0 000 0.004
0.03 0.02 0.01
(1.00
- 30
- 20 - 10 0 Surface temp., "C. Fig. 3.--Plots of: (a) agas a function of T , (eq. i),( b ) a* as a function of T,* (eq. 5 ) , and. (c) ag as a function of T , (eq. 4) for Alty's experiments with carbon tetrachloride at 1.6". ag us. T , and the a* us. T,* dependencies for the water experiments. The carbon tetrachloride results are presented in Fig. 3. ( a ofor carbon tetrachloride = 1, as quoted by Alty, not shown.) One would expect that an accommodation coefficient should be solely a function of the surface condition. For a pure liquid-vapor system, the surface temperature is presumed to describe adequately the surface condition. On such a basis, the accommodation coefficient as derived from usual theory, eq. 2 or 4, appears to be inadequate in the intermediate regions. Note in Fig. 1 that at identical measured surface temperatures the calculated accommodation coefficients in the intermediate regions are progressively lower as the bath temperature is decreased. In other words, by this equa-
tion as is apparently dependent upon the thermostat temperature, a condition which is not considered likely. The same data shown in Fig. 2 indicate some unique functionality of the pairs a*-Ts* and ag-Ts. I t seems important that these relations result in an accommodation coefficient that is relatively independent of the temperature of the thermostat in which the experiment is performed. -1very pronounced change in slope for the carbon tetrachloride a*-Ys* dependency is shown in Fig. 3 which is not apparent in the correqpoiidiiig ag-T, and as-Ts plots in the same figure. The change in slope occurs a t a derived surface temclose to the freezing point of perature near - U 0 , carbon tetrachloride. However, it iq also suspected from previous analysis4 5 that nucleate h i l i n g is beginning a t this region. If true, the calculated a* would be reduced as a result of the increnyed w r face area. In conclusion, the results reported herein indicate that the problem of a mass accommodation (or condensation3) coefficient a t a pure liquid-vapor boundary warrants further clarification before its features can be used implicitly. SOTE ADDED IS PROOF -Recently, the n o r k of Littlen ood and RideaP has been brought to the authnr'q attention. Their results shorn that the surface temperature of benzophenone was lolyered 2 8" zn cucuo (10-l mm ) a t 20', as measured %ith thermocouples that \\ere 25 microns in diameter, whereas their calculations indicate that the temperature drop should be approximatelv 6" They estimated the heat flux for Alty's experiments to be 5 X l o 3 times greater in comparison, which indicates that the temperatiires reported by Alty are higher than the temperatiireq nhich actually evist a t the liquid surface Littlenood and Ritleal conclude that "evaporation coefficients" are unity. but the limitations of the heat supply causes a difference hetn een the actual and the measured surfare temperatures Fig 2h of the present article is based 011 t h r lonest surface temperature 1% hich must exist
Acknowledgment.-The author n ishe. to acknowledge stimulating discuscions IT ith Dr. R. J. tant Profewor at the Illinoi. Inqtitute of Technology. and staff a w & i t e s :it the A4rmour 1iese:irch Foundation. (6) R 1,ittlewood and R Rideal, Trans r a r n i i i i u S o c , 62, 1598 (19.513).
NOTES T H E RELATIOXSHIP BETWEEN 0-H STRETCHIKG FREQUESCY AND ELECTROKEGATIVITY I K HYDROXIDES O F VARIOUS ELEMENTS' BY ROBERT WESTA N D RONALD H. BANEY LTni7,ersity of Wisconsin, M a d i s o n , M isconsin Received December 19, 1968
The influence of inductive effects of subst>ituent (1) This research was supported by t h e United States Air Force through t h e Air Force Office of Scientific Research of the 4 i r Research and Development Command, under Contract S o . AF 49(638)-28.5. Reproduction in whole or part is permitted for a n y pnrpose of t h e United States Government.
groups on infrared frequencies has been studied in a number of different systems.2 Among compounds of several types, linear relationships have been found between t'he electronegativities of subst'it>uents and certain T-ibrational frequencies. The 0I3 stretching frequencies of alcohols$ and phenols5 ( 2 ) I,. J. Bellomy, "The Infrared Spectra of C o i n l ~ l e s~ I o I ~ c I I I ~ ~ s , ' ~ Second Edition, Llethuen, London, 1958, 1). 389-39 k. ( 3 ) L. J. Bellarny. J . Chem. S o c . . 4231 (1955); J . \-. Bell. .T. HFisler, El. Tannenbaum and J . Goldenson, J . d m . Chem. d o c . , 7 6 , 7185 (195.1); R . E. Kagarise, ihid., 77, 1377 (1955). (4) 11. I. Battier, A . P. Meshcheryakoi. and A . D. Llatveevn, Z h u r . E k s p t l . Teoret. P'iz., 2 0 , 318 (1950): C.A., 4 4 , 627Ci (1%50). ( 5 ) L. L. Ingraham, J. Corse, 0 . F. Bailey and 1:. S t i t t , J . A m . Chern. Soc., 74, 2297 (1952).
June, 19130 are decreased by electronegative substituent groups, in accord with theoretical prediction.? However, alcohols are abnormal in that the 0-H frequencies fall going from primary to secondary to tertiary alcohols.6 Since the opposit,e would be expected from the kiiowri inductive effects of these groups,' the observed trend suggests that a hyperconjugat,ive effect is also operating. This art,iclereports the study of the 0-H stretching band frequency in a series of hydroxyl compounds in which the OH group is bonded to different elements. The five triphenyl-hydroxy compounds of t'he group I17B elements were investigated, ha\.iiig the general formula (C&)&IOH, where AI = C, Si. Ge, Si1 and Pb. Four other hydroxyl compounds, dipheiiylsilaiiediol, phenyldihydroxyborane, N-phenylhydroxylamine and tM y 1 hydroperoxide, also were studied. The 0--H frequencies are compared with the electronegativit,ies of the element's to which the hydroxyl group is Eontled. The elect'ronegativities of the elements of periodic group IYB recently have been studied carefully by -Allred and Rochow, and are now known with exceptional accuracy.$ Experimental Compounds.-The preparation and properties of the triphenylhydroxy compounds of the group IT'B elements, and of diphenylsilanediol, will be described elsewhere .9 Phenyldihydroxyborane and S-phenylhydroxplamine were obtained from .K and K Laborat,ories, Inc., and t-but,yl hydroperoxide was purchased from Matheson, Coleman and Bell. These compciunds were of reagent grade and were used without further purification. 1Ierck carbon tetrachloride from freshly-opened bottles was used as a solvent. Spectra.-The infrared spectra of the cornpounds in the OH region wt:re determined using a Perkin-Elmer Model 112 spectrometer with a lithium fluoride prism, calibrated against water vapor and ammonia. The compound8 were examined as approximately 0.01 JI solutions in carbon tetrachloride at a path length of 0.3 em. At this concentration 0-H bands due to self-associated species were negligibly weak. Triphenyllead hydroxide was soluble in carbon tetrachloride only t o the extent of about 0.001 J4 and was studied as a saturated solution. Band posit'ions were reproducible to == ! 1 cm. -1 and tre believed accurate to rt 2 cm. -1.
Discussion The free 0-H frequencies for all of the compounds are listed in Table I. For compounds in which the hydroxyl group is bonded to carbon, tin, lead, nitrogen and oxygen, a remarkably good linear relationship is found between the electronegat'ivities of t'hese atoms and the 0-H frequency. The relationship is in the direct'ion predicted from inductive effects?; as the electronegativity of the element bonded to oxygen decreases, inductive release of electrons is facilitated, and the OH bond is strengthened and its force constant is increased. A least,mean-squares treatment of the data for the C, N, Sn and Pb compounds gave the equation vOH = 3i50.6--54.1~, where x is the electronegativity of the element bonded to the hydroxyl group. Band positions for the four hydroxy compounds of these ( 6 ) F. A . 1,. .$net and P. AI. 0. Bavin, Can. . I . Chem., 34, 1756 (1956): 31. I. Batriev and .I. U. Alatrreva, Izuest. A k o d . S a u k S . S . S . K . , Otdel. Riim. S a u k , 118 (1951); .4.R . H. Cole and P. R. Jrffrries. J . Chem S O C .1791 , (1950). ( 7 ) R . TV. T t f t . .Jr.. J . :im C i e m . Sac.. 74, 3126 (19.52). !8) .i. 1,. .Allred enti E. C;. Rorhow, J . f n o r g . Sucl. Chem., 6, 269 ( 1958). (Y) R. West and R. H. Bancy, J . Am. Chem. Soc.. in press.
KOTES
823
elements did not deviate from this linear relat'ionship by more than the experimental error of * l cm.-l (Table I). The OH frequency for the oxygen rompound t-butyl hydroperoxide was wit hili 3 c ~ i i . -of~ that, predicted from t'lie formula. TABLE I 0-H STRETCHISG FREQUENCIES A N D
~LECTROSECrhTITITIES,
XI0
Compound
Ph3COH Ph,SiOH PhuSi(O H ) ? Ph3GeOH I'h3SnOH PhSPhOH PhB(OH)? PhNHO H
x 2.60 1 .heequat,ion
cm. -1
n el-ia tion, rm.-'t~
3600 -1 3677 +20 3682 :3 3 :3651 0 3647 -1 3818 0 :3666(3632) $23 33586 (:%E')) 0
+
-
3558 YOH
- :3
= 3750.6 - 5 4 . 1 ~ .
The 0-H frequencies for triphenylsilanol, diphenylsilanediol, triphenylgermanol and phenyldihydroxyborane, however, deviate significantly from the linear relationship discussed above. In all of these compounds the 0-H absorption occurs a t higher frequency than expected (Table I). Considerable evidence for exuteiisive dat'ive T bonding from oxygen t'o a vacant 3d orbit'al on silicon14 in silanols has been presented by the authors in a series of recent papers.13,15 The 2p orbital on boron can also accept partial double bonding from oxygeii.16 The authors suggest that dative n-bondiiig takes place in all four of the compounds mentioned above, increasing the s character of the 0-H sigma bond, and thereby increasing the 0-H bond force constant and frequency. This O-H frequency shift parallels the well known frequency increase for C-H absorptions with increasing s character in the bond hybridization at carbon. li The fact' that the frequency enhancement is greater for t riphenylsilanol than for t'riphenylger(IO) The Allred-Rochow "best raliies" of electronegativities for the group IVB elements8 were used. For other eirnients, valries given by the same arithors based on elertrostatic calcrilations have T h e ronclusions of this study are not dependent on heen taken." these choices. A similar straiqht line, differing only in rninor respects. is obtained using other sets of electronegativity \-allies recently calculated. 11, * * T h e effecti1.e electronegatirities of the substituent atoms should depend somewhat on the nature of the other &-oops bonded t o them. For this reason v e ha\-e used phenyl substituied compounds in this study whenever possible; however, we have shown elsewhere t h a t the influence of this secondary inductive effect on the 0--H frequenry is slight. 1 3 (11) -4. L. .illred and E. G. Rochow. J . Inorg. J-ucl. Chem.. 6 , 264 (1958). (12) LI. A . Fineman and R. Daignault, ibid., 10, 205 (1959): cf. H. 0. Pritchard and H. A. Skinner, Chem. Reus., 6 5 , 745 (1955); R. T . Sanderson, J . A m . Chem. Sac., 74, 4792 (1952). (13) R . Went and R . €1. Baney, J . Ani. Chem. S a c . , 81,6115 (1959). (14) I?. G. A . Stone and D. Seyferth, J . I n o r y . .Vur/. Chem., 1, 112 ( 1955). (15) R . West and R. H. Baney, ibid., 7 , 287 (1958); c/. L. H. .Allred, E. G. Rorhow and 1:. G . A . Stone, ibid., 2 , 416 (1956): R. H. Baney, K. .J. Lake, R. \Test and I>. S. Whatley, CFemistri, J n d u s i r y , 1121 (1959). (16) E. W. .&bel, W. Gerrard. M. F. Lappert and R. Shaffer~nan, J . Chem. Soc., 2895 (1958). (17) L. J. Bellamy, ref. 3, p , 387-389.
824
T'ol. 04
XOTES
manol,1* and that no enhancement is found for the tin, lead and carbon compounds, IS consistent with recent studies of the acidity and basicity of these triphenylhydroxy compounds, which indicate that oxygen-to-metal x-bonding is strongest in the silicon compound, n eaker for germanium, and negligible in the tin, lead and carbon compounds.Y The 0 -H absorption of pheiipldihydroxyhorane is abnornial in that a iecond somewhat broader band appear? at 3632 mi - I , 34 cm.-' below the free 0 - H ireyuency. Both bands are found even at low c'oiiceiitrations. Two hydroxyl frequencies might he expected for this compound, since the two hydroxyl groups i n phenyldihydroxyborane may not he equivalent. However, both the magnitude of the splitting and the appearance of the lowerfrequency band suggest that this hand may denote :t hydi*ogm honded hydroxyl group Intraniolecular h \ di ogtn bonding betn een hydroxyl groups may tztke p1:~c.e111 pheiivldih!rdroxyborar~e,or poiyihlv a hydrc,geii-honded cylic dimer may be preseiit 111 dilutc solutioni of the c~mipound. It is intereitiiig that tlie structurally iimilar (.ompound diphenylsilanediol ihon only a single sharp band a t 3682 ciii --' The near infiared spectrum of S-phenylhydroxylamine IS also complex. In addition t o the free 0-H band at :358.5 cm.-', weak bands are found a t 3480,3398 and 3320 cm.-l, \T hich may be attributed to the S H and 0-H groups. t-Butyl hydroperoxide Fhons only a single free 0-H band a t 3558 crn.-' 111 dilutc solution. I t is noteworthy that this absorption frequency, while quite low for a nonhydrogen bonded hydroxyl group, is more than 100 cm. higher than that reported for hydroperoxidri by RLI.~ i a nI\ orkers ?" (18)
rccult. arp ohtaint ii i f o t h e r recPntl\ -ralruiarpd cletfrontxati i t \ \a1 le\ a l e I I S P ~ (19' R \I t i t and R €I Ba papel prisented at tlie 15th Soiitlixe.t ReLiu?ai l l e e t i n g iiilriican Clieniiial S o r i e t \ , Baton Ruiigr I ouisiana De cembt>r l(j5q ( 2 0 ) i Y K a r i a A i n a n d V 4 YiLitin T z i p s t l k n d \ a 7 ~ h r i f ~ z1 7 , 0 3 0 ( 1 0 5 3 ) -1ii111ai
-
BY
I>A\ICI,
12
f l l i f i o i ~S t n t c
I)E4D\fORE .4SD JAMES
Gtological Sur1 ey, 7-rbana
8.f\rACHIU ~ ~ ~ 1 ~ 1 0 7 s
I < i < c i i r d J a n u a , u 11. 1960
I n the course of a rather broad investigation of the stability of certain inorganic fluorine-bearing compounds, attention \ m s directed t o binary mixtures of some alkali and alkaline earth fluorides. The T,iF-CaF, system was included because it map be considered to be a weakened model of the important _11g0-Th02 system1 and because of this niay gi7.e some clues to relations in this very refractory system. Experimental Procedures.-The liquidus and solidus data reported herc were obtained from cooling curves. A tengram batrh was meltcd to a clear liquid in an 8-ml. platinum rrucible and rooletl at rates of 3 to 10°/min. The temperature was followed with a bare Pt-Pt 10% R h thermocouple immersed in the melt. The thermocouple waa cali-
+
____-
n.?I.
(1) (18.501.
R . R o y and E,, F. OHborrr, J. Am. Ccr.
R
