NOT 'E8
884
collision factor PZ is approximately lo4 moles/]. sec. This result indicates that its apparent normal behavior is the result of both a very low collision factor and a small activation energy. No induction period ever was observed. This probably was due to the fact that the solutions were of very high purity and free of foreign materials that could act as inhibitors. However, it also tends to rule out mechanisms in which a certain concentration of an intermediate must be built up before the decomposition can proceed. Many homogeneous mechanisms were considered but none were found that had a low enough activation energy. If it is assumed that the decomposition involves strongly adsorbed hydrogen peroxide on the quartz surface, it is possible to write a mechanism with a sufficiently low activation energy and zero-order kinetics. Unfortunately the results obtained in this study are not complete enough to establish clearly this decomposition mechanism. However, they do support the notion that the decomposition of concentrated liquid hydrogen peroxide takes place primarily if not completely by a heterogeneous mechanism.
Vol. 61
salt.1 The bond angle of the amide ion and the N-H stretching vibration force constant (5.99 X lo6 dyne/cm.) were calculated using Linnett's formula.' (6) J.
W.Linnett, {bid.,
,
41, 223 (1945).
THE VAPQR PRESSURE OF SODIUM FLUORIDE1 BY KARLA. SENSPI? C. A. ALEXANDER,R. E. BOWMAN, R.W.STONE AND R. B. FILBBRT, JR. Battells hfemotid Institute, Columbue, Ohio Rsceivsd Oatober 88, 1068
This work was undertaken because information on the vapor pressures of sodium fluoride was needed in the 930-1075" temperature range. The apparatus and experimental procedure of the transpiration method used have been adequately described in the previous papers.*,* The sodium fluoride used was J. T. Baker highest grade. The results are given in Table I. TABLE I VAPOR PREBSURXI OF SODIUM
THE STRUCTURE OF THE AMIDE ION B Y 8.F. M A 8 O N ' Auatralian National Univsrrity, Ds arlmmt of Medical Chsmirtry, Uniusrsity Colleps, fondon, W.C. 1 Received Bsptembsr 10, 1068
The crystal structures of sodium amidel and lithium amidea have been reported recently. In these determinations the H-H and N-sH distances in the amide ion were assumed* to be 1.60 and 1-01 A., respectively. It has been shown, from the proton magnetic resonance spectrum of potassium amidell that the H-H distance in the amide ion is 1.63 f 0.03 k , and in the present work an approximate value of 104' for the bond angle has been calculated from the infrared spectrum of lithium amide, giving the N--H distance of 1.03 A. for the ion. The infrared spectrum was obtained with a weighed sample of purified lithium amide pressed into a disc with potassium bromide, using a PerkinElmer Model 12C spectrometer with a lithium fluoride prism, The amount of lithium amide in the disc was subsequently checked by titrating an aqueous solution of the disc potentiometrically against standard acid. The asymmetric stretching frequency was observed at 3315 f 1cm.-l, with a molecular extinction coefficient of 6.5,and a band half width of 10 cm.-l, and the symmetric frequency at 3261 cm.-', with an emax of 17.7, and a band half width of 14 ern.''. These bands are sharp and symmetrical in shape, and no other bands were observed in the N-H stretching vibration region, Thus the amide ion does not hydrogen bond in the crystal, as expected from the large minimum N--N distance (3.81A.) in the sodium
*
( I ) Chemistry Department, The Univcrsity. Exeter, England. (2) A. Zalkin and D. II. Tcmpleton, THISJOURNAL, 60, 821 (1956). (3) B. Juga and K. Opp. 2. anorg. allgem. Chem., 266, 313 (1951). (4) Freeman and R. E. Rioharda, Tram. Faraday Sac.. 6% 802 (1@66).
n.
Prwure. mm.
Temp.,
I
Flow ratr,
Obsd.
Calod.
Dev. %
0.108 .142 .173 .211 266 .336 .385 -452 .663
0.108 .143 .172 .213 ,263 .332 .a89 .466 .648 .579 .654 :702 .834 1.01 1.32 1.68
0.0 -0.7 +0.6 -0.9 $1.1 +1.2 -1.0 -2.6 +2.7 +0.2 -0.2 +0.6 -0.2
OC.
934.6 946 9 956.0 964.5 974.0 984.7 992.0 1001 1011 1014 1021 1032 1035 1047 1084 1075
FLVORIDXI
I
.680 .653 *
797
832 1.02 1.30 1.68 *
+ I .O -1.5 0.0
nitro en cm.~flmI~.
47.3 60.9 48.2 60.0 49.1 49.2 48.6 49.3 49.4 50.3 49.6 49.3 48.2 45.4 44.0 40.5,
By use of a least-squares correlation the following P-T relationships were derived. From 034-996° log p (mm.) = 11.3316
- 14856 ---TI
OK.
AH,ut.~im.t,on= 68.0 kcal./mole
From 996-1075' log p (mm.) = 9.4188
-
12428 -T,OK.
AHv.po.~r.t~on56.9 kcal./mole
(3) (4)
The melting point, 9 9 6 O , was obtained by equating (1) and (3). These results are based on the assumption that, at the temperature range studied, the sodium fluoride molecule exists as a monomer. If dimers or higher polymers are present in the vapor phase, the resulting vapor pressures would, of course, be lower. ( I ) Work performed tinder AEC Contract W-7405-eng-92. (2) K. A. Sonse, M. J . Snyder and J. W. Clegg, Tma JOURNAL, 68, 233 (1954). (3) K. A. Sense, M. J. Snyder and R. B. Filbert, Jr., ibid., 18, 096 (1954).
c
