Feb., 1947
ELECTRIC MOMENTS OF ALIPHATICFLUORIDES,CYANIDES AND AXINES
lCONTRIBUlIOS FROM
THE
1)EPARTMENT O F CHEMISTRY O F THE UNIVERSITY OF CALIFORTIA AT ICEDZIE CHEMICAL I>ABORATORY, MICHIGAN STATE COLLEGE]
LOS
ANGELES
137 A S D THE
The Electric Moments of Some Aliphatic Fluorides, Cyanides and Amines BY MAXT. ROGERS
A comparison of the electric moments of the aliphatic chlorides, bromides and iodides shows that there is a small increase in moment with increase in length of the hydrocarbon chain, and a further increase with chain branching in the secondary and tertiary compounds. LIeasurements for most other series are not extensive enough to reveal definite trends and, since the values might give some information concerning hyperconjugation in these molecules, data have been obtained for the aliphatic fluorides, cyanides, and amines. Few mc:asuretiients of aliphatic monofluorides have been made but the values reported for namyl and t-amyl fluorides in carbon tetrachloride solution1 are low compared with the presumably more reliable vapor measurements on methyl and ethyl fluorides? and would indicate that the trend here was in the opposite direction from that in the other halide series, ,4lthough the fluorides might be expected to show unusual behavior, it seemed desirable to confirm these values and therefore namyl, t-amyl, and benzyl fluorides have been studied in benzene solution. Evidence from measurements i n the vapor state indicates that all aliphatic nitro compounds beyond nitroethane have the same moment, and it would appear from available data"? that the same would be true for the c3-anidesalthough no values are availeble for secondary, tertiary, or longchain primary aliphatic cyanides. Measurements of i-a.my1, i-propyl arid t-butyl cyanides have therefore been made along with normal, secondary and tertiary butylamines to determine the effect of chain tn-anching in these series; none of the cyanides (:r amines has been reported previously. Experimental Preparation of Materials .--Benzene was purified as in previous work," 0.87315. %-Amyl Fluoride .-+Amyl iodide (prepared from namyl alcohol and phosphorus triiodide and fractionated befoi e use) was dropped slowly 017 a mixture of anhydrous silver fluoride and sand. The products were swept b y a stream of dry nitrogen into a Dry Ice-cooled receiver. The mixture of amyleiie antl amyl fluorides was washed with sodium bicar?miatc solution, water, dried over calcium chloride and fractionated through a n efficient packed column, b. p. ii2..(l-(i2.5" (751 mm.), d2540.7849, t ~ 1.3573. S n w t s 6 reports 0.7880, n z o 1.3550 ~ (by interpolation). The secondary fluoride ( b . p . 55") formed by readdition of hydrogen fluoride t o pentene-1, is difficult t o ~ ~ I ~ I O completely. VC' t-Amyl Fluoride .-Trimethylethylene obtained from t h e dehydration of t-amyl alcohol was fractionated through a (1) A. Audrleyand F. G o s s , J. Chern. Soc., 407 (1942). (2) S m y t h :&nd >Ic..\lpine, J . Chem. Phys.. 2, 499 (1934). (3) C. P. S m y t h . Tsrs J O L . K N A L , 63, 57 (1941j; Groves a n d Sugden, J . Chem. Sr.,1 3 3 (1!1:37). (4) Cowley and Partington, J. Chem. Soc., 604 (1935). (5) M. T. Rogers ami J . D. Roberts, THISJOURNAL. 68,843(1946). (6) Swarts, /3rril. Soc. Chint. Beig., 30, 302 (1921).
packed column and a fraction boiling at 3X", i i l j ~1.3812, d354 0.6564 was obtained. This was added dropwise with stirring t o a n excess of anhydrous liquid hydrogen fluoride contained in a copper vessel held a t -75". After three hours the product ITas poured onto ice i i i a rnonel beaker and the excess acid neutralized with potassium hydroxide solution. The upper layer was . washed with sodium bicarbonate solution, water over anhydrous sodium sulfate. The product was fractionated through a packed column, b . 11. (752 inm.), n% 1.3462. After about 2 g. had distilled a t i d " decomposition started and samples collected thereafter fumed strongly, etched the containing vials and became cloudy. The sample used for ineasuremeiit kept well ant1 showed no evidence of decomposition even after a day in lxiizeiie solution. A second preparation gave a high yield of crude fluoride but repeated attempts at fractionation all resulted in partial decomposition. The moment reported is, therefore, based on only one reliable measurement. The method of preparation is that of Grobse antl Linti' who, however, gave no experitnental details. They report nZ51)1.3477, J f h 24.36. The addition of arihytlrous hydrogen fluoride t o a douhle hontl a t loiv temperature is the most satisfactory tiie~hotlfor preparing ciure seconda r y and tertiary fluorides. Benzyl Fluoride .-Benzyl fluoride wa.: preparcti by the pyrolysis of benzyl trimethylammonium the product was fractionated through a n efficient packed column and the fraction used boiled a t (2"!ti7 m m . ) , n Z 51.4908. ~ About 1 g. of pure material \vas obtained after which rapid autocatalytic decomposition destroyed t h e remainder of the material. T h e solutions used for measurement showed no evidence of decomposition. i-Amyl Cyanide .-+Amyl cyanide mas prepared froiii i-amyl bromide anti potassium cyanide, dried over calcium chloride and fractionated, b . p. 65.2" (35 inin.), n 4 : ~ 1.4040, d2&40.80271. i-Propyl Cyanide .- i-PI-opyl cyanide was prepared by the dehydration of isobutyramide with phosi)horus pentoxide. The crude product was fractionated ai 202 m m . and the fraction boiling a t (i3.1" used, n Z 5 D l . X l 2 , d25, 0.76572. t-Butyl Cyanide .-Trimethylacctamide was dehydrated by heating with phosphorus pentoxide. The crud; nitrile which distilled over n-as fractionated, 1). p . 58.9 , ?Zz5D 1.3751, dz540.75857. t-Butylamine.--t-Butylarnirie was preparcti from trimethylacetamide by the Hofniaiin reaction, (lried over barium oxide and fractionally diitilleti, 1., 1). 41.5' (732 m m . ) , nZ5D 1.3iCi9. N- and s-Butylamines.-Eastrnarl Kotiak Co. \\'hiie Label materials were fractionally distilled froiil barium oxide: n-butylamine, b. p. 7Ci.2" 1752 i n i r i . ) , da4 i I . i X 4 , TZ*:D 1.3992; s-butylamine, h . p. 62.0' (73% rnm.), n'z5D 1.3900. Acetone Cyanohydrin.-Material supplied by Dr. 'rod ~ 6 ~ Campbell was fractionated at 40 min., b. p. 95', d'5( 0.9267, 1 z z 5 1.3980. ~ Chloroacetonitrile .-Eastman %%te Label material was dricd and fractionated a t 100 inm., b . p. OO.:%jl.ijo, d"r 1.1893. nZ5D1.4202. Measurements and Calculations.-The electric moments were measured in dilute benzene solution at 25". Dielectric constants were measured with a heterodynebeat apparatus described and densities \\-ere measured with a modified Ostwald pycnometer . ' I Chloro(7) Grosse, Wackherand Linn. J. I'hys Chem., 44, 275 t l { l 4 0 ) . ( 8 ) C. K. Ingold a n d E. H. Ingold, J . Chem. Soc.. 2249 (19281 (9) G. K. Robertson, I n d . E x g . Chcm., 11. 464 (1?139)
MAXT. ROGERS
458
acetonitrile was measured using a new low drift heterodyne-heat apparatus. The dipole moments m r e calculated from the measured dielectric constants e and densities d of solutions of solute mole fraction f2 with the usual equations.la T h e experimental data are shown in Table I and Table I1 list.. the values of P,, J ~ R and D p for each compound. The values of Pafor the most reliable samples of benzyl ant1 t-amyl fluoride were taken equal t o P,. This increases the probable error in the moment somewhat but, since the values of P2 for fluorides change only slowly with concectration in dilute solution, the moments are probably accurate t o about 0.05 debye. Values of M R D are from experimental values of n and d .
TABLE I DIELECTRIC (:OXSTANTS, L)E?;SITIES A N D hIOLAR POLARIZATIOSS OF BESZESES o L r r I o s s AT 25" iz € d Pz %-Amylfluoride 0.87345 0 . (~0000 (2.2725) Pi = 26.636 . (10723 2.302 ,87235 94.0 2.305 ,87206 97.0 . !I0731 . 87164 2.337 94.2 . (11552 2.319 .E37144 95.3 .(I1820 2.3fj0 ,87091 93.9 .02123
0 . C'O745
t-Amyl fluoride 2.306 0.87260
99.9
0.c.1886
Benzyl fluoride 2.354 0.87640
95.4
;-Amyl cyanide 2.309 0.8'7334 2.347 ,87317 2.396 ,87292 2.424 .Si260 2,474 .87233 2,61*i .87136
279.4 280.2 277.7 276.0 273.0 266.6
&Butyl cyanide 2.335 0.87293 2.373 ,87273 2.392 ,87252 .87244 2.417 2.504 ,87167 . 87002 2.648
293.3 290.0 283.3 290.0 287.8 275.3
0.00218
. C'044l . COT29
.C0896 .("1200 . C2033
0.00454
.c n L m ,00683 .00795 .(11265 . (12097 O.OO301 .(I0523 .UC)956 .(11301
.01%4 .02517 0.00822 .(io979 ,01409 .02079
.040ll
. 05008
i-Propyl cymitle I). 8733b 2.326 2.366 ,87301 2.442 872IiO 2.502 , 87226 2.598 ,87121 2.718 ,87108 92-Butylamine 2,293 0.87230 2.295 ,87178 2.305 ,87116 2.321 ,87002 2.36: .8fj697 2.418 . 8ti346
281.5 282.6 277.2 272. F 268.9 261.8
65.4 03.8 64.0 64.1 64.0 64.4
(IO) S m y t h , 'Dielectric constants and Xolecular Structure," Chemical Catalog Co., Reinhold Publishing Corp., New York. N. Y . , 1931, chap. I.
Vol. 69
0 01144 01885 ,03273 ,01222
00x43 06386
s-Butylamine 2.293 0.87131 2.309 . 87011 2.335 .86755 2,354 .86565 2.379 .86326 2.395 ,86173
57.2 58.6
58.3 58 7 58 4 38.2
0.0080 1 01336 ,02444 03718 ,02005 .03304
&Butylamine 2.291 n. 87183 2.297 ,87085 2.318 ,86840 2,331 ,86557 2.309 80930 2.336 ,86647
0.00324 .00135 .00620 .(I0903 .01186 .01601
Acetone cyanohydrin 2.316 0.87360 2.330 .87359 2.356 .87373 2,392 .Si383 2.428 ,87399 2.479 ,87424
223.2 221.4 222.1 217.5 213.7 208.4
0 01271 ,01576 ,01947
Chloroacetonitrile 2.434 0.86722 .87693 2.474 2.522 .87774
198.0 197.7 196.0
60 7 57.5 38.3 58.3 5q 1 59 4
T-4BI.E 11 POLARIZATIOXS, MOLE REFRACTIONS ASD DIPOLE MoMENTS
Substance
It-Amyl fluoride t-Amyl fluoride Benzyl fluoride i--\myl cyanide i-Propyl cyanide t-Butyl cyanide n-Bu tylainine s-Bu tylamine t-Butylamine Acetoile cyanohydrin Chloroacetonitrile
