THERMODYNAMIC FUNCTIONS OF ALKYLNAPHTHALENES
June 20, 1956
2707
servation, the entropy difference between the PuOZ+ then a weighed quantity of standardized hydroand PuOZ+*ions in molar perchloric acid a t 25' has chloric acid was added to make the final concentrabeen found to be 9.5 e.u. in the present work. An tion 0.50 M hydrochloric-0.50 M perchloric acid. interesting comparison of entropy changes for The plutonyl ion was titrated with P i 3 in acid of + ~ posimilar reactions of neptunium and plutonium in 1 the same composition. The P u + ~ - - P uformal ,VI perchloric acid a t 2 5 O can be made. For the reac- tential in 0.50 M hydrochloric-0.50 JI perchloric H + acid, -0.9750 volt, was used in the computation of tions X+3 H + X f 4 l'2H2 and XO+* F! X02-* l/*H2,Cohen and Hindmanll found the ratio, ~ ( P U I ~ ) / ( P Uthus + ~ )the , assumption that -31.2 and 6.4 e.u. for neptunium ions, whereas for the Z(PuIV) = (PuOz+) is not invalidated by the plutonium ions the values of the entropy differences chloride complexing of P u + ~ .A value of -0.9124 have been found to be -30.2 and 6.0 e.u., respec0.0001 volt was obtained for the Pu02+-PuO2+' tively. However, for the reaction X f 4 2Hz0 $ formal potential in this solvent a t 25". The more X02+ 3H+ '/%Hz,the value of 62.3 e.u. has positive value of this couple in 0.50 -21 hydrobeen reported1' for neptunium and a value of 50.1 chloric-0.50 M perchloric acid appears to indicate e.u. has been computed from the plutonium (111)- the formation of a plutonyl chloride complex. (IV) and (VI-(VI) couples together with the Pu(1V) disproportionation results. It appears that the Since formal potential measurements yield only difference between these two A S values reflects a differences in the stabilities of the complex ions, it measure of the difference in the structure of the is necessary to use some other means to obtain the degrees of complexing of one of the ions directly. neptunium and the plutonium ions. Potentials of Plutonium Couples.-In Table IV Complexing of Pu02+*by Chloride Ion.-From alterations in the absorption spectrum of plutonyl are given the formal potentials of the plutonium ion as the solvent is changed from perchloric to couples in molar perchloric acid a t 25.00'. The and ~ the Pu02+-Pu02+' potentials have hydrochloric acid it has been concluded that a P u + ~ - P u + chloride complex is formed.12 It has been ob- been measured directly. The remainder of the served that a color change visible to the unaided eye potentials have been calculated from these values occurs upon the addition of hyTABLE 11drochloric acid to a Derchloric acid FORMAL POTENTIALS O F PLCTONIUM COUPLES AT 25" solution of plutonyl ion. A solu- 0.9819 - 1.1721 -0.9133 tion of plutonyl ion was prepared HCIOl p u i s Pu'4 PUO? PUO,'~ by the ozonization of a perchloric - 1.0433 I -acid solution of Puf3. At the
+ + +
+
+
+
*
+
+
A
completion of the oxidation period, the dissolved ozone was removed by bubbling helium through the solution, (12) R . E. Connick, M. Kasha, W. H. RIcVey a n d G. E. Sheline, "The Transuranium Elements," Natl. Nuclear Energy Ser., I V , 14-B McGraw-Hill Book Co., Inc., New York, N . Y . , 1949, p. 5 5 s .
[CONTRIBUTION FROM
THE
I
~
.-
- 1.0228
A
and the Pu + 4 disproportionation equilibrium quotient. Los ALAMOS,SEW MEXICO
DEPAXTMENT OF CHEXISTRY A N D CHEMICAL ENGINEERING, USIVERSITYOF CALIFORNIA, BERKELEY]
Thermodynamic Functions of Alkylnaphthalenes from 298 to 150O0Ka1 BY DOLPHUS E. MILLIGAN, EDWIND. BECKERAND KENSETHS. PITZER RECEIVED JASUARY 21, 1956 The values of the heat content function, free energy function, heat capacity and entropy of the diniethylnaphtlialeties of the 1-n-alkylnaphthalenesand 2-n-alkylnaphthalenes and of three methylethylnaphtha(except 1,8-diinctli?-lnaphthalene), lenes have been calculated by the method of increments. The functions are tabulated from 298 t o 15OO0K. The barriers to internal rotation of the methyl group in 1- and 2-methylnaphthalenes have been determined to be approximatell- 3.8 and 2.3 kcal./mole, respectively. The entropy uncertainty of approximately 0.5 cal./deg. mole yields ranges 2.5-5.6 and 0.93 . 5 kcal./mole for the potential barriers.
Values of the thermodynamic functions of naphthalene in the ideal gas state have recently been calculated on the basis of a complete vibrational assignment for this molecule. These functions, together with the previously published functions of paraffin^^,^ and a l k ~ l b e n z e n e s , ~ furnish ,~ the basis (1) This research was a p a r t of t h e program of Research Project 50 of t h e American Petroleum Institute. (2) A. L. McClellan and G. C. Pimentel, J . Chem. Phus., 23, 215 (19.55).
(3) IC. S. Pitzer, I n d . E x g . Chein., 86, 829 (1944). (4) Taylor, Wagman, Williams, Pitzer and Rossini, J . Research S n t i . Buy. S t o , i d a i d s , 3 1 , 95 ( l U 4 C ) . (3) "Selected Values of Physical and Thermodynamic Properties of
for a calculation of the thermodynamic properties of various alkylnaphthalenes. We have used the method of increments6 to calculate values of the heat content function, free energy function, heat capacity and entropy of all dimethylnaphthalenes (except 1,8-dinlethylnaphthalene), all 1-n-alkylnaphthalenes and 2-n-alkylnaphthalenes and 2-methyl-3-ethyl-, 2-methyl-6-ethyland 2-methyl-7-ethylnaphthalene. In certain cases the potential barriers to internal rotation are exHydrocarbons and Related Compounds," Carnegie Press, Pittsburgh 1953. ( 6 ) For a discussion of this method see, for example, reference 2
D. E. MILLIGAN, E. D. BECKERAXD K. S. PITZER
2708
pected to differ from the values found for the benzene series. Entropy values for 1- and 2-methylnaphthalenes' are used to evaluate potential barriers for the naphthalene series. 1- and 2-Methylnaphthalenes.-Experimental thermodynamic data are available for only these two alkylnaphthalenes. In each case we have the entropy of the liquid7 a t temperatures up to 360'K. and precise vapor pressure measurementsa in the range 410-520'K. This leaves a gap of about 50' across which an interpolation must be made if we are to obtain thermodynamic functions for these substances in the gaseous state. We used several methods based upon independent assumptions for this interpolation but will describe only the simplest here. The others yielded concordant results. I n the absence of other information as to the functional form of the liquid heat capacity-temperature relation, straight lines with the equations
+
C, = 22.52 0.10442" (1-methylnaphthalene) C, = 23.66 f 0.09972" (2-methylnaphthalene)
(1) (2)
were fitted to the experimental points between the melting point and 360'K., and these lines were used for extrapolation of the liquid heat capacity to higher temperatures and calculation of the entropies of the liquids a t temperatures above 360'K. These heat capacity extrapolations were checked in a manner to be described below. The values of the entropy of vaporization a t several temperatures were calculated from the vapor pressure equations of Cainin and Rossinia on the assumption that the vapor volumes follow the Berthelot equation of state with critical constants T , = 773'K. and P, = 38 atm. These values were estimated from the known values for naphthalenelo ( T , = 753*K., P, = 41 atm.) by the use of the approximate increment for the addition of a CH2 group found for the paraffins and alkylbenzenes. The correction of the entropy to the ideal gas state was made with the aid of the Berthelot equation and the entropy of compression was then added to yield the values shown in Tables I and I1 for the entropies of the ideal gases a t the standard pressure of one atmosphere. TABLE I ROTATION IS CALCULATION OF THE BARRIERTO IXTERNAL 1-METHYLNAPHTHALENE Temp.,
OK.
sT(liq) A S " (at T ) S(ideal gas) - S(rea1 gas) S(l atm.) - S(v.p.)
425 82.08 29.38
440 81.43 27.88
450 85.97 26.93
470
500
89.05 25.20
93.57 22.85
0.00
_______
0.02 -5.08
0.03 -4.08
0 04 -3.46
~
-2.31
0.11 -0.80
S;
106.40
108.26
109.48
112.00
115.73
S ; (freely rotatin:: Ineth,-lnaphthalene) ( S r - SIT l'a/Rl' l'o(cal./mole)
107.60 1.20 4.30 3710
109.42 1.16 4.26 3720
110.65 1.17 4.27 3820
113.09 1.09 4.01 3740
116 76 1.03 3.81 3790
_
(7) Private communication from Dr. G . \\'addington, U. S. Rureau of Rlines, Bartlesville, Oklahoma. (R! D. L. Camin and F. D. Rossini, J . P h y s . Chem., 69, 1173 i1ri i.i) , (9) Some other m e t h o d s are diaciisied in an American I'etralewn Copies m a y be Institute Project 50, Report of September 2 6 , 19:5.
obtained from t h e authors. (10) E. Schroer, 2 . p h y s i k . C h e n . , B49, 2 i l (1941).
CALCULATION OF Temp., OK. Sr(1iq) ASv(at T) S(idea1 gas)
TABLE I1 BARRIERTO INTERNAL ROTATION IN 2-METHYLNAPHTHALENE THE
425 82.83 28.99
-
-
440
450
85.15 27.47
86.68 26.61
470 89 69 24.90
500 9-1 15 22 57
0.03 -3.89
0.04 -3.28
0 07 -2 1-1
0 12 - 0 64
106.96
108.76
1 1 0 . 0 5 112 52
116 20
107.60 0.64 2.70 2280
109.42 0.66 2.74 2395
1 1 0 . 6 3 113.09 0.00 0 57 2.58 2 40 2306 2325
116 76 0.30 2.48 2463
S(rea1
gas)
S ( l atm.)
Yul. 7s
S(v.y.)
S;
0.02 -4.88
-- _ _ -
sg (freely rotating methylnaphthalene) (Sf - S)T VdRT Vo(cal./mole)
The values shown in Tables I and I1 for a freely rotating methylnaphthalene were obtained by the following equation
+
S = S(naphtha1ene) S(to1uene) - S(benzene) - R In 3/2 (Sf - S)(750 cal. barrier)
+
(3)
The first three terms give a base value for a methylnaphthalene which must be corrected by the fourth term for symmetry and the fifth term for the 730 cal./mole potential barrier which was employed in the toluene calculations. The lower parts of Table I and I1 show the calculations of the apparent potential barriers to methyl group rotation in the methylnaphthalenes. The tables of Pitzer and Gwinnll were used together with a moment of inertia of 5.52 X g.cna The uncertainty in the entropy values may be estimated to be about 0.5 cal./mole. This leads to ranges of 2.5-5.6 and 0.9-3.5 kcal./mole for the potential barriers. Thus we may safely conclude that a substantial barrier exists in l-methylnaphthalene, and this is very reasonable in view of the interference between the methyl group hydrogen atoms and that in ring position 8. The apparent value found for 2-methylnaphthalene seems high in comparison with the value of 750 cal./mole in toluene and in m- and $-xylene, but the lower limit of the range of uncertainty for the barrier is below 1 kcal./mole. Also, it should be remembered that naphthalene is much less symmetrical than benzene. Consequently there may remain a threefold barrier in 2-methylnaphthalene, whereas in toluene the threefold terms must cancel and leave a sixfold symmetry for the barrier. Indeed the 1-2 bond is known to bel2 about 0.04 A. shorter than the 2-3 bond in naphthalene, and the simplest resonance picture yields 12/3 bond in 1-2 location and only 11/3 bond in the 2-3 position. We _ are now able to calculate the heat capacity of gaseous 1- and 2-methylnaphthalenes by the equation equivalent to (3) but with correction for the potential barriers just determined, Also, each ACp of vaporization is available from the vapor pressure equation and the equation of state for the vapor. Thus we are able to check our extrapolations of the liquid heat capacities. The comparisons are made in Table 111. In view of the uncertainties involved in the calculations, the agreement (11) 6.S . Pitzer a n d \V. D. Gwinn, J . O > < , ,I I' hI .j ~ . , 10, 12: (1942). ' . l s / . ,6 , Ij!iY (12) D. W. J. Cruickshank and A . I 1933).
June 20, 1956
THERhlODYNAMIC
FUNCTIONS O F ALKYLNAPHTHALEXES
TABLE I11 CHECK O N EXTRAPOLATION OF THE HEAT CAPACITY OF LIQUID1- AND 2-METHYLNAPHTHALENES T.
O K .
425 440 450 470 500
I-Methyl Eq. 1 Calcd.
?,-Methyl Eq.2 Calcd.
66.9 68.5 69.5 71.6 74.7
66.0 67.5 68.5 70.5 73.5
68.1 69.1 69.8 71.2 73.8
67.1 68.1 68.8 70.5 73.1
2709
of the liquid heat capacity and the treatment of the gas imperfection are more uncertain. Consequently the good agreement in the middle range suffices as a check on the extrapolation. Calculated Properties of Gaseous Alkylnaphtha1enes.-The heat capacity, heat content, entropy and free energy of the alkylnaphthalenes were calculated by the use of the following incremental equations together with corrections for the potential barrier specified.l 3
TABLE IV FREEENERGY FUNCTION OF ALKYLNAPHTHALENES IN THE IDEALGAS STATE( -Fo Alkylnaphthalenes Naphthalene I-Methyl I-Ethyl 1-n-Propyl I-n-Butyl 1-n-Amyl 2-Methyl 2-Ethyl 2-%-Propyl 2-n-Butyl 2-n-Amyl Increment per CHz group 1,Z-Dimethyl 1,3-Dimethyl 1,6-Dimethyl I,?-Dimethq 1 1,4-Dimethyl 1,5-DimethyI\ 2.3-Dimethyl 2,o-Dimethyl 2,7-Dimethyl 2-,Methy1-3-ethyl 2-Met hyl-ðyl 2-Methyl-7-ethyl
i
298 16
300
400
63 36 6 3 . 4 6 69.11 70 34 7 0 . 4 4 77.05 76 62 76.74 84.45 82 43 82.59 91.5 88 41 8 8 . 5 9 98.5 94 51 9 4 . 7 1 105.7 70 71 7 0 . 8 1 77.49 76.99 7 7 . 1 1 84.89 82 79 8 2 . 9 7 9 1 . 9 98.9 88 79 88.92 94.89 9 5 . 0 9 106.1
500
600
700
Temperature (OK.) 1000 800 900
74.65 83.54 91.98 100.1 108.1 116.3 84.00 92.44 100. *5 108.6 116.7
80.08 89.89 99.31 108.4 117.3 126.4 90.39 99.81 108.9 117.8 126.9
85.40 96.14 106.50 116.5 126.3 136.3 96.60 106.96 117.0 126.9 136.8
9 5 . 5 6 100.40 90.56 102.16 107.99 113.66 113.42 120.11 126.60 124.3 131.8 139.1 135.0 143.3 151.4 145.8 155.0 163.8 102.59 108.41 114.02 113.85 120.56 126.96 124.8 132.2 139.5 135.4 143.7 151.8 155.3 164.2 146.3
Ho")/T, (CAL./DEG.MOLE)
1100 105.07 119.06 132.79 146.1 159.1 172.3 119.43 133.16 146.4 159.5 172.6
1200
1300
109.58 124,33 138.81 152.8 166.6 180.6 124. 69 139.17 152.2 167.0 180,Q
113.93 129.37 144.58 159.3 173.7 188.3 129.71 144.92 159.7 174.1 188.7
1400 1500 118.14 122.20 134.27 138.98 150 18 1 5 5 . 5 5 105.6 171.8 180.7 187.4 196.0 203.3 134.62 139.29 I50 54 155.86 165.9 172.0 181.0 187.7 196.3 203.6
5 . 9 7 9 5.999 7 4 . 5 6 74.66
7.061 82.23
8.043 89.68
8.970 9.856 1 0 . 7 0 5 11.516 12.299 13.053 13.781 14.477 15.151 15.798 96.95 1 0 4 . 1 3 111.01 117.67 124.17 130.30 136.33 142.06 147.65 153.01
74.94
82.68
90.14
97.45
75.04
104.59
111.44
118.09
124.53
130.67
136.69
142.40
148.00
153.32
73.19
73.29
80.86
88.31
9 5 , 5 8 102.76
109.64
116.30
122.80
128.93
134.96
140.69
1 4 6 . 2 8 151.64
73.86
74.01
81.98
89.63
97.01
104.17
111.05
117.70
124.11
130.28
136.24
141.96
1 4 7 . 5 3 152.87
97.02
74.12
74.22
82.04
89.60
104.16
111.02
117.69
124.09
130.26
136.27
141.98
147.60
81.52
81.69
90.7
99.4
107.8
116.0
123.6
131.2
138.5
145.4
152.1
158.6
164.8
170.8
8 1 . 7 8 81.89
91.6
100.2
108.5
116.6
123.6
131.7
138.5
l45,4
152.1
158.6
164.8
170.9
152.90
TABLE V HEATCOXTENT FUNCTION O F ALKYLNAPHTHALENES I N THE IDEAL GAS ST.4TE 500
GOO
Alkylnaphthalenes
298.16
300
Naphthalene I-Methyl 1-Ethyl 1-n-Prop v I I-n-Butyl I-n-Amyl 2-Methyl 2-Ethyl 2-n-Propyl 2-n-Butyl Z-iz-Amyl Increment per CHz group 1&Dimethyl 1,3-Dimethyl 1,6-Dimethyl 1,7-Dimethyl 1,4-Dimethyl 1,5-Dimethyl 2.3-Dimethyl 2,O-Dimethyl 2,7-Dimethyl 2-Methyl-3-ethyl Z-Methyl-6-ethyl 2-hfethyl-7-ethyl
17.07 19.87 23.32 27.12 30.42 33.75 20.12 23.57 27.37 30.67 34.00 3.330 22.67
17.16 19.99 23.45 27.26 30.57 33.92 20.26 23.71 27.52 30.83 34.18 3.344 22.82
22.34 27.47 32.28 26.19 3 2 . 1 8 3 7 . 7 3 30.46 37.23 43.50 34.9 42.3 49.2 39.0 47.1 54.7 43.0 51.9 60.1 2 6 . 3 5 32.26 3 7 . 7 1 30.62 37.31 4 3 . 4 8 35.1 42.5 49.3 39.2 47.2 54.7 43.2 52.0 60.1 4 . 0 6 3 4 . 7 7 4 5.439 30.04 36.89 43.18
36.68 42.83 49 26 55,6 61.6 67.7 42.75 49.18 55.5 61.6 67.6 6.062 48.98
22.92
23.08
30.20
48.90
i
1
1
1
400
36.97
43.16
(H"- Ho")/T, (CAL./DEG.MOLE)
Temperature (OK.) 700 800 900 1000 40.67 47.43 54.43 61.3 67.9 74.6 47.35 54.35 61.2 67.8 74.5 6.643
1100
1300
1300
1400
54.1Y
44.27 51.61 59.13 66.5 73.7 80.9 51.45 58.97 66.4 73.5 80.2 7.176 58.95
47.54 55.40 63.40 71.3 78.9 86.6 55.23 63.23 71.1 78 8 80.4 7.663 63.26
50 50 58.81 67.24 75.5 83.6 91.8 58 63 67.03 75.4 83.5 91.6 8.112 67.12
53.19 55.64 57 89 61.91 64.77 67.36 70.74 73 97 76.89 79.5 83.1 86.3 88.0 92.0 95.6 96.5 100.9 104.8 61.71 64.55 67.13 70.54 73.75 76.66 79.3 82.9 86.1 87.8 91.8 95.3 96.4 100.7 104.6 8.528 8.908 9,258 70.63 73.90 76.83
54.10
58.79
63.09
66.94
70.43
73.68
1500 50.94 69.75 79 GO 89.4 98.9 108.5
69.53 79.38 89.1 08.7 108 3 9.582 79.5ti
76.60
79.34 79 56
22.67
22.82
30.04
3Ci.89
43.18
48.98
54.19
58.95
63.26
67.12
70.63
73.90
76.83
24.36
24.48
31.16
3 7 , 5 8 43.58
49.10
54.14
58.72
62.91
66.73
70 21
73 39
76 32
79.01
23.56
23.72
30.74
37.39
43.44
49.10
54.25
58.84
63.11
66.82
70.39
73.61
7C.51
79.24
27.81
27.95
35.4
42.7
49.4
55.5
61.1
66.2
70.9
75.1
79.1
82.6
85.9
88.9
27.01
27.18
35.0
42.5
49.2
55.5
61.2
66.4
71.1
75.4
79.3
82.8
86.0
89.1
within 0.5 cal./deg. mole is entirely satisfactory in the middle temperature range. A t the lowest temperatures the vapor pressure equation can Of be expected to an accurate the second derivative which is required for At the highest temperatures both the extrapolation
+
G(n-alkylnaphthalene) = G(naphtl1alene) G(n-alkylbenzene) - G(benzene) - ln 3/2 (13) T h e barrier for the rotation of the ethyl group in ethylhenzene is 1080 instead of 750 for toluene. T h e effect of this difference is so small t h a t t h e same correction terms were used for ethyl a s for methyl rotation.
D. E. MILLIGAN, E. D. BECKERAND K. S . PITZER
2710
VOl. 78
TABLE VI ENTROPY OF ALKYLNAPHTHALENES I N THE IDEAL GASSTATESa ( C A L . / D E G . MOLE) Alkylnaphthalenes Naphthalene 1-Methyl 1-Ethyl I-n-Propyl I-iz-Butyl I-n-Amyl 2-Methyl 2-Ethyl Z-n-Prog>I 2-n-Butyl 2-n Amyl Increment per CH, group 1,!&Dimethyl 1,3-Dimethyl 1,G-Dimethyl 1,7-Dimethyl 1,4-Dimethyl 1,s-Dimethyl 2,3-Dimethyl 2,B-Dimethyl 2,i-Dimethyl 2-Methyl-3ethyl 2-Methyl-0ethyl 2-Methpl-7ethyl
298. 16 80.43 90.21 99,94 109.55 118.83 128.26 90.83 100.56 110.18 119.46 128.89
,!
300 80.63 90.43 100.19 109.85 119.16 128.63 91.06 100.82 110.50 119.81 129.28
400 500 91.44 102.11 103.24 115.72 114.91 129.21 142.4 128.4 137.5 153.2 148.7 168.2 103.8-& 116.26 115.51 1 2 9 , 7 5 127.0 142.96 138.1 155.8 149.30 168.7
700 600 112.36 122.07 127.62 138.97 142.81 155.76 172.1 157.6 188.0 172.0 204.0 186 5 128.10 1 3 9 . 3 5 143.29 156.14 158.2 172.4 172.5 188.3 187.10 2 0 4 , 4
Temperai.ure (OK 900 800 131 22 139.83 149.59 159.60 167 85 179.24 185 6 198.3 202 9 217.0 220 4 236.8 149 9 4 159.80 108.20 1 7 9 . 5 0 188 0 198.6 217.2 203 3 220 7 236.0
) 1000
147 93 169 06 190 00 210.4 230 3 250.4 169 25 190 19 210 0 230 5 250 G
1100 155.56 177.87 200.03 221.6 242 7 264.0 178,OO 200.19 221.8 242.0 264.2
1200 162.77 186.24 209.55 232.3 254.4 277.0 180.40 209.71 232.4 254.7 277 1
1300 169,5i 194.14 218.58 242.4 265.7 289.2 191.20 218.67 242.5 265.8 289 3
1400 178.03 201.03 227 07 251.9 276 3 300 8 201.75 227.21 252.0 276 4 300.9
500 182.14 208.73 235.15 261.0 286.3 311 8 208.82 235.24 2131. 1 286. i 311.9
9.309 97.23
9 . 3 4 3 11.124 12.817 14.409 15.918 17.348 1 8 . 0 9 2 19.962 21.165 22.309 23.385 2 4 . 4 0 9 25.380 97.48 112.27 126.57 140.13 153.11 165.20 176 02 187.43 197.42 206.96 215.96 224.48 232.57
97.86
98 12
112 88
127.11
140 01
153.49
105.55
170.88
187.62
197.G1 207.12
216.08
224.60
232.08
1 9 5 86
90 11
110 90
125.20
138.76
131.i4
103.83
175 25
186.06
196.05 205.59
214.59
223.11
231.20
98 22
98 49
113 14
127.21
140.59
153.27
165.19
1713.42
187.02
197.01 206.45
215.36
223.85
231.88
) 97.68
97 9 1
112 78
126.99
140.46
153.26
165.27
176.53
187 20
197.18
208.06
215.59
224.11
232.14
109 33
109 64
126 2
142 1
157.2
171 5
181.8
197.4
209.3
220.5
231.2
241.2
250.7
259.7
) l o 8 79
109 07
125 9
141.9
157.0
171.$
184.9
197.6
209.5
220.8
231.4
211.4
250.9
260.0
J
HEATCAPACITY Alkplnaphthalene Naphthalene I-Methyl I-Ethyl 1-n-Propyl I-n-Butyl l-?i-Amyl 2-RIethy1 2 - E thy1 2-~-Propyl 2-n-Butyl 2-n-Amyl Increment per CH? soup 1,2-Dimethyl 1,3-Dimet hyl 1,B-Dimethyl 1,7-Dimethyl l,&Dimethyl 1,j-Dimethyl 2,3-Dimet hyl 2,B-Dimethyl 2,i-Dimethyl 2-Methyl-3-ethyl 2-Methyl-6-ethyl \~ 2-RIethyl-7-ethyl
i
1 /
1
298.16 32.08 38.13 44.02 49.74 55.18 60 6 5 38.19 44.08 19 80 55 24 80.71
300 32.28 38.37 44.30 50 01 55.51 01.01 38.42 41.35 50.04 53.56 61.00
OF
400 43 20 50 74 58 2%; 65 3 72 2 79 2 50 50 58 01 05 1 72 0 79 0
TABLE 1-11 ALKYL:VAPIITHALENES IS THE I D E A L GASSTA4TE c p 600 59.94 69.79 79.65 89.1 78.4 80.6 98 4 107.8 91 9 ns 31 60.87 69.68 7 9 , l i 88.6 78.0 97.9 86.2 107.3 94,s
500 52.41 61.25 i o . 06
5 . 4 6 6 5.494 6 . 9 4 1 8 . 2 4 6 9.342 7 9 , 04 44.18 44 46 58 28 7 0 . 0 6
700 66.01 7F.76 87.47 97 8 108 1 118 4 70.2s 86 99 97.4 107.7 117 9
Temperature (OK.) 1000 800 900 7 5 13 78.59 71 00 91.21 8 2 . 4 8 87.19 93.91 99.24 103.79 105.1 111.1 116.2 122.8 128.5 116.1 140.9 127.2 134.6 82.03 86.81 9 0 . 8 6 93.46 98.86 103.44 115.8 104.6 110.7 128.1 113.7 122.4 134.2 140.5 120 8
(c:AL./DEG.M O L E )
1100 81.52 94 63 107.67 120.6 133.4 146.2 94.28 107.32 120 2 133 1 145.9
1200 84.00 97.51 110.96 124.3 137.6 150.9 97.21 110.06 124,0
137,3 150.G
1300 86.11 99.97 113.77 127.5 141,1
154.8 99 71 113.51 127.2 140.9 154.6
1400
87,93 102.08 118.19 130.2 144.2 158.2 101.86 11.L9i 129.9 143.9 157.9
1500 89.49 103.93 118.31 132. fi 146.9 161.2 103.72 118.10 132.1 116.7 160 9
10 276 87,51
11.065 11,746 1 2 . 3 3 12.84 93 96 9 9 . 2 5 103.83 107.74
18.28 13.00 111.02 113.83
13 98 14.27 116.23 118.37
87.03
93 51
110.72
113.57
116.01
118 10
113.83
116.23
118 37
98 87
103.48
107.39
44.24
44.51
58.04
C9.68
79.16
44.18
44.46
58.28 70.06
i 9 04
87,.71
93.96
99.25
103.83
107.74
111.02
8(i 0 2
92 R8
0 8 10
102.78
1063.76
110.163 113.07
11.>.59 117 7 5
11 41
44.6.7
.57.-19
68 7 5
78 18
44.71
44.97
58.0i
G9.45
78.77
86.49
103 14
107.05
110.43
113.31 115 80
117.95
88 0
96 8
104.0
110.1
113.3
119.8
123.6
126.9
129.7
132.1
88 7
97.3
104.4
110.6
115.7
120.2
123 8
127.2
130.0
132 3
50.30 50.60
30.57
50.90
65 0 O5.f:
77 ,5 75.2
with Correction from 1;) = 7.50 to 1.0 = 3800 for 1series and to VO= 2300 for ?-series. G( 1,2-dimethvlnaphthalene)= ZG( 1-methg Inaphthalene) G(napht1ialene) - R In 4 G( 1,4-dimetliylnaplithalene) = G( 1,5-dimethylnaplithalene) = 2G( 1-inethvlnaphthalene) - G(naphtha1ene) . . .~ Rln 8 G( 1,3-dimethylnaphthalene)= G( 1,6-dimeth~.lnaphthalene) = G( 1,7-dimethylnaphthalene)= G( l-methylnaphthalene) G(Z-methylnaphthale~le)- G(naphtha1ene) R In 4. G(2,8-di1nethylnaphtlialenej = G(naphtha1ene) G(o-xylene) - G(benzene) - R In 3; G(2,6-dinleth~.lnaplithalene)= G(%,7-dinletllyln,i~,Iltiialene) = G(napht1ialene) G(n~-xylene)- G(benzene 1 R In 3
+
+
+
with correction from T:,
=
7.50 to
lTp =
2300.
93.09
98 51
G(L-tnethg 1-3-ethg Inaphthalene) = G(naphtlialet1e) 1 G(l-inethyl-2-eth) lbenzerie) - G(benzene) - K In 3 G(2-methyl-6-ethylnaphthalene)= G(2-methyl-i-ethg 1naphthalene) = G(naplit1ialene) G( 1-methi 1-3-ethl Ibenzene) - G(benzene) - R In 3
+
with correction from IT0 = i 3 0 to 1-0 = 2300 for both internal rotations about bonds adjacent to the aromatic ring system. In these equations G represents CE, S o , (11"13:) / T or - (F' - H t ) 'T. The logarith~iitern1 applies only to So and - ( F " - H : ) / T . The coinponent values come from sources mentioned above,2 4 5 11 The calculated values are listed in Tables IVVII. The increments per CH2 group given in the tables c a l l be used to calculate the functions for 11-
MOLECULAR STRUCTURE OF TRIFLUOROETHANOL
June 20, 1956
alkylnaphthalenes higher than amylnaphthalene. The values of McClellan and PimentelZ for naphthalene are included for convenience. These authors estimate that their values are probably accurate to A0.5 cal. per degree mole. The values for the substituted naphthalenes are subject to additional uncertainty. We estimate the uncertainty [CONTRIBUTION FROM
THE
DEPARTMENT O F CHEMISTRY
2711
to range from 0.5 for the simpler derivatives a t the lower temperatures to 1.0 for the larger molecules a t the higher temperatures. Acknowledgment.-We wish to acknowledge the aid of Mr. Donald E. Petersen in assisting with some of the calculations. BERKELEY 4, CALIF.
AND THE P U R D U E
RESEARCHFOUNDATION, P U R D U E UNIVERSITY]
An Electron Diffraction Investigation of the Molecular Structure of Trifluoroethanol' BY R. L. LIVINGSTON AND G. VAUGHAN RECEIVED JANUARY 9, 1956 The molecular structure of trifluoroethanol has been investigated by electron diffraction using the visual corrtlation procedure. Th: structural parameters as determined by this investigation are as follows: C-F = 1.34 zk 0.02 A , , C-C = 1.52 =k 0.05A.. C-0 = 1.41 =k O . O 5 f i . , L F C F = 108.5 =t 1,5",and LCCO = 110 =t 4".
Introduction There has been considerable interest in the effect of halogen atoms on the carbon-carbon bond distances in simple organic halides. Early results2 gave a C-C distance of about 1.45 A. in CzFe and CFpCHBbut more recent work indicates that these distances are considerably longer, probably between 1.50 and 1.54 L4.3'4The determination of the structure of trifluoroethanol was undertaken to determine further the effect of fluorine atoms on the C-C distance and, in addition, to determine any effects on the C-0 bond length and the CCO angle.
VIS
Experimental
K3
The sample of trifluoroethanol used in this work was purchased from the Minnesota Mining and Manufacturing Company. A 60-1111. sample was rectified in a glass helices packed column which was equivalent to fifteen theoretical plates. Ten milliliters of the middle fraction, b.p. 77.7 =k 0 : l " (uncorrected), was collected for use in preparing the diffraction photographs. The infrared spectrum of this fraction showed no spurious features when compared with the spectrum from a sample with a known purity greater than 99%. The diffraction photographs were obtained in the usual manner5 using a camera designed and constructed by Professor H. J. Yearian of the Purdue Physics Department. Twelve satisfactory photographs of varying density were obtained from the sample described above, using a camera distance of 108.2 mm., an electron wave length of 0.05923 A. and Eastman Kodak 33 plates. Visual interpretation and measurements of the patterns were obtained out to a qvalue of approximately 95 from three of the best plates. Interpretation of the Diffraction Pattern.-The visual correlation method5j8and the radial distribution method73 were used in the interpretation of the diffraction pattern, The measurements of the patterns are summarized in Table I. The qo-values are based upon measurements of each feature by two independent observers. The qualitative (1) Contains material from the Ph.D. thesis of G. Vaughan, Purdue Research Foundation Fellow in Chemistry, 1951-1953. ( 2 ) A survey of electron diffraction results through 1949 is found in the tabulation by P. W. Allen a n d L. E . Sutton, Acla Cryst., 8 , 46 (1950). (3) J. L. Brandt a n d R. L. Livingston, THISJOURNAL,76, 2096 (1954). (4) J. L. Brandt, Ph.D. Thesis, Purdue University, 1952. (5) L. 0. Brockway, Rev. Modern Phys., 8 , 231 (1936). (0) L. Pauling and L. 0. Brockway, J . Chem. Phys., 2 , 867 (1934). (7) L. Pauling and L. 0. Brockway, THISJOURNAL,67, 2684 (1935). ( 8 ) P A . Shaffer, V. Schomaker and L.Pauling, J . Chenr. P h y $ . , 14, G.59 (194G).
EF3 Q3 Q2 K4 J2 K2
E3
G3 u2 L2
I
,
I 20
,
I
40
I
I
60
,
I 00
I
I I00
Fig. 1.-Radial distribution, visual intensity and theoretical intensity curves for trifluoroethanol.
