Influence of Alcohols Upon the Uncatalyzed Reaction Between Resorcinol and Formaldehyde

Abstract

The rate of the conderisatior~ o l an uncatalyzed, eq~~in~olecular s o l~~l i o n of resorcinol and formaldehyde in water was determined a t 60°C. By replacing a portion of the water in this systern with aliphatic alcohols, a reduction in the ratcs of corldensation was noted a t the same temperature. Ho\vever, these reaction rates were found to vary widely among themsel\-es, depending 011 the alcohol used. These results are explained under the assumption of the intermediate forn~ation of herniacetals from the free formaldehyde and the alcohols. The retarding effect of these alcohols on the resorcinol-formaldehyde condensation is inversely related to their different tendency to form esters with acids, or acetals w~t h aldehydes, as reported by other authors. The gencral ilnportance of the formation of he~lliacetals is emphasized where forrnaldehycle is applied in the presence of alcohols. Discussion of Previous ExperimentsPrevious work (15) on the lti~letics of the i~ncatalyzed reaction of resorcinol and for~llaldehyde had shown the considerably higher reactivity of resorcinol as compared to phenol and to alkylated monophenols. For the various ternperatures ancl the different ratios of resorcinol t o formaldehyde which were investigated, a first ordcr rcaction rate constant served best t o represent the experimental data. These co~ldensations had been studied on solutions of resorcinol in dioxane and water, to which the calculated amounts of aqueous formaldehyde solutions were added. The charges were prepared in such a way t h a t the combined weights of resorcinol plus forn~aldehyde (as C H 2 0 ) represented 40% of the total weight of the solutions; the dioxane amounted to 2G.7y0; 33.3% water was present, partially introduced as part of the aqueous formaldehyde solutio~~. These mixtures were reacted in a resin flask kept in a constant temperature bath, and the progress of the reaction determined from the gradual decrease in free forn~aldehyde on san~ples removed during the experiment. Influence of SolventsSince i t appeared of interest to learn the influence of solve~lts upon the reaction rate of the uncatalyzecl resorcinol-formaldel~yde condensation, equinlolecular mixtures of resorcinol and formaldehyde were reacted a t GO°C., in which the dioxane in the above formulation was replaced by various aliphatic alcohols. One experiment was also carried out in an all aqueous mecliu~n, replacing the dioxane by water. As found in dioxane, a first order reaction rate constant served best to represent the experinlental data.

Electronic Interpretation of the Uncatalyzed Reaction Between Resorcinol and Formaldehyde in Alcohols and Dioxane

“…The reaction of alcohols was recognized by Raff and Silverman (16) as the reversible formation of a hemiacetal, equations for which are given below for reaction under mildly acid conditions: I t should be pointed out that R-0-H in the abovc mechanism inclucles not only the alcohol added to moclify the resorcinol reaction but also rcpresellts resorcinol itself which is also competing writ11 the resorcinolate ion. Reversible forination of hell~iacetals, therefore, is felt to take place bctwecn resoi-ci~lol ancl formaldehyde as well as between the added alcohol ancl forn~aldeh>-de.…”

“…Raff and Silverman did not attempt to explain in their papers (15,16) the retarding effect of aqueous clioxanc on the condensation of resorcinol and formaldel~yde. Since dioxane is probably too stable to be rupti~recl by formaldehyde under these conditions, a chemical reaction in this sense is ii~lliltely.…”

Kinetics of malachite green fading in alcohol–water binary mixtures

“…Solvent effects on reactivity may be very large. Alcohols, as cosolvents, can change the rate of organic, inorganic, and enzymatic reactions 1–9. Malachite green (MG + ) is a triphenylmethane dye.…”