Sept., 1960
COMMUNICATIONS TO THE
COMPOUNDS USED IN THIS been cited t o explain the higher Am,x of cyclopen-
RESEARCH Refractive B.P., ‘C. Compounds mp index (mm.) ?-Propanone 277 n 2 0 1 ~ 1.3588 56 (755) ?-Butanone 278 ~ Z O D 1.3788 79 (748) 3-PPntanone 579 ~ Z O D 1.3921 102 (760) 3-~Lethvl-2-hutsnone 283 I L ~ 1.3881 ~ D 94 ( i 6 l ) L ,i-Diniethyl-3-pentanone 287 ) i Z 3 D 1 . 3 b 5 9 123 (76%) 3.:~-Diniethyl-2-butano11e 285 1 ~ 2 1.4016 0 ~ 106 (755) ?-Hexanone “79 n20D 1.4003 128 (755) 2 , %-Dinietii?l-:~-licntanone 288 n23n 1,4050 129 (760) ~,~,4-Trinietlivl-:(-lientanonc 290 n% 1.4000 136 (780) 2.2,4, ~-Tetrainetli?l-:J-pentanone 297 n2@n1,4193 153 (760) I-Chloro-Z-groiianone 289 n 2 b 1 . 4 3 1 2 G I (110) 1,1-Dichloro-?-propanone 295 n 2 5 ~1,4142 121 (760) 1,3-Dichloro-5-l1ropanone 300 ,,, , , . .. 173 (760) m.p. 43-44’ I , l,l-Tsichloro-”-liropanunl: 281 ~ ? O D 1.4lj50 133 1,1,3,3-Tetrachlr~ro-2-rJ~o~,anone301 n18D 1.,5000 17-48 ( 5 . 5 ) 1,1.1,3-Tetrachloro-L’-l,ro]~anone 299 n16D 1,4900 47-18 (6 .0) 1 . 1 , 1 , 3 , 3 - P e n t a r l i l o ~ ~ - ~ - ~ ~ r o ~298 i a n o n c2 k 1.4955 189 (750) Amax,
1.1,1,3.3.R-€Ierachloro-2propanone Xlethrl cyc1oi)ropyl ketone Dicyclopropyl ketone E t h y l acetoacerate Cyclopentanone Cyclohexanonr
1343
The effect of strain a t the carbonyl carbon has
TABLE I AKTS OF THE
EDITOR
298 276 27(j 278 300 289
n231,
i.5090 201 (750)
71%
1.4222 111 (758) 16X (760) 1.4192 50 ( 7 . 0 ) 1.4335 130 (755) 1.4497 155 (755)
n z 5 ~1.4657 1720D
n% ~ * O D
groups.’ This shift has been ascribed variously to the positive inductive effect of t8hemethyl group, or t o hyperconjugation; and it, also has been described simply as the “methyl effect.” I n this investigat,ion it has been observed that t’he “red shift” is more dependent on the symmetry of substitution than on the number of entering methyl groups. possible explanation for this effect is the steric requirements of t,he entering group aiid the strain produced by t’he opposiiig groups a t the carbonyl carbon angle-a.
c
/ \ It, R*
tanone 1’s. ~yclohexanone.~The observation that “hexamet,hylacetone” and “hexachloroacetoneJJ have A,., values which are almost identical supports the contention that, in this case, the effect is steric. The following series can be observed for a “red shift” produced by changing the complexity of R inethl-1 < ethyl 5 n-butyl < i-propyl < t-butyl The same order is preserved for R1 cs. R2 and t’he effect is accentuated by the degree of complexity of R,and R2.4 The apparently greater effect of an i-propyl group when compared with other groups possibly could be the modifying effect of “B” strain in such a group. Where steric strain is t,he primary consideration, the case of the chloro-subdtuted ketones appears to be the same as tha,t observed in the alkyl ketones. Hovever, for tmhecompounds in which the substitution is symmetrical and a-hydrogens are present, simple st,eric effects do not appear to offer a complete explanation. The resonance estreme shown
la, 8
H ~biS H e
&c--c=a I
-
-
H
H
is possible and may be a partial a,nswer: howe\-er, this is pure conjectme. The case for the cyclo-alkyl ket’ones is perplesiiig and no simple explanation is offered for the observed spectra. Hart,5 et al., have reported these same compounds, pre7-iously, without any explanat,ion for the spectral data. ( 2 ) .4. E. (;illam and E. 8. S t e m , “ A n Introduction t o Electronic Absorption Spectroscopy i n Organic Chemistry,” 1:dward .4rnuld L t d . , London, 1984, pp. 47-51. (3) XI. S. N e w m a n , “Steric Effects in Organic Chemistry,” . J O ~ I I I Wiley and Sons, Inc., New York, N . Y.. 1936, pp. .i06-507. (4) R . P.XIariella a n d R . R . R a u h e , J. dm. Chrm. Soc.. 7 4 , 518 (1952). H. Hart arid 0 . E. Curtis, i b i d . , 78, 112 11933).
COMMUNICATIONS TO THE EDITOR C O ~ 1 3 1 1 C ~ rOWS THE AIECH,ISISlI 0 1 ’ THE I{KACTI()s OF Awnix XITKU(:ES \VITII ETH1 I,ESIi, AS11 SITKIC‘ OXI11E h 1 I’:
11 1 s t h c plll~po.(~oi thl. ~ ’ o I ~ l l l l l l l l l ~ ’ : l t 1 to0t l SllO\\ that the ri+uIi- oi \7crhel\c a i d \\’iiihlcrl raii 1 ) ~ iiiterpretrcl t y awiiniiig that thc. oiily c.oiiititueiit of active iiitrogeu
11 hich reacts n i t h nitriv oxide IS atomic iiitrogeii in contradistinction to their cmic~lusion~ This reartioii is quantitative. The reh u l t s obtained for the reaction between acti1-e iiit,rogen and ethylene theii ran be explained by a iiierhanim :rn:tlogous to I;rey’< iiiechaiiiLn1 for thc 11 I‘JtiOl
< t
I
\ Ihchr dnd I
1. \ \ i n i l e r . J. Phijs C h e m . . 64, 319
COMMUNICATIOKS TO THE EDITOR
1344
v
valent rare earth ion, Ce+, as the solute species,2 and the enormous apparent molar volume of 500 cc. per mole of mobile electrons, in dilute solution.' The recent discovery3 of solid halides of divalent neodymium and prasedymium such as SdC12 and PrC12.3supports our own view that cerium enters the solution in molten CeCL as Ce+*, but clarification of the aforenientioned findings appeared desirable. A reinvestigation was started in connection with the general study of molten salt-metal systems a t this laboratory. The nature of our first results is such as t o warrant an early report. In agreement with available thermodj-namjc data n e have found that refractory ovides such as sintered alumina ("Morganite Triangle RR") or sapphire single crystals are not s u i t d for use with even dilute solutions of Ce in molten CeCI3 as they react readily to form cerium oxychloride :tccording to: MZOg 2y13Ce y/3CeC13 = yCeOC1 2.11. For instance, 0.9 g. of cerium metal and 1 G 3 g. of CeC13 prepared by dehydration 111th N&C1 and subsequent qublimation were kept molten under argon a t 850" in a Jlorgaiiite rrucihle for two hours. After leaching with water, 1.62 g. of an insoluble residue consisting mainly of purplish-white crystal platelets of cerium oxychloride were recovered (X-ray identification). The inner wall of the crucible showed severe attack znd its weight was reduced by 0.25 g., corresponding t o approximately 75% completion of the above reaction. Aluminum metal also was identified. Similar results were obtained x-ith a single crystal of l I g 0 or n slice of high-densi ty T h o 2ceramic 111 a molybdenum crucible. ( A control experiment nitdi such a crucible, without refractory oxides, yielded only traces of CeOC1.) On the basis of these findings it is certain that the data obtained in the e.m f . and conductivity measiiremeiits which had heeii carried oi!t in Morganite rruciblesl dzcl n o t pcrtazn to thc c'c -CcC13 systpin ! Rather, the added cerium must h:L\ c heen largely, i f not cnmplctcly, cmverted to Ce( C1. Although uIldri' thc circuni+mces any at tempi :it interpretati oii of t h o h e me:i siirciiieii t s In t i 4 he I i d e q u a t e , the o h w , \ et1 tl.m.f.? ni:ij' pcr1iaI)i lie ; i Y ( ~ i l x c l to :L cell
+
trogen is successively titrated with nitric oxide and ethylene in a given system the variable ( H C ~ p r o d n c e d / ? i O d e s t r o y e d ) . x (1 - HCxproduoed/ ?jOdestroyed)-l will be a linear function of the reciprocal of the total pressure. Figure 1 shows that Verbeke and Winkler's data can be correlated in this way. The slope of this correlation is 1.9 i 0.3 mm. (90% confidence limit); the intercept is 0.6 h 0.6.
x
/
1'01. G i
'\
CH2--CH2 is inherently unstable so that it may be destroyed by other reactions besides the one given above under appropriate experimental conditions. For example, Winkler3 has found recently that with increasing temperature, the HCX vield from the reaction of ethylene and active iiitrogen increases when an unpoisoned vessel is used. This indicated that the wall catalyzed decoriipositioii of CH2-CH, competes with reac-
Aio ~
~ ~ A T E R I A1 L J E ~X I;LOPXfENT
~
o
~C ~ O ~ C I~cCcij , i (-cc~3 q , (;le
ari:ihic oxygen cwnceiitr:itioii in the fonii of CeOCI. \*e IT 1io:i I i i i h c p i ' o c c ~of clrclopiiig nieiliods of investigating t h c C'c-CeC1 teins 111 such a maiitic'r a'> to void ~ n ~ i ~ i t n bcontniticr le mntcmali. Of ular interest is the question u-hckther the simult:meoiis prehcwcc of the t u o \ . , d r \ i i c t s it:ites of wr111111. Ce+-- and Celt, lend. to < t high electroil mobility. I\ ith T
t ioii five uiitler these conditions. LABORA~ORY
I
