Stable simple enols. 17. Linear free energy relationship between keto .dblharw. enol equilibrium constants of stable .beta.,.beta.-dimesityl and unstable .beta.,.beta.-unsubstituted .alpha.-substituted enols

1987 ◽  
Vol 109 (15) ◽  
pp. 4730-4731 ◽  
Author(s):  
Zvi Rappoport
Keyword(s):  
Free Energy ◽  
Equilibrium Constants ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Equilibrium constants for a series of simple aldol condensations, and linear free energy relations with other carbonyl addition reactions

1978 ◽  
Vol 56 (7) ◽  
pp. 962-973 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Free Energy ◽  
Acetic Acid ◽  
Carbonyl Compounds ◽  
Equilibrium Constants ◽  
Linear Free Energy Relationship ◽  
Reaction Products ◽  
Free Energies ◽  
Linear Free Energy ◽  
Energy Relations ◽  
Relationship Of

A set of equilibrium constants for aldol condensations of acetaldehyde, acetone, acetophenone, and acetic acid as nucleophiles and formaldehyde, acetaldehyde, benzaldehyde, acetone, and acetophenone as carbonyl acceptors has been evaluated. The four values determined, directly or indirectly, by experiment have been augmented by values calculated from thermo-chemical data and equilibrium constants for enone hydration, and by estimation of free energies of formation of the reaction products by use of hypothetical disproportionation reactions. When the carbonyl nucleophiles are compared to other nucleophiles which can add to carbonyl compounds, it is found that they can be incorporated in the linear free energy relationship of Sander and Jencks, with γ values of 0.45 for acetaldehyde, 0.16 for acetone, 0.05 for acetophenone, and 3.56 for acetic acid. These results make it possible to predict the equilibrium constants for any of a large number of aldol condensations from the equilibrium constant for the addition of any nucleophile to the carbonyl accepter compound.

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

Linear free energy relationship rate constants and basicities of N-substituted phenyl glycines in positronium-glycine complex formation

1987 ◽  
Vol 137 (5) ◽  
pp. 471-474 ◽  
Author(s):  
Rongti Chen (Y.T. Chen) ◽  
Jiachang Liang ◽  
Youming Du ◽  
Chun Cao ◽  
Dinzhen Yin ◽  
...  
Keyword(s):  
Free Energy ◽  
Complex Formation ◽  
Rate Constants ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

scholarly journals Rationalisation of the activities of phenolic (vitamin E-type) antioxidants

2003 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Christopher J. Rhodes ◽  
Thuy T. Tran ◽  
Philip Denton ◽  
Harry Morris
Keyword(s):  
Free Energy ◽  
Vitamin E ◽  
Gibbs Free Energy ◽  
State Theory ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Gibbs Free Energy Change ◽  
Linear Free Energy ◽  
Free Energy Of Activation ◽  
Enthalpy And Entropy

Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

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