Noms
0
I1 (11) m. p. 47.3-47.5'
(1) m. p. 107-108" oxime rn.p. 134-135"
t
Picard and Kearns AI(0Pr)z _ (91%1 __f
sideration by the fact that both conlpounds I1 and V retain essentially the same nielting points after repeated meltings, after reCrOs 0 crystallizations from a variety of solvents, 0 -+----H and after prolonged drying a t reduced pressures over desiccants. (IV) (84%) (V) It has not been possible to apply the exm. p. 102-103" rn.p. 92-93' isting data for compound V to any reasonoxime m. p. 135-136' able structures of possible products from Compounds I and IV are identical, as shown by the treatment of 4,4'-difluorobenzophenone with mixed melting points, and by comparisons of their aluminum isopropoxide oximes and 2,4-dinitrophenylhydrazones. It would ordinarily be anticipated that the The analytical comparisons carried out in these aluminum isopropoxide reduction of the ketone laboratories are summarized in Table I. would proceed normally, with greater chances for stray reactions with a zinc and alkali reduction. TABLEI Hence, the results obtained are puzzling. The AXALYTICAI, COMPARISONS OF COMPOUNDS I N SYNTHETICclaim of Picard and Kearns is, nevertheless, in SCHEMES error, and the substance supposed by them to be Analyses, % the substituted benzhydrol was not completely Mol. wt. Carbon Hydrogen Compound Sourcea Calcd. Found Calcd. Found Calcd. Found characterized and in fact does not even show the I G&B 218 220 7 1 . 9 6 ... 3 . 9 3 required analysis for this substance. The data I 2,4-dinitrophenylsummarized here do support the assigned struchydrazone G&B ... ... .. .. 397 407 ture of our compound I1 as 4,4'-difluorobenzhyI1 G&B 220 218 7 0 . 9 0 7 0 . 5 8 4 . 5 2 4 . 5 8 drol. I1 $-nitrobenzoate G&B 369 368 65.03 65.16 3 . 5 5 4 . 0 0 Experimental.-The reactions diagrammed 204 206 7 6 . 4 6 7 6 . 9 0 4 . 9 4 5 . 1 9 I11 G&B and sources of parent ketones are presented and I11 3,3'-dinitroderivative G &B . , . ... 53.07 5 3 . 2 6 2 . 7 4 2 . 9 4 discussed in the literature cited, with two exceptions. The conversions of I1 and I11 t o I and IV P&K ,., ... 71.96 ., . 3.93 .. G&B of V to IV were accomplished in the yields shown V P & Kb 220 361 7 0 . 9 0 73.57 4 . 5 2 4 . 7 2 with the aid of chromic anhydride in acetic acid, " A s prepared by Gunther and Blinn (G & B) or by in the usual manner. All other comparison Picard and Kearns ( P & K ) . As prepared by P & K , data were obtained with accepted procedures. but recrystallized and analyzed by G & B from sample Melting points are uncorrected. obtained from Dr. Picard.
Fc)-g-c>F
Compounds I1 (b. p. 150-154" (5 mm.)) and V (b. p. 143" (3 mm.)) exhibit depressed melting points in admixture. They are probably not dimorphic since supercooling the melts of each and cross seeding did not effect conversion of one to the other. Their ultraviolet absorption characteristics are shown in Table 11. TABLEI1 ABSORPTION CHARACTERISTICS EtOH Compound Amin.
e
239 202 v 241 367 I1 V" 240 367 a I1 = 45.3%, v =
I1
+
EtOH hmax.
e
EtOH hmin.
c
EtOH Xmax.
265 1431 269 868 271 265 1352 269 867 271 265 1463 269 900 271 54.7%.
(3) See Wilds, "Organic Reactions," Vol 11, John Wiley & Sons, Inc., New York, N . Y., pp. 178-223.
DIVISIONOF ENTOMOLOGY UNIVERSITY OF CALIFORNIA CITRUSEXPERIMENT STATION RIVERSIDE, CALIFORNIA RECEIVED JUNE 5, 1950
The Preparation and Properties of 5-Ethyl-5(1-methyl-1-nitroethyl)-barbituric Acid BY E. B. HODGE
e
1211 1234 1266
Solvation phenomena are eliminated from con-
The preparation of ethyl ethyl-(1-methyl-1-nitroethy1)-malonate has recently been reported. Since i t seems that there is no record of the hyp(1) E. E. Van Tamelen and G . Van Zyl, THISJOURNAL, 71, 835 (1949). Since this note was written, the preparation of 5-methyl-5(1-methyl-l-nitroeteyl)-barbituric acid has been reported; E. E . Van Tamelen and G. Van Zyl, ibrd., 72, 2979 (1950).
.I172
NOTES
..C
notic properties of a barbituric acid with a 3-alkyl substituent containing a nitro group, i t was thought to be of interest to prepare the barbituric acid from the above compound. Considerable difficulty was experienced in bringi:ig about the condensation between urea and ethyl ethyl- (I -1iietliy1 1 -nitrorthyl)-malonate. The desired compound was firidly obtained in 9% yield using a modification of a procdure described hy AZcElvain arid Gorst .'The pharmacological properties of the sodium salt of the conipound were studied by Lk. J. S . Spencer of the Phdrrnacology 1)epartment ot this 1,aboratory. He reports the following properties. Intraperitoneal LDaU(iiiici 360 mg./kg. 490 mg /kg Oral LD50 (mice) Hypnotic dose (EL) in mice) 110 mg./kg KO hypnotic action observed follo~%iiig oral administration in i i i i u ~ Experimental 5-Ethyl-5-( 1-methyl-1 -nitroethyl) -barbituric Acid ,-To a mixture of 4.8 g. (0.08 mole) of urea, 11 g. (0.04 mole) of ethyl ethyl-(l-methyi-l-nitrc~thyl) malonate, and 100 ml. of dry t-butyl alcohol was added 0.5 g. of sodium methoxide. The alcohol was distilled from the stirred mixture at about 30 ml. per hour and fresh t-butyl alcohol was added continuously at the same mte. One-half gram portions of sodium methoxide were added every hour until 3.5 g. had been added. One hour after the last portion of sodium methoxide had been added, the t-butyl alcohol was distilled under reduced pressure. The residue was cooled, 100 ml. of water was added, and, after a short period of stirring, the water was extracted with 50 ml. of ether. Acidification of the water with concd. hydrochloric acid gave 0.9 g . of white ppt., in. p. 233-237". Recrystallization from ethanol raised the in. p . (cor.) to 238-240" (dec.). Anal. Calcd. for C9€11&305: C, 44.44; H , 5.31; S , 17.27. Found: C, 44.53; 11, 5.46; N, 17.00. iMcElvdin and Goesez had used sodium 6-butoxide as a catalyst In the reaction reported the more readily available sodium niethox~rlcwLi\ found to give equally good rcsul t i (2)
S bl McLSlvain and 31 1 C O C ~ P THIS , JOURNAL, 66, 222G
i1943)
PHARMACEUTICAL RESEARCH U~vrsrolr COMMERCIAL SOLVEVTS CORPORATION RECEIVED J U V E 5, 1950 'rERRE H ?UTE, I VDiAYA
The Resonance Energy of Benzene BY L)c,i. ' i r n 1' HC)RNI(.
Only a small displaceiiient of the carbon atoms is necessary to distort a normal benzene molecule with 1.39 A. C-C bonds t o a configuration where C-C bonds are alternately 1.34 and 1.51 -Le.,
a.;
the configuration represented by a single Kekul6 structure without resonance. Since the displacements are small, the energy expended in distorting the molecule can be obtained from the force constants derived from the vibrational spectrum. If, as is sometimes assumed, the bond length is a sufficient criterion of bond type, this energy might be expected to equal the resonance energy.
Vol. 72
Since the C-H distance and H-C-C angle of KekulC benzene are the same as those of benzene, the distortion involves otily the two symmetry coordinate$' 0 >,I
= (l/v'f;)(rl
+
c
Y?
= (l/dt3)(yJ -
Y-
r3
+ + + rd
-t y 3 -
rl
rd
y5
+ I:, -
ih)
whose forms are illustrated in Fig. 1. The 7's are the changes in the C-C bond lengths. The force constants corresponding to these symmetry coordinates have been designated A, and A2 by Crawford and &filler1who found that AI = 7.83 X 1Oj dynelcm. Inserting the frequencies of the Bz, vibrations obtained by Mair and Hornig2 (Table I) into the equations of Crawford and Miller, two possible sets of force constants for the 132,, species are obtained. They are given in Table 11. TABLE I FREQUENCY OF BzuVIBRATIONS IN BENZENE Cornpound
VI#,
CfiHG CtJL,
cni
ns, cm. - 1
--I
1311 1887
1147 825
TABLE I1 HI
