Results The least-squares treatment of the ionization constants of cis-3- phenylcyclobutanecarboxylic acid and its p-OCH3, m-CHa, pF, mF, and m-CF3 derivatives in 50% aqueous ethanol (by volume) at 25'(Table I) us. uo values3 gives p=+ 0.256, with an average deviation of rt0. 013 pK,, and-log KO= 5.985.