DISSOCIATION OF 1,2-CYCLOPROPANEDICARBOXYLIC ACIDS
&May5 , 1963
TABLE V RATEOF PHOTODECOMPOSITION OF A 3.108 X
TABLE 111 AXALYSISOF COPOLYMERS Calcd. for homopolymer, Monomer C H
I I1 I11
78.26 4 . 3 8 i9.97 6.67 28.84 0 . 8 0
--Found, C
73.15 7 . 3 7 74.97 8 . 3 9 37.30 3.13
72.44 6 . 6 4 . . 73.95 i . 9 9 1.00 35.98 2.16 ..
%-H
N
TABLE IV ULTRAVIOLET SPECTRA OF POLYMERS A N D MODELCOMPOUNDS' hnax,
mw
log
r
295 2.93* Poly-( 1,4-phenylene oxide) 277 3.15 Anisole 278 3.26 Diphenyl ether 281 3.48 4-Hydroxydiphenyl ether 280 3.43 4-Methoxydiphenyl ether 28i 2.84* Poly-(2,6-dimethyl-1,4-phenylene oxide) 265 2.78 2,6-Dimethylanisole a I n chloroform * Extinction coefficient calculated on the basis of a 1: 1 copolymer. tetramethyltetrahydr~furan~' a t 0' afforded 0.16 g. (255; ) of yellow polymer, 74yc of which was soluble in benzene and had an intrisic viscosity of 0.059. Subjecting 2,6-diniethyl-p-benzoquinone diazide t o similar treatment afforded only a trace of (31) L. H e n r y , C o m p f . rend., 145, 490 (1900).
[COSTRIBUTION FROM
THE
JP SOLUTIOS
OF 2,6-DlMETHYLBESZOQUISOSE-4-DlAZIDE
Calcd. for copolymer, % C H
Compound
1321
Time X 10-2, sec.
In (Co/C)
Time X IO-?, sec.
2.1 3.9 5.7 7.2
0.193 ,367 510 ,677
9.0 11.4 13.8
In (Co,'C)
0.982 1.344 2.064
polymer. Thermal decomposition of 0.jC.l solutions of the two monomers a t reflux temperature (111. O D ) produced only traces of polymer. D. In Tetrahydrofuran.-Summarized in Table I1 are the results of decompositions in tetrahydrofuran. Tables 111 and I V give analytical and ultraviolet spectral data, respectively. The products from p-benzoquinone diazide are slightly yellow and those from 2,6-dimethyl-p-benzoquinone diazide are v hite. Polymer samples prepared from the hydrated nionomers only showed weak bands a t 1695 cm.-' (C=O str., conj.) in the infrared region while all polymers showed maxima a t 1195-1200 ern.-' (C-0-C s t r . ) . 31 (Fig. 1) Kinetics.-Tetrahydrofuran solutions 2.325 X and 3.108 X lo-* ,If (Table V ) in 2,H-dimethrl-P-benzoquinone diazide were placed in a flask equipped wit^ a meciianical stirrer, and blanketed by an atmosphere of nitrogen. Th$ apparatus was partially immersed in a bath maintained at 0 . During irradiation with a G . E . rlH-4 mercury vapor lamp, 1-ml. aliquots were withdrawn, diluted t o 10 ml. in the dark and placed in a Beckman DU spectrophotometer a t 0" to determine optical density a t 357 mfi. The quantum yield was obtained by using both uranyl nitrate and oxalic acid as standards.
DEPARTMEST OF CHEMISTRY, COLUMBIA UNIVERSITY, NEW YORK2 i ,
Iv. Y
]
The Acid Dissociation Constants of Some 1,Z-Cyclopropanedicarboxylic Acids. Some Comments Concerning Acid Dissociation Constants of Dicarboxylic Acids1 BY LAYTON L. McCoy2 AND GUENTERW. NACHTIGALL RECEIVED OCTOBER15, 1962 The acid dissociation constants of twenty-three substituted 1,2-cyclopropanedicarboxylicacids are reported. Some of the trends in the relationships between structure and dissociation constants are pointed out and discussed. A general discussion of some problems connected with acid dissociation constants, especially for dicarboxylic acids, is given.
As a result of previous studies on the preparation of polysubstituted cyclopropanes, 3-6 we have accumulated a number of sets of substituted isomeric 1,2-cyclopropanedicarboxylic acids. Many of the compounds were new, and others were not readily accessible previously. Earlier studies of the physical and chemical properties of substituted cyclopropanes often have been limited to readily available alkyl-substituted compounds. As the result of our work making cyclopropanes with carboxyl, ester, nitrile groups and halogen available, we have considered it desirable to investigate the physical properties of these cyclopropanes substituted with electron-withdrawing groups. The present report gives an initial survey of the acid dissociation constants of most of the 1,2-diacids available to us. Because our compounds comprise a rather heterogeneous group, we have not aimed for extremely refined results, but rather we have tried to obtain adequate data for the following purposes: (1) To observe any trends in the relationships between structure and acid dissociation constants, and if such trends were discernible to see if they matched similar trends in related succinic acids or maleic-fumaric acids. ( 2 ) To use 1 1 1 P a r t of this report is taken from a senior honors project b y G. W , Sachtigall (2) To whom inquiries should be sent. Present address: D e p a r t m e n t of Chemistry, University of Kansas C i t y , Kansas City 10, Mo. (31 I*. I,. McCoy, J . A m . Chem. So-disubstituted-l,2-diacids) to this generality concerning Kl and it is questionable whether other available data are adequate to support it. 4 rapid survey of all of the values for sets of cis-trans isomeric dicarboxylic acids listed by Kortiim, Vogel and Andrussow?5 indicates t h a t there are more exceptions than there are followers of the rule. Consequently, we doubt t h a t there is any validity of the "rule" t h a t K 1 for a dicarboxylic acid is larger for the cis isomer of a cis-trans pair. Conjugation of a cyclopropane ring with a carboxyl group is a possibility, and in so far as this can happen, an "explanation" of some of our results might be given as substituents hindering or aiding this conjugation. This would be based on similar proposals given to explain the increased acidity of cis-a,P-unsaturated acids relative to the corresponding trans isomer.26 However, we have some doubts about the completeness of the arguments concerning steric inhibition of resonance in these systems. In Table I1 we have listed various In spite of this error. the value of Kt,'K? somehow has essentially the correct magnitude (17) E. S. Gould, "Mechanism a n d Structuie in Organic Chemistry," Henry Holt and Co.. New York, S.\'., 1934, p , 243. (18) I ) . H . Ileutsch and E . R . Buchman, E x p e u i e f i l t a , 6, 462 (lY:O), ( 1 9 ) T h e values of K1 a n d K2 reported for ti.aiis-1,3-cyclobutanedicarboxylic acid b y Wassermann9 are 3.81 a n d 3.28, respectively, a t 23' and these values agree moderately well with our d u e s fur l-methyl-tvai~s-l.2-cycloi~rolianrdicarboxylicacid (Table I ) (20) E:. R . Buchman, A . O Xeims and h f . J Schlatter, J . A m ('hein. .Snc 6 4 , 270:: ( 1 9 4 2 ) . ( 2 1 ) R . K u h n and 4.\Vassermann, Heli8. G h t i n A r l o , 11, !io0 (1928) ( 2 2 ) H Bode, B e y . , 67B,3 3 2 (1934). ( 2 3 ) Reference 17, p. 211. ( 2 4 ) E . I, Bliel, "Sterochemistry of Carbon Compounds," hIcGraw-Hill Huuk C o . , Inc., S e w York, S .Y . , lY(;'2, p p . 187, 327-328. (2.5) G Kortiim, \V Yogel a n d K . Andrussow, "Dissociation Constants q B f Organic Acids in Aqueous Solution," Butterumrths, I,ondon, 1 S f i l 120) (a1 F u r discu
