872
NOTES
VOL.
25
in each case was prepared from equal volumes of absolute ethanol and either distilled water or 4N sulfuric acid. Immediately prior to use the samples of stilbene and 4-dimethylaminostilbene were purified by chromatography on alumina followed by recrystallization from ethanol thereby, ensuring that any traces of the cis isomers were removed.
sorption and emission spectra of a variety of arylsubstituted oxazoles were reported. Similar data have been obtained for another important class of liquid scintillator solutes, the lJ3,4-oxadizaoles. The synthesis4 of these compounds and evaluation as liquid scintillator solutes6 have been reported DEPARTMENT OF ORGANIC CHEMISTRY previously. Two new pyridyl derivatives are deOF ADELAIDE UNIVERSITY SOUTHAUSTRALIA,AUSTRALIA scribed in the Experimental. The absorption and fluorescence data are presented in Table I; the mean wave length, is that wave length which bisects the area under the Liquid Scintillators. XII. Absorption and fluorescence spectrum. Fluorescence Spectra of 2,5-Diaryl-1,3,4The effect of an oxadiazole nucleus on the specoxadiazoles trum of an aromatic system is very similar to that of a p-phenylene group. p-Terphenyl (Amax 280, DONALD G. Om, VERNONN. KERR, F. NEWTONHAYES, e 2.5 X lo4), p-quaterphenyl (Am, 300, E 3.9 X AND ELIZABETH HANSBURY lo4),and p-quinquephenyl (A, 310, E 6.3 X 104)6 may be compared with the five analogous oxadiReceived November 6, 1969 azoles having the equivalent number of rings.
x,
The importance of spectral properties of scintillators has been o ~ t l i n e d ,at ~ ?which ~ time the ab(1) Work performed under the auspices of the U. S. Atomic Energy Commission. (2) D. G. Ott, F. N. Hayes, E. Hansbury, and V. N. Kerr, J . Am. Chem. Soc., 79, 5448 (1957).
(3) R. K. Swank, W. L. Buck, F. K. Hayes, and D. G. Ott, Rev. Sci. Znstr., 29, 279 (1958). (4) F. N. Hayes, B. S. Rogers, and D. G. Ott, J . Am. Chem. SOC.,77, 1850 (1955). (5) F. N. Hayes, D. G. Ott, and V. N. Kerr, Nucleonics, 13, No. 12, 38 (1955). (6) A. E. Gillam and D. H. Hey, J . Chem. Soc., 1939, 1170.
TABLE I ABSORPTIONAND FLUORESCENCE SPECTRAL DATA^
282 300b 313 310 292 298 285 284 308 317 308 289 30 1 283 294 297 303 313b 331 297 313 335 332 29gb
2.6 4.5 1.8 2.7 3.3 2.4 2.3 2.5 4.0 2.3 3.2 3.1 3.3 2.4 3.2 3.6 3.7 6.1 3.6 2.6 2.4 2.3 3.3 4.0
336 364 372 364 364 373 355 335 372 380 366 342 356 335 344 347 344 378 406 355 377 392 370 354
350 380 392
396 422 370 390 408 388 370
360 388 392 380 372 388 362 360 394 402 386 366 380 358 370 374 382 396 442 378 420 412 388 378
315c
4.8
373
390
392
-
-
353 390 396 382 354 370 350 362 360
-
a Wave lengths are in mu; the solvent was cyclohexane for absorption and toluene for fluorescence unless otherwise indicated. Solvent was 2% chloroform in cyclohexane. Solvent was chloroform; a band at 325 mu, E 4.8 X lo4, is also present.
Fluorescence and absorption maxima of the o5aadiazoles occiir a t shorter wave lengths than f a r the corresponding oxazoles. Substituent groups influence the maxima in essentially the same manner for both types of compounds, and thus the discussions presented previously regarding correlation of spectra with structure of the oxazoles2 apply, qualitatively, to the 1,3,4-oxadjazoles. EXPERIMENTAL'
The following compounds were prepared by the procedures given previously4: l-Benzoyl-2-nicotinoylhydrazinee, m.p. 234-234.5', after recrystallization from ethanol.
(7) Melting points are uncorrected. Microanalyses are by Micro-Tech Laboratories, Skokie, Illinois.
Anal. Calcd. for CI3HllN3O2:C, 64.72; H, 4.60. Found:
C,64.69; H, 4.56. 3- [5-Ph.en&%( 1,S,+$-ozadiazolyl) ] pyridirze, m.p. 121.5122O, white needles from toluene-ligroin. Anal. Calcd. for C&N30: C, 60.94; H, 4.06; N, 18.83. Found: C, 70.03; H, 4.24; N, 18.38. I-Benzoyl-2-isonicotinoylhydrazinelm.p. 232-233.5", white needles from toluene. Anal. Found for Cl3H1lN302: C, 64.77; H, 4.80. 4- [6-Phenyl-2-( l,d,4-ozadiazolyl) ]pyridine, m.p. 142-1 43 O , white needles from toluene. Anal. Found for Cl8HgN~O:C, 70.16; H, 3.98; W, 18.82. Fluorescence and Absorption Spectra were obtained as described earlier.*
Acknowledgment. The authors are grateful for the technical assistance of Mrs. Ruth Lier. BIOMEDICAL RESEARCH GROUP Los ALAMOS SCIENTIFIC LABORATORY OF CALIFORNIA UNIVERSITY Los ALAMOS, N. M.
