Analysis of Mixtures of M e t a - and Para-Cresols and Their Butylated Products DONALD R. STEVENS
AND
J. E. NICKELS, M e l l o n
Data are presented for the analysis, b y freezing point and cloud point determinations, of binary cresol and butylated cresol mixtures such as are encountered in the butylation-fractionation-debutylation method of separating m- and p-cresols. The procedures are simple end rapid, and yield results which are readily duplicated. A cloud point method for determining small amounts of water in glycols end glycerol is suggested.
F
ROM their mixtures m- and p-cresols are separated by a
method involving alkylation with isobutylene, separation by fractional distillation of the tertiary butyl derivatives so produced, and dealkylation of the individual di-tert-butylcresols to give the pure parent cresols ( 3 ) . In the commercial operation ( 4 ) it is important that reliable and quick methods be available for analyzing the various distillates handled. The determination of freezing points is a convenient method of analysis. A measurement of the critical sorution temperature of the phenolic mixture in diethylene glycol and other solvents offers another rapid and accurate test for this purpose.
FREEZING POINTS
METHOD. A sample of 5 to 10 grams of the cresol mixture waa placed in an unsilvered evacuated Dewar test tube (16x150 mm., inside dimensions) equipped with a glass loop stirrer and a calibrated thermometer, readable to 0.1 O C., held in place by mean8 of a cork stopper (an rlnschiitz thermometer was found very suitable for this work). When the material +as a solid, the tube was first heated to melt the sample. After a preliminary trial, the Dewar test t u p was placed in a water bath held a t a temperature about 2 below the indicated freezing point. The
Table
Name of Compound
I.
Properties Boiling Point a t 20 Mm. 0
Freezing Points of Mixtures of m-Cresol and ' Mono-tert-butyl-m-cresol rn-Cresol in 3lono-tert-butyl-m-cresol Nono-tert31ono-tert-butyl-m-cresol in m-Cresol butyl-m- Freezing Mono-tertmFreezing m-Cresol cresol point butyl-m-cresol Cresol point ~
%
%
%
%
%
0.8 2.4 4.4 7.8 ie.0 13.1 16.1 19.0 22.2
100.0 97.6 95.6 93.0 9B.B 86.9 83.9. 81.0 77.8
c.
11.5 10.2 9.2 7.9 6.4 4.7 3.1 1.3 -0.3
IV.
c.
%
70
0.0 2.2 4.9 10.5 16.5 22.7 25.7 32.6 36.0 39.3
100.0 97.8 95.1 89.6 83.5 77.3 74.3 67.4 64.0 60.7
51.7 50.5 48 9 45 8 42.0 38 3 36 0 31 0 29 2 27 3
%
%
0.0 2.0 5.0 10.0 16.0 21.7 27.3 32.4 34.8
100.0 98.0 95.0 90.0 84.8 78.3 72.7 67.6 65.2
c.
21.3 20.2 18.5 15.5 11.9 6.4 0.0 -3.2 -4.8
OC.
%
V.
Freezing Points of Mixtures of Mono-tert-butyl-m-cresol and 4,6-Di-tert-butyl-3-methylphenol 3lono-tert-butyl-m-cresol in 4,6~Di-tert-butyl-3-methylphenol 4,6-Di-tert-butyl-3-meth?.iphenol in LIono-tert-butyl-m-cresol A 4_," 6butyl- -. n i - f.. r r t. - Mono-turt=,"fi-ni.trrt. " Mono-tertbutylbutyl3-methyl- Freezing 3-methylbutylFreezing m-cresol Dhenoi Doint phenol m-cresol point % 7c c. % R c. 21.3 0.0 100.0 62.1 100 0 0.0 20 6 98.8 1.2 61.0 98 7 1.3 20.0 97.6 2.4 59.0 96 6 3.4 16.8 95.6 4.4 56.9 94 6 5.4 17 4 93.1 6.9 54.7 92 7 7.3 16 0 90.8 9 2 52.2 90 6 9.4 15 0 89.3 10.7 49.7 88.3 11.7 14.1 12 2 87.8 41.9 85.0 15.0 12 4 85.2 14 8 40.4 81 5 18.5
Table
-.
Freezing Points of Mixtures of m- and p-Cresolsn Freezing Freezing m-Cresol Point p-Cresol m-Cresol Point
c.
c.
~
II.
%
0
21.3 20.4 18.8 16.9 14.9 12.7 10.2 7.6 5.2 3.6
Freezing Points of Mixtures of Mono-tert-butyl-m-cresol and 2-tert-Butyl74-methylphenol hlono-tert-butyl-m-cresol in 2-tert-Butyl-4-methylphenol in 2-tert-Butyl-4-methylphenol Mono-tert-butyl-m-cresol Mono-tert: 2-tert-Butyl2-tert-Butyl- Mono-tertbutvl4-methvl- Freezing 4-methylbutylFreezing phenol m-cresol point m-cresol phenol point
Table
...
p-Cresol
%
100.0 99.8 97.0 94.6 92.1 89.3 86.2 82.9 80.0 78.6
1.0 3.0 5.4 7.9 10.7 13.8 17.1 20.0 21.4
Freezing Point
C.
11.P ... m-Cresol 34.70 ... pCresol 21.3 Mono-tert-butyl-m-cresol 51.7 l26:5 2-tsrt-Butyl-4-methylphenol 62.1 167.0 4 6-Di-tert-butyl-3-methylphenol 69.7b 147.0 2:6-Di-tert-butyl-4-methylphenol 174.9-5.3' Trihobutylene W. Seaman Laboratory for Analytical Research, Calco Chemical Division Americ'an Cyanamid Co., Bound Brook, N. J. (private communioation), 'reports highly purified m- and p-cresols t o freeze a t 11.65' and 34 63' C respectively. i Meltlhg point. C A t 745.7 mm.
Table
111.
0.Q
The m- and p-cresols employed in securing the data reported herein were Eastman practical grade chemicals which were subjected to a purification sequence comprising fractional distillation under reduced pressure and a t about 15 to 1 reflux ratio through a 20-plate packed glass column, collecting only the middle portion which came over within a 1 C. temperature range. This material was melted, allowed to cool, and seeded. When the crystallization was about half complete, the crystals formed were separated from the mother liquor and distilled through. the 15-plate column, again collecting only a heart cut. The tertiary butylated derivatives of these cresols were prepared by alkylation Yith isobutylene (3) and purified by fractionation-recrystallization-fractionation treatments. Triisobutylene was made by the action of 63% sulfuric acid on Eastman tert-butyl alcohol and purified by means of an alkali wash, a rough distillation through a Hempel column, and two fractional distillations through the 20-plate column. The cresols, their butylated
Pa.
derivatives, and the triisobutylene were believed to be of a t least 99.5YGpurity. Their properties are listed in Table I.
MATERIALS
Table
Institute of Industrial Research, Pittsburgh,
c.
"I.
Freezing Points of Mixtures of Triisobutylene and m-Cr,esol Triisobutylene in m-cresol ~~~~~i~~ Triisobutdene in m-cresol ~~~~~i~~ Triisobutylene m-Cresol Point Triisobutylene m-Cresol Point % % c. % % c. 100.0 11.5 14.1 85.9 6.8 0.0 81.9 6.0 97.4 10.3 18.1 2 77.6 5.6 94.8 9.2 22.4 5 .. 62 8.7 91.3 8.1 24.4 75.6 5.4 10.7 89.3 7.6 Table
a Freezing point d a t a on m- and p-cresol mixtures have been reported by Deaseigne (I), who used cresols freezing a t 10.1' and 34.5' C., respectively.
260
VI.
ANALYTICAL EDITION
April, 1946 Table VII. Weight Percentage of 2,6-Di-tert-butyl-4methylphenol 75.0 58.2 49.1 47.4 37.5 27.0 Table
Vlll.
Critical Solution Temperatures Weight Percentage of Diethylene Glycol 25.0 41.8 50.9 52.6 62.5 73.0
Clou!
Point, C. 181.2 190.0 190.2 190.1 189.0 181.7
Critical Solution Temperatures Cloud Point, ' C. (Weight Ratio of Phenolic Mixture to Diethylene Glycol = 1.0 to 1.0) 198.2 188.5 185.4
Weight Percentage of 4,6-Diterl-butyl-3-methylphenol in 2,6-Di-tert-butyl-4-methylphenol 0.00 1.45 3.42 5.76 8.79
181.5 176.0
Table IX. Critical Solution Temperatures Weight Percentage of MonoCloud Point, C. (Weight Ratio of Phenolic Mixture tert-butyl-nt-cresol in 2,6-Dito Diethylene Glycol tert-butyl-4-methylphenol 1.0 t o 1.0) 0.00 190.2 184.0 3.50 179.3 6.00 173.5 8.75
-
sample was then stirred until it was supercooled about 1" C. and, if necessary, seeded to bring about crystallization. After crystallization had started, the stirring was intermittent, about 0.5 to 1 minute between sets of 2 or 3 strokes of the stirrer. Under these conditions the temperature was found to rise t o a maximum, where it remained until the greater part of the material froze. The maximum value was taken as the freezing point temperature of the sample. The data obtained, given in Tables I1 to VI, are for the full range of m- and p-cresol mixtures, and for the particular distillate compositions handled in practice. CRITICAL S O L U T I O N TEMPERATURES
The observation that mono- and di-tert-butyl-m-cresols and mono-tert-butyl-p-cresol effect a pronounced lowering of the critical solution temperature of 2,6-di-tert-butyl-4-methylphenol with diethylene glycol, and that 2,6-di-tert-butyl-4-methylphenol appreciably raises that of 4,6-di-tert-butyl-3-methylphenoln-ith a 20-80 volume mixture of glycerol-ethylene glycol was used as a basis for a cloud point method of analysis for mixtures of the butylated cresols. The cloud points can be dctermined rapidly with ease and are duplicatable to within 0.1' C. ( 2 ) . For the two systems investigated, the consolute temperatures occurred very near the 50-50 weight ratio of butylated cresol and solvent (see Tables VI1 and XI). It is advantageous to use this particular proportion, for small errors in making up the mixtures are not serious because of the small change in temperature with composition a t this point. The determinations were made by weighing into the Dewar test tube (the same as used for freezing point determinations) equal amounts of butylated cresol mixtures and the solvent, immersing in an electrically heated bath of clear oil, and stirring until complete solution was effected. Then, on slow cooling and with continued stirring, the cloud point was readily discernible. The data collected for binary mixtures of 4,6-di-tertbutyl-3-methylphenol, mono-tert-butyl-m-cresol, and monowith ditert-butyl-p-cresol in 2,6-di-tert-butyl-4-methylphenol, ethylene glycol as the solvent, are listed in Tables VIII, IX, and X. Determinations made with binary mixtures of 2,6-di-tert-butylwith a 20-80 4-methylphenol in 4,6-di-tert-butyl-3-methylphenol, volume mixture of glycerol-ethylene glycol as the solvent, resulted in the data given in Table XII. Because 2,6-di-tertbutyl-4-methylphenol is considerably less soluble in such a mixed solvent, its effect is to raise the cloud point. Diethylene glycol,
261
Table X. Critical Solution Temperatures Weight Percentage of 2-tertCloud Point, O C. Buyl-4-methylphenol in 2,6-Di(Weight Ratio of Phenolic Mixture tert-butyl-4-methylphenol to Diethylene Glycol = 1.0 to 1.0) 0.00 190.2 185.3 2.42 179.3 5.24 175.7 6.87 171.0 8.69 169 6 9.10 Table XI. Critical Solution Temperatures Weight Percentage of Weight Percentage of 4,6-Di-tert-butylBlend (207, Glycerol and Cloud Point 3-methylphenol 80% Ethylene Glycol, by T'olume) C. 32.8 67.2 174.4 39.2 176 0 60.8 49.0 51.0 179.2 50.0 178 9 50.0 47.4 179 2 52.6 57.0 43.0 179 0 34.3 173.5 65.7 Table
XII.
Critical Solution Temperatures Cloud Point, C. (Weight Ratio of Phenolic Mixture to Glycerol-Ethylene Glycol Blend = 1.0 t o 1.0) 178.7 181.9 189.3 199.2
Weight Percentage of 2,6-Di-tertbutyl-4-methylphenol in 4,6-Ditert-butyl-3-methylphenol 0.00 1.08 3.98 8.68
Table XIII. Effect of Water on Cloud Points of Alkylphenol Mixtures in Diethylene Glycol or in a Glycerol-Ethylene Glvcol Blend Cloud Point Rise Water Added Equiweight mixture Equiweight mixture to Solvent of (k) in ( I ) of (i) in (j)
70
oc.
O C .
0.0 0.0 0.0 0:5 2.7 2 9 1.0 4.0a 5,2 1.5 6.ga ... Erratic results obtained caused by loss of water from solvent b y vaporization. (i) = mixture of 4% 4,6-di-tert-butyl-3-methylphenoland 96% 2,6-di-tertbutyl-4-methylphenol. (j) = diethylene glycol (sp. gr. 1.1135/80° F.). ( k ) = mixture of 4% 2,6-di-terl-buty1-4-methyl~henol and 96% 4,6-di-tertbutyl-3-methylphenol. (1; = blend comprising 20-80 volume mixture of glycerol and eth5lene glycol.
could not be employed as the solvent in this instance on account of its high solubility for 4,6-di-tert-butyl-3-methylphenol. I n the determination of these data, Eastman quality glycerol, ethylene glycol, and diethylene glycol were employed. The ethylene glycol was heated to 190" C. to drive off water before use. The solvents were characterized by the specific gravities: 20% glycerol-807o ethjlene glycol (by volume) Dieth) lene glycol
1.260 1.110 1.142 1.1135
a t 8Oo/6O0 F. a t 80°/600 F. a t 80"/60" F. a t 8Oo/6O0F.
Small amounts of water in the solvents have considerable effect on the cloud points, and for this reason it should be emphasized that the data presented are intended to serve only as a guide. A new set of curves can be constructed readily for each batch of solvent by determination of a few key points, or the solvents might be standardized by matching definite cloud point values when mixed with selected pure tertiary butylated cresols. Table XI11 exemplifies the influence of water. This pronounced effect suggests the use of cloud points, with alkylated phenols or other suitable compounds, as a method for determining accurately low percentages of water in glycols and glycerols. LITERATURE CITED
(1) Desseigne, Mbm. poudres, 26, 147 (1934-5). (2) Seaman, N o r t o n , a n d Foley, IND.ENQ.CHEM.,ANAL. ED., 15, 159 (1943). (3) S t e v e n s , IND.ENG.CHEM.,35, 655 (1943). (4) W e i n r i c h , I b i d . . 35, 264 (1943).
