Volumetric Study on the 1,3-Dipolar Cycloaddition Reaction of Diazodiphenylmethane with Several Olefins

Article abstract of DOI:10.1246/bcsj.56.680

A high pressure kinetic study was made of the 1,3-dipolar cycloaddition reaction of Ph2CN2 with dimethyl maleate (DMM), dimethyl fumarate (DMF), methylacrylate (MA), maleonitrile (MN), fumaronitrile (FN), and acrylonitrile (AN) in toluene at 25 deg C.The activation volumes (ΔV^*) at 1 bar obtained for DMM, DMF, MA, MN, FN, and AN are -23.4 +/- 0.5, -22.3 +/- 0.2, -19.8 +/- 0.4, -21.5 +/- 0.6, -21.0 +/- 1.1, and -23.9 +/- 0.5 cm³ mol^-1, respectively.The reaction volume (ΔV) for the reaction between Ph2CN2 and DMM was determined dilatometrically by taking advantage of supersaturation of the cycloadduct in solution; ΔV = -24.5 +/- 0.5 cm³ mol^-1 and ΔV^*/ΔV = 0.955.The present volumetric information coupled with a kinetic analysis shows that Firestone's biradical mechanism is not the case; the concerted mechanism is supported.The experimental result is compared with that of a recent ab initio molecular orbital calculation with respect to the activation and reaction volumes.