To det.ermine the scop e of the rc~ction of zinc oxide with iso mers of eugenol, t he effect of change~ I.n the posltl<;ln of the substltuents in the benzene ring on the ionization co nstants and reactivity of these Isomers has been studied.The ionization .const~nts of eugenol i~o mers as well as those of newly synthesized all yland pTopenylbenz.Ole aCids ",.ere d etermined by spectrophotometric and potentiometric techl1lques. The ll1fiuence of ll1ductive, r esonance and stcric effects of t he substituents on the io,nization constants has been discussed and the s ubstituent constant for the Hammett equatIOn pJ(o-pJ( = up has been calculated. For the 4-and 5-substituted allyl and propenyl derivatives, the Hammett equation is valid.. Vicinal trisubstituted iso mers do not harden r eadily with zinc oxide due to the steri e hindrance of the side chain. The unsy mmetrically trisubstituted d erivatives react rapidly III the presen?e of Zll1~ acetate. BeSides the stenc effect s of ths s ubstituent gro ups the rate o~ the chelatIOn reactIOn IS to a lesse r degree dependent on the ionization constants as indicated. by the s horter setting time of chavibetol-zinc oxide slurries cOITlpared to those eontallllng eugenol.

Tht' thermodynamic ioniza li on conSlanls of mela and para subs lituled allyl· and p ropenyl benzoic ac ids wer£' detNmined poten tiom elr ically in aq ueous e thanol of varying elhanol co ncentra tion. The /)/\ va l ups increasl' wit h increasing e thanol content. The rela li ve acid s trength does not vary wi th 1\,.\ \Vor,\': 1 \11 , 1-alld prol,en yll)(' ll wi(' acid s. ('hangc of pK wil h dieleclric co nSl a nl , Hamm e ll Sit!IlHI constall t s. ion i zatio n ('(l il s t a llt s . pK va lu es in e thanol -wa te r, s igma ('o ns t an ts ill l't ba nol-,,,,I(' r . ,ubS lillll ('d "('nwi(' acids.