ISSN:
0009-2940
Keywords:
C—C Bond cleavage, kinetics of
;
Heat of formation
;
Radicals, stability of
;
Capto-dative effect
;
Geminal substituents, energetic interaction of
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Substituent Effects on the Strength of C—C Bonds, 13[1]. - Kinetic and Thermodynamic Stability of α1-alkylated α1-Amino Acid Esters - Energy of Stabilization of α1-Amino-α1-(ethoxycarbonyl)alkyl RadicalsThermolytic cleavage of 1a-c and 2a-c into radicals in solution are clean first-order processes. The activation parameters for C—C bond homolysis were determined. Compared with the corresponding data for hydrocarbons of equal strain a decrease of bond strength of 14.4 kcal/mol results by the combined interaction of the amino and the ethoxycarbonyl substituents. The heat of formation of 5 was determined by combustion calorimetry [δHco (1)=- 1207.75 ± 0.20 kcal/mol] combined with the heat of vaporization (δHvo=13.31 ± 0.10 kcal/mol). Compared with the additive behaviour of group increments the resulting heat of formation (δHfo (g)=- 112.02 ± 0.24 kcal/mol] suggests a synergetic, geminal destabilization of Hsyn=1.9 ± 1.4 kcal/mol. Combination of the kinetic data of bond homolysis of 1a-c and 2a-c with the synergetic ground-state destabilization leads to a synergetic, capto-dative radical stabilization of Hsyn (rad)=6.7 kcal/mol.
Additional Material:
6 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260425
