NOTES
Sept., 1962
1739
About five concentrations of different ketones were taken and from the slope of the straight line (2). AB was calculated by the least squares method. Relaxation times were determined by a 3-em. BYH. PI’. SRIVASTAVA,~ K. C. LAL,AND M. N. SHARMA standing wave technique as described earlier.8 The viscosities of different solutions were dePhysies Ilepartrnent, Lucknow Unaverscty, Lucknow, Indza termined by Hoppler’s precision viscometer. Received March 6, 196.2 The results recorded in Table I show that (a) I n an earlier communication,* the relaxation the ratio of the relaxation time, 7 , to the “averaged times of some aliphatic ketones in dilute solutions mutual viscosity” increases with the molecular calculated from the equations proposed by Debye3 size; (b) for the same ketone the ratio T / ~ A B and Wirtz and c o - w o r k e r ~mere ~ . ~ 10-15 times and shows better agreement in decalin as well as bentwice the experimental values, respectively. On zene as compared to r / r ] B ; and (e) on calculating the basis of Debye’s equation, the relaxation times the relaxation time by replacing TB by $AB in the of methyl ethyl ketone and methyl n-propyl Debye equation, the calculated values still are ketone also were not proportional to the solvent considerably higher than the experimental results. viscosities, Le., benzene and d e c a h 2 Acknowledgment.-The authors are grateful to Hi116 has shown that relaxation time in dilute solution is related to the “mutual viscosity” be- Dr. P. N. Sharrna, D.Sc., Professor of Physics, for tween the solvent and the solute. More recently guidance. (8) A. Vsas and H. N. Srivastava, J . Set. Ind. Re?. (India), 18B, Vaughan, Purcell, and Smyth’ have derived a n expression for a quantity called “averaged mutual 399 (1959). viscosity,” ?AB, defined by
RELAXATION TIMES BND “AVERAGED MUTGAI, VISCOSITIES” O F SOME ALIPHATIC KETONES
?)in
= fA“A
4-fB2r]B
+
2fAfEGAB
(1)
where qrn is the viscosity of the mixture, fA and f~ the mole fractions of the solute and the solvent, and and V B the corresponding viscosities. It also has been shown that “mutual viscosity”6 as well as “averaged mutual viscosity” have the same order of magnitude. Equation 1was rewritten as
Y
=
XGAB
+ vn
(2)
where
Methyl ethyl Benzene“’ 3 . 7 .. 6.24 .. ketone I>ecalin 2 . 7 0.52 1 . 3 1 5.19 Methyl n-propyl Benzene ,I.5 .54 7.59 8.34 ket,one Decalin 4.4 .70 2 . 1 5 6.29 RIet,hyl n,-a ivy1 kdme t3eenaene 5 . 6 ,Cil 9 . 4 4 8.73 I fi-n-propyl k pt,one Br~llzcl-rr 5 . ‘1 , (i:< 9 . I 1 8.5’7 - V A B could not he measured for niixtures of benzene and methyl ethyl ketone because of the low viecosit,y. Accuracy of relaxation time measurements mas &10%. Accuracy of viscosity measurements was f 2 % . .-
( I ) Meteorological Office, New Delhi, India. ( 2 ) H. N. Srivastava, J . Sci. I n d . Res. (India). under publication. (3) P. Debye, “Polar Molecules,’’ Chemical Catalog Co., 1929. (41 A. Spernol and K. Wirtz, 2. Naturforsch., Sa, 522 (1953). ( 5 ) A. Gierrer and K. Wirta, ibid., Sa, 532 (1953). (6) N. E. Hill, Proc. Phgls. Soc. (London), 61B,149 (1954). (7) Tv. E. ‘Vaughan, W. P. Purcell, and C. P. Smyth, J . Am. Chem. Soc.. 83, 571 (1961).
THE LTJILIINESCEKCE OF CYCLOPEKTANONE BY S. It. L 4 P4GLIA AND B. C. Roauriml Aeronautical Research Laboratory, Wright-Patterson Air Force Rase, Dauton, O h m Roceized March 20, 1962
I n several recent reports on the photochemistry of cyclopentanone2-4 Srinivasan has suggested that the first oexcited singlet state (exciting wave length, 3130 A.) of cyclopentanone has three distinct modes of uiiimolecular decomposition. Emission also may occur from the excited state(s); however, a previous attempt3 to observe luminescence in liquid cyclopentanone failed, and only a weak afterglow was observed in solid solution at 77OK. It was deemed important to examine the luminescent properties of cyclopentanone as a solute in liquid and solid phases as a preliminary to any study of light, emission by gaseous cyclopentanone. Only the gas phase luminescence behavior of cyclopentanone has a very direct bearing on the intcrpretation of the gas phase photolysis. Eastmaii Whitc Label cyclopentanoiie was aiialyzed by vapor phase chromatography and foiind to consist of only one compomiit. Holyever. before use, the cyclopentanone was freshly distilled and a middle fraction was taken. Absorption spectra of cyclopentanone solution were in compl The1 fluoresagreemeilt with literature c ~ i i c eof cgclopentanone in hexane was observrd spectrophotornctrically with a double nioiiochrometer device using a high pressure xenon light source, a photomultiplier detector, and a recording galvanometer. To record the phosphorescence spectrum, a dilute EPA solution of cyclopentanone was cooled to 77‘K. in a quartz dewar. It was (1) Visiting Research Associate a t the Aeronautical Research Laboratory, 1961-1962. ( 2 ) R. Srinivasan, J . Am. Chem. floc., 81, 1546 (1959). (3) R. Srinivasan, z b z d . , 83, 4344 (1961). (4) R. Srinivasan, abad., 83, 4348 (1961). ( 5 ) D. J. Cram and H. Steinberg, zbzd., 76, 2753 (1964). (6) W. D. Kumler and A. C. Huitric, ibid., 78, 3374 (1986).
NOTES
1740
viewed by the spectrophotometer through a rotating can (-10,000 r.p.m.) type of shulter. For both fluorescence and phosphorescencg the exciting light was of wave lengths 2900-3000 A. To measure the lifetime of phosphorescence, the cyclopentanone in a dilute glass a t 77OK. was excited by a light flash of short duration. By means of a Corning 7-54 filter the exciting light was limited to the region 2400-4000 A., while the emitted light that reached the photomultipljer was limited to wave lengths longer than 4600 A. by a 4-65 filter. The flash triggered one sweep by a fast oscilloscope connected to the photomultiplier. Under identical conditions, the pure glassy solvent showed no emission, while a glass containing cyclopentanone (0.1 A f ) showed an easily measurable luminescent decay with a lifetime of 1.1 X lov3sec. If the fluorescence spectrum is normalized t o the absorption intensity and plotted on a waye number scale, the resultant spectra show an approximate ii mirror image symmetry." The maximum of the fluorescence band lies a t 4000-4100 A. aiid is structureless. Dilute solutions (10-2-10-3 &I hexane, 25') were used, to avoid self-quenchmg or re-absorption of fluorescence or the localization of the fluorescence near the incident face of the cuvette. Any of these reasons would account for the failure to observe fluorescence in the pure l i q ~ i d . ~ We found the phosphorescence, like the fliroresceiice of cyclopentanone, to be without structure ; this probably is due in some measure to the low resolving power of the spectrophotometer. The phosphorescence maximum (4400-4500 A.) and sec.) of the lifetime of phosphorescence (1.1 X cyclopeiitanone are quite reasonable for an aliphatic ketone under these conditions. McClure7reported an average phosphorescence frequency of 23,000 cm.-l for the aliphatic ketones and lifetimes of 0.6 x loe3 see. (acetone), 1.26 X sec. (diethyl ketone), and quite similar lifetimes for the triplet states of other aliphatic ketones under conditions equivalent, to those described above. The observed phnsphoresc.eiicc anti drmy time t herefort. are ascrikrd to the t ripltit state of c.yclopt:rit:iiioiic. (7') B S M
