metric Analysis,” p. 488, Interscience, Kew York, 1957. (9) Ledingham, G. A., Neish, -4. C., “Industrial Fermentations,’’ L. A. Underkofler and R. J. Hickey;, eda., p. 39, Vol. 2. Chemical Publishme: Co.. New
(11) Manewal, R., Baking Ind. 104, (KO,1310), 43, (1955). (12) Otterbacher, T. J., Baker’s Dig.,33, 36 (1959). (13) Robertson, Florence M . , Neish, A. C., Can. J . Research 26B,737 (1948). (14) Sykes, H. G., Baker’s Dig. 33, 48 (1959). (15) Wilson, C. E., Lucas, H. J., J . Am.
Chem. SOC.58,2396 (1936). (16) Wiseblatt, L., Kohn, F. E., Cerea Chem. 37, 55 (1960). RECEIVEDfor review June 29, 1960. Accepted September 12, 1960. Division of Analytical Chemistry, 137th Meeting, ACS, Cleveland, Ohio, April 1960. Paper No. 254, Journal Series, Central Research
Laboratories, General Mills, Inc.
as Chromatographic Analysis of Chloromethylated Phenyl Ether WALTER B. TRAPP, JOHN L. PILLEPICH, and EVAIN D. RUBY Aromatics Research and Chemical Physics Research Inborafories, The Dow Chemical CO., Midland, Mich.
b Thermally unstable chloromethylated phenyl ether may b e analyzed b y hydrogenolysis to the corresponding methyl-substituted phenyl ether mixture followed b y gas chromatographic analysis. Eight components ob the reaction mixture have been qualitatively and quantitatively analyzed. An application of the method i s described wherein the six major components are traced throughout the course of the chioromethylation to provide data for a kinetic profile of the reaction. of phenyl ether (common name, diphenyl oxide, hence the symbol, DPO) has been reported by Brunner (1) who isolated p-phenoxybenzyl chloride. Funke et al. (3’) isolated the p,p’-di species, bis(a - chloro - p - tolyl) ether, but did not describe it. However, the compound mas subsequently described by Toniita and Kimura (6). A knowledge of the complete composition of the reaction mixtures from DPO, HCHO, and HC1 a t various stages was desired. These mixtures were generally thermally unstable, tending to undergo benzyl-type polymerization with the evolution of HC1. Therefore, analysis of this material by a direct thermal method was not practicable. However, these chloromethyl compounds can be converted quantitatively to the thermally stable methyl analogs b y palladium-catalyzed hydrogenolysis:
use of relative retention data obtained by chromatographing known standards of tolyl ether isomers. Thus, DPO, omono, p-mono, o,p’-di, and p,p’-di were identified as principal components while mmono, and m,p’-di were identified as minor components. The “tri” species was so assigned because of its position on the chromatogram. Figure 1 shows an elution curve for a typical unknown. Quantitative accuracy and reproducibility are illustrated in Table 1. To use the average error as a calibration, the known blend should be designed to match closely the propor-
tions of components found in a given unknown. Gross errors in these analyses may be detected by comparison of the analyzed chlorine value of the chloromethylated DPO mixture with a theoretical value calculated from the gas chromatogram. Calculation of the latter value is illustrated in Table 11. EXPERIMENTAL
Hydrogenolysis Apparatus. Microhydrogenators as described b y Gheronis and Entrikin (2) were made from 125-mi. Claisen flasks. Several
HE CHLOROYETHYLATION
The product mixture from this reaction is analyzable b y gas chromatography. The individual components comprising these systems were identified by the
Table 1.
Example of Accuracy and Reproducibility Conducted on Synthetic Blend of DPO and Tolyl Ethers
Mole yo Component DPO o-monom-monop -mon oo,p’-dirn,p‘-dip , p ’-di-
Table II.
Found
As
blended 20.21 5.00 0.98 50.58 5.05 1.11 17.06
1 19.5 5.5 1.2 50.3 4.7 0.64 18.2
1 2 20.0 6.7 0.72 49.6 5.0 1.1 17.9
Average error
2
2 19.75 5.6 0.96 50.0 4.85 0.87 18.15
Reproducibility
(1 - 2) -0.5 -0.2 $0.5
-0.5 +0.6 -0.0 -0.6 -0.20 -0.2
+0.7 -0.3 -0.5 +0.3
+1.1
Derivation of Theoretical Chlorine Value and Comparison with Found Value for Unknown System Shown in Figure 1
Component DPO o-mono m-monop-monoo,p‘-dim,p ’-dip,p’-diTri-
Chloromethyl Species % C1 for each Ca!culated wt. % homolog % c1
Mole yo 0.26 3 4 0:73 32. 16. 0.47 45. 1.9
\J
1
0.18
...
...
31.65
16.24
5.14
65.77
26.54
17.46
2.40
33.80
0.81 23.4 Found Yo C1: 22.7
a = - 0.7
VOI. 32, NO. 13, DECEMBER 1960
*
1737
The known tolyl ethers were prepared by conventional Williamson ether syntheses using the appropriate cresol and bromobenzene or bromotoluene typified by the procedure of Ullman and Sponagel (6) for phenyl p-tolyl ether.
p-Mono-
i\
APPLICATION OF METHOD
30 MI
90 HIN.
TIME
Figure 1. Gas chromatographic elution curve for tolyl ether mixture derived from chloromethylated phenyl ether of 22.7% chlorine which corresponds to a degree of chloromethylation of approximately 1.6 -CHzCI groups per DPO unit
of these were attached to a common hydrogen inlet manifold. Hydrogenolysis Conditions. A sample of dried crude chloromethylated D P O ranging in quantity from 0.1 to 10 grams was dissolved in 50 grams of dry toluene and placed with 1 gram of 5% Pd/C catalyst in a microhydrogenator. The mixture was heated in a water bath t o 50' C. and then hydrogen was bubbled through. T h e excess hydrogen swept out the released HC1 and the end of the reaction was signaled by a negative AgN03 test for chloride in the exit gas. I n some cases the HC1 was trapped in water and titrated to determine the chlorine in the original material. Upon completion of the reaction the mixture was cooled, filtered to remove catalyst, and vacuum-stripped to remove solvent. The residue was analyzed by gas chromatography, Gas Chromatographic Analysis. A gas chromatographic instrument of conventional design using a hot wire thermal conductivity cell for detection was employed. The best column for this analysis was a &foot length of '/4 inch inside diameter stainless steel tubing containing 207, by weight of bis [a-(2-tolyl)-p-tolyl] ether (4), on 30- to 60-mesh Johns-Manville Chroniosorb. The column bath was maintained a t 250" C. and the carrier gas (helium) flow rate was 130 *cc. per minute. These conditions gave an analysis time of approximately 90 minutes. While the above column conditions gave resolution of all the species, in-
Table 111.
Time Mh.'
DPO ADP0
o
3.3
76
0.3
3.1
105
0.3
1.7
A0
ANALYTICAL CHEMISTRY
I6 24
21 39
IO
I5
-
+PER CENT CHLORINE c C H L O R O M E T H Y L EQUIVALENT--
25 37 I9
26 54 20
I-
5 60 u U a W W _I
g
40
20
0 0
20
Figure 2.
P
-2.9 30
-1.4
B 85
05
BO
52
6.0 -3
o
100
Balance of Disappearing
40
1738
cluding the minor meta isomers, a similar column 10 feet in length operated at 220" C. with a helium flow rate of 150 cc. per minute gave satisfactory resolution of the major species with an analysis time of less than 60 minutes. After determining the accuracy and reproducibility of the latter column conditions, these conditions were employed for the analysis of the group of samples which comprise the kinetic profile described in the Application of Method section of this paper.
This method of analysis was used to follow the course of the chloromethylation of DPO. Eleven samples were withdrawn for analysis at specified time intervals throughout the reaction. The results are illustrated in Figure 2 wherein the six major species are plotted in terms of mole per cent us. time. The same data may be plotted with the horizontal axis linear in "chlorine content," degree of reaction (chloromethyl equivalent) , or other desired parameters. While Figure 2 represents a practical kinetic picture of this reaction the reaction temperature is constant a t 70" C. only in the region from 60 to 180 minutes. Prior to this point the temperature gradually rises from 40' C. a t the beginning of the reaction up to 70" 6. In constructing profiles such as this, the validity of the graphic representation may be increased by consideration of the afore-mentioned chlorine value comparisons, and the balance of forming
14
40
60
100 TIME, MINUTES
80
120
140
180
160
Kinetic profile of chloromethylation of diphenyl ether
(XD)and
Forming (2,) Species in the Chloromethylation of DPO (Taken from Figure 2 data) Mole yo Ap o,p' Ao,p' p,p' Ap,p' Tri ATri ZD 8.4 29 1.4 +1.1 -27.9 -22 +8.6 2 5 17 48 +2.2 -17.4 - 16 +4 10 21 58 4.7
+
ZF
+28.7
+16 2
and disappearing species. A balance of increments among experimental values used in Figure 2 was calculated as shown by the example in Table I11 covering the range of 40 to 105 minutes. Over the entire range of 0 to 180 minutes the totals of the increments were 2 2 =~ -128.9 and Z Z F = 132.8. This is considered a reasonable balance for a valid profile. This method might be applicable generally for the analysis of mixtures containing labile halogen \{-here the reduction products boil below 400" C.
Ger. Patent 569,570 (Feb. 4, 1933). (2) Cheronis, I\J. D., Eiitrikin, J. B.,
ACKNOWLEDGMENT
The authors thank E. H. Rosenbrock for the preparation of several of the tolyl ethers used as known standards, H. G. Scholten and D. F. Kisniewski for development work on the utilization of bis[a - (z - tolyl) - p - tolyl] ether column liquid, and J. D. Doedens and H. E. Hennis for helpful suggestions and discussions.
"Semimicro Qualitative Organic Analysis," 2nd ed., p. 331, Interecience, lieu, York. (3) Funke, Albert, Engeler, C. O., Jacob, Joseph, Depierre, France. Compt. rend. 228,716 (1949). (4) E. S. patent applied for. (5) Tomita, M., Kimura, K., J . Pharm. SOC. Japan 70,44 (1950). (6) Ullman, F.,Sponagel, P., Ann. 350, 83 (1906). RECEIVEDfor review May 28, 1,960. Accepted September 21, 1960. Divlslon
LITERATURE CITED
of Analytical Chemistry. 137th ICIeeting, ACS, Cleveland, Ohio, .ipril 1960.
(1)Brunner, Arnold (to I. G. Farbenind.),
Gas Chromatographic Characterization of Fatty Acids Identification Constants for Mono- and Dicarboxylic Methyl Esters THOMAS K. MIWA, KENNETH 1. MIKOLAJCZAK, FONTAINE R. EARLE, and IVAN A. WOLFF Northern Utilization Research and Developmenf Division, Agricultural Research Service, U. S. Department of Agriculture, I8 I5 North University, Peoria, 111. Readily reproducible numerical constants were determined for characterizing mono- and dicarboxylic methyl esters by gas-liquid chromatography. For a specified column packing and carrier gas, these constants, called equivalent chain lengths, are independent of experimental conditions. A combination of two values, obtained by use of polar and nonpolar packing, is sufficient to characterize most fatty acids.
c
identification of components on a gas chromatogram is established by comparing retention times. volumes, or ratios with those of standards. These retention characteristics, however, vary according to experimental conditions-e.g., changes in column temperature. James (6) has proposed a graphical means of identifying homologs using curves based on retention ratios that are subject to change in slope when the ratios change. I n screening seed oils to select those having industrially interesting fatty acid compositions (S), retention values that remained constant regardless of changes in experimental conditions were needed to characterize known and unknown components. A scheme was devised whereby each coniponent on the chroniatogram was expressed by a chain length equivalent to a homolog of the saturated straight-chain monocarboxylic acids. For a specified column packing and carrier gas, in the range where the relationship between molecular u-eight of the reference saturated straight-chain monocarboxylic methyl esters and logarithm of their ONVENTIONALLY,
temperature, but the E.C.L. remained constant. This procedure IT-as applied to a variety of fatty acids from oils containing conjugated unsaturation or hydroxy. epoxy. cyclopropenoic, carbonyl, and other groups contributing to the complexity of their qtructure. Dicarboxylic acids commonly encountered in degradative studies of unsaturated fatty acids were characterized in similar manner. After submitting an abstract to present this paper, describing the E.C.L. procedure used here since January 1959, an article by Koodford and van Gent (15) came to our attention in which they independently proposed a similar scheme, and refer 'to their parameter as a "carbon number." I n the present article me provide con-
retention times was linear, interpolation between the retention times of the reference esters permitted determination of an equivalent chain length (E.C.L.) for each component. This E.C.L. value was independent of operating conditions such as column temperature, carrier gas flow rate, and column diniensions. I n practice, a reference curve was established by plotting on a semilog graph the retention times (log-scale) of two or more known, normal, saturated monocarboxylic methyl esters against their chain lengths (number of carbons in the acid). Values for components of subsequent samples put through under the same operational conditions were then read from the curve using observed retention times. The slopes of the curves varied mith changes in column
Table I.
Conditions for Experimental Comparison of Retention Values
Col. Structure (Glass, U-
Shaped),
Set A
0 6 X 275
of Helium,
R.ll./hIin.
Theor. Plates (Palmitate), Thousand
30 (40p.5.i.)
250
30
90 (40p.s.i.) 87 (25 p.e.i.) 30 (25 p.5.i.)
Same as A
5 0
228
Same as 4
2 1 2 2
100 (40p,s.i.)
190
2.3
Same as E
210
2.8
Flow Rate
I.D. X
Length, Cm.
Temp. of Column +th, C.
Stationary Phase Apiezon L o n Celite 545, 100-150 mesh (20:SO)
B C
Same as 9
D
0 6 X 125 0 3 X 125
E
0 6 X 200
F
Same as E
Same a s A SameasA Same as 4 ,except 60-100 mesh (15:85)
Resoflex 446 on Celite 545, 100150 mesh (20:80) Same a s E
VOL. 32. NO. 13, DECEMBER 1960
Q
1739
