How do protons cross the membrane-solution interface? Kinetic studies on bilayer membranes exposed to the protonophore S-13 (5-chloro-3-tert-butyl-2′-chloro-4′ nitrosalicylanilide)

1987 ◽  
Vol 95 (1) ◽  
pp. 73-89 ◽  
Author(s):  
John Kasianowicz ◽  
Roland Benz ◽  
Stuart McLaughlin
Keyword(s):  
Kinetic Studies ◽  
Bilayer Membranes ◽  
Tert Butyl ◽  
Solution Interface ◽  
Interface Kinetic

Article

1998 ◽  
Vol 76 (12) ◽  
pp. 1805-1816
Author(s):  
L Ross C Barclay ◽  
Jennifer K Grandy ◽  
Heather D MacKinnon ◽  
Heather C Nichol ◽  
Melinda R Vinqvist
Keyword(s):  
Oxygen Uptake ◽  
Singlet Oxygen ◽  
Sodium Azide ◽  
Lignin Content ◽  
Sodium Dodecyl ◽  
Kinetic Studies ◽  
Product Distribution ◽  
Geometrical Isomers ◽  
Photo Oxidation ◽  
Tert Butyl

3,5-Di-tert-butyl-ortho-quinone, 6, and 1-(3,4-dimethoxyphenyl-2-(2-methoxyphenoxy)-1-propanone, 7, models for oxidized lignin and for lignin, were used as sensitizers of photo-oxidation. Product studies by HPLC from oxidation of methyl linoleate in solution sensitized by 6 or 7, and in sodium dodecyl sulfate (SDS) sensitized by 6, showed a product distribution of six hydroperoxides, the four conjugated 9- and 13-hydroperoxides of the geometrical isomers: trans-10, cis-12 (2), cis-9, trans-11 (3), trans-10, trans-12 (4), and trans-9, trans-11 (5)-octadecadienoates plus two nonconjugated hydroperoxides. The higher cis/trans to trans/trans (ct/tt) of geometrical isomers (2 + 3//4 + 5) compared to ct/tt from known thermal free-radical peroxidations (Type 1) indicate that singlet oxygen (Type 2) oxidation occurs in reactions sensitized by 6 or 7. Kinetic studies by oxygen uptake are reported on oxidations of hydrocarbons 1-phenyl-2-methylpropene,8, and trans-stilbene,9, sensitized by the quinone, 6, or by a dye, Rose Bengal. Quenching studies imply singlet oxygen reactions. Milled wood lignin undergoes self-initiated photo-oxidation in water, and oxygen uptake was quenched by sodium azide. Cellobiose, a cellulose model, undergoes sensitized photo-oxidation using model quinone, 6, in a mixture of tert-butyl alcohol and water or using the sensitizers benzophenone or the lignin model, 7, delivered on a solid support, silica gel, and these oxidations were quenched with sodium azide. These results implicate singlet oxygen in the photo-yellowing of high lignin content wood pulps.Key words: lignin models, ortho-quinone, photo-oxidation, singlet oxygen, lignin, cellobiose.

Kinetic studies on the mechanism of the decomposition of a number of β-substituted tert-butyl α, α -dimethylperpropionates

1977 ◽  
Vol 55 (4) ◽  
pp. 612-618 ◽  
Author(s):  
Dennis D. Tanner ◽  
H. Yabuuchi ◽  
H. Lutzer
Keyword(s):  
General Formula ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Neighboring Group ◽  
Group Participation ◽  
Tert Butyl ◽  
Bond Scission ◽  
Neighboring Group Participation

A series of ter-butyl peresters having a general formula corresponding to I were synthesized.[Formula: see text]The thermally initiated rates of decomposition of these peresters were determined at several temperatures and the activation parameters for these thermolyses were calculated.The rates of decomposition were relatively insensitive to the substituents and followed the order I > C2H5 > C6H5S > H > Br > Cl. The activation parameters and product studies were consistent with a simple two bond scission mechanism and no evidence could be found for neighboring group participation in these homolyses.

Kinetic Studies on the Reactions of [(TLtBu)PtCl]+ and [Pt(tpdm)Cl]+ Complexes with Some Thiols and Thioethers

2013 ◽  
Vol 66 (5) ◽  
pp. 534 ◽  
Author(s):  
Enisa Selimović ◽  
Biljana Petrović ◽  
Dragan Čcanović ◽  
Živadin D. Bugarčić ◽  
Jovana Bogojeski
Keyword(s):  
Variable Temperature ◽  
Kinetic Studies ◽  
Substitution Reactions ◽  
Tert Butyl ◽  
Naclo4 Solution ◽  
Entropy Of Activation ◽  
Methyl Pyridine

Substitution reactions of the complexes [(TLtBu)PtCl]+ and [Pt(tpdm)Cl]+, where TLtBu = 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine and tpdm = terpyridinedimethane, with nucleophiles: S-methyl-L-cysteine (S-Met-L-Cys), L-cysteine (L-Cys), glutathione (GSH) and L-methionine (L-Met) were studied in aqueous 0.1 M NaClO4 solution in the presence of 10 mM NaCl using variable-temperature UV-vis spectrophotometry. The higher reactivity of the complex with the tpdm ligand could be attributed to the influence of the bulkiness of the tert-butyl-groups from the [(TLtBu)PtCl]+ complex. The order of reactivity of the studied ligands is: S-Met-L-Cys > L-Met > GSH > L-Cys. The thioethers (S-Met-L-Cys and L-Met) are more reactive than the thiols (GSH and L-Cys). This order of reactivity is in relation with their electron properties and structures. The negative values reported for the entropy of activation confirmed the associative mode.

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