Sergej Verevkin

Geminale Substituenteneffekte Teil 5. Standardbildungsenthalpien von alkylsubstituierten Malonsa¨ure-und α-Aminocarbonsa¨ureestern

Abstract The title compounds 1a–1k were prepared in high purity. Δ H ° c (1) of 1 was measured using an isoperibolic calorimeter Δ H vap of 1 was obtained from the temperature function of the vapour pressure measured in a flow system. The following heats of formation have been obtained in the liquid phase and the gas phase: Δ H ° f (1) and Δ H ° f (g) for 1a −191.13 ± 0.15, −176.35±0.24; 1b −197.50±0.13, −183.69±0.21; 1c −205.17±0.10, −191.86±0.21; 1d −235.8±1.0, −220.3±1.0; 1e −133.94±0.33, − 123.35±0.34; 1f −135.48±0.25, −125.62±0.25; 1g −99.03±0.16, −88.53±0.19; 1h −108.68±0.10, −97.31±0.23; 1i −105.33±0.18, −94.26±0.32; 1j −119.88±0.18, −108.±0.31; 1k −299.30±0.25, −280.37±0.30 kcal mol −1 . The values of the excess destabilization or stabilization energy caused by the geminal substituents is discussed in relation to the branching at the central C atom.