Nov., 1960
HEATSOF COMBUSTION AND FORMATION OF NAPBTHALENES
1723
HEATS OF COMBUSTION AND FORMATION OF NAPHTHALENE, THE TWO METHYLNAPHTHALENES, cis AND transDECAHYDRONAPHTHALENE, AND RELATED COMPOUNDS1 BY DIMITRIOS M. SPEROS AND FREDERICK D. ROSSINI* Chemical and Petroleum Research Laboratory, Carnegie Institute of Technology, Pittsburgh I d , Pennsylvania Received M a y
is91960
Measurements were made of the heats of combustion of naphthalene (c), 1-methylnaphthalene (liq), 2-methylnaphthalene (c), cis-decahydronaphthdene (liq), and trans-decahydronaphthalene (liq), a t 25'. With these a.nd related other data, values were calculated for the standard heats of formation a t 25" for naphthalene and 2-methylnaphthalene in the solid, liquid and gaseous states, for 1-methylnaphthalene and the c i s and trans isomers of decahydronaphthalene in the liquid and gaseous states, and for the higher members of the series of l-n-alkyl naphthalenes and 2-n-alkyl naphthalenes in both the liquid and gaseous states. Equations are also given for the standard heats of vaporization at 25' for the last two series of compounds. The relation between energy content and molecular structure is discussed.
I. Introduction Lack of reliable data on the heats of formation of naphthalene, the two methylnaphthalenes, and the cis- and trans-decahydronaphthalenes has greatly hampered the making of reliable calculations of the thermodynamic properties of the important reactions in which these hydrocarbons take part. To evaluate the heats of formation, isomerization and hydrogenation, as appropriate, of these compounds, precise and accurate measurements of the heats of combustion are required. With such data available, the relation of energy content with structure can be studied for these molecules. The present investigation reports experimental data on the heats of combustion of naphthalene, l-methylnaphthalene, 2-methylnaphthalene, cis-decahydronaphthalene and trans-decahydronaphthalene, and presents the results of the calculations made therefrom. In particular, it was possible to calculate values for the heats of combustion and formation of all the higher members of the normal alkyl series of 1-naphthalene and of 2 - n a ~ h t h a l e n ein , ~ both ~ ~ the liquid and gaseous states.
The compounds measured in the present investigation were API Research hydrocarbons, made available through the API Research Project 44 from materials purified by the API Research Project 6. The samples had the following values of purity, in mole per cent.: naphthalene, 99.97 f 0.03; 1-methylnaphthalene, 99.97 f 0.03; 2-methylnaphthalene, 99.92 f 0.06; cis-decahydronaphthalene, 99.93 f 0.05; trans-decahydronaphthalene, 99.97 =k 0.03. Description of the purification and determination of the purity of these samples has already been given.686 The impurities in these samples are similar to the parent substances, as a result of the methods of purification, and are believed to have an insignificant effect on the results. The three hydrocarbons that were liquid at room temperature were enclosed in sealed t.hin-walled glass ampoules of appropriate volume,, as previously de~cribed.33~The 2-methylnaphthalene, F t h melting point near 34.6', was similarly sealed in thm-walled glass ampoules using a special procedure of introducing the melted material in portions and letting the material in the ampoule solidify each time. The naphthalene, with melting point near 80.3', was burned in the form of a solid, pressed pellet, unsealed. It was determined from measurements made in the balance case that the loss in weight of the unsealed naphthalene was small enough to be insignificant. I n the lat>tercase, the error arising from vaporization of the naphthalene in the bomb would be that due to the heat of sublimation of the vaporized naphthalene, the determination of the amount of reaction being unaffected.
11. Apparatus and Experimental Procedures
111. Data of the Present Investigation Table I gives the results on the determination of the energy of ignition. I n these experiments, only the standard amount of fuse wire was burned in oxygen, using the same procedure and ignition apparatus as in regular combustion experiments. The energy equivalent of the standard initial calorimeter system was determined from a series of six combustion experiments with NBS Standard benzoic acid, No. 39g, using the value 26,433.8 joules/g. mass for the heat of combustion of this sample under the conditions of the standard bomb process a t 25", with appropriate corrections for the differences between the actual and standard bomb processes. The results of these calibration experiments are given in Table 11. The symbols are as previously defined.4 The results of the calorimetric combustion experiments for naphthalene, 1-met,hylnaphthalene, 2-methylnaphthalene, cis-decahydronaphthalene and trans-decahydroiiaphthalene are given in
The experimental values of this investigation are based on the absolute joule as the unit of energy. Conversion to the defined thermochemical calorie is made using the relation 1 calorie = 4.184 (exactly) joules. For internal consistency with other investigations from this Laboratory, the molecular weight of carbon dioxide was taken as 44.010 g./mole. I n this investigation, the chemical and calorimetric apparatus and procedures were the same as described by Browne and R ~ s s i n i . ~The rise ,Of temperature in each calorimetric experiment was near 2 , with the final temperature being near 30°, the temperature of the jacket of the calorimeter. The amount of reaction in each hydrocarbon combustion experiment was determined from the mass of carbon dioxide formed in the combustion 8,s previously described.' The bomb had an internal volume of 380 ml. One ml. of water was placed in the bomb prior to each combustion experiment. The pressure of the oxygen for combustion was made 30 atmospheres (calculated to 25').
* Department of Chemistry, University of Notre Dame, Notre Dame, Indiana. (1) This investigation was supported in part by a grant from the National Science Foundation. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry at the Carnegie Institute of Technology. (2) E. J. Prosen and F. D. Rossini, J . Research NatZ. BUT.Standards, 34, 263 (1945). 64, 1530 (3) Sr. 11. C. Loeffler and F. D. Rossini, THIEJOERY.&L. (1960). (4) C. C. Browne and F. D. Rossini, {bid., 64, 927 (1960).
(5) A. J. Streiff, L. F. Soule, C. M. Kennedy, M. E. Janes, V. A. Sedlak, C. B. Willingham and F. D. Rossini, J . Research Natl. Bur. Standards, 46, 173 (1950). (6) A. J. Streiff, A. R. Hulme, P. .1. Coaie. N. C. Krouskop and F. D. Rossini. Anal. Chem., 27, 44 (1955).
VoI. 64
DIMITRIOS M. SPEROS AND FREDERICK D. ROSSINI
1724
TABLE I RESULTSON
THE
DETERMINATION OF THE ENERGY OF IQNITION
Eipt.
Mass of iron wire, g.
A R , ohm
Total energy of ignition, j.
1 2 3
0.008190 .008080 .008000
0.000440 .000429 .000432
90.6 88.4 88.9
Energy due t o combustion.of iron wire, 1.
Energy due to electric current, j.
54.3 53.6 53.0 Mean value Av. deviation
Dev. from the mean, I.
36.3 34.8 35.9 35.7
+0.63
-0.87 $0.24
f0.6
TABLE I1 RESULTSOF THE CALIBRATION EXPERIMENTS WITH BENZOIC ACID No. of expt.
6
Range of mas8 of benzoic acid, g.
Range of K, ohm
Range of k, min. -1
Range of U,ohm
Range of ARC, ohm
Range of Range of qn, I .
qi, 1.
Range of j./ohm
Ei,
Mean and stand. dev. of the mean, j./ohm
1.52015to 0.001544to 0.000780to 0.000067to 0.195401to 13.9to 89.0to 206,127to 2 0 6 , 1 4 2 f 6 1.55820 0.001610 0.000913 0.000266 0.199643 17.3 90.2 206,160
TABLE I11 RESULTSOF No.
Range of Mass of
THE
cor
formed, g.
Range of k, min.-1
Range of K ,ohm
6
3.31467 to 3.55938
0.001575 t o 0,001607
0.000771 t o 0.001083
0.000048to 0.000176
6
3.38429 to 3.48652
0,001562 to 0.001630
0.000734to 0.001071
0.000048to 0,000144
5
3.33895 to 3.57303
0,001577 to 0.001610
0.000626to 0.000947
0.000080to 0.000208
6
2.85643 to 2 96221
0.001580to 0.001608
0.000896 to 0.001588
0.000048to 0.000112
5
2.81739 t o 2 97173
0.001580to 0.001629
0.000674to 0.001126
0.000016to 0.000129
of expt.
Range of U,ohm
COMBUSTION EXPERIMENTS Range of Avi, ohm
Range of A m , ohm
Ran e of B ohmfg. CO;
Mean and stand. dev. of the mean ohm/g. eo:
0.000437 to 0.000441
0.000015 t o 0.000024
0.0567830 to 0.0568398
0.0568155 f 0.0000088
0.000020to 0.000027
0.0581990to 0.0582528
0,0582352 f 0.0000082
0.000023 to 0.000033
0.0580821 t o 0.0581193
0.0581078 f 0.0000368
0.000018to 0.000044
0.0691824 to 0.0692173
0.0691993 0.0000045
0.000008to
0.0690844 t o 0.0690859
0.0690753 St 0.0000045
Range of ARo, ohm
Naphthalene (c) 0.18866Oto 0.202686
I-Methylnaphthalene (liq) 0,198129 to 0.203484
0.000439to 0.000443
2-Methylnaphthalene (c) 0.194489 to 0.200811
0.000437 to 0.000441
.
cis-Decahydronaphthalene (liq) 0.198124to 0.205475
0.000425to 0.000443
*
trans-Decahydronaphthalene(liq) 0.195091 t o 0.205760
0,000437 to 0.000447
0,000049
TABLE IV VALUESa O F THE STANDARD HEATSO F COMBUSTION FOR NAPHTHALENE, 1-METHYLNAPHTHALENE, 2-bfETHYLNAPHTHALENE, Cis-DECAHYDRONAPHTHALENE AND t?WM-DECAHYDRONAPHTHALENE AH0 a t 30°, e -
.
-
-
Compound B a t 30°, A F n a t 30°, A S 0 a t 30°, Name Formula State ohms/ 1) (14) naphthalene(g) = cis-decahydronaphthalene(g)
-
AH02g816 = -76.70 f 0.71 kcal./mole (10) naphthalene(g) = trans-decahydronaphthalene(g) 16 = -79.79 f 0.71 kcal./mole (11) naphthalene(1iq) = cis-decahydronaphthene(1iq) A H o ~ g 816 = -75.47 0.44 kcal./mole (12) naphthalene(1iq) = trans-decahydronaphthalene(1iq) AH0~98 16 = -78.16 i 0.44 kcal./mole (13)
*
With the values for the heats of formation at 25" given above for 1-methylnaphthalene and 2methylnaphthalene, together with previously reported data, it is possible to calculate reliable values for the heats of formation for the entire series of the 1-n-alkyl naphthalenes and the 2-n-alkyl naphthalenes, in both the liquid and gaseous states. It has been shown that, within the limits of presentday measurements, there is a constant increment per CH2group in the standard heat of formation of the members of any normal alkyl series of hydrocarbons, beyond the first several members, for both the gaseous and liquid state^.^.^ At 25", the increment per CH2 group in the standard heat of formation is -6.106 kcal./mole for the liquid state and -4.926 kcal./mole for the gaseous state.2 It has been shown18 that the increment per CH2 group changes most markedly from constancy for the introduction of the first CH2 group on the end group Y to start the normal alkyl chain, with the deviation from constancy being much less for the next substitution to make an ethyl group, and approaching constancy from then on. The proper increment to be added to 1-methylnaphthalene to form 1-ethylnaphthalene may be taken the same as between lJ2-dimethylbenzeneand 1-methyl-2-ethylbenzene. Similarly, the proper increment t o be added to %methylnaphthalene to form 2-ethylnaphthalene may be taken the same as between 1,3dimethylbenzene and 1-methy I-3-ethylbenzene. (18) E. J. Prosen, W. H. Johnson and F. D. Rossm, J. Research Nat2. Bur. Standards, 37, 51 (1946).
1-n-naphthalenes(g): AHfO = 33.57 - 4.926m kcal./mole ( m > 1) (15) 2-malkyl naphthalenes(1iq): AHfO = 20.17 - 6.106m kcal./mole ( m > 1) (16) 2-n-alkyl naphthalenes(g): AHfo = 33.02 - 4.926m kcal./mole ( m > 1) (17)
In the foregoing equations (and also following), m is the number of carbon atoms in the normal alkyl chain attached to the end group Y, as Y-(CH,), - H, with Y being here naphthalene (less one hydrogen atom) and the point of attachment of the radical being in the 1- or 2-positions as indicated. From the foregoing, one may write the following equations for the standard heat of vaporization, from the liquid to the gaseous state, at 25", for the members of these series beginning with the ethyl members 1-n-alkyl naphthalenes: AHvO = 13.19 1 . 1 8 kcal./mole ~~ (m
+ > 1) 2-n-alkyl naphthalenes: AHvo = 12.85 + 1.18m kcal./mole ( m > 1)
(18)
(19)
VI. Discussion In addition to providing base lines from which one may calculate the heats of formation, for both the liquid and gaseous states, for a great number of compounds that have not been, and may never be, measured experimentally, the data of the present investigation give quantitative information on the relation between energy content. and molecular structure for these substances. For the two isomers of methylnaphthalene, the present data indicate that, within the limits of uncertainty of the measurements, the two isomers have substantially the same energy) in both the liquid and the gaseous states, -the actual dif(19) W. H.Johnson, E. J . Prosen and F. D. Rossini, {bid., 36, 141 (1945).
Nov., 1960
THERMAL DECOMPOSITION OF AMMONIUM PERCHLORATE IN THE SOLIDSTATE
ferences being, respectively, 0.12 f 0.53, and -0.18 f 0.88 kcal.!mole at 25”. With regard t o the cis and trans isomers of decahydronaphthalene, the data indicate that, for the liquid state a t 25”, the trans isomer is more stable (lesser energy content) with respect to energy than the cis isomer by 2.69 f 0.31 kcal./mole. For the gaseous state, the difference increases slightly to 3.09 f 0.77 kcal./mole. This value is in substantial accord with the theoretical calculations which have been made, involving the non-bonded skew interactions in these molecules, considering khat the cis isomer is largely comprised of two [‘chair”
1727
forms of cyclohexane joined together (with loss of two carbon and four hydrogen atoms) in “cis” fashion and that the trans isomer is largely comprised of two “chair” forms of cyclohexane joined together in “trans” fashion.1e-25 (20) K. S. Pitzer and C. W. Beckett, J . Am. Chem. Soc., 6 9 , 977 (1947). (21) C. W. Beckett, K. 6 . Pitzer and R. Spitzer, ibid., 69, 2488 (1947). (22) R. B. Turner, ibid., 1 4 , 2118 (1952). (23) W. 5. Johnson, kbtd., 1 5 , 1498 (1953). (24) H.D. Orloff, Chem. Reus., 54, 347 (1954). (25) W.G. Dauben, 0. Rohr, A. Labbauf and F. D. Rossini, THIS JOURNAL, 64, 283 (1960).
THE EFFECTS OF X-RAY AND GAMMA RAY IRRADIATION ON THE THERMAL’ DECOMPOSITION OF AMMONIUM PERCHLORATE Ih’ THE SOLID STATE BY ELI S. FREEMAN, DAVIDA. ANDERSONAND JOSEPH J. CAMPISI~ Pyrotechnics Chemical Research Laboratory, Picatinny Arsenal, Dover, New Jersey Received M a y 18, 1960
The effect of exposure of ammonium perchlorate to X-ray and ?-ray radiation on its chemical reactivity with respect to thermal decomposition was investigated. The course of the reaction was followed by differential thermal analysis and by thermogravimetric experiments conducted under ambient and reduced pressures. Decomposition was also studied by microscopic observations. The data show that several stages of reaction are involved in the decomposition of ammonium perchlorate and that the low temperature stages are appreciably enhanced as a result of pre-irradiation. The relative importance of the various stages of reaction were found to be a function of the exposure dose. Although direct evidence is lacking it is suggested that the increased reactivity of the irradiated substance may be due t o the presence of positive holes which would favor an electron transfer mechanism of decomposition. The effect of impurities such as Ag+, Cu++ and Iions on decomposition seem to support the suggested mechanism. The decomposition pattern of samples exposed to ?-rays is similar to that of the X-ray irradiated ammonium perchlorate.
Introduction Research concerning the effects of high energy radiation on ionic crystals has been principally concerned with physical changes and chemical reactions induced by radiation. There is little in the literature, however, concerned with the effects of pre-irradiation on the chemical reactivity of inorganic solids. This important aspect of the problem of radiation effects is considered in this paper with respect to the solid state thermal decomposition of ammonium perchlorate. An indication that radiation affected the isothermal decomposition of NHICIOl was reported by Bircumshaw and P h i l l i p ~ who , ~ found that the induction period for reaction was reduced after exposure to ultraviolet light. Further preliminary evidence for increased chemical reactivity was reported by Freeman and Anderson14 who showed that the differential thermal analysis reaction spectrum of KH4C101 was altered after being irradiated with X-ray radiation. In the present work the effects of X-rays on the thermal decomposition of NH4C104were more fully investigated and the effects of y-ray irradiation were also probed. (1) This paper was presented in part before the Division of Physical Chemistry a t the Boston National Meeting of the ACS, April 1959. (2) Explosives and Propellants Laboratory. (3) L. I,. Bircumsham and R. R. Phillips, J . Chern. SOC.,966, 4741 (1957). (4) E. F. Freeman and D. A. Anderson, THISJOTXWAL, 6 3 , 1344
(1959).
Decomposition was investigated a t atmospheric and reduced pressures by differential thermal analysis (d.t.a.) and by recording changes in sample weight as temperature was continuously increased. By increasing sample temperature a t a pre-determined rate, the transition from one stage of reaction to another may be observed continuously over the complete temperature range of reaction resulting in unique reaction spectra. Experimental Samples of ammonium perchlorate (Fisher Scientific Co., certified reagent grade) were irradiated with X-rays under a vacuum of 2 mm. in Pyrex tubes, 1.8 cm. diameter and 5 cm. long. The analysis given on the label is, C1-, O.OOO%, SO4-, 0.003%; ClOs, O.OOO%, Fe, 0.0?04% and heavy metals, 0.000270. The principal radiation source was an OEG-50 X-ray tube with a molybdenum target, which was operated to give a dose rate of 2.1 X 105 roentgens/hour. Samples were also irradiated a t the Brookhaven National Laboratory a t B rate of 1.0 X 1 0 6 r./h. for and 24 hours using a cobalt-60 source. The exposure doses were determined by ferrous sulfate dosimetry.5 The ferrous sulfate doses were converted to ammonium perchlorate doses by multiplying the dosimeter values by the ratio of electron densities of NH&101 and the dosimeter. The radiation units are reported in e.v. absorbed/molec. D.t.a. experiments were conducted on 250-mg. samples heated a t the nominal rate of 5’/min. in air snd under a pressure of 1 mm. An equivalent amount of powdered alumina was used as the reference material. The apparatus was the same aa that previously described6 with the excep( 5 ) H. G. Swope, “Dosimetry in the Argonne High-Level Gamma Irradiation Facility, ANL,”-5819, Jan. 1958.
