Buy article online - an online subscription or single-article purchase is required to access this article.
organic compounds
The single-crystal X-ray structures of two photochemical products of 2-cyclohexenone have identified them as the head-to-head and head-to-tail cis-anti-cis dimers (C12H16O2) formed by 2 + 2 addition. The cyclobutane ring is twisted in the head-to-head isomer but flat in the head-to-tail compound.