ULTRAVIOLET SPECTRA OF ,~-AROYLACRYLIC ACIDS
May, 1949
2,P-Dichloroethanol by Reduction of 2,P-Dichloroacetyl Chloride.-A one-liter three-necked flask fitted with a reflux condenser, mercury sealed stirrer and dropping funnel was charged with 275 ml. of rigorously dried ether. To this was added 13.6 g. (0.36 mole) of pulverized lithium aluminum hydride (20% excess). Stirring produced a milky suspension. After fifteen minutes the addition of 88.6 g. (0.60 mole) of 2,2-dichloroacetyl chloride was begun and continued a t a rate determined by the r d u x ing of the ether. Two hours and a half was required for the addition, vigorous stirring being maintained throughout the addition and for thirty minutes thereafter. Excess hydride was destroyed by dropwise addition of water while the flask was cooled in a water-bath. Considerable heat was evolved and a white curdy precipitate, presumed t o be aluminum hydroxide, was formed. Hydrolysis of the intermediate was effected by the addition of 500 ml. of 10% sulfuric acid. The pale yellow ether layer, combined with two ether extracts of the aqueous layer, was dried over anhydrous magnesium sulfate, the ether removed by distillation at reduced pressure and the organic residue fractionated
[CONTRIBUTION FROM
THE
1711
under vacuum through an 18' column packed with glasz helices. The fraction collected between 37" and 38.5 (6 mm.) amounted to 44 g. or 63%. At T39 mm. pressure this boiled a t 145' (Heilbron lists 146 , pressure unknown). Analysis for chlorine was carried out by the Rauscher method.a Anal. Calcd. for C2H,ClZO: C1, 61.7. Found: C1, 61.2, 61.3.
Summary The three chloroacetic acids, their esters and acid chlorides are reduced smoothly by lithium aluminum hydride, the principle product in most cases being the chloroalcohol. The method is recommended as a procedure for the synthesis of 2,2-dichloroethanol. (3) Rauscher, Ind. Eng. Chcm., Anal. E d . , 9, 296 (1937).
BUFFALO,N. Y.
RECEIVEDNOVEMBER 19, 1948
RESEARCH LABORATORIES O F THE VICK CHEMICAL COMPANY]
Ultraviolet Absorption Study of Some Substituted P-Aroylacrylic Acids and 2-Carboxy-ychromones and Chromanones BY CHARLESI. JAROWSKI' In the preceding paper evidence was presented for the assignment of the 2-carboxy-5,7-dihydroxy- y-chromanone structure to the acid obtained by the acylation of phlorglucinol with maleic anhydride. hguments were also set forth to indicate that alkaline hydrolysis of 2carbethoxy-5-hydroxy-y-chromanone followed by acidification resulted in the formation of the corresponding acid.2 A study of the ultraviolet absorption of some 2carboxy-y-chromones, 2-carboxy-y-chromanones and @-aroylacrylicacids was initiated in order to add more evidence in favor of the structures postulated. Furthermore it was of interest to determine if the following chalcone-y-chromanone type of equilibrium did occur with the two acids studied
I
OH
8
I,R-H 11, R = OH
I OH
8
for it was quite possible that alkaline hydrolysis of the ethyl ester of I had opened the y-chromanone ring but that acidification resulted in cycliza( 1 ) Present address: Char. Pfizer & t o . , Inc., 11 Bartlett St., Brooklyn, N. Y. (1) Jaraaski, Uoran and Cramcr Taxa JOURNAL, 71,944 (1949).
AND
GLENNB. HE&
-
tion of the desired @- (2,6-dihydroxybenzoyl) acrylic acid to give the closed structure. Some chromophorically related compounds were likewise included in order to gain a better insight into the structural features accounting for the characteristic bands observed.
Experimental The compounds listed in Table I were previously prepared in this Laboratory by methods already described in the literature. Absorption Measurements.-Absorption determinations were made on a Beckmann Model DU Quartz spectrophotometer, using 1 cm. cemented quartz cuvettes and a hydrogen discharge lamp as the light source. Samples were made up in the range of 0.1% w./v. and dilutions to 0.01 and 0.001% were made with the same solvent. Samples which were run in 0.05 N alcoholic potassium hydroxide were made up to a concentration of 0.1% w./v. and dilutions were made with alcoholic potassium hydroxide. All samples except P-mesitoylacrylic acid followed Beer's law in the concentrations used. @Mesitoylacrylic acid gave anomalous results in the range from 250-300 millimicrons in the shift from 0.001 to O . O l ~ o concentration. Results shown in this range are the absorptions for the O . O l ~ osolution. Discussion of Results In Fig. 1 are shown the absorption curves obtained by plotting log E as a function of the wave length expressed in mp. The groups of curves have been displaced vertically by one log E unit,
CHARLES I. JAROWSKI AND GLENNB. HESS
1712
TABLE I MAXIMA, MINIMA AND LOGt VALUES FOR Curve Number
5
1
6
1
Structure of compound
,
THE COarPOUNDS STUDIED Solvent Xrnax. Loge
95% EtOH KOH-EtOH
CH-COOH
3
Ref.
*
95% EtOH
I1
4
I1
10
111
OH
KOH-EtOH
8
Vol. 71
Xmin.
Logr
274 351 243 282 382
3.94 3.48 4.07 3.84 3.75
243 302 264 310
3.15 2.81 3.52 2.56
283 320" 310 340"
4.29 3.60 4.53 3.80
244
2.83
264
3.10
*
95% EtOH
272 348
3.96 3.45
242 302
3.40 2.91
*
95% EtOH
253 316
3.88 3.47
237 284
3.62 2.92
'
95'% EtOH
238 252" 311
4.20 3.84 3.81
286
3.61
e
95% EtOH
247 272 345
4.19 4.00 3.43
233 261 315
4.06 3.97 3.24
*
95% EtOH
250 278" 355 238
4.03 3.98 3.55 4.29
230 270 320 345
3.92 3.96 3.27 3.08
95% EtOH
413 278" 238 260" 360
3.51 3.76 4.05 4.00 1.88
345
1.86
KOH-EtOH
244 270"
4.08 3.48
95%EtOH
296 370"
3.11 2.06
278
3.07
95% EtOH
271 344
3.92 3.36
242 302
3.16 2.84
OH
9
IV
7
v
8
VI
~ > ~ ~ c o o c z H 6 OH
,/ OH
1
VI1
2
VI1
14
VI11
13
VI11
Kc/ji:-cooH II
6
,I
CH 15
A
IX
I
OH
a
KOH-EtOH
-
13) Cramer, Schroeder. Moran, Nield, Edwards, Jarowski and Puetzer, J . Amcr. Pharm. Assn. Sci. Ed., 31, 439 (1948). (4) Rubemann and Bausor, J . Chcm. SOC.,19, 473 (1901).
(5) Kozniewski and Marchlewski, Bull. Acad. Sci. Crncuw, 81-95, (1906); J . Chcm. SOC.A h . , 90, 1, 759 (1906). (6)Russell and Frye, "Organic Syntheses," 81, 22 (1941).
ULTRAVIOLET SPECTRA OF &AROYLACRYLIC ACIDS
May, 1949
1713
TABLEI (Continued) Curve
Structure of compound
Number
Ref.
Solvent
hmax.
Log
Xmin.
Log
t
Shoulder in curve.
The maxima and minima together with their log E anol to @-(p-bromobenzoy1)-acrylicacid in the values for each curve are summarized in Table I. presence of sodium methoxide." In the absorption curves of simple a,p-unsaturated ketones the ethylenic band occurs between 220-250 mp.* Although the compounds . dealt with in this paper are not simple unsaturated ketones it is of interest to note that with the exception of the two trimethylphenyl derivatives (IX, XI), the ketonic compounds studied which are a,@-unsaturated (V, VI, VI1 and VIII) show a peak in the ethylenic region. In the curves for the substituted y-chromanones (I, 11, 111, and IV) and 2,6-dihydroxyacetophenone there is no peak in the 220-250 mp region. Consequently the absorption in this region appears to be significant in enabling one to choose between 1 a &aroyl acrylic acid and 2-carboxy-y-chromanone structure. A chromophoric relationship between o-hy6 droxyacetophenone and flavanones has been described by Tasaki? He showed that 2-hydroxyhydrochalcone gave a similar spectrum to flavanone. Notice the close agreement in the, absorption curves of I and X. The curves for I1 and phloroacetophenone are similarly related. lo These interrelationships are additional arguments in favor of the y-chromanone structure for I and 11. The general effect of alkali on the absorption curves of the four examples shown is to cause a shift toward higher wave length. In the curve for compound VI11 the carbonyl peak a t 358 mp is missing in alkaline solution. This suggests that in alkaline media the following might occur
s"
@ :
H
5 I
H
: C-C
