The Komarowski Reaction FREDERICK R . DUKE, Kedzie Chemical Laboratory, East Lansing, AMMich.
H
EXPERIMERTAL R E S U L T S AND DlSCUSSIOY
I G H E R alcohols react with aromatic aldehydes in concentrated sulfuric acid to produce highly colored products; this observation is generally credited to Komaromlti ( 4 ) . The reaction has been adapted t'o the colorimetric determination of traces of higher alcohols in the presence of ethanol (1, 3,5 ) . S o study of the actual chemistry involved in the reaction has ever been reported, although a fairly complete listing of compounds other than alcohols which produce color has been made (2). I n the present study, i t was found possible to isolate only resinous material from the reaction products in concentrated sulfuric acid. From 12 144 hydrochloric acid or 9 M sulfuric acid, however, products were isolated which indicate the mechanism of the rcaction. The alcohols studied include the eight loiver aliphatic alcohols, methanol through the butanols, and cyclohesanol; benzaldehyde was the other reactant, although one series of experiments was done with p-dimethylaminobensaldehyde. Benzyl chloride was always isolated from the reaction products when the alcohols, excepting methanol, ethanol, and tert-butanol, were allowed to react with benzaldehyde in 12 M hydrochloric acid. The secondary alcohols, isopropanol and cyclohesanol, yield, in addition, dibenzalacetone and dibenzalcyclohexanone, respectively. tert-Butanol produced a large quantity of resin, hut no benzyl chloride or other pure compound.
The results of Experiments I and I1 are listed in Table I, and those of Experiment I11 in Table 11. Experiment IV demonstrates that the oxygen of the benzaldehyde appears, after reaction, I? the aliphatic carbonyl group. The following mechanism IS proposed: R2CHOH RjHC
[
Ce3-C-
R2C= 0
+
+
+RZHC
+
+ H2O
(1)
H CsHsCHO +CsHb -C-OC RI + H
0-,C
H'
]+
R1
+ CsH,CHO+colored
CeH,CH>'
.
+ R2C
=
(2) 0
(3)
aldol condensation products (4)
Primary Alcohols. The concentration of carbonium ion in equilibrium n-ith primary alcohol in concentrated hydrochloric acid is extremely small; hence, the reactions indicated by Equations 2 and 3 proceed very slowly. The aldehyde which is formed condenses rapidly to yield colored resinous products. lfethanol and ethanol are converted t o the corresponding carbonium ion only with estreme difficulty, if at all; hence the lack of reaction. Secondary Alcohols. Secondary carbonium ions exist in a relatively much higher equilibrium concentration under given conditions than do primary ions. Thus, the oxidation of secondary alcohols proceeds more readily. Furthermore, the aldol condensation products involving ketones are more slowly formed and in general, more stable to polymerization than the aldehyde products. Thus, not only is benzyl chloride isolated, but t h e aldol anhydride RS rrell; the slower reaction of the ketones also allows their isolation as dinitrophenylhydrazones (Experiment
EXPERIMENTAL
I . Ten grams of the alcohol (c.P. or U.S.P., carbonyl-free), 10 grama of redistilled benzaldehyde, and 50 ml. of 12 M hydrochloric acid w r e gently boiled together under a reflux in a 500-ml. round-but?omed flask for 4 hours. -kt the end of this time, the unreacted benzaldehyde and alcohol were removed by steamdistillation, and the residue was esaniined. The experimc'rits were repeated using 9 M sulfuric acid with no significant change in results. , From the isopropanol reaction, yellow crystals (from alcohol) of dibenzalacetone were isolated, melting point 112" C. (corrected). Calculated for C1,HlrO; C 87.157,, H 6.02%; found, C 8i.28%, H 6.157,. From tlie cyclohesanol reaction, yellon- crystals (from alcohol) of dibenzalcyclohexanone were isolated, melting point 118 C. (correctedi. Calculated for C U O H ~ ~CO 87.567,, , H 6.617,; found, C Si.5070, H 6.72%. 11. Esprrinients I were repeated, but instead of being steanidistilled. the reaction mixture was transferred to a separatory funnel, 50 nil. of ether were added, and the aqueous layer was discarded. The ether layer was extracted successively with four 50-ml. portions of 8574 phosphoric acid follon-ed by 50-nil. portions of' 807, sulfuric acid until the last portion remained colorless. (If 9 JI sulfuricacid was used as the catalyst, 10 ml. of concentrated hydrochloric acid \yere added before the phosphoric acid extractions t o convert any benzyl alcohol to benzyl chloride.) After being washed with water, 5% sodium bicarbonate solution, and water, the ether layer was dried with anhydrous calcium chloride and distilled. Benzyl chloride, boiling point 177" C. (corrected), was obtained. Calculated for C;H,Cl, C1 28.01 %; found, C1 27.97%. 111. Ten grams of the alcohol and 10 grams of p-dimethylaminobenzaldehyde were mixed with 50 mi. of 9 M sulfuric acid in a 250-ml. distilling flask equipped with a condenser. The mixture was heated until 10 ml. of distillate had been collected; this was treated with 10 nil. of a 1% solution of 2,4-dinitrophenylhydrazine in 6 .VI hydrochloric acid. T h e precipitated hydrazones were dissolved in acetone and passed through a column (1 X 15 cm.) of activated alumina. The aliphatic hydrazone passed through the column, while the aromatic hydrazone was retained. Evaporation of the acetone followed by recrystallization from alcohol provided the compounds upon which melting points were run. I\'. Ten grams of isopropyl chloride and 10 grams of benzaldehyde were mixed and saturated with anhydrous hydrochloric acid. After the mixture had stood for 5 days a t room temperature, i t was concentrated by distillation a t 10-mm. pressure. The residue was recrystallized from alcohol, yielding yellow crystals of dibenzalacetone, melting point 112"C . (corrected).
111). tert-Butanol yields no benzyl chloride or pure aldol condensation product. It is the opinion of this investigator that a different mechanism is involved in the tertiary alcohol reaction; this point is now under investigation.
O
'
+
+H
Table I. Reactions with Benzaldehyde Alcohol
Benz,yl Chloride Grams
Condensation Product Grama .......... 0
Methanol 0 Ethanol 0 .......... 0 n-Propanol 0.1 Resin 0.2 n-Butanol 0.2 Resin 0.5 Isobutanol 0.3 Resin 0.7 Isopropanol 0.6 Dibenzalacetone 1.3 aec-Butanol 0.7 Resin 1.4 Cyclohexanol Dibenzalcyclohexanone 1 . 5 0.8 tert-Butanol 0 Resin 2.0 Concentrated hydrochloric acid a8 catalyst. Sufficient unreacted benzaldehyde was recovered t o indicate t h a t main reaction products are those indicated.
Table 11. Dinitrophenylhydrazones Obtained hleltipg Dinitrophenylhydrazones Point, C. Alcohol Obtained (Corrected) Primary alcohols 0 Isopropanol Acetone (trace) 125 sec-Butanol Methyl ethyl ketone (trace) 11 1-2 C yclohexanol Cyclohexanone (trace) 158-9 tert-Butanol 0 9 M sulfuric acid as catalyst, pdimethylaminobenzaldehyde the aromatie constituent.
661
662
V O L U M E 19, N O . 9
Color. I n acid solution, the condensation product is capable of resonance without separation of charge after the addition of a proton to the carbonyl osygen:
I n support of this view, benzyl chloride, aldol conderisation products, and ketones (as dinitrophenylhydrazones) hsor been isolated from the reaction between benzaldehyde and higher aliphatic alcohols in high concentrations of hydrogen ion. -1mechanism for the oxidation is proposed, which ip supported by the formation of dibcnzalacetonc f om benzaldehyde ani1 isopropyl chloride under anhydrous conditions.
T h i s type of resonance undoubtedly accounts for ,he color. SUMMARY
Experiments have been performed which indicate that the color produced in the Iiomarowski reaction is due to aldol condensation products which are formed through the two consecutive reactions:
+ RzCHOH +C,H,CH?OH + RzC 0 R,C = 0 + CsHjCHO +condensation products
CeHjCHO
LITERATURE CITED
Coles, H. W., and T o u r n a y , IT.E., ISD.EX.
C H m f . , -4x.k~. ED., 14, 20 (1942). Fellenberg, Th. von, Chon.-Zfg.. 34, 791 (1910). Fellenberg, Th. von, M i f f .Lebensm. Hyg., 1, 311 (1910). Komarowski, C h e m - Z f g . ,27, 807, 1806 (1903). Penniman, W. B. D., S:nith, D. C., and Lawshe, E. I., IND. ENO. CHEM.,ANAL.ED.,9, 91 (1937).
PRESENTED before t h e Divieion oi .Inalytical and hlicro Chemist,ry a t t h e 108th Meeting of the .IJIERIC.AN CHEMICAL SOCIETY, rltlantic City, pi. J K o r k done in part in Frick Chemical Laboratory, Princeton, N . J.
Analysis of Hypochlor ite-Hypo bromite Sohtions LADISLAUS FARKAS AND I)I@NhCHERI LEWIN Department of Physical C h e m i s t r y , T h e Hebrew C'niversity, Jerusalem A method for the simultaneous determination of sodium hypochlorite and hypobromite, without and in the presence of bromide, chloride, bromate, and chlorate, is based on the selective reduction of hypobromite under certain conditions with alkali phenol solution; the sum of hj-pochlorite and hypobromite is estimated by arsenite and iodine in the usual way. The most suitable conditions for the analytical procedure are given, and the influence of various salts and other factors on the accuracy of the determination is described.
I
S T H E course of a n investigation carried out in this laboratory on the reaction between sodium hypochlorite and bromides ( I ) , an analytical procedure was required for the determination of sodium hypochlorite and sodium hypobromite separately in the presence of chloride, bromide, chlorate, and bromate ions. Various methods for determining hypochlorite in the presence of chlorite, chlorate, and hypobromite in the presence of bromite and bromate are described in the literature. (2, 3). T h e methods a r e based on the different osidation potentials and oxidative capacities of the substances in these two series of osyhalogen acids. Hair-ever, the system containing bo! h series of oxyhalogen acids has not yet been sufficiently investigated. The only publication on this subject is in the book of de Konirlcli and lleineke (If), b u t their procedure does not differentiate between bromide and hypobromite ions and allows only the total bromine to be estimated. Similar difficulties are encountered in the estimation of hypobromite by oxidizing it t o bromate, since the bromide present would also be oxidized t o bromate (10, 12). The method presented in this paper is based on the different' rates a t which phenol reacts in alkaline solution with hypochlorite and h>-pobroniite. T h e bromination of various phenols has been thoroughly investigated by Francis and Hill (6, 7 ) . These authors and Sprung (15) used this reaction for the quantitative determination of phenols. The brominating agent used was elementary bromine in acid solution obtained by acidifying a bromide-bromate mixture and estimating the excess bromine iodometri::illy. In a similar way, Kolthoff (8) used the bromination method for determining salicylic acid and Iiolthoff and Lingane (9)extended this method to the determination of other phenol deriyatives. They worked with a large excess of bromine water and converted phenol into trihromophenol bromide which was detrrniiiied either gravimetrically or iodometrically. Pollak ( I S ) u s d phenol in order to determine bromine in acid solutions.
Chapin ( 2 ) was the first to usti phenol for the reduction of sodium hypobromite. He found that phenol reacts selectively with sodium hypobromite, but not n.ith sodium bromite, and dweloped a method for the determination of bromite in alkaline solution in the presence of hypobromite. The chlorination of phcnol by hypochlorous acid was studied by Soper and Smith (Id), who found that the rate of reaction is proportional t o the concentrations of the free hypochlorous acid and the phenoxide ion. Esperiments on the reaction of phenol n.ith hypohromite-hypochlorite mixtures are described below, and an analytical method for the simultaneous estimation of both the hypochlorite and the hypobromite is given.
Table I. Influence of Salts and of the pH of Hypobromite Solution on Reduction of H\pobromite with a n ilLaline Phenol Solution ( I n each PH
experiment
12.1 12.1 12.1 12.1 12.1 12.1.
9.2 8.6 9.2
0 5975 millimole oi sodiuni h ~ p o b r o m i t etnben)
Salts Added Giam 0.2 SaCl 0 . 6 SaCl 1.0 SaCl 2.0 SaCl 0 . 2 CaCh
SaBrO Error llzllzmoie
., . . . . .
0 0000 0 0005 0 0000
+ 0 . 2 lrgcil 0 2 CaCh - 0 . 2 3IgC19
. . ..
-0
0 2 CaCh
2 NaClr
0 0 0 0 0 0
0000 0005 000x 0036 0047 0060
