THESYSTEM OCTADECYLAMINE-ACETIC ACID
May, 1945
775
discrepancies in dyes 2G, 27 and 28 hdve already been discussed. The case of no. 58 (phenolindophenol) caniiot be interpreted until the cause of the great difference in absorption of the water a i d methanol solutions is found. Some of the remaining large discrepamics are doubtless due to experimental error. If we arbitrarily exclude the eight cases with the largest A, the average value of A beconies 3 nip. I t may therefore be reasonably predictecl that when new members of these five great classes of dyes are investigated, the average difference between calculated and observed values will not be over 3 mp. Indeed, if we should consider the various factors that we have noted but not used, this difference would probably be reduced to 2 mp.
into one family. The wave length, X, of the main absorption band of any member of the family is determined by two rules. The first, theoretical, states that X is always greater, the greater the fraction of the characteristic positive charge that is on the auxochromes. The second, empirical, states that the effect upon X of various groups is additive. Thus a number of additive constants are obtained, from which X can be calculated, and which are all qualitatively consistent with the theoretical rule. However, in the acridine dyes the calculation applies, not to the first ( x ) band, but to the second (y) band. With this proviso, the table shows that with new dyes of the family X can be predicted with an average error of not more than 3
Summary
mI.4. BERKELEY, CALIFORNIA RECEIVED DECEMBER 29, 1944
Six great classes of dyes are brought together
[CONTRIBUTION FROM THE
RESEARCH LABORATORY OF ARMOUR AND
COMPANY]
The System Octadecylamine-Acetic Acid BY W. 0. POOL, H. J. HARWOOD AND A. W. KALSTON The present irivestigation is a continuation of work dealing with the of high molecular weight aliphatic comllounds and reports the behavior of binary mixtures of octadecylamine and acetic acid.
modifications with such speed that true solution temperatures could not be obtained. To secure an approximate solution temperature, the tube was warmed in hot water until the contents were ehtirely liquid. The tube was then placed in thc bath which had a fixed temperature slightly below the melting point of the most stable modification. The mixture would generally supercool and remain liquid. The tube was then removed from the bath, immersed momentarily in cold water and replaced immediately in the bath. If the crystals, which had formed by the rapid cooling, wcnt into solution, the fixed temperature of the bath was lowered, and the entire proccdure was rcpeated. In this way two temperatures were obtained, an upper a t which the unstable crystals remelted, and a lower a t which the unstable crystals remained or underwent a transformation to a more stable modification. The upper of these two temperatures, which were usually within 0.5' of each
Method Preparation of Materials.-Anhydrous acetic acid was prcLpared by partially freezing 99.5% glacial acetic acid and allowing the liquid portion to drain from the crystals. The frcczing point of the acid used was 16.83'. Fatty acid from hydrogenated soybean oil was converted to nitrile which was then hydrogenated to anline. After a preliminary distillation the octadecylarnine was fractionated in a Stednian-packed column. The freezing point (53.02")of the fraction used was in 'good agreement with the best literature value' (53.06'). The .octadecylammonium acetate was prepared in benzene arid after several crystallizations had a freezing point 80 of 84.4". Determination of Equilibrium Temperatures.-Mixtures containing more than 55 mole % of acetic acid were preparcd by weighing octadecylammonirim acelate and acetic acid into small glass tubes which were then sealed. Octadecylamine aiid acetic acid were used to prepare 60 samples roritairiing 3 to 53 inole yo of acetic acid. Misturcs having less than 3 inole % of acetic. arid were pre- ,i) pared from octadecylamine and octatlecylamriioniii~n acetate. Equilibrium temperatures were obtained by ob- 6. servation of the tubes as they were rotated vertically about 40 their short axes in a water-bath. The teniperature of the bath was electrically controlled arid was subject to very :lice adjustment. A condition of eqriilihriurn was proved by noting the temperature at which a solid phase disappeared as the sample was warmed slowly and comparing 20 this temperature with that at which a trace of crystals defwitely exhibited growth as 4he sample was cooled slowly. These two temperatures were always within a few tenths of a'degree of each other. The filled circles in Fig. 1 represent the upper or solution temperatures. In some cases unstable crystals transformed to the stable
-
(1) Ralston, Hoerr, Pool and Harmood, J . (1944).
Oyg.
Chrm., 9, lo2
I I I I I I 70 50 30 10 Mole per cent. of acetic acid. Fig. 1.-The system octadecylainine-acetic acid.
I
90
!
i
-z >
W. 0. POOL,H. J. HARWOOD AND A. W. RALSTON
((0
other, is plotted as a n open circle in Fig. 1. Broken lines represent unstable m o d h a t i o n s and are drawn in the manner which seemed most logical. The transitory nature of the unstable modifications made positive proof of their composition impossible. Differences in the appearance of the three forms support the interpretatiop shown. The eutectic formed by octadecylammonium acetate and octadecylamine contained less than 0.1 mole % of the amine and was located by means of a cooling curve of a mixture containing 1.2 mole % of acetic acid. The only observable thermal change occurred at 52.96' and corresponds to the freezing point Of the eutectic.
Experimental Results.--The results are given in Table I and are shown graphically in Fig. 1. ~ A U IL ~ OCTADECYLAMINE-ACETIC ACID
Eouilibrium temDerature. 'C.--Least InlerMost mediate stable stable
7 -
AcOH, mole %
100.0 !17.9 9ti. 4 94.8 89.9 84.8 79.8
10. 63 16.4 14.8 16.2 28 t I
Nolle
None
SOllC~
xolle ?;one 13 7 Indet. 30.5 40 5 50 ti 50 0 49 9 51 1 51 52 40 5 41 1 42 3 Indct. 13 2 4fi 2 48 7
Vol. 67
tains 96.6'mole % ' of acetic acid. Octadecylamine and octadecylammonium acetate appear to form a monotectic system; the eutectic, if any, lies only 0.06' below the freezing point of octadecylamine. The stable compound C18H3,NA2. 2HC%H302has two other modifications indicated by the curves DEF and GH. Octadecylammonium acetate also has two other modifications indicated by the curves JK and LM. The mixture having a composition of 1 mole % of acetic acid exhibits two crystalline forms. The equilibrium temperature shown a t N is evidently due to one of the lower melting forms of the ammonium salt. Between 1 and 57 mole 7 6 of acetic acid, unstable modifications of octadecylammonium acetate occur, but transformation to the stable crystal takes place so rapidly that equilibrium temperatures cannot be obtained.
Discussion Davidson, Sisler and Stoenner,2 in an investiIndet. gation of the acetic acid-ammonia system, showed iJ2.7 40.0 the existence of five solid compounds. It is in42.6 51.1 teresting to note that the octadecylamine analogs Not detd. S o t detd. 74.11 of 5NH3-4HGH302, 9NH3.HGH3O2 and 2NH3. .53.6 73.0 59.3 HCZH~OZ do not exist. The absence of bimolecu53.3 72.0 69.8 lar compounds of octadecylamine and acetic acid 58.3 GO. 4 70 8 containing more than two acetic acid molecules Indet. GO. 3 70 7 is in keeping with the observation by Ralston, 58.3 60.3 70.5 Hoerr and Hoffman3 that the degree of hydration 51.4 62.0 68.8 of octadecylamine is less than that of dodecyl5G 63.2 68,3 amine or octylamine. These authors found that I tidet . 64.9 67.5 octadecylamine formed only a &ono- and a di56.8 ti4.8 ti:, 4 hydrate, whereas dodecylamine formed a tetraIndet . G.4 ti;. 1 hydrate, and octylamine formed a hexahydrate. 59.1 67.7 ti5.2 It is probable that the ability of amines to form got detd. 72.7 63.1 acid salts decreases as the homologous series is 563 72.5 80.9 50.9 ascended. Indet. Indet. 84.0 52.4 Summary Indet. Indet . 50.0 8+.4 Indet. Indet. i9.5 33.3 1. The temperature-concentration curve for -Indct. Itidet. 26 0 1 1 . 1 the system octadecylamine-acetic acid has been Indet. Indet. 73.5 1-1 t i completed throughout the entire concentration Indet Indet. ti 2 70.4 range. Indet. Indet. 67.9 :i 7 2. The existence of the new solid compound 52 9 Indet. 62.6 I 0 tlsHa7NHz.2HCzH3O2 has been demonstrated. 3 . Three modifications of ClgHa,NH2*2HC*From Fig. 1 i t is evident that only two stable 0 2 and ClgHnNH2.HC2H302have been shown cornpouiids ( C I & H ~ ~ N H ~ . H C Z H and ~ O ZClxHa7- H 3 occur. NH2.2HC2H302) are formed between octadecyl- to 4. It has been suggested that the formation of amiiie and acetic acid. The first of these conipounds has heen known and melts a t 84.4'. The the acid salts of the alkyl amine series parallels sccoricl compound melts a t (i0.S' and forms a the formation of the arnine hydrates. RECEIVED JANUARY 8, 194q-l li-i-. rneritectic system a t B having a submerged maxi- CHICAGO, mum a t C. The eutectic between C18H37NH2. (2) Davidson, Sisler and Stoenner, THISJOURNAL, 66, 779 (104 4) ( 3 ) Ralstou, Hoerr- and Hoffman, i b i d . , 64, 1516 (1942). 2HCzH302and acetic acid occurs at 14.2' and conNo11c Nfl11c
