SEYMOUR MEYERSON
3340
reciprocals of the specific rate constants. The equilibrium constants are the negatives of the abscissa intercepts. The equilibrium constants can also be calculated by dividing the urdinate intercepts, l / k , b y the a n d k obtained for the slopes, l / ' k K ~ .T h e values of hTZ three temperatures are listed in Table 11.
TABLE I11 \.ARIATION
T,O
K,
C
2 50
60 niin. 75 :tiin. 90 inin. 105 rnin. 4 hr. 5 hr 6 hr.
TABLE I1 EQUILIBRIUM CONSTANTS FOR T H E P Y R O DECOMPOSITION IN EQLrIMOLAR (Na,K)NOs K x 101. K X 108,
SPECIFIC K A T E AND SULFATE
T,OC
k X 107, m i n . - l
ref. ;3
this study
250 275 300
31 i 6 74 f 3 162 f 1
26
7,2f0.7 21.8 f 2 50.8 f
K1 (250') K , (:300")
= =
( 2 . 7 i 0.3) X (5.7 i 0 . 1 ) x 10-24
If the assumption is made t h a t the enthalpy of dissociation is constant over the temperature range 250-300", the enthalpy of dissociation can be calculated from the Clausius-Clapeyron equation. T h e AH" value thus obtained and the AGO and A S " values for the nitrate ion dissociation are given in Table IV.
[CONTRIBUTIOX FROM
THE
x
OF 1077
3 . 79 3,98 4.93 5.01
K,
LVITH
T.
TIME
300
6.74 7 89 10.40
x
K:
oc
6 rnin. 10 min. 16 min. 25 rniti. 30 inin. 38 inin.
10'Z
"32 3.54 t5.48 X 3fi 9.89 11.91
TABLE I[* VALUES OF AH', AGO, A X D A S ' FOR THE SITRATE ION DISSOCIATION
1
T h e concentration of total acid, Ta, present a t any time was determined by an iodometric t i t r a t i ~ n . ~ Six or seven samples were taken a t each of two temperatures, 250 and 300°, and the corresponding potentials recorded. T h e constant K 1 was determined from each sample with the aid of eq. 9. At both temperatures it was observed t h a t the dissociation constant K1increased with time. This increase can probably be explained by taking into account the increase in sulfate ion concentration which had been assumed t o be constant in the derivation of eq. 9. Since the sulfate ion concentration was known accurately initially, the data a t each temperature were extrapolated back t o zero time. T h e experimentally determined values of K 1 are listed in Table 111. T h e values of K 1at zero time are
Vol. 85
T,O
C
AGO kcal
250 275
60 9
300
60 6
A H o kcal
~ 5 ' ,e
ii
4 6 63 3 4 7
No mention has been made as to what form the oxide ion takes when in solution in fused nitrates. T h e measurements so far involved only require the oxide ion t o exist as such on the electrode surface and an equilibrium between the oxide ion and any solvated species It seems reasonable t h a t in a solution of alkali nitrates the oxide ion could exist in forms containing N a + , K T ) or NOs-. The existence of an orthonitrate ion, N04-3, has been postulated by several workers, among the more recent of which is K ~ h l m u l l e r who , ~ prepared both sodium and potassium orthonitrates by dissolving alkali oxides in alkali nitrates I t may be t h a t the orthonitrate ion can exist in solution in alkali nitrate solvents, a t least in small concentrations However, a spectroscopic analysis of such a solution would be needed t o establish unequivocally the existence of the orthonitrate ion (7) R Kohlmuller A n n chrm ( P a r i s ) , 4 , 1183 (1959)
RESEARCH A N D DEVELOPMEVT DEPARTMENT, AMERICANOIL Co , WHITING, IND]
Organic Ions in the Gas Phase. XIII. Cycloheptatriene-7-d; Decomposition of C7&+ and C7&++ from Cycloheptatriene and Toluene BY SEYMOUR MEYERSON RECEIVED MAY31, 1963 T h e mass spectra of cycloheptatriene unlabeled and -7-d show t h a t , a4 in other C ~ Hisomers, P the eight hydrogen atoms lose positional identity in nearly all the decomposition reactions of singly ionized molecules produced by electron impact Such loss of identity occurs also in decomposition of doubly ionized cycloheptatriene t o CiHi+- and to C7H6+*and of doubly ionized toluene to C,H6++, but, in the process whereby doubly ionized toluene loses a hydrogen atom t o form C,H,-+, any one hydrogen in the methyl group is about four times as likelj to be lost as one in the ring Thus t h e distinction between methyl and ring hydrogens survives in t h e excited doubly ionized state or states involved
Loss of a hydrogen atom from toluene under electron impact--to give a C7H7+ ion t h a t most probably has the symmetrical tropylium structure',2-is preceded or accompanied by a rearrangement in which the eight hydrogen atoms lose identity, as shown b y the mass spectra of variously deuterated species of toluene.l!Jd!lti2): R r i l l ' i i s ' r h i , n 82, 717 U!Jli:i)
(13) S. Sfeyerson a n d P. S . R y l a n d e r , J . P h y s i ' h r i i i , 6 2 , 2 (l!4.58) (14) S. hfeyerson, J . C h r i n . P h y s . , 3 4 , 2 O i f i ( I t I R 1 ) . (1.5) S . Meyersr,n. T . I ) . S e v i t t . a n d P. N I
