DONALD S. NOYCE AND LLOYD R.SNYDER
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Kinetic Measurements.-Measurements were carried out as described previously.J Thermostated solutions were mixed to give reaction solutions of the appropriate concentrations, and samples were withdrawn periodically and the
[CONTRIBUTION FROM
THE
Vol. 81
concentration of thc unsaturated ketone determined spectrophotometrically. BERKELEY 4, CALIF.
DEPARTMENT O F CHEMISTRY, UNIVERSITY OF CALIFORNIA, BERKELEY]
Carbonyl Reactions. VIII. The Kinetics of the Acid-catalyzed Condensation of Benzaldehyde and p-Nitrobenzaldehyde with Methyl Ethyl Ketone. Some Observations on p-o Correlations1 BY
DONALD s. NOYCEA N D LLOYDR.
SNYDER
RECEIVED AUGUSI11, 1958 The condensation of benzaldehyde and methyl ethyl ketone in acetic acid, catalyzed by sulfuric acid, proceeds v i a the inter(11); I1 undergoes competitive cleavage, esterification mediate 8-fiydroxy ketone, 4-phenyl-4-hydroxy-3-methyl-2-butanone and dehydration in this medium. The condensation of p-nitrobenzaldehyde with methyl ethyl ketone proceeds similarly, but with no evideiice of cleavage or esterification of the intermediate P-hydroxy ketone. The examination of the p-o correlation gives further insight into situations where such correlations may fail. acid in acetic acid as solvent. When 4-(p-nitrophenyl)-3Introduction methyl-3-buten-2-one was prepared following the procedure I n continuing the study of the mechanism of acid- of Burckhalter and Johnsons material identical to that obcatalyzed reactions,2-6 we have carried out kinetic tained above (m.p. 94-95") was obtained, in contrast to the (Burkhalter and Johnson). Heller studies of the condensation of benzaldehyde (I) reported value of 1"0: a value of 96 . and of p-nitrobenzaldehyde (IV) with methyl reports Kinetic Procedures.-Anhydrous acetic acid and sulfuric ethyl ketone, to supplement the study previously acid were prepared as described previously.2 The kinetic rep~rted~ of. ~anisaldehyde and methyl ethyl ke- procedures were those outlined Rate data tone. The results obtained are generally similar were obtained by following the appearance of the characteristic absorption bands for the unsaturated ketone and the to those reported earlier. There are, however, regenerated aldehyde as appropriate using a Beckman DU differences in degree which make necessary a fairly spectrophotometer. detailed kinetic analysis for each system. The Preparation of Intermediate 8-Hydroxyketones.-From similarities and divergencies provide additional preliminary kinetic results the following conditions were chosen to isolate the intermediate 8-hydroxyketone, 4-pheninsight into the reaction processes involved. yl-4-hydroxy-3-methyl-2-butanone(11), from the condenGettler and Hammett' have studied the kinetics sation of benzaldehyde and methyl ethyl ketone. To 156 g. of the base-catalyzed condensation of benzaldehyde of methyl ethyl ketone was added 10 g. of sulfuric acid. The and methyl ethyl ketone. They have also carefully temperature was adjusted to 23" and 92 g. of benzaldehyde After maintaining the resulting solution a t 25' for reviewed and corroborated the evidence showing added. 12 minutes, the mixture was poured into ice, extracted with that the formation of 4-phenyl-3-methyl-3-buten-2- benzene, and the combined extracts washed with water. one (111) takes place in acid to the essential The excess solvent and methyl ethyl ketone and unreacted exclusion of the isomer, l-phenyl-l-penten-3-one1 benzaldehyde were removed under reduced pressure below An oily brown residue (20 g.) resulted, which was apwhich is formed exclusively under basic conditions. 60". proximately 75y0 keto1 11. Crystallization of this oil from Similarly the formation of 4-(p-nitrophenyl)-3- pentane a t Dry Ice temperature yielded flocculent, colorless methyl-3-buten -2-one occurs under conditions of crvstals. melting well below room temDerature. Anal. Calcd: for CI1HlaO2:C, 74.i2; €1, 7.92. Found: acid-catalyzed condensation. i 4 . 5 i ; H, 8.21. From the results to be reported here, it is pos- C,The spectral characteristics of the isolated material indisible to detail the effect of substitution in the cated that i t was contaminated with 270 of benzaldehyde and aromatic ring upon the relative rates of the various 27, of the unsaturated ketone 111. In a similar fashion following conditions dictated by prereactions processes which have been shown to be liminary kinetic results, an impure sample of .l-(p-n;trokinetically important. phenyl)-4-hydroxy-3-methyl-2-butanone (IV) was prepared.
