Substituent Effects in Unimolecular Ion Decompositions. II. A Linear Free Energy Relationship between Acyl Ion Intensities in the Mass Spectra of Substituted Acylbenzenes1,2

1966 ◽  
Vol 88 (3) ◽  
pp. 529-536 ◽  
Author(s):  
Maurice M. Bursey ◽  
F. W. McLafferty
Keyword(s):  
Free Energy ◽  
Mass Spectra ◽  
Substituent Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Substituent Effects on the Chymotrypsin-Catalyzed Hydrolysis of Specific Ester Substrates

1971 ◽  
Vol 49 (2) ◽  
pp. 210-217 ◽  
Author(s):  
R. E. Williams ◽  
M. L. Bender
Keyword(s):  
Free Energy ◽  
Rate Constants ◽  
Substituent Effects ◽  
Phenyl Group ◽  
Linear Free Energy Relationship ◽  
Acylation Reaction ◽  
General Base ◽  
Linear Free Energy ◽  
Base Mechanism ◽  
Hydrolysis Of

The substituent effect on the chymotrypsin-catalyzed hydrolysis of several phenyl esters of specific substrates has been studied. The second-order acylation rate constants (kcat/Km(app)) obey a linear free energy relationship with ρ = +0.63 for phenyl hippurates and ρ = +0.46 for phenyl N-benzyloxycarbonyl-L-tryptophanates when substituents are introduced into the phenyl group of the ester function. These results further support the previously proposed general acid – general base mechanism for the acylation reaction and the formation of a tetrahedral intermediate in the course of the reaction.

Substituent effects in naphthalene. III. Saponification of 6- and 7-substituted Methyl 2-naphthoates and application of the Hammett equation

1966 ◽  
Vol 19 (2) ◽  
pp. 221 ◽  
Author(s):  
PR Wells ◽  
W Adcock
Keyword(s):  
Free Energy ◽  
Alkaline Hydrolysis ◽  
General Feature ◽  
Substituent Effects ◽  
Linear Free Energy Relationship ◽  
Reaction Centre ◽  
Hammett Equation ◽  
P Values ◽  
Linear Free Energy ◽  
Aromatic Systems

The rates of alkaline hydrolysis in 70% v/v aqueous dioxan at 25� have been determined for the 6-and 7-NO2, 6- and 7-CN, 6- and 7-F, 6- and 7-Cl, 6- and 7-NMe2, 6-Me and 6-OMe substituted methyl 2-naphthoates, methyl 2- naphthoate, m-NO2, p-NO2, p-Me substituted methyl benzoates, and methyl benzoate. An examination of the application of the Hammett equation reveals that this linear free energy relationship applies with high precision but that it yields different p values for different substituent-reaction centre dispositions. This may be a general feature for all aromatic systems although in many cases the differences are not larger than the experimental uncertainties.

Half-wave potentials of quinone methides in dimethylformamide: Substituent effects

1981 ◽  
Vol 46 (4) ◽  
pp. 861-872 ◽  
Author(s):  
Josef Krupička ◽  
Bohumír Koutek ◽  
Lubomír Musil ◽  
Libuše Pavlíčková ◽  
Milan Souček
Keyword(s):  
Free Energy ◽  
Substituent Effects ◽  
Linear Free Energy Relationship ◽  
Quinone Methides ◽  
Linear Free Energy ◽  
Diffusion Controlled ◽  
Half Wave ◽  
Substituent Constants ◽  
Series Type ◽  
Spin Densities

Half-wave potentials of two series of quinone methides A have been determined in 0.1M tetrabutylammonium perchlorate in dimethylformamide. the first series (type I; 14 compounds) contained fuchsones substituted in positions 2 and 2,6 of the quinonoid ring, the second series (type II and III; 17 compounds) consisted of 2,6-ditert-butylquinone methides, with substituents at the exocyclic C(7) carbon atom. Properties of the first polarographic wave proved that in both series the reaction is one-electron, reversible, diffusion-controlled process. Linear free energy relationship was found between E1/2 and dual substituent constants σI and σR. Statistical analysis of linear free energy relationship for 2- and 2,6-substituted derivatives proved absence of steric factor in transmission of electronic substituent effect. The experimental results were interpreted on the basis of LUMO energies and spin densities, calculated by the HMO method.

Linear Free Energy Relationship Analysis of Solvent Effects on Singlet Oxygen Reactions

2003 ◽  
Vol 7 (9) ◽  
pp. 799-819 ◽  
Author(s):  
Else Lemp ◽  
Antonio Zanocco ◽  
Eduardo Lissi
Keyword(s):  
Free Energy ◽  
Singlet Oxygen ◽  
Solvent Effects ◽  
Linear Free Energy Relationship ◽  
Relationship Analysis ◽  
Linear Free Energy

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

2004 ◽  
Vol 82 (8) ◽  
pp. 1294-1303 ◽  
Author(s):  
Vanessa Renée Little ◽  
Keith Vaughan
Keyword(s):  
Free Energy ◽  
Chemical Shifts ◽  
Linear Free Energy Relationship ◽  
Piperazine Ring ◽  
Linear Free Energy ◽  
In Series ◽  
Methylene Groups ◽  
Diazonium Coupling ◽  
The Difference

1-Methylpiperazine was coupled with a series of diazonium salts to afford the 1-methyl-4-[2-aryl-1-diazenyl]piperazines (2), a new series of triazenes, which have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis. Assignment of the chemical shifts to specific protons and carbons in the piperazine ring was facilitated by comparison with the chemical shifts in the model compounds piperazine and 1-methylpiperazine and by a HETCOR experiment with the p-tolyl derivative (2i). A DEPT experiment with 1-methylpiperazine (6) was necessary to distinguish the methyl and methylene groups in 6, and a HETCOR spectrum of 6 enabled the correlation of proton and carbon chemical shifts. Line broadening of the signals from the ring methylene protons is attributed to restricted rotation around the N2-N3 bond of the triazene moiety in 2. The second series of triazenes, the ethyl 4-[2-phenyl-1-diazenyl]-1-piperazinecarboxylates (3), have been prepared by similar diazonium coupling to ethyl 1-piperazinecarboxylate and were similarly characterized. The chemical shifts of the piperazine ring protons are much closer together in series 3 than in series 2, resulting in distortion of the multiplets for these methylenes. It was noticed that the difference between these chemical shifts in 3 exhibited a linear free energy relationship with the Hammett substituent constants for the substituents in the aryl ring. Key words: triazene, piperazine, diazonium coupling, NMR, HETCOR, linear free energy relationship.

Absorption Spectra of Substituted 2-Phenylindan-1,3-Dion-2-YL Radicals in Solution

1983 ◽  
Vol 38 (12) ◽  
pp. 1337-1341
Author(s):  
J. Zechner ◽  
N. Getoff ◽  
I. Timtcheva ◽  
F. Fratev ◽  
St. Minchef
Keyword(s):  
Free Energy ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Bathochromic Shift ◽  
Substitution Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Abstract Flash photolysis of a series of 2-phenylindandione-1,3 derivatives substituted in the 4′ position results in both the formation of stable benzylidenephthalides and of phenylindan-1,3-dion-2-yl radicals. The u. v. absorption maxima of these radicals are dependent on the solvent and show a bathochromic shift upon substitution. These substitution effects were correlated by means of a linear free energy relationship. Attempts were made to draw conclusions concerning the changes in the gap of the states involved and their curvature due to substitution.

Correlation of Human and Animal Air-to-Blood Partition Coefficients With a Single Linear Free Energy Relationship Model

2008 ◽  
Vol 27 (9) ◽  
pp. 1130-1139 ◽  
Author(s):  
Laura M. Sprunger ◽  
Jennifer Gibbs ◽  
William E. Acree ◽  
Michael H. Abraham
Keyword(s):  
Free Energy ◽  
Partition Coefficients ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy ◽  
Relationship Model

Kinetics and linear free energy relationship of wittig reaction between substituted benzaldehydes and substituted benzylidenetriphenylphosphorane

Tetrahedron ◽  
1986 ◽  
Vol 42 (15) ◽  
pp. 4161-4167 ◽  
Author(s):  
Li Donxia ◽  
Wu Dexian ◽  
Li Yaozhong ◽  
Zhao Huaming
Keyword(s):  
Free Energy ◽  
Wittig Reaction ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy ◽  
Substituted Benzaldehydes ◽  
Relationship Of
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