The UV and polarized IR spectra of argon matrix isolated cyclobutadiene and its Id-, 1, 2-d2-, 1, 4-d2-, I%", l, 2-W2-, and I, I-W2-1abeled derivatives are reported. Above 250 nm, the UV spectrum contains no peaks with an extinction coefficient larger than 10 L Ml cm-l, but a weak absorption tail extends throughout the UV region. The absorption rises abruptly below 250 nm. The IR peak positions mostly agree with previous reports where these are ...
![3-oxabicyclo[3.2.0]hept-6-ene-2,4-dione Structure](https://image.chemsrc.com/caspic/183/10374-07-9.png)
![3-oxabicyclo[2.2.0]hex-5-en-2-one Structure](https://image.chemsrc.com/caspic/476/22980-23-0.png)
