NOTES
1262
-
0.0
0.2
Mole Figure 1.
0.4
Fractlon
0.6
d
0.8
p-Dioxone
Phase diagram for p-dioxane-anisole.
the same eutectic was observed a t each composition and no other temperature halts or irregularities were observed i n the cooling curves, the conclusion was made that no compounds were present between the extreme compositions studied. The composition was chosen to include mixtures corresponding to 1: 2, 1: 1, and 2 : 1 molecular ratios. One would expect that the most likely bonding site on the dioxane molecules would be the oxygen atoms. Any one of at least three parts of the anisole molecule might be involved: (1) the ring, (2) the oxygen, or (3) the methoxy hydrogens. Substances related to anisole but chosen to enhance the activity of each of the three sites mentioned above were then investigated. Inasmuch as anisole has a high electron density in the ring, other aromatic compounds of varying ring electron density were studied. No compound formation was observed in mixtures of dioxane with nitrobenzene, CY,a,a-trifluorotoluene, chlorobenzene, benzene, toluene, 0-,m-, and p-xylenes, and K,N-dimethylaniline. Since the electron density in the ring of anisole is less than in X,Y-dimethylaniline but greater than in the rest of the compounds, it would appear that The Joiirnal o j Phgsical Chemistry
the ring is not significantly involved in the dioxaneanisole interaction. Anisonitrile and 2-methoxypyridine were chosen as compounds similar to anisole in size and structure, but with more electropositive methoxy hydrogens. Seither of the two formed a compound with dioxane. This fact appears to be evidence against the possibility of attachment through the methoxy hydrogens. Diphenyl ether and phenetole were used to study the effects of replacing the aliphatic radical of the mixed ether with another group which would in one case enrich and in the other case deplete the electron density around the oxygen. Seither substance formed an addition compound with dioxane, which fact implies that the extent of electronegativity of the oxygen in anisole is not significant in the formation of the anisoledioxane compound. Finally, mixtures of tetrahydrofuran and anisole were studied, and even in this system, no addition compound formed. On the basis of these results, it appears likely that the formation of the dioxane-anisole 1: 1 compound may be caused more by a favorable crystal geometry than a strong specific interaction. The activity coefficients of the dioxane in the liquid mixtures give support to this conclusion. A comparison of the freezing point depression of dioxane in the three systems for which the information is available (dioxane with anisole, diphenyl ether, and N,N-dimethylaniline) shows slightly less interaction for dioxane in anisole than in diphenyl ether and only slightly more interaction than in dimethylaniline.
Acknowledgment. We wish to acknowledge the support given this project by the Office of Army Research (Durham). We also thank Mr. Arnold Loveridge for his assistance with the freezing point measurements.
The Ultraviolet Spectra of Transients Produced in the Radiolysis of Aqueous Solutions'
by S. Gordon, E. J. Hart, and J. K. Thomas Chemistrg Division, Argonne National Laboratory, Argonne, Illinois (Received December 87, 1963)
The spectra of several transients have been observed in the radiolysis of aqueous solutions by 15-R/Iev. electrons by a pulse radiolysis method similar to that (1) Based on work performed under the auspices of the U. S. Atomic Energy Commission.
already reportcd by Gordon, et aL2 I n the latter experiments, it was impossible to observe spectra below 3000 A. except for 2337 A. S o w with an improved light source arid sirnplificd optical arrangement we have extended this range to 2000 11. In the present work a 450-watt X130, 450 W/p Osram xenon lamp was used in conjurietion with a regulated d.c. powcr source. This gave a strong continuous light output from 8000 to 2000 Ai.The light from this lamp was focused by a built-in quartz lens of 5-cm. focal length through a 4-cm. quartz irradiation cell to a mirror from which it was reflected back through the cell, hence giving an effective light path of 8 cm. The resultant light after a 45' reflection was then focused by a :iO-em. focal length quartz lens into an f 3.5 Hausch and 1,omb grating monochromator. Interchangeablc gratings covering the 180-400- and tho 350--800-mp spectral regions were used. A If'28 photomultiplier tube was placed at the exit of the monochromator and the output for this tube was amplified and photographed on a Tektronic oscilloscope No. 551. The lenses in the system were adjusted to give the hest photomultiplier output for the particular wave length region that was of interest with a minimum of scattered light (Tahle I). The procedure for filling the 4-cm. cell has been described.2 For the work cited here, 0.4-psec. electron pulses of varying currents were used, yielding from 1 to 3 pmoles of H and OH radicals per pulse. The dosimetry was carried out by observing the hydrated electron absorption band at X 5770 A. in deaerated water where the molar extinction coefficient is 10,000M-' The solutions studied were aerated 0.1 N sulfuric acid and unbuffcred aqueous isopropyl alcohol, aqueous acetone, and aqueous 0-, m-, and p-phthalate ions. Vigures 1 and 2 show the observed spectra. A transient with a maximum at 285 mp was observed in the aerated 0.1 N HzS04.3a No transient was observed in the absence of oxygen. It was suspected t h a t this species was the H 0 2 radical as reported by B a x ~ n d a l e . ~Two ~ decay curves were observed for this species a t 2500 A. The first is a fast decay with 2 psec. and a slower decay of see. This is precisely the behavior predicted4 for the HOz via
-
.I4 .I3 .I2 .II .I6
,I5
,
.IO
.09 .08
o
HO; A
A
10-2M ISOPROPANOL
~ ~ ( 1 ~8 . 0 ~ ~. 7 ) ~ 1~ 0 ~ ~
.
-
.O? -
.05 .04 .03 .02 -
d .06 0
.01
I
I
I
I
i
A
j i
0
I
j
A
i
I
I
PARA-PHTHALATE-.--
o ORTHO-PHTHALATE-----
META-PHTHALATE-
A
I !
-
OH
+ HOz
fast
HzO
-4
Tl/,(sec.)
2
and
.I7
x
+ OZ
2000
3000
WAVELENGTH 4000 (Ao)
5000
6000
Figure 2. T h e absorption spectra of the transients produced in the radiolysis solutions of 0-, t u - , and p-phthalate ions. Experimental conditions as in Fig. 1.
10-2
(2) 9. Gordon, E. J. Hart, M. Matheson, J. Itabani, and J . K. Thomas, -1. A m . Chem. Soc., 85, 1375 (1963); Discussions Faraday
Soc.. 3 6 , 193 (1964).
(3) (a) This bond has been reported by G . ('zapski and L. Doifman, J . f'hys. Chem., 68, 1169 (1904); (b) J. H. Baxendale, Radiation R E S . , 17, 312 (1962).
Volume 6%. Number 5
M a y . lOfi/t
1204
r\;OTES
~ ~ ratc i of c appearance of tlic traiisieiit at x 2400 A. was also ot)scrvcd i l l solutiolis of 0.1 N HzSOr with oxygcn conceiitrations varying from 20 to 100 MM. Ilia ratc of appearance of tlic spccics was first ordcr and the rosult of dctcrmiiiatiotis gave k1i+02 = '2.1 X I O L o 1 I f - I see.-'. This agrcos very well with previous estimatcs of 1.2 X lO'", 2.0 x IO1", aiid 1 . 9 x 10I" for this r c a c t i ~ i i . ~ - ~ Solutiolis of isopropyl alcohol w r c irradiated i i i tlitt ahsolice of' oxygen. A traiisient, jvith an absorptioii band from 2000 to :3000 A. was observed. The spectrum t:xhibited an absorption it1 thc saiiie wavc length region as t h o CI&-CI3-OH radical reported by I h r f mail and Taut).' [ S o absorbing spocics was detected after irradiation of deaerated lo--*Jl mctliaiiol solutions where the CFIZOII radical is cxpcct,cd. ] Wcattribut,e thc observed absorption to the (CHI)2COII formrd by H abstraction by tho OH radical aid t'he 1-1atom. Aqueous deaerated solutions of acetone were irradiated and gave a transient absorbing at 20003000 A. This spcctrum was very similar to that obtairicd with the isopropyl alcohol radical. PreviouslylZ we have observed that the hydrated clectron, which would bc formed in the above solutions, reacted rapidly with acctone. The reaction schcme may be I
,
(CHa)zC==O
+ eaq---+
(C€lS)zc-O-
I1
+
(CH,)zC-OH This would account for the similar spectra for the acctone arid isopropyl alcohol solutions. In following the decay of the hydrated electron at 5770 1.in solutions of o-, m-, and p-phthalate ions at pH 13, it was noted that for the meta and para compounds, composite decay curvcs wcre obtained. These were due to tho simultancous decay and transient build up. If it is assumed that the transient results from reaction of the solute with c,,,,-, the curves can be treated as a pareiit-daughter relationship with TI,, c , , ( ~
