammett Equation ◽  
Resonance Effects ◽  
Inductive Effects

The 13C n.m.r. chemical shifts for the non-substituted rings of azobenzene, stilbene, 26 monosubstituted azobenzenes and 28 monosubstituted stilbenes are reported. The effects of substituents in one ring on the chemical shifts of the other have been interpreted in terms of their inductive and resonance effects by means of a dual substituent parameter analysis. The results show that inductive effects are transmitted to the remote ring from the meta and para positions with equal efficiencies and polarize the phenyl group independently of the rest of the molecule. Resonance interaction is greatest when the substituent is para to the azo or vinylene linking group and is relayed with greatest efficiency to the ortho and para carbons of the remote ring. The results of the study are compared with previously unreported data for the corresponding ring carbons of the ethyl arylazo- and arylethenyl-cinnamates, and with literature data on para-substituted biphenyls and terphenyls.

Reactions of Aryl Diazonium Salts and Arylazo Alkyl Ethers. IV. Substituent Effects on the Rates of Some Reactions of syn-Arylazo Ethyl Ethers in Ethanol

1979 ◽  
Vol 32 (5) ◽  
pp. 1031 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Substituent Effects ◽  
Diazonium Salts ◽  
Recombination Mechanism ◽  
Alkyl Ethers

Substituent effects on the rates of ionization (kIS), decomposition (kD) and syn-anti interconversion (kp) for a number of syn-arylazo ethyl ethers have been measured. The rates of ionization and syn-anti interconversion correlate well with sigma while the rates of decomposition correlate with σ+. Substituent effects on the ionization of the syn-ethers are compared to those for ionization of the anti-ethers. Substituent effects on the rate of syn-anti interconversion support the proposed ionization-recombination mechanism.

scholarly journals The substituent effects on the 13c chemical shifts of the azomethine carbon atom of n-(phenyl substituted) salycilaldimines

2012 ◽  
Vol 77 (8) ◽  
pp. 993-1001
Author(s):  
Sasa Drmanic ◽  
Aleksandar Marinkovic ◽  
Jasmina Nikolic ◽  
Bratislav Jovanovic
Keyword(s):  
Carbon Atom ◽  
Schiff Bases ◽  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
13C Chemical Shifts ◽  
Resonance Effects ◽  
Inductive Effects ◽  
Substituent Constants ◽  
Significant Resonance

The Hammett correlations between 13C-NMR chemical shifts of the azomethine carbon atom and the corresponding substituent constants for thirtheen Schiff bases were established. Successful correlation of the chemical shifts with electrophilic substituent constants ?+ indicate significant resonance interaction of the substituents on the aniline ring with the azomethine carbon atom in the examined series of imines. The demand for electrons in the investigated compounds was compared to that of the N-benzylidenanilines and N-(phenyl substituted) pyridinealdimines. The way of transmission of the substituent effects was discussed and they are separated into resonance and inductive effects. Inductive effects prevail over resonance effects.

Reactions of aryl diazonium salts and arylazo alkyl ethers. VI. A comparison of the available methods for the measurement of the rate of ionization of (Z)-arylazo alkyl ethers in alcoholic solvents

1982 ◽  
Vol 35 (2) ◽  
pp. 319 ◽  
Author(s):  
TJ Broxton ◽  
MJ Mcleish
Keyword(s):  
Substituent Effects ◽  
Ionization Rate ◽  
New Method ◽  
Diazonium Salts ◽  
Advantages And Disadvantages ◽  
Diazonium Ions ◽  
Alkyl Ethers ◽  
Trapping Agent ◽  
Ionization Rates

Two previously reported methods for the determination of the ionization rate of (Z)-arylazo alkyl ethers by using x-naphtholate ions as a trapping agent are compared. A new method, which uses thiophenolate ions to trap the free diazonium ions formed in this ionization, is reported. This method is recommended in preference to the earlier methods because it includes a correction for the effect of the ionic strength of the solution on the rate of ionization. Rates measured by the thiophenolate method are consequently lower than those measured by either of the two previous methods. The advantages and disadvantages of the new method are discussed. The magnitude of salt effects and substituent effects on the ionization of (Z)- and (E)-arylazo alkyl ethers are compared.

Kinetic study of hydrolysis of benzoates. part xxvii. ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous Bu4NBr

2009 ◽  
Vol 74 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Signe Vahur ◽  
Oksana Travnikova ◽  
Ilmar A. Koppel
Keyword(s):  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Pure Water ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Resonance Effects ◽  
The Media ◽  
Substituted Benzoic Acids ◽  
Hydrolysis Of ◽  
Ortho Substituent

The second-order rate constants k (in dm3 mol–1 s–1) for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, have been measured spectrophotometrically in aqueous 0.5 and 2.25 M Bu4NBr at 25 °C. The substituent effects for para and meta derivatives were described using the Hammett relationship. For the ortho derivatives the Charton equation was used. For ortho-substituted esters two steric scales were involved: the EsB and the Charton steric (υ) constants. When going from pure water to aqueous 0.5 and 2.25 M Bu4NBr, the meta and para polar effects, the ortho inductive and resonance effects in alkaline hydrolysis of phenyl esters of substituted benzoic acids, became stronger nearly to the same extent as found for alkaline hydrolysis of C6H5CO2C6H4-X. The steric term of ortho-substituted esters was almost independent of the media considered. The rate constants of alkaline hydrolysis of ortho-, meta- and para-substituted phenyl benzoates (X-C6H4CO2C6H5, C6H5CO2C6H4-X) and alkyl benzoates, C6H5CO2R, in water, 0.5 and 2.25 M Bu4NBr were correlated with the corresponding IR stretching frequencies of carbonyl group, (ΔνCO)X.

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

Substituent Effects on the Hydrolysis of p-Substituted Benzonitriles in Sulfuric Acid Solutions at (25.0± 0.1) °C

2008 ◽  
Vol 63 (9) ◽  
pp. 603-608 ◽  
Author(s):  
Khamis A. Abbas
Keyword(s):  
Sulfuric Acid ◽  
Rate Constants ◽  
Inductive Effect ◽  
Substituent Effects ◽  
Acid Solutions ◽  
Rate Determining Step ◽  
Inductive Effects ◽  
High Concentrations ◽  
Sulfuric Acid Solutions ◽  
Hydrolysis Of

The rate constants of the hydrolysis of p-substituted benzonitriles with sulfuric acid solutions (18.2 M to 10 M) have been determined spectrophotometrically at (25.1±0.1) °C. It was found that the catalytic activity of sulfuric acid was strongly inhibited by water. The logarithms of the observed rate constants were correlated with different substituent inductive (localized) and resonance (delocalized) constants. The results of the correlation studies indicated that the rate-determining step of the hydrolysis of benzonitriles in 18.2 M sulfuric acid was the addition of a nucleophile, and the hydrolysis was clearly enhanced by the electron-withdrawing inductive effect, while the rate-determining step of the hydrolysis of p-substituted benzonitriles in 10.0 M sulfuric acid was most probably the protonation of benzonitriles, and the rate constants increased by both electron-donating resonance and inductive effects. A mixture of the two mechanisms most probably occurred in 15.3 to 17.0 M sulfuric acid. HSO4 − rather thanwater most probably acted as nucleophile in the hydrolysis of benzonitriles especially at high concentrations of sulfuric acid solutions.

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