KOTES
1336
Yol. 64 TABLE I EQCIVALENT CONDUCTANCE AT 25' 10' e
Fig. 1.-DeDendence of ionic resistance on number of atoms: 1, Mg4N; 2, E 4 N ; 3, P s N ; 4, MerNEt; 5, MesN(CHzCHzOH); 6, MeSN(CH~CHIOH)?. ethanol, and recrystallized from ethanol; m.p. 272-273' with decomposition. Analysis, 54.9, 54.7% I us. 54.9% calculated. Dimethyl-di-(2-hydroxyethyl)-ammonium iodide forms less readily than the preceding compound. It was made by mixing equimolar quantities of methyl iodide and methyl-diethanolamine, and heating at 40' for 12 hours. On chilling in Dry Ice, the mixture crystallized. The hygroscopic product was twice recrystallized from ethanol, dried under vacuum and stored over PzO~. The compound melted to a translucent liqpuid a t 90-98'; the liquid became transparent nt 98-101 . Recrystallization from 50-50 benzene alcohol gave a product melting a t 102-104'. Analysis: 48.7, 48.8y0 I us. 48.7 calculated. Addition of methyl iodide to triethanolamine produce: only the hydroiodide of triethanolamine (m.p. 168-169 ; analysis, 45.7, 45.7, 45.5% I us. 45.8 calculated). Addition of methyl bromide likewise gave the hydrobromide instead of the expected quaternary salt. Possibly the triethanolamine contained some di- or mono-ethanolamine, which would lead to the observed products. Addition of ethylene bromohydrin to triethanolamine gave a good yield of the hydrobromide of triethanolamine instead of the desired quaternary salt with n = 4. Lack of time unfortunately prevented further attempts to prepare salts with n = 3 or 4. Conductances were measured a t 25.00' in an erlenmeyer cell with a constant of 0.9054, using a modified Shedlovsky bridge.2 The conductances are summarized in Table I. The data were analyzed on the IBM 650 computer, using a modified form of Kay's program3 to determine the constants AO and a which appear in the conductance equation' for unassociated electrolytes A = A. - Sc'h Ec log c J ( a ) c - FAoc J2ca/r The constants are summarized in Table 11. The small value of J obtained for the first salt suggests that a slight association may occur here; analysis of the data using the equation4for A K , defined as AK = A SC'/*- EC log c - J C f FAOC gave K A = 0.8 f 0.8, A. = 118.06, when d = 5.2 was used to evaluate the coefficient J of the linear term. This is almost negligible association, but probably is real; the example serves to emphasize the fact that the Jc term and the association term in the conductance equation oppose each other and hence a too small &-valuecan always be compensated by the ad hoc assumption of slight association. Reliable conclusions concerning association evidently can only be obtained from data covering a range of dielectric constants,
+
+
102 c
A
A
14.133 9.454 3.2052 2.2604
EtNMeJ 106.08 1.9472 108.35 I .3905 112.77 1 1760 113.58 0.9750 0.6287
21.037 11.254 10.760 9.214
102.00 105.59 105.76 106.56
5.491 5.163 3.920 2.1619 1.5549
108.40 108.72 109.56 111.04 111.76
19.534 9.568 6.430
97.78 101.61 103.18
5,3376 2.7650 1.3723
103.84 105.73 107.27
113.98 114.58 114.79 115.11 115.61
TABLE I1 DERIVED CONSTANTS Ao J d xo Salt 118.05 f O . 0 5 (193 f 9) (3.62f 0.16) 41.2 MeaNEtI MeaN(CHrCHS0H)I 115.22f .03 280 f 3 5.39 f .07 38.4 MexN(CHzCH2OH)d 110.45 i .04 254 f 4 5.04 f .09 33 G +
through the markedly different sensitivity of J and K A to this parameter. The single ion conductances for the cations were obtained by subtracting XO- (1') = 76.84 from the observed limiting conductances. Krauss has shown that the equivalent ionic resistance (l/h+)of alkyl quaternary ions is a simple function of the number of carbon atoms surrounding the central nitrogen. The solid circles in Fig. 1 are for the ions Me4N+, EtdN+ and Pr4N+,from data obtained a t Brown,O and the open circles correspond to the three salts of Table 11. It will be noted that the points for the two salts containing the external hydroxyl group fall quite near the line through the points for the alkyl salts. If there were any strong interaction between the -CH2CHzOH group# of the cations and the solvent molecules, we would expect these ions to move more slowly than purely alkyl ions and the points should then lie above the smooth curve. Since they do not, we conclude that any hydrogen bonding between the ethanol groups and the solvent is completely mobile; the -OH group simply slows the ion by its bulk, much as would a methyl group. (5) C. A. Kreus. J. Chem. Educ., 36, 324 (1958): M. J. MoDowell and C. A. Kraus, J . Am. Chem. SOC.,78, 3293 (1951). (6) H. M. Daggett, Jr., E. J. Bair and C. A. Kraus, ;bid., 73, 799 (1951).
+
+
(2) H. Eisenberg and R. M. Fuoss, J. A m . Chem. Soc., 7 6 , 2914 (1953). (3) R. L. Kay, ibid., 82, 2099 (1960). 61, 668 (1957); (4) R. M . Fuoss and L. Onsager, THISJOURNAL, R. M. Fuoss, J. Am. Chen. S O L ,81, 2659 (1959).
THE CRYOSCOPIC AND SPECTROSCOPIC PROPERTIES OF METHYL BORATE AND OF ITS AZEOTROPE WITH METHANOL BYPHOEBUS hl. CHRISTOPHER* Deportment of Chemiatry. New York Universiiu, New York 3,N . Y .
Received March 16. 1060
CHsOH and (CH30)aBreadily form an azeotrope having a lower boiling point than either of the respective components. It is relatively difficult to separate the components of the azeotrope. Too, the tendency for boron to become tetracoordinated and the preparation and characterization of numerous stable salts of the type M [B(RO)d], where M
* Department of Chemistry. Newark College of Engineering, Newark 2. N . J.
Sept., 1060 may be Li, Na, Ca or other strongly metallic elements, has led to some speculation’ into the possibility for the existence of a parent tetraalkoxo acid, (CH30)4BH. The findings previously reported’ concerning this speculation, although showing the azeotrope to be essentially a mixture, were inconclusive. The results of the present work, however, make possible the elucidation of definite conclusions. Experimental Infrared spectra were taken of CHBOH, (CH,O)?B., and of the azeotrope, in an attempt to observe any shifts in the absorption peaks of the separate components after forming the azeotrope. A Baird Infrared Spectrophotometer was used; the cells were of 0.025 mm. thickness and had AgCl windows. The spectra were scanned from 2-16p at a speed of lp/min. with a programmed slit width. The molecular weight of the azeotrope in the vapor state was previously reported’ as being slightly higher (69.7 g./ mole) than the average value for this property from an equimolar mixture (68.0 g./mole). In the present investigation, a cryoscopic study was made of the azeotrope in solutions of nitrobenzene, benzene and p-dioxane. The molecular weight of (CH30)3Bin the same solvent media also was determined, after a search of the literature failed to disclose any investigations OF this nature for the borate. A simple Beckmann method was used for the cryoscopy, consisting of a 5’ thermometer (in hundredths) immersed in an 8 in. tmt-tube containing the solutions under observation; this was surrounded by a slightly larger glass tube which served to insulate it from the water-ice bath used for all determinations. The solute and solvent were in all cases weighed out directly, and no special attempts were made to correct for the amount of solvent that may have frozen out during the process of supercooling (although this was negligible in most csses, since the cooling bath was maintained so as to keep the amount of supercooling a t a minimum). The highest reading at which the temperature remained constant was taken as the freezing point. A manually operated glass-ring stirrer was used for the nitrobenzene solutions, and a steel stirrer for the benzene and p-dioxane solutions. The (CHBO)~B and azeotrope (courtesy Callery Chemical Co.) were distilled and assayed for borate content by means of the standard mannitol-phenolphthalein analysis. The borate assayed 100.1% (CH30)3B (the high assay probably is the result, of the Dresence of small amounts of dissolved &Boa, formed by’ partial hydrolysis). The azeotrope (b.p. 54.5’ (758 mm.)) contained 74.83% (CHa0)sB (this value being slightly lower than that to be expected for a 1 :1mixture).
1337
KOTES
0.66
r
0*42 0.38 !L/ 0
L.
0.1
0.2
0.3
0.4
m. Fig. 1.-Cryoscopic
plot of the CHaOH-(CH30)3B azeotrope.
TABLE I Solvent
Kr
Nitrobenzene Benzene p-Dioxane
6 . 8525 5.06P 4.636
G. boratP/kg. solvent
20.78-40.32 26.80-62.27 16.87-60.29
M (g./niole)
104.3 i 0.5 1 0 3 . 4 f .4 104.0 jz . 7
The results reported in Table I show the molecular weight of (CH30)SB (theoretical 103.9) to be normal in the solvents employed. Figure 1 is the cryoscopic plot for the azeotrope in the same solvent media listed in Table I. The ratio of the apparent to the theoretical molecular weight, M / M o ,where JIois 13G.0 g./mole, is plotted against the molality, m. Since the azeotrope has been shown to be a true mixture, the curves in Fig. 1 should all be straight lines that approach a limiting value of M / M o = 0.5 at infinite dilution if the solutions obeyed Henry’s law. This relationship is evident for the nitrobenzene plot, which is almost linear, and for solutions in p-dioxane greater than 0.1 m. The benzene plot, on the other hand, shows no such concordance. Table I shows the molecular weight of the borate to be normal in all three solvents; Results and Discussion therefore one must attribute any deviations from Spectroscopic.-The infrared spectra of the linearity and from the limiting value of M/Mo to CHSOH and (CH30)3B mere found to be identical the presence of the CH3OH and to systematic exwith the spectra already reported for these com- perimental errors. The nitrobenzene and p-dioxp o u n d ~ . * - ~The spectrum of the azeotrope showed ane plots, however, demonstrate an early view that the presence of the B-0 stretching peak a t 1348 in the cryoscopic method it is the molecular weight cm.-’, the OH stretching peaks (with intermolecu- of the solute as vapor which is obtained.’ lar hydrogen bonding) a t 3200-3400 cm.-’, in addiConclusions tion to the other characteristic assignments found 1. A spectroscopic examination in the infrared in the separate component^.^-^ Thus the complete additivity of the component spectra indicates region (2-16 p) of the methanol-methyl borthe absence of any tendency for compound forma- ate azeotrope gave no evidence for compound formation. 2. Methyl borate exhibits a normal tion. Cryoscopic.-Table I presents the results of the molecular weight in solutions of nitrobenzene, bencryoscopic study made on the (CH3O)aB. Six de- zene and p-dioxane. 3. The azeotrope obtains texminations were made in each solvent medium. molecular weights in nitrobenzene and p-dioxane that are characteristic for a true mixture in solu(1) T. J. ‘Cully a n d P. M. Christopher, THIBJOURNAL,61, 1578 tion, and a t infinite dilution gives the same value (1957). for this property as the one previously reported for (2) H. If. R a n d a l l , R. G. Fowler, N. Fuson a n d J. R . Dangl, “Infrared Determination of Organic Structures,” D. Van Nostrand Co., the vapor state.’ The presence of methanol in the Inc., New T c r k . 1-. Y . , 1949, p. 191. (3) L. J. Bellamy “The Infra-red Spectra of Complex Molecules,” J o h n Wiley a n d Sons, Inc., Xew York, N. Y., 1958, p. 348. (4) R . L. Werner a n d I
