ChemInform Abstract: 1994 R.U. Lemieux Award Lecture. Hydrolysis of Acetals and Ketals. Position of Transition States Along the Reaction Coordinates, and Stereoelectronic Effects.

ChemInform ◽  
2010 ◽  
Vol 26 (18) ◽  
pp. no-no
Author(s):  
P. DESLONGCHAMPS ◽  
Y. L. DORY ◽  
S. LI
Keyword(s):  
Transition States ◽  
Reaction Coordinates ◽  
Stereoelectronic Effects ◽  
Hydrolysis Of

1994 R.U. Lemieux Award Lecture Hydrolysis of acetals and ketals. Position of transition states along the reaction coordinates, and stereoelectronic effects

1994 ◽  
Vol 72 (10) ◽  
pp. 2021-2027 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Yves L. Dory ◽  
Shigui Li
Keyword(s):  
Ab Initio ◽  
Reaction Pathway ◽  
Transition States ◽  
Experimental Results ◽  
Reaction Coordinates ◽  
Stereoelectronic Effects ◽  
Theoretical Support ◽  
Semi Empirical ◽  
Hydrolysis Of ◽  
Support Evidence

Past and recent experimental results on the formation or hydrolysis (or isomerization) of various acetals and ketals including α-and β-glycoside models are presented. Ab initio investigations of simple acetals are also briefly reviewed as well as recent experimental and theoretical support evidence for a synperiplanar effect. A detailed study using the semi-empirical Hamiltonian AM1 defining the reaction pathway in the hydrolysis of various acetals and ketals is reported. This overall study shows that the hydrolysis of acetals and ketals is controlled by powerful stereoelectronic effects.

The Hydrolysis of Bis(2-chloroethyl) Sulfide (Sulfur Mustard) in Aqueous Mixtures of Ethanol, Acetone and Dimethyl Sulfoxide

1993 ◽  
Vol 46 (3) ◽  
pp. 293 ◽  
Author(s):  
RI Tilley
Keyword(s):  
Transition State ◽  
Dimethyl Sulfoxide ◽  
Rate Constants ◽  
Charge Separation ◽  
Sulfur Mustard ◽  
Transition States ◽  
Aqueous Mixtures ◽  
Sulfide Sulfur ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of bis (2-chloroethyl) sulfide (sulfur mustard) in aqueous mixtures of ethanol, acetone and dimethyl sulfoxide has been measured and compared with previously reported values. Rate constants in water at 25°C for the two consecutive hydrolysis reactions undergone by sulfur mustard were estimated to be (2.93�0.15)×10-3 and (3.87�0.14)×10-3 s-1. Charge separation of 0.42 in the transition states was indicated together with significant solvation of the positive end of the transition state dipoles.

The hydrolysis of thioacetic, thiobenzoic, and three substituted thiobenzoic acids in perchloric and sulfuric acids

1978 ◽  
Vol 56 (7) ◽  
pp. 935-940 ◽  
Author(s):  
John T. Edward ◽  
Graeme Welch ◽  
Sin Cheong Wong
Keyword(s):  
Sulfuric Acid ◽  
Activity Coefficients ◽  
Acid Concentration ◽  
Perchloric Acid ◽  
Transition States ◽  
Sulfuric Acid Concentration ◽  
Thiobenzoic Acid ◽  
The Difference ◽  
Different Response ◽  
Hydrolysis Of

The rates of hydrolysis of thioacetic, thiobenzoic, and three substituted thiobenzoic acids increase with concentration of solvent sulfuric or perchloric acid to a maximum in 30–40% acid and then decrease. Yates–McClelland r, Bunnett–Olsen [Formula: see text], and Hammett ρ parameters, and entropies of activation indicate an AAC2 mechanism over this range of acid concentrations. In acid concentrations above 50–60% the rates increase sharply and the same mechanistic criteria now indicate an AAc1 mechanism. The difference between the rate–acidity profile of thiobenzoic acid and that of ethyl thiolbenzoate can be explained by the different response of the activity coefficients of their transition states to increase in sulfuric acid concentration.

Pattern of Intrinsic Reaction Coordinates and Separatrices for a Symmetry-Forbidden Reaction

1986 ◽  
Vol 41 (3) ◽  
pp. 529-531 ◽  
Author(s):  
Ariel Fernández
Keyword(s):  
Structural Stability ◽  
Transition States ◽  
Chemical Species ◽  
Basins Of Attraction ◽  
Thermal Isomerization ◽  
Relative Distribution ◽  
Reaction Coordinates ◽  
Jahn Teller ◽  
Stability Principle ◽  
Good Agreement

The relative distribution of the basins of attraction of the chemical species and of the transition states is derived for the thermal isomerization of cyclobutene to butadiene.It is shown that the transition states for the symmetry-allowed and symmetry-forbidden pathways are lumomers of one another. Use is made of the structural stability principle of Ariel Fernández and Oktay Sinanoglu to show that these transition states are respectively the conrotatory and disrotatory Jahn-Teller distortions of the 2-butene diradical.The results exhibit good agreement with J. A. Berson’s conclusions in the sense that even the forbidden pathway is concerted.

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