Trans-1,2-bispyrazylethylene (t-BPE) shows many interesting photoreactivities compared to those of stilbene because of lone pair electrons on the pyrazine ring nitrogen atoms. Since $(n, π^{*})$ state has about the same energy as $(π,π^{*})'$ state in t-BPE, the photochemical addition of t-BPE to tetramethylethylene is a good model reaction to see whether major reaction is $(π^{2s} + π^{2s})$ concerted photocycloaddition reaction or photoaddition reaction through a radical intermediate.
The major product was isolated by column chromatopraphy and fractional vaccum sublimation and is characterized to be a noncyclic photoaddition product, 2,3-dimethyl-5,6-bispyrazyl-2-hexene.
The structure of the adduct was confirmed by the characteristics in their NMR, IR, UV, and Mass spectra and by elemental analysis.
trans-BPE는 피라진 고리에 있는 질소 원자의 비공유전자쌍 때문에 stilbene과 비교하여 어려가지 다른 광반응성을 나타낸다. 또한 $(n,π^{*})'$ 상태와 $(π,π^{*})'$ 상태의 에너지 준위가 거의 동등하므로 TME에 대한 t-BPE의 광반응은 이의 주반응이 photocycloaddition 반응인지 아니면 radical 중간체를 거치는 photoaddition 반응인지를 구별하는 좋은 모형이 될 수 있다.
주 생성물은 column chromatography와 분별진공승화에 의해 분리하였고 이의 구조는 NMR,IR,UV,Mass Spectra와 원소 분석에의해 광부가생성물인 2,3-dimethyl-5,6-bispyrazyl-2-hexene임을 알았다.
