Ionization constants and reactivity of isomers of eugenol

Abstract

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.

Ionization constants of substituted benzoic acids in ethanol-water

“…This is especially true for the p·propenyl group since p-propenylphenol is not very stable in basic media. A comparison of the secondary a con· stants determined previously from the pK values in water of guaiacol and substituted guaiacols [1], and the primary constants obtained from the respective benzoic acids are given in table 7. These values for the allyl groups agree within ± 0.02.…”

“…[1]-The precise end point was obtained by plotting ~pH/~ ml or its recipro cal versus milliliters of NaOH ' added and taking as the end point the number of millilite rs of NaOH at which ~pH/~ rnl is a maximum or ~ ml/ ~ pH is a minimum [2]-From the law of mass action and as s uming (1) +---:----"-;====== [HA] ~ concentra tion of th e undi ssoc iated ac id , and [A -] = co nce n t ration of anion of th e acid .…”

A review of zinc oxide-eugenol type filling materials and cements

“…Addition of 1 to 10^polystyrene or poly(methyl methacrylate) produces a modest Increase In strength, adhesiveness and marginal sealing characteristics [22, [ 36 ]. The effect of the position of substituents on the behavior of the Isomers as evidenced by their Ionization constants and reactivity with zinc oxide has been determined [37].…”

EBA cements :

“…Attempts to synthesize the cupric or nickel isoeugenolates also were unsuccessful. (23) and the effect of the position of substituents on the behavior of the isomers as evidenced by their ionization constants and reactivity with zinc oxide was determined (24).…”