Some Physical Properties of the Trimeric and Tetrameric Phosphonitrilic Fluorides C. P. HABER and R. K. UENlSHl U. S, N a v a l Ordnance Laboratory,
Corona, C a l i f .
A
simple one-step s y n t h e s i s of trimeric a n d tetrameric phosphonitrilic fluorides from t h e corresponding phosphonitrilic chlorides h a s been developed. T h e vapor press u r e s and h e a t s of vaporizations, sublimations, and fusions for t h e trimer and tetramer h a v e been determined and compared with t h e previously reported corresponding phosphonitrilic chlorides.
T h e measured data on which t h e s e v a l u e s were b a s e d a r e tabulated below.
T, 'I(. P, mm. Wt., gram V, liter
Trimer 297 43.5 0.0834 0.1414
Tetramer 297 38.9 0.0991 0.1414
EXPERIMENTAL Preparation of Trimeric and Tetrameric Phosphonitrilic Fluoride. Anhydrous, chemically-pure potassium fluoride
Table
(Baker Chemical) w a s dried in an oven at 316'C. for 36 hours. Anhydrous sulfur dioxide (Matheson Co.) w a s further dried through a column packed with phosphorus pentoxide and calcium sulfate. Technical grade phosphonitrilic chloride, approximately a 3 to 1 mixture of trimer to tetramer (Berkeley Chemical Corp.) w a s freed of moisture and nonA weighed volatile impurities by several sublimations. amount of potassium fluoride and a trimer-tetramer mixture of phosphonitrilic fluorides w a s thoroughly pulverized and mixed together in an inert atmosphere chamber and loaded into a dry s t a i n l e s s steel bomb equipped with a valve. A calculated weight of sulfur dioxide w a s distilled into t h e bomb, which had been previously evacuated. T h e bomb w a s heated to between 120' and 125OC. i n an oven for 67 hours, and t h e n cooled t o room temperature. After t h e volatiles were distilled from t h e bomb, pure tetramer and nearly pure trimer were isolated by several fractionations through cold U-traps held a t t h e following temperatures: -22', -45', -63', -83', and -196' C. P u r e trimer w a s isolated by fractional distillation through a vacuum-jacketed, helicespacked column. A typical run i s shown below. 2KF Grams Moles
+
30 0.52
250, 80 1.33
+ PNC1,
120°
Pressure, Mm. Temp., 'C.
1.
0.2 2.5 3.8 5.4 7.2 9.3 11.5
13.3 15.4 17.4 19.3 21.7 24.1 25.8 26.8 27.3
- 1 2 5 o c . > PNF,+ 2KCl +2SO,
Liquid
27 0.233
AP, Calcd. Obsd.
-
+
35.5 43.6 47.9 55.0 63.1 75.9 91.1 104.7 123.0 141.1 165.9 195.0 234.0 269.0 288.3 295.0
-0.8 +0.4 +0.3 -0.5 -0.4 f0.4 +0.6 -0.3 0.5 -2.0 +1.3 -0.7 1.5 f2.2 +2.5 -1.6 1679 Phase, Empirical Equation Log P = 8.065
-
-+ T
302.4 331.5 367.8 397.5 427.5 466.0 506.5 547.2 591.5 644.3 688.0 741.0
27.5 29.5 32.0 34.0 35.7 37.8 39.9 42.0 44.0 46.3 48.1 50.2
14.6 0.176
+
302.7 329.6 366.4 398.1 426.6 463.4 503.5 547.0 591.6 645.7 690.2 746.5
f0.3
- 1.9 -1.4 f0.6 -0.9 -2.6
-30 -0.2
+os 1
+1.4 2.2 +5.5
+
M e l t i n g Points, B o i l i n g Points, H e a t s of Vaporization, Sublimation, and Fusion, and Trouton Constants of Phosphonitrilic Fluorides and c h l o r i d e s
M.P., OC.
(PNF3,
26.8 27.2-27.4' (28.1) 30.4 (32.1) 114 (114.9) 123.5
(PNC12)Cd
36.3 43.2 47.6 55.5 63.5 75.5 90.5 105.0 122.5 143.1 164.6 195.7 235.5 266.8 285.8 296.6
67 hours
Compound
(PNCIJ '3
Calcd.
T
A H vap.,
(PNFJ,
Obsd
-2806 Solid Phase, Empirical Equation Log P = - 11.81
T h e combined trimer and tetramer yield, b a s e d on PNCl, and P N F , monomer units, corresponds t o 75.5%. Analysis. Calculated for PNF,: Phosphorus, 37.30; nitrogen, 16.83; and fluorine, 43.87. Found. Phosphorus, 37.02; nitrogen, 17.30; and fluorine, 45.68 (by difference). Molecular weights of t h e trimer and tetramer were measured by vapor d e n s i t i e s as 251 and 333 (calculated 249 and 332).
Table
I I . Vapor Pressure of Trimeric Phosphonitrilic Fluoride
R P . , 'C. (760 Mm.)
Kcal./Mole at 760 Mm.
A H vap./T. E. U.
A%
AH*
at 760 Mm.
Kcal./Mole
Kcal. /Mole
(50.7)' 51.8
7.68
23.7
12.8
4.97
(89.6) 89.7 2 56
8.91
24.5
13.9
5.03
13.2
25.0
18.2
5.0
328.5
15.5 (3)
25.7
....
....
eBoiling points in parenthesis calculated from the empirical equations; those not in parenthesis found experimentally by other investigators ( I , 5). bMelting point determined by capillary tube method. Melting points in parenthesis evaluated from solid-vapor and liquid-vapor equations. 'Physical properties for phosphonitrilic chlorides extracted from work of Audrieth, Steinman, and Toy (I).
1958
CHEMICAL AND ENGINEERING DATA SERIES
323
Table
111.
Vapor Pressure of Tetrameric Phosphon i t r i I i c F Iuoride
Pressure, Mm. Temp., OC.
ObSd.
Calcd.
Ap, Calcd. -0bsd.
-
3046 Solid Phase, Empirical Equation Log P = -
+ 11.85
T
0.1 6.3 11.5 156 19.6 23.0 29.6
40 9.1 13.9 18.0 28.0 34.3 62.3
5.0 8.9 14.1 20.0 28.2 37.2 61.7
+
1.0 -0.2 +0.2
+20
-
+0.2 -0.1 -0.6
1947 Liquid Phase, Empirical Equation Log P = - 8.247
T
32.2 36.0 39.1 43.7 47.6 49.9 53.5 56.6 59.2 62.3 65.2 69.0 72.2 75.2 77.8 80.5 83.5 86.5 89.0
73.3 89.0
103.0 125.7 150.5 165.4 197;O 224.0 250.0 282.0 317.0 364.7 411.0 459.4 501.5 551.7 610.5 673.4 732.3
7 46 89.1 102 2 126.4 150.5 166 2 193.5 22 1.0 245.5 277.2
3120 361.0 407,O 456.0 50 1.0 553.0 616.0 682.0 743.3
+
+
1.3 +O. 1 -0.8 +O. 7 0.0 +0.8 -3.5
-3.0 -4.5 -48
-5,o -3.7 -4.0 -3.4 -0.5 +1.3 +5.5 C8.6 +11.0
P h y s i c a l Properties. Melting Points. T h e melting points of the first two homologs were determined using the magnetic plunger method described by Stock (4, 6). T h e melting point for the trimer determined by t h i s method w a s found to be slightly lower than the value first reported by Seel and Langer (5); however, t h e capillary tube method gave a
slightly higher value than that reported by the same inA Harshaw 0.2’ graduated thermometer, vestigators. checked at the freezing point and boiling point of distilled water, w a s used for melting point determinations (Table I). Vapor Pressures of T r i m e r and Tetramer. A water bath equipped with a n efficient stirrer and two heaters, one having a thermoregulator, w a s used for a l l the measurements. T h e temperathres were read from Harshaw 5 0 ° , 0.2 graduated, thermometers, and the pressures were read from a mercury manometer with a cathetometer. All the vapor pressures were determined using a tensimeter similar t o that described by Burg and Schlesinger (2). T h e results a r e summarized in T a b l e s I1 and 111. T h e constants t o the empirical equations were determined by plotting log P vs. 1 / T and drawing the best straight line. T h e heats of vaporization and sublimation were calculated from the corresponding empirical equations, and the heat of fusion w a s calculated from the differences of h e a t s of vaporization and sublimation. Comparative physical data for the trimer and tetramer are summarized in T a b l e I. ACKNOWLEDGMENT
Thanks are due to A. J. Bilbo for h i s assistance during the fractional distillation of t h e trimer and C. M. Douglas during the preparation of t h i s article. LITERATURE CITED (1) Audrieth, L. F., Steinman, R., Toy, A. D. F., Chem. Revs. 32, 109 (1943). (2) Burg, A. B., Schlesinger, H. L., I. Am. Chem. SOC. 59, 780 (1937). (3) Moureu, H., de Ficquelmont, A , Compt. rend. 213, 306-8 (1941). (4) Sanderson, R. S., “Vacuum Manipulation of Volatile Compounds,” p. 96, Wiley, New York, 1948. ( 5 ) Seel, F., Langer, J., 2. sngew. Chem. 68, 461 (1956). (6) Stock, A., Ber. 50, 156 (1917). Received for review October 14, 1957. Accepted April 25, 1958. Research conducted under sponsorship of the Buresu of Ordnance, Foundational Research Fund.
Preparation and Comparison of the Physical Properties of Alkyl and Alkforyl Silicates HERBERT C. KAUFMAN and ORlN R. D O U T H E T T B. P i e r c e Foundation, N e w Haven, Conn.
John
N o r m a l alkyl and alkforyl alcohols reacted with silicon tetrachloride to produce tetraalkyl and tetraalkforyl silic a t e s (8) a s well as hexaalkoxy and hexaalkforyloxy disiloxanes. Differences were noted in their mode of reaction and physical properties. A comparison of t h e physical properties of t h e three series of organosilicates exhibited some unusual variations. Unfortunately, a more complete comparison w a s not possible b e c a u s e of t h e unavailability or the high cost of t h e alkforyl alcohols in this homologous series. Nonetheless, generalizations may b e made concerning t h e three s e r i e s from t h e available data. Although the alkyl s i l i c a t e s a r e stable thermally (1,2), t h e object of t h i s study w a s to compare the thermal stability, physical properties, a n d hydrolytic stability of t h e s e with the l , l , ( n + 2>trihydroalkforyl silicates and the 1,l-dihydroalkforyl silicates. T h e s e silicates may be represented by t h e following general formulas:
324
INDUSTRIAL AND ENGINEERING CHEMISTRY
Tetra-n-alkyl silicate [HsC fCH2),4
- CH2 - O j 4 Si
Tetra-1,1 (n + Z>trihydroalkforyl silicate
-
-
[HFzC f c F 2 ) ~ CHp Of
4
si
Tetra-1,l-dihydroalkforyl silicate [F3C { C F ~ ) N - C H ~ - O ]s~i
Hexa-n-alkoxy &siloxane [“a C f CH2)p.
- c H p - Of
3
si - 0
- 51 f 0 - CHp f C H ~ ) N- c H d 3’
VOL. 3, NO. 2
