Abstract
Photoacoustic calorimetry was used to quantify the antiaromaticity of 1,3-cyclobutadiene (CBD) by measuring the heat release accompanying its formation via photofragmentation of a polycyclic precursor. In combination with quantum yield measurements and thermochemical calculations, this measurement provides an enthalpy of formation for CBD of 114 ± 11 (2σ) kilocalories per mole (kcal/mol). The extraordinary reactivity of this prototypical antiaromatic hydrocarbon had previously made its heat of formation inaccessible except by theoretical calculations. Relative to a hypothetical strainless, conjugated diene reference, CBD is destabilized by a total of 87 kcal/mol, 32 kcal/mol of which can be attributed to ring strain and 55 kcal/mol to antiaromaticity (compared with 21 kcal/mol for the aromatic stabilization of benzene). Relative to a reference with isolated double bonds, CBD9s antiaromaticity is 48 kcal/mol (compared with 32 kcal/mol for the aromaticity of benzene).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
