NOTES
Jan., 1942 n
A,, = (1/2)
(-l){-'/(i i=1
- I)!
(7)
TABLE I HEAT CAPACITY DATAFOR GASEOUS2,2,4-TRI-
%ME
METHYLPENTANE
and n
S,
179
(n - i
= 1/2
+ 1)(-
- I)!
(8)
i-1
When n is large, A, represents the average number of isolated functional groups of either variety, X or Y , per substituent.' The series in (7) converges rapidly as n increases giving in the limit A, = l/*e. That is, a fraction equal to '/ze, or 18.4%) of the functional groups is isolated a t completion of the condensation. Esso LABORATORIES CHEMICAL
DIVISION OF THE
STANDARD OIL DEVELOPMENT Co. ELIZABETH, N. J.
RECEIVED OCTOBER17, 1941
Units are cal. per degree per mole. CP (1 atm.) CPO T,
OR.
423 442 442 448 449 458
Expt.
(61.6 63.8 64.6 65.6 65.3 66.7
* 0.6) * 1.0 * 1.0
* 1.0 * 1.0 * 1.0
Calc. eq. 1
Expt.
Calc. eq. 2
61.6 63.7 63.7 64.3 64.4 65.4
(61.1) 63.4 64.2 65.2 64.9 66.3
60.3 62.2 62.2 62.9 63.0 63.9
550" for Pc and T,, respectively. The calculated values for Cpoin the last column have been obtained from Pi tzer's general empirical equation for gaseous paraffins Cpo
- 0.62 + t ( O . O l l l ~+ 0.0158)
= 6.65%
(2)
where n is the number of carbon atoms and 1 is the centigrade t e m p e r a t ~ r e . ~While he suggests that this latter equation is probably applicable to BY MILOKIPERASH AND GEORGE S. PARKS branched paraffins as well as to the normal comRecently Pitzer' has reported a single experi- pounds, it apparently runs a little low in the case mental value for the heat capacity a t 423'K. and of this highly branched compound. In passing, 1 atm. (constant pressure) of gaseous 2,2,4-tri- we should note here that heat capacity values methylpentane. On the basis of statistical calcu- calculated for 2,2,4-trimethylpentane by the lations and with the guidance of this value he also semi-theoretical methods of Bennewitz and Rossner4are of the order of 10 per cent. low, or more, as has suggested the general equation Pitzer likewise found in the case of their experiC, = -227.3 + 110 log T (1) mental determination on n-heptane. for the heat capacity of this hydrocarbon as a (3) Pitzer, THIS JOURNAL, 63, 2413 (1941). function of the absolute temperature. (4) Bennewitz and Rossner. 2. p h y s i k . Chem., B89, 126 (1938). Two years ago, in connection with some other DEPARTMENT OF CHEMISTRY UNIVERSITY RECEIVED OCTOBER 14, 1941 work on organic compounds in the gaseous state, STANFORD STANFORD UNIVERSITY, CALIFORNIA we likewise made five determinations of the molal heat capacity a t 1 atm. pressure of gaseous 2,2,4trimethylpentane. A "constant flow" method, The Identification of Alcohols in Aqueous briefly described elsewhere by Parks and ShoSolution mate12was employed, and the uncertainty in the BY WILLIAM N. LIPSCOMB AND ROBERT H. BAKER' resulting data is probably within 1.5%. Our results lie between 442 and 458'K. and are given The identification of an alcohol when it appears in the second column of Table I. For comparison in aqueous solution as from the saponification of the value of Pitzer is included parenthetically. an ester usually involves its isolation by repeated Column 3 contains the corresponding values cal- distillation, salting out, and drying. Henstock2 culated by Pitzer's equation, from which our data was able to avoid this time-consuming procedure differ on the average by 1.4%. In view of the by the use of the Schotten-Baumann reaction of p facts this is a reasonable check. nitrobenzoyl chloride a t - 15'. In Column 4 appear O C , values for the gas at We have found that the more satisfactory 3 3 zero pressure. These have been derived from the dinitrobenzoates may be formed by slight modifiprevious experimental results by use of Berthe- cation of the Henstock procedure. The process lot's equation of state C (O , = C, - 81RPTc3/ involves adding alkali and sodium acetate to the 32PcT3)and with the assumption of 25 atm. and aqueous solution of the alcohol and shaking it a t Some Heat Capacity Data for Gaseous 2,2,4Trimethylpentane
(1) Pitzer, THISJOURNAL, 68, 1224 (1940). (2) Parks and Shomate, J . Chcm. Phys., 8, 428 (1940).
(1) Present address. Northwestern University, Evanston, Illinois. (2) Henstock, J . Chcm. Soc., 216 (lQ8a).
