NOV.20, 11152
LbSORPTION SPECTRA AND IODINE
[CONTRIBUTION FROM THE
REACTION OF DIHYDRO-0-NAPHTHOIC ACIDS
LABORATORY O F CHEMICAL PHARMACOLOGY, XATIONAL CANCER ISSTITUTE, O F HEALTH, PUBLIC HEALTH SERVICE, FEDERAL SECURITY AGESCY]
5660
KATIOSAL IKSI’ITUTES
Components of Podophyllin. VII. Absorption Spectra and Reaction with Iodine of the Dihydro-0-naphthoic Acids1 BY
LhTHOXY
iv. SCHRECKER, GERTRUDE Y. GREENBERG AND JONATHAN
L. HARTWELL
RECEIVED MARCH 27, 1952 The ultraviolet and infrared absorption spectra of the dihydro-P-naphthoic acids are reported. with iodine in aqueous bicarbonate has been studied.
In connection with the investigation of the structure of the apopicropodophyllins,2 it was desired to compare the absorption spectra of simple model compounds, and the readily prepared3--j dihydro6-naphthoic acids were selected for this purpose. The ultraviolet absorption spectra of these acids do not appear to have been published previously. However, related data have been presented by v. Auwers and M011er,5 who studied the molecular refractions and dispersions of the corresponding ethyl esters and found that the exaltations increased in the order : 1,4-dihydro-?-naphthoic acid ( I ) , 1,2-dihydro-2-naphthoic acid (11) and 3,ddihydro-2-naphthoic acid (111). This was explained by v. Auwers as follows: I n I, which is analogous to an a-alkyl-a$-unsaturated fatty acid, there exists only a single conjugation between the carboxyl group and the ethylenic double bond. I1 is analogous to styrene, with the double bond conjugated with the aromatic ring. Finally, there exists a “cumulated” conjugation (ring-double bond-carboxyl group) in 111, which is analogous to an a-alkyl cinnamic acid. Comparison of I11 with @-naphthoicacid (IV) showed that the exaltation of the refraction was somewhat lower in the former, and the exaltation of dispersion higher.
I
I1
The ultraviolet absorption spectra (Fig. 1) are consistent with the observations of v. Auwers. 1,d-Dihydro-2-naphthoicacid (I) does not show any absorption maximum down to 203 mp, with the exception of the low intensity peak a t 273 mp, which is also present in 1,2,3,4-tetrahydro-2naphthoic acid (V), Since the a,@-unsaturated carboxyl is not in conjugation with the benzene (1) Paper V I : M. V. N a d k a m i , P. B. M a u r y and J. L. Hartwell, THISJ O U R N A L74, , 280 (1952). (2) A. W. Schrecker and J. L . Hartwell, ibid., 74, 5676 (1952). (3) A. Baeyer a n d E. Besemfrlder, A n n . , ‘266, 187 (1891). (4) C. G . Derick and 0. Kamm. THISJ O I J R N A L , 38, 400 (1916). (.ii) I;. v . Auwers a n d R Muller, J . p v a k t . Chem., [ 2 ] 109, 124 ( 1925). ( 6 ) T h e spectrum of 1,2,3,1-tetrahydio-2-naphthoic acid a n d t h e v c r y similar spectrum of tetraliu appear in I
