'The racemization of (+)-2,3-divinyloxirane is facile at 150°, log (k1/s−1) = (11.3 ± 0.5) − (30.1 ± 0.4)/θ where θ = 2.303 RT in kcal mol−1. A slower but competitive rearrangement yields racemic 2-vinyl-2,3-dihydrofuran. The mechanisms of these reactions are discussed in terms of electrocyclic processes.