Synthesis and ionization constants of meta- and para-substituted 3-carboxy-1-phenyl-2-methylcyclopropenes

3-Carboxy-l-phenyl-2-methylcyclopropene and the p-OCH[lowered 3], m-CH[lowered 3], p-F, p-Cl and m-Cl derivatives were prepared by the addition of ethyl diazoacetate to the appropriately substituted 1-phenyl-propyne, followed by hydrolysis. The ionization constants were determined in 50 percent ethanol at 25[degrees]. A plot of -log Ki as a function of the appropriate [sigma][degrees] values gave a Hammett rho value of 0.57 (-log K[lowered o] 6.45).