ALEXASDER I. I’OPOV AKD Iioam
774
naphthylamine the magnitudes of the deviations from ideality are determined mainly by the negative changes in n s E . Some values of Z s E and a s E for the three solvents are given in Table TI. The positive values of a s E for squalaiie $how that a greater ease of manoeuverability exists in this solvent, which decreases as the size of the molecule increases. The positive values of H s E for 7,8-benzoquinoline and a-iiaphthylamine occur as a result of the loss in cohesive energy between solvent molecules and the negative values of z s E are due to the solute molecules adopting a less random configuration. The value of AXsE for isooctane on a-naphthylamine is however positive and appears to be particularly large. The slightly larger numerical values of ASsE for p-xylene than for m- and o-xylene with these stationary phases indicates that a slightly more ordered orientation is imposed on the solute molecule. This may arise through steric hindrance caused by the terminal methyl groups of the pxylene molecule or through the manner in which both solute and solvent molecules are mutually polarized. With regard to the second aspect, it is interesting to observe that the order of elution and degree of separation of the CSC9 aromatic hydrocarbons achieved with both 7,8benzoquinoline and a-naphthylamine can be accounted for in the light of their electron polarizabilities. (Table VI1 shows the boiling point and electron polarizabilities of some of these hydrocarbons.) m-Xylene and ethylbeiizene having somewhat larger polarizabilities than p-xylene are selectively retained, the p-xylene now being difficult to separate from ethylbenzene. o-Xylene is eo well retained (ae” = 11.84 X that it
L).
HOLM
1-01, 65
emerges with isopropylbenzene (ae” = 11.50 X despite the difference in boiling point (ca. 8’). On 7,8-benzoquinoline, p-ethyltoluene and m-ethyltoluene are not resolved but severe peak broadening is evident. However, with the more selective a-naphthylamine a t 81’ the two isomers are partially resolved, the para isomer emerging first from the column despite its higher boiling point. This reversed order to that of their volatilities is due to selective retention of the methyltoluene, which may be attributed to its slightly higher polarizability. Again despite the closeness of the boiling points of 1,3,5-trimethylbenzene and o-ethyltoluene the latter is well retained for apparently the same reason (separation factor ca. 1.10 at 81’ on 7,8-benzoquinoline, relative volatility 1.003). TABLE
VI1
ELECTRON POLARIZABILITIES Hydrocarbon
Ethylbenzene p-Xylene m-Xylene 0-Xylene Isopropylbenzene p-Ethyltoluene m-Ethyltoluene o-Ethyltoluene 1,3,5-Trimethylbenzene
B.p., ‘C.
136 138 139 144 152 161 161 165 164
19 35 10 41 39 99 31 15 72
Electron polarizability per unit volume
11 58 X 11 54 11 61 11 84 11 50 11 56 11.60 11 75 11 65
Acknowledgments.-The authors wish to thank the Chairman and Directors of the British Petroleum Company for permission to publish the paper and Mrs. D. M. Irving who assisted with the experimental work.
ELECTRIC MOMENT OF 3-ETHYL-3-METHYLGLUTARIMIDE BY ALEXASDER I. POPOV~ AND ROGERD. HOLM Department of Chemistry, Northern Illinois University, DeKalb, Illinois Received September 23?1860
The electric moment of 3-ethyl-3-methylglutarimide has been found to be 2.84 D. in benzene solution. The structure and the direction of the group moments is discussed. It is shown that estimates of bond moments in such compounds are as yet inadequate. The H-h bond moment appears to be smaller than commonly supposed.
Introduction Barbiturates and hydantoins both possess anticonvulsant properties, and both share imide structures. Yet, 3-ethyl-3-methylglutarimide, (“Megimide,” Abbott Laboratories) while possessing a similar structure, is an effective antidote in cases of barbiturate poisoning. It was felt that the structural similarities and physiological activities of these compounds merited further attention, and that an investigation of the electric moments of these drugs may reveal significant differences in the electron distributions of certain bond systems associated with the observed activities. A survey of the literature reveals that exceed-
ingly little information is available on the dipole moments of imides. Accordingly, a study of the dipole moment of Megimide was undertaken as part of a general investigation of dipole moments and physiological activity. and as a means of obtaining information concerning the electron distribution in imide structures. Experimental Part
(1) Department of Chemistry, Northern Illinois University, De-
( 2 ) C. P. S m s t h and W. S. Walls, J. Am. Ckem. Soc., 64, 1854 (1932).
Kalb. Illinoi..
Reagents.-Thiophene-free benzene was purified by shaking it with concentrated sulfuric acid, with water, with sodium carbonate solution, and then again with distilled water. Following the extractions benzene was dried, distilled from PzOj, fractionally crystallized twice, again distilled from P 2 0 6 and then refluxed over sodium ribbon and distilled as needed, n% 1.4980, lit.2 1.4981.
r--
i 13
Cyclohexane W:LS shaken with a 1:1 mixture of concentrated sulfuric and nitric acids, with distilled water, dried overnight over calcium chloride, and then refluxed for several weeks over sodium ribbon. After distillation, it was fractionally crystallized seven times, refluxed over fresh sodium and then slowlv fractionallv distilled immediately before use, m.p. 6.4', lit.i 6.5". The 3-ei,hyl-3-methylglutarimide was sublimed a t 100' under 3 mm. pressure, m.p. 125.9- 126.2" cor., lit.4 123.5124". Bnal. Calcd. for C8H13NOz:C, 61.92; H, 8.44. Found: C, 61.94; H , 8.34. Apparatus and Procedure.--d navy heterodyne-type frequency calibrating instrument, model LM-16, was employed in measurements of dielectric constant .6 Provision was made for insertion of an external measuring cell in parallel with a precision capacitor having a capacitance range of 50 to 170 mmf. The precision capacitor was calibrated by noting the frequency produced by the variable oscillator a t different dial settings. This was accomplished by adjusting the heterodyne frequency between a harmonic of the variable oscillator with the precision capacitor, and a harmonic of the rrystal oscillator in the instrument to exactly 1000 cycles. -21000 cycle tuning fork was employed as a "zero beat" indicator. The sequence of harmonics was identified by the order and strength of the heterodyne signal. Solution dielectric constants, e x , were determined a t 91 .OOO kc. by means of the equation
where LC', is the inductance-capacitance product of the cell with solution. plus the reactance of the leads to the measuring instrument. Similarly, LC', and LC', represent the effective inductance-capacitance products when the cell is filled with a siandard substance (cyclohexane) and dry nitrogen, respectively. The tg and es are the corresponding dielectric constants of cyclohexane (2.0173)6and dry nitrogen (1.00058),7 respectively. Such a procedure eliminates the effects of the leads and permits measurrments to an accuracy of f0.01%,. The measuring cell is designed after that of Smyth and Morgan,* and conaists of three concentric platinum cylinders mth annular spacings of 0.05 cm. enclosed within the walls of a dewar flask. The total air capacitance of the cell was 72 mmf. and the cell volume was approximately 25 ml. During the measurements the cell was immersed in a mineral oil-bath maintained a t 25.00 f 0 . 0 1 O . Specific volume3 were measured using a Robertson variatione of the Ostwald-Springer pycnometer. Refractive indexes were measured a t 25.00 i. 0.01" with a Pulfrich refractometer, using a sodium lamp as a source of illumination. Calculation of Dipole Moment Values .-Least squares lines were applied to the solution data plotted against the weight fraction of the solute, w?. €12 = 61 awz (2) Y12 = Y1 PW? (3) nZ12= nZ1 ywg (4) The slopes of the lines, cy, P and y , respectively, represent dv12/dwz, dnZlg/dw, and dnlg/dw,. The subscripts 1 and 2 refer to the solvent and solute, respectively. The total molar polarization Plmwas calculated according to the Halverstadt-Kumler modificationlo of the Hedestrand equation."
+ + +
(3) R. W. Crowe and C. P. Smyth, J . Am. Chcm. S o c . , 73, 5406 (1951). (4) S. Benica a n d C . Wilson, J . A m . Pharm. Assor.. 39, 451 (1956). ( 5 ) H. Thompson a n d M. Rogers, J. Chem. Ed., 32, 20 (1955). (6) L. Hartshorn, ,J. V. 1,. Parry and L. Essen. I'roc. Phus. Soc., 68B,422 (1955). (7) R. J. W. LeFevre, "Dipole Moments." :3rd ed.. .\Iethuen a n d Co., Ltd., London, 1953, p. 45. ( 8 ) C. P.Bmyth a n d S. 0. Morgan, J . d m . Chem. S o r . , 60, 13.47 (1928). (9) G. R. Robertson, Ind. Eng. Chem., Anal. Ed., l i , Jci1 11939). (IO) I. F. Halverst.edt and W. D . Kumler, J . Am. C h p n ~ .S O C .64, . 2988 (1942). (11) G. Hedeetrand. Z.p k y s i k . Chem., 93,428 I l 9 W ) .
r n = 1.3 D m2 = 0 . 4 D
C-4
m3 = 2.4 D
\0 -m,
m,
m,
m4 =
+
2m,cos 60'
+
0.4
D
t Zm,
2 m 3 c o s 60'
= 2.3 D
bond
( a ) Amide
moments
applied
to
an
imide
P
/C.C,H
\
\0 (b) S u c c i n i r n i d r b o n d Fig. 1.-Electric
moments
moments of imides.
The i l l 2 represents the solute molecular weight. The distortion polarization was assumed equal to the molar refraction obtained for the sodium D-lines, and the calculation of RD was made by substituting n21 and y for €1 and a! in equation 5. The dipole moment of the solutr v a s calculated from the equation. p
= (0.2212) (P2- -
RD)V?
(6)
Results and Discussion The experimental data and calculated values are listed in Table I. The molar polarization and refraction indicated a dipole moment of 2.84 D. TABLE I MEGIMIDE Wt. of solute, E.
10aw2
0.00644 ,01471 ,02318 ,06490 ,11691 ,20824 ,28454
1.484 3.366 5.267 14.86 26.77 47.74 65.13
