CRYOSCOPY 01'DIARYL SULIWNES IN SULFURIC Acru
Sepl. SI 19,X TABLE V
pK' VALUESIK WATERAND
IN
TABLE
x H 3-OCHa 4-OCHa 4-Br 4-CHa
3.54 3.60-6.54 2.68-3.89 1.81-2.30 3.33-6.20
tJK'
1.97 1.97 1.96 1.99 1.96
50% aqueous m e t h a n o l 4 2 M LiCl Moles/l. gKlC X 10% (relative)
6.71-8.87
2.49
6.53-6.75 6.60-6.75 5.24-6.78
2.57 2.48 2.52
VI
HYDROLYSIS RATECONSTANTS IN 50% DIOXANE BENZYLIDENEPYRUVIC ESTERSXGHL!H=CHCOCOOCH3
50% METHANOL AT 25"
BENZYLIDBNEPYRUVIC AC~DS; XCH4CH=CHCOCOOH Water Moles/l. x 10%
4395
H H H 4-OCH3 4-Br 4-CHa
Reference acids", Benzoic 5.30-11.60 4.15 7.18 5.03 Cinnamic 1.49-3.23 4.47 7.30 5.10 Average deviation of PK' values in pK' units: benzylidenepyruvic acids in water, 0.05; in 50% methanol, 0.02; reference acids in water, 0.02; in 50% methanol, 0.01. J . F. J . Dippy, ref. l a , p. 206, lists the following values a t 25': benzoic acid in water, K' = 6.27-6.527 X f O - 5 (pK' 4.185-4.20); trans-cinnamic acid in water, K = 3.65 X (pK' 4.43). Dippy's values were determined by conductivity measurements and include activity corrections of about f0.02 pK unit. 'The pK' values in methanol were obtained by substituting pH values as given 'by the glass electrode, and have only relative validity.
f0.2". Calculated ergy E for d In k/dt =
oc.
HC1,b moles/l. x 102
25.0 25.0 44.9 25.2 25.2 25.0
10.37 4.28 4.28 4.28 4.28 4.28
Temp.,Y
x
Ester, moler/l.
x
20.00 8.00 8.00 8.00 6.40 8.00
10'
k' X 10s hr.-'c
14.3 6.0 29. 6d 5.9 6.1 5.6
Reference ester: ethyl acetate 25.2 4.28 22.76-24.44 12.6 Determined by titration a t zero time. probable error f 1%. The activation enmethyl benzylidenepyruvate calculated from E / R T 2 , is about 15'kcal./mole.
drolysis of the methyl benzylidenepyruvates, however, is about 90 times as fast as that of the methyl benzoates. In the benzoates, steric hindrance by the phenyl group inhibits the addition of water to the carbon atom of the carboxyl group as postulated in the Ingold mechanism.14 Ethyl alyst were found to have the expected first-order acetate was hydrolyzed as a reference substance hr.-l, or twice as kinetics with respect to the concentration of ester with a rate a t 25' of 12.6 X and of hydrochloric acid. The activation energy fast as the methyl benzylidenepyruvates. Methyl for the hydrolysis of benzylidenepyruvic acid cal- pyruvate in water solution hydrolyzes 1.2 times as culated from rates a t 25' and a t 45' was found to be fast as methyl acetate15 and ethyl cinnamate has a ~ ethyl about 15 kcal./mole. Timm and Hinshelwood4 rate 0.22 times that of ethyl a ~ e t a t e . In report a value of 18.24 kcal./mole for the activa- cinnamate and methyl benzylidenepyruvate the tion energy of methyl benzoate in 60% methanol phenyl group is farther away from the carboxyl and 16.20 kcal./mole for ethyl acetate in 60% group so that i t exerts little steric effect, and as a result the rates are higher than that of methyl ethanol. The effect of substituent groups on the rate of benzoate. acid-catalyzed hydrolysis of methyl benzylidene(14) S. C. Datta, J. N. E. Day and C. K. Ingold, J . Chem. SOL.,838 (1939). pyruvate is slight (K' = 5.6 to 6.1 X hr.-l) (15) A. Skrabal, F. Pfaff and H. Airoldi, Mo?totsh., 46, 148 (1924). and is of the order of magnitude of these effects in the benzoic acid series. The actual rate of hy- hTEW YORK,?r. Y.
[CONTRIBUTIOSFROM
THE
DEPARTMEST O F CHEMISTRY, DUQUESKE USIVERSITY ]
The Cryoscopic Behavior of Organic Compounds in Sulfuric Acid. 111. Diary1 Sulfones BY H . HARRYSZMANT
AND
RONALD L.
LA4PINSKI
RECEIVED JASUARY 14, 1952 Additional cryoscopic data of substituted diaryl sulfones in sulfuric acid are reported. The effect of the substituents on the basicity of the sulfone group is interpreted in terms of changes in the electronic structure of the latter.
In a recent publication' from this Laboratory it was shown that sulfones are weak bases in sulfuric acid, and that substituents present on the two aryl groups affect equilibrium (1) so that the observed "i" factor can vary between the values of 1 and 2 . In view of the fact that di-(p-nitroR)SO,
R'
+ HnSO4
[
:)SO*H]+
+ HSO4-
(1)
phenyl) sulfone gave an c i i l l factor of 2 while di(p-nitrobenzyl) gave an i ' i l l factor Of 3 it was concluded that the site of the protonation is the (rather than nitro) group' Since the (I)
11. I1 Szni;rnt :rncl C,, A . 13rost,'l'ii1s J O ~ J R X A I , , 73,4 1 i , ? (19.51).
cryoscopic study of the sulfones in sulfuric acid seemed to offer an opportunity to compare the basicity of the sulfone group as a function of the electronic effects caused by the substituents R and R', we have extended this work so that a total of eleven diaryl sulfones has now been investigated. Experimental Di-(p-chlorophenyl) sulfone, di-(p-aminophenyl) sulfone, and bis-(3-nitro-4-chlorophenyl) sulfone were obtained from the Monsanto Chemical eo. and were carefully purified and dried before use. Di-(m-nitrophenyl) sulfone2was prepared by the nitration of phenyl sulfone, while 2,4-dinitrophenyl phenyl sulfone3 and 2,4-dinitrophenyl 4-chlorophenyl sul( 2 ) C . A. Ruehler and J C.Masters. J . Ova. Citcin., 4, 262 (1!43!)), ( 3 ) Ullrnann and Pasdermadjian, Ber., 34, 1131 (1901).
H. HARRY S z m n AND RONALD 2.LAPINSKI
-1396
Yol. 7-1.
folie4 were prepared by the Friedel-Crafts reactioci of %,4- R, /O--II... Og,..O-H -e-+ dinitrophenylsulfenyl chloride with benzene and chloro\O( - ) benzene, respectively, followed by the oxidation of the sul- R j s ” , O . . H-O/+ fitlcs. o-Nitrophenylphenyl sulfone3 was prepared by the K ,,@...H-O -H oxidation of the sulfide obtained froin the rcactioii of thiophenol and a-chloronitrobenzene. .. ()/+ \O( - ) The apparatus and experimental tccliniquc \\-ii4 thc sainc 111 a b previously described.6 Keprcseiitiitivc cryo5col)ic ITICRSurcments arc listed iri TLiblc 1. The arguments used in arriving a t the above-
.
\# R>yo-H .
Ani
Ui-(J~c-nitrophenyl) 0.04013 sulfone 0.04186 Bis-(3-nitro-4-chloro- 0.03288 phenyl) sulfone 0.03318 Di-(p-chlorophenyl) 0.03073 sulfone 0.03521, o-Nitrophenyl phenyl 0,04088 0.04253 sulfone 2,4-Dinitrophenyl 0.03798 phenyl sulfone 0,03586 2.4-Dinitrophenyl 4- 0.03671 chlorophenyl sulfone 0.03917 Di-(p-aminophenyl) 0,01484 sulfone 0.01407 0-Nitrophenyl 0.02748 p-tolyl sulfone 0.02914
Time,
F.p,, “ C .
hr.
(initial)
9
10.040 9,725 9.947
5.5 17.5 8 .3 78.5 23 . 73
1!1 24 3 23 22.5 8 68 2 weeks 3 5
10.130 9,863 !I 673 !I . 990 9.705 !3 71.5 {t , 9 2 2 1) 774
9.902 $ ) . 873
9.546 9,951 !). 755
AT
“i”
1 28 0 , 3 5 5 I :i1 0.24; 1 . 2 0 0.248 1 . 2 2 0.188 0 . 9 6 0.21s 1.06 0.30.i
0.283 0 297 0 317 0,297
0.307 0,324 0.327 0,305 0.226 0 , 248
1 , 18 1.14
1.36 1.35 1,36 1 , i3.5
:
