Statistical Analysis of the Hammett Equation. III. Evidence against para Through-resonance for --M Substituents in Phenylacetic Acids and Phenylpropionic Acids.

Sjöstróm, Michael; Wold, Svante; Rasmussen, Poul; Larsen, Charles; Nielsen, Per Halfdan; Norgård, S.; Kjøsen, Helge; Liaaen-Jensen, S.

doi:10.3891/acta.chem.scand.30b-0167

Cited by 16 publications

(22 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reactivity of meta-6 is noticeably different to that of the para-fluorophenyl steroid 4. It seems that the meta-fluorine atom inductively destabilises a developing carbocation at C [17] and promotes the rearrangement whereas the para-fluorine in 5 provides mesomeric stabilisation and promotes a straightforward E1-elimination.…”

Section: Resultsmentioning

confidence: 97%

Synthesis of fluorinated analogues of the neurosteroid GABAA receptor antagonist, 17-PA

Deniau

Sillar

O’Hagan

2008

Journal of Fluorine Chemistry

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 97%

Synthesis of fluorinated analogues of the neurosteroid GABAA receptor antagonist, 17-PA

Deniau

Sillar

O’Hagan

2008

Journal of Fluorine Chemistry

View full text Add to dashboard Cite

“…10 On the basis of this model, a constrained tetralinear version of the Hammett equation was developed 11 which yielded values for the para/meta ratio of the field or inductive effect in excellent agreement 11 with Dewar et al 's model. 12 Then we referred to difficulties encountered while fitting data for the pyridinium ion series with sigma-plus constants, and to Sawada et al 's contribution 13 to the controversy on the proper scale to describe the pyridine reactivity.…”

Section: Introductionmentioning

confidence: 99%

“…In our paper on the hyperbolic model 9 for the unified sigma-zero scale, 10 an annoying change of subscripts occurred in the expression for the standard errors in ' 4 / ' 3 . The expression given in footnote b to and the values in the last column of that table amended accordingly.…”

Section: Revised Parameters For the Hyperbolic Modelmentioning

confidence: 99%

See 1 more Smart Citation

Improved Yukawa-Tsuno equation and the substituent effect on pyridine basicity

Reis

Segurado

Oliveira

1998

J. Phys. Org. Chem.

View full text Add to dashboard Cite

An improved Yukawa-Tsuno equation was obtained by inserting the resonance demand parameter r in the tetralinear extension of the Hammett equation constrained by a hyperbolic relation between meta and para substituent effects. The new equation with five adjustable parameters and other Yukawa-Tsuno models were applied to selected literature data for the ionization equilibria of 21 meta-and 20 para-substituted pyridinium ions in water at 25°C. The data are best described by the new equation using either the sigma-benzoic acid scale with r = 1.35 AE 0.16 or a truncated sigma-plus scale (in which sigma-zero constants are assigned to 4-alkyl substituents) with r = 0.29 AE 0.04. Standard errors were estimated by Monte Carlo simulation. The results for the pyridinium ion demonstrate that the hyperconjugative effect by alkyl groups is inoperative and that through-resonance effects by electron-donating substituents are considerably hindered. The origin of this hindrance is ascribed to the particularities of nitrogen orbitals in heteroaromatic compounds. It is concluded that the pyridine reactivity lies between those of benzoic acid and benzylic cation, being much closer to the former.

show abstract

“…Wold [14], a Hammett plot could be drawn and the ρ value of 2.20 ± 0.03 deduced. This value suggests partial positive charge formation in the rate determining step [15].…”

Section: Dependence On the Substratementioning

confidence: 99%

Further studies on hydration of alkynes by the PtCl4–CO catalyst

Israelsohn

Vollhardt

Blum

2002

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

Dedicated to Professor Myron Rosenblum on the occasion of his 75 th birthday in recognition of his outstanding contribution to chemistry AbstractUnder CO atmosphere, between 80 and 120˚C, a glyme solution of PtCl 4 forms a carbonyl compound that promotes hydration of internal as well as terminal alkynes to give aldehyde-free ketones. The catalytic process depends strongly on the electronic and steric nature of the substrates. Part of the carbonyl functions of the catalyst can be replaced by phosphine ligands. Chiral DIOP reacts with the PtCl 4 -CO compound to give a catalyst that promotes partial kinetic resolution of a racemic alkyne. Replacement of part of the CO by polystyrene-bound diphenylphosphine enables to attach the catalyst to the polymeric support. Upon entrapment of the platinum compound in a silica sol-gel matrix, it reacts as a partially recyclable catalyst. A reformulated mechanism for the PdCl 4 -CO catalyzed hydration is suggested on the basis of the present study.

show abstract

Statistical Analysis of the Hammett Equation. III. Evidence against para Through-resonance for --M Substituents in Phenylacetic Acids and Phenylpropionic Acids.

Cited by 16 publications

References 0 publications

Synthesis of fluorinated analogues of the neurosteroid GABAA receptor antagonist, 17-PA

Synthesis of fluorinated analogues of the neurosteroid GABAA receptor antagonist, 17-PA

Improved Yukawa-Tsuno equation and the substituent effect on pyridine basicity

Further studies on hydration of alkynes by the PtCl4–CO catalyst

Contact Info

Product

Resources

About