Homogeneous decomposition of vinyl ethers. The heat of formation of ethanal‐2‐yl

The thermal unimolecular decomposition of three vinylethers has been studied in a VLPP apparatus. The high‐pressure rate constant for the retro‐ene reaction of ethylvinylether was fit by log k (sec −1 ) = (11.47 + 0.25) ‐ (43.4 ± 1.0)/2.303 RT at < T > = 900 K and that of t ‐ butylvinylether by log k (sec −1 ) = (12.00 ± 0.27) ‐ (38.4 ± 1.0)/2.303 RT at < T > = 800 K. No evidence for the competition of the higher energy homolytic bond‐fission process could be obtained from the experimental data. The rate constant compatible with the CO bond scission reaction in the case of benzylvinylether was log k (sec −1 ) = (16.63 ± 0.30) ‐ (53.74 ± 1.0)/2.303 RT at < T > = 750 K. Together with Δ H f ,300 0 (benzyl·) = 47.0 kcal/mol, the activation energy for this reaction results in Δ H f ,300 0 (CH 2 CHO) = +3.0 ± 2.0 kcal/mol and a corresponding resonance stabilization energy of 3.2 ± 2.0 kcal/mol for 2‐ethanalyl radical.