C. S. XARVGL, J, W. SHACKLETON, C. M. HIMELAND
1824
[CONTRIBUTION FROM THE
JOHX
Vol. 64
WHITSOX
NOYESCHEMICAL LABORATORY, UNIVERSITY
OF ILLINOIS]
XI.' The Effect of Naphthyl and Biphenyl
The Dissociation of Hexaarylethanes.
Groups BY C. S. MARVEL, JOHNW. SHACKLETON, CHESTER M. HIMELAND JOHN WHITSON Work by Bachmann and Kloetzel*has indicated that the very high dissociations reported in the older literature for triarylmethyls containing pbiphenyl, a-naphthyl and &naphthyl groups are in error. This communication confirms their results and extends them to a larger number of derivatives. The dissociations were measured by the magnetic susceptibility method previously de~cribed.~ To be comparable degrees of dissociation should be measured at the same concentration. This is not always possible because of solubility difficulties. It is possible, however, to calculate all the dissociations at 0.1 molar concentration by applying the mass law. That this calculation is justified for toluene solution has been shown recently by Preckel and S e l ~ o o d . We ~ have extended this to benzene solutions and determined the degree of dissociation of di-a-naphthyltetraphenylethane a t 25' a t different concentrations. The results of these experiments are given in Table 1. 'rABLB 1 DISSOCIATION OF DI-a-NAPHTHYLTETRAPHENYLETHANE AT 25" IN BENZENE SOLUTION
%
- x Sol
Ethane
Molarlty
7 0 6 63
0.107
:i 31
I ti; 0 SVI
1 0:i f)2,5 0 I2.i
X 108
a. %
0 0315
25'2 27-12 36*2 L5*4 i i f j *7
ti296 6550 675 o832
a a t 0 1 M calcd. from mass law, %
26*2 27 1 2 27 =t% 26 + 3 ' ( 1 +. i
L .
The aryl substituted ethanes which have been studied are reported in Table I I .
Discussion of Results A11 except one of the ethanes have been studied previously, and our methods of preparation and the properties of the intermediates in general checked those reported. The new ethane, diphenyltetra-P-naphthylethane,was prepared by standard procedures and characterized as the peroxide. Bachmann and Kloetzel measured the molecular weight in freezing benzene and calculated the dissociation of di-p-biphenyltetraphenylethane as 16Y0 a t 0.032 M , of hexa-p-biphenylethane as 76% a t 0.0086 M, of di-a-naphthyltetraphenylethane as 28--31% a t 0.04 X , and of di-P-naphthyltetraphenylethaneas 6-9% a t 0.04 M, If these values are calculated t o 0.1 Jf by means of the mass law they become 9, 86, 30 and .i:"L, respectively. These values are in fair agreement with the values determined by the magnetic susceptibility method. I t should be rioted that Muller, MullerRodloff and Bunge,j have shown that tri-p-biphenylmethyl is 100% free radical in the solid state. Apparently the free radical is less soluble than the ethane and in the solid state only the one phase exists, whereas in solution the radical and ethane are in equilibrium. The dissociations of the series of ,&naphthyl derivatives show that there is a steady increase in dissociation as the number of P-naphthyl groups increases, but the degree of dissociation of the hexa-substituted compound is less than that reported by Tschitschibabin and Korjagim6 The marked difference in the dissociation of the di-i3
TABLE I1 Ethane
Tetra-fi-biphenyldiplienylHexa-p-biphenylDi-fi-naphthyltetraphenylTetra-p-naphthyldip heuylHexa-p-naphthyl-
Di-a-naphthyldi-p-biphenyldiphenyl-
21
Concn. ethane,
0.1 .0125 .1
.1 .0002 ,0125 .I
(1) F o r the eleventh communication in this series see THISJOUR63, 1892 (1941). (2) Bachmann and Kloetzel, J . Ore. Chcm., 8, 362 (1937). (3) Miiller, ef al., A n n . , 610, 235 (1935); 621, 89 (1935); Roy and hlarvel, Tms JOURNAL, 59, 2622 (1937). ( 4 ) Preckel and Selwood, rbid.. 63, 3397 (1941). NAL,
%
8.9 1.34 6.16 7.85 0.56 1.113 8.3
- - x Sol. X
a Measured,
105
%
a calcd. a t 0.1 'M,%
0.6539 .0874 .B887 .GGB8 .6928 ,6869 ,5512
lS* 2 56 =t 10 6* 2 13* 2 80 * 15 53 * 10 54* 2
18+ 2 26+ 5 6* 2 13" 2 21 *10 24* 5 54+ 2
naphthyl derivatives (6 ;t 2%) and of the di-anaphthyl derivative (26 * 2%) indicates again (6) Miiller, Mliller-Rodloff and Bunge, Ann., 680, 251 (1935). ( 6 ) Tschitschibabin and Korjagin, J. p r a k f . Chem., 88, 303 (1918).
THE: PREPARATION OF ORTHOESTERS
Aug., 1942
1825
The following new compounds were characterthe importance of the steric factor. This was also ized : pointed out by Preckel and Selwood.* Phenyldi- 6-naphthylmethy lperoxide, m. p. Another point which should be emphasized is that there is a difference in the di- and tetra-sub- 168-1 69O . stituted @-naphthyl derivatives (6 and 13%), Anal. Calcd. for C,4Ha02: C, 90.25; H, 5.30. whereas in the alkyl substituted compounds in Found: C, 90.12; H, 5.84. this general series these differences between diPhenyldi-p-biphenylmethylperoxide,m. p. 151and tetra-substituted compounds were not found.] 152'. However, the hexa-substituted derivatives in the And. Calcd. for ClsH4602: C, 90.51; H, 5.59. alkyl and aryl series all seem to fall in about the Found: C, 90.54; H, 5.94. same range (25-357,). From the data of Gomberg Phenyldi-0-naphthylmethylchloride,m. p. 159and Schoepfle' it seems likely that our 0.1 M 160'. solutions of di-a-naphthyltetraphenylethane were Anal. Calcd. for C2,H17C1: C1, 9.42. Found: supersaturated. C1, S.92. All of the aryl-substituted ethanes except tetraSummary p-biphenyldiphenylethanewere relatively stable The degrees of dissociation of several hexaas indicated by the constant value for their magnetic susceptibilities over twenty-four hour pe- phenylethanes combining a-naphthyl, @-naphthyl riods. Tetra-p-biphenyldiphenylethanesolutions and $-biphenyl radicals have been examined by deposited heavy white crystalline precipitates in the magnetic susceptibility method. The dissotwenty-four hours. ' Hexa-p-naphthylethane ciations observed are lower than reported in the showed a decrease in color and a change in mag- older literature. The difference in the effect of an netic susceptibility on exposure to diffused day- CY- and a @-naphthylgroup on the degree of dissociation is very marked. light over a period of one week. (7) Gomberg and Schoepfle, THISJOURNAL, 89, 1682 (1917).
[CONTRIBUTION FROM THE
URBANA, ILLINOIS
LABORATORY O F ORGANIC CHEMISTRY
RECEIVED MAY 18, 1942
OF THE UNIVERSITY OF WISCONSIN]
The Preparation of Orthoesters BY S. M. MCELVAIN AND J, WALTER NELSON
The work in this Laboratory to date indicates that the only general method that is available for the preparation of ketene acetals of the type RCH=C(OEt)z involves the elimination of the elements of ethyl hypohalite from an a-halogenated orthoester by the action of metallic sodium. l Consequently, the preparation and study of these higher ketene acetals are dependent upon the availability of the corresponding orthoesters as starting materials. The present paper is a summary of a large number of experiments which had as their objective practical and reliable procedures for the preparation of the esters of ortho acetic acid, certain of its derivatives and higher homologs. Two methods of preparation of orthoesters that would seem to be of general applicability have been reported in the literature. One of these is (1)
Walters and McRlvain, THISJOURNAL, 8!4, 1482 (1940).
the Tschitschibabin procedure2 which involves the reaction of a Grignard reagent with ethyl orthocarbonate RMgX + C(OEt), +RC(0Et)a 4- EtOMgBr This procedure is analogous to the widely used Tschitschibabin method for the preparation of acetals by the reaction of a Grignard reagent with ethyl orthoformate, HC(OEt)3. While the latter reaction is a very useful preparational method, all of the experience in this Laboratory points to the conclusion that the reaction between a Grignard reagent and orthocarbonic ester is not a satisfactory method of preparation of orthoesters. Instead of the desired orthoester the reaction products are practically wholly a mixture of the ketal RZC(0Et)z and the ether RsCOEt and all attempts to alter this result have been consistently unsuccessful. (2) Tschitschibabin, Bar., 88, 563 (1905).
(3) McBane, M.S. Thesis, University of Wisconsin 1 Y 4 I
