1164
ANALYTICAL CHEMISTRY
odor-producing characteristics. The neutral group was detected at a concentration of I1 p.p.b., and the phenolic and acid groups at a concentration of 50 and I60 p.p.b., respectively. Tracing Industrial Wastes. Isolation of the organic compounds gives a clue as to the type of industry responsible for contributing the waste material. By this means a contributor of a given waste may be identified. The method has also proved useful in the direct examination of certain industrial wastes. Study of Reactions in Dilute Solution. The concentration method is useful in the study of certain reactions in dilute solution. The reactions of chlorine and phenol in dilute solution are being studied in this laboratory. T o obtain a sufficient amount of the reaction product for study, large quantities of the dilute solutions are treated with active carbon. The carbon is removed by filtration, followed by ether evtraction and recovery of the product formed in the reaction. These chlorinated phenolic products have been isolated and their identification is being investigated. Other reactions that may be studied include the
products formed by use of chlorine dioxide and ozone when added to various compounds present in water. Possible Basis for Physiological Study. The physiological effect, if any, of small concentrations of organic compounds in drinking water has not been studied. The method presented is helpful in providing sufficient material for studies of a physiological nature. LITERATURE CITED (1) Feigl, F., “Qualitative Analysis by Spot Tests,” pp. 313-17. Kew York, Elsevier Publishing Co., 1946. (2) Ibid., pp. 392-3. (3) Shriner, R. L., and Fuson, R. C., “Systematic Identification of Organic Compounds,” 2nd ed., pp. 252-3, Kew York, John Wiley & Sons, 1940. RECEIVED October 31, 1950. Presented before the Division of Water, S e a age, and Sanitation Chemistry at the 117th Meeting of t h e AMERICAN C H E x l C h L SOCIETY. Detroit, hIich.
Determination of Dipentaerythritol in the Presence of Pentaerythritol JOSEPH H. JAFFE AND SHRAGA PINCHAS Weizmann Institute of Science, Rehovoth, Israel
RIEDRICH and Brun ( 2 ) have shown that the pentaerythFritol prepared by condensation of formaldehyde and acetaldehyde in the presence of calcium hydroxide is always accompanied by a certain and sometimes an appreciable proportion of dipentaerythritol which cannot be removed by any simple method. As for some purposes, only limited quantities of dipentaerythritol are permissible, a quick and easy method for the estimation of the latter in a mixture is important. The methods of Kraft ( 3 ) and Ryler ( 6 ) ,in which the pentaerythritol is determined quantitatively, can (1) be used for the estimation of dipentaerythritol only if one is sure that no other impurities are present in the sample of pentaerythritol, while the chromatographic method suggested by Lew and coworkers ( 4 ) is somewhat lengthy. An attempt was therefore made to estimate dipentaerythritol in the presence of pentaerythritol by infrared spectroscopy. As both substances dissolve in nonpolar solvents with great difficulty and polar solvents are generally unsuitable for this purpose, the absorption of the corresponding acetates-namely, pentaerythrito1 tetraacetate (I) and dipentaerythritol hexaacetate (11)-was measured in carbon tetrachloride solution.
sorption band due to this group has been reported ( 5 )a t about 1120 em.-’ This band was found for I1 a t 1115 cm.+ (Figure 1); a neighboring band of the carbon tetrachloride may somewhat distort it a t very low concentrations of 11. At this frequency, I has a weak general absorption, but there is no trace of a band. Synthetic mixtures of I and I1 were therefore prepared, and it was shown that even in the presence of much I the optical densities a t 1115 cm.-’ permitted a reasonably good estimation of I1 in the mixture. It is suggested that dipentaerythritol be determined in crude pentaerythritol by acetylation (1)and determination of the optical density of a dilute solution of the total resulting acetates in carbon tetrachloride a t 1115 em.-’ The range investigated is 10 to 70% dipentaerythritol in pentaerythritol. For quantities of the contaminant much smaller than IO%, it will probably be advisable to enrich the dipentaerythritol in the sample before applying the method of assay described. Any higher “polymer” of pentaerythritol will be determined by this method as dipentaerythritol. EXPERIMENTAL
I1
CH3.COOCH2
CHpOOC.CH3
CH3.COOCH2
CH?OOC.CHB
\ / CH,.COOCHz-C-CH2-O-CH2-C-CH,OOC.CH, / \
The only significant differences between the spectra of these compounds were to be expected in the regions of the absorption of the HpC-O-CHz linkage, whirh nrrurs in I1 only. -4n ah-
The infrared absorption measurements were made xith a Perkin-Elmer, Model 12 C spectrometer, using a rock salt prism and a slit width of about 0.4 mm. In order to minimize interaction between I and 11, very dilute solutions (total concentration of about, 0.01 gram per ml.) were used and a cell of 2-mm. thickness was constructed so as t o obtain a sufficient absorption. The cell consisted of a pair of rock salt plates, between which a lead ring was amalgamated as spacer. Samples were introduced by means of a hypodermic syringe needle, through two small holes drilled in the spacer. During the measurements, these holes were closed with pins in order to reduce evaporation of the solvent. In the quantitative work, it was found more accurate t o set the spectrometer a t 1115 cm.-I, the absorption maximum of the H2C-O-CH2 group, than to measure the complete absorption spectrum. A blank measurement with the pure solvent was carried out immediately before that with the solution, and the difference was taken as the optical density of the solution.
V O L U M E 2 3 , NO. 8, A U G U S T 1951
1165
Table 11. Results on RIixtures of Pure Compounds Optical Density, d (Ohsd.) 0.253 0.368 0.37
Concentration, G./JIl.
I1
I
0.00128 0.0021 0.00234 0.00256 0.00704 0.00604
0.0116 0.0158 0.0142 0.0061 0.0086 0.00238
'
0.285
0.68 0.515
% of I1 Calcd. from d 10.9 12.3 15.0 30.0 45.2 70.4
Deviation,
70
Actual 9.9 11.7 14.2 29.6 45.0 71.7
+1.0 +0.6
+0.8
+0.4 +0.2 -1.3
where d = optical density measured, c = total concentration in grams per ml., E = cell thickness in mm., and z = percentage of I1 in the mixture. Hence,
x =
I
2.86 X d ~
ex1
-
17,1
For the absorption measurements in the infrared, greatest accuracy is achieved when a dilution is used which gives an optical density of the order of 0 . 2 to 0.5.
Figure 1. Infrared Spectra t i p p e r . Carbon tetrachloride Lower. Dipentaerythritol heraacetate (0.007 gram) i n 1 ml. of carbon tetra-
chloride
Experimrnte using acetonitrile as solvent gave less satisfactory results than those obtained with carbon tetrachloride (Tables I and 11). The propionates in a variety of solvents gave inferior results to the acetates.
Expt. KO.
1 2 3 4 5
Pentaerythritol, G. 4 0 1 1 2 1
Dipentiterythritol,
G.
0.5 1.0 2 0 0.5 0.5
0 0 0 0
The pure compounds, I and 11, were prepared from pure pentaerythritol and dipentaerythritol, respectively, by the method of Bograchov ( 1 ) . The polyvalent alcohols (10 grams) were refluxed for 6 hours with acetic anhydride (50 grams) and anhydrous sodium acetate (15 grams). The hot mixture was poured into an exresq of water (100 ml.), and the solid was filtered, dried, and recrystallized repeatedly from petroleum ether. Melting poiiit of I,85-87" C.;of 11, 73' C.
Final Yolurne, .\I 1. 400 812.5 900 450 225
Optical Density, d 0.493 0.230 0.393 0.305 0.490
Results on Pure Compounds
Concentration. Extinction Coefficient, G./Ml. Optical Density for 1 G./MI., 1-Mm. Cell 0.00396 (11) 0.325 41 0 . 0 0 3 6 8 (11) 0.30 41 0 . 0 0 3 5 (11) 0.29 41.5 0.0069 (I) 0,085 6 0.21 0 . 0 1 8 (I) 6 0 . 0 2 5 (I) 0.27 5.5 0 . 0 4 0 5 (I) 0.49 6 For I, very nearly the same extinction oopfficient was found for solutions in acetonitrile.
Dipentaerythritol. % Calcd. Found Deviation 12.4 11.1 +1.3 50.0 -1.5 48.5 +o. 1 66.8 66.7 +0.6 20.6 20.0 33.3 +1.0 34.3
T o the calculation of the percentage, x, of dipentaerythritol in the mixture, the following forniu1:ts apply: a x LL x 1.99 a(l d = - loo X l X 4 1 +
&) X 2.24
V
x = Table I.
=
Analytical Procedure. Mixtures of accurately weighed quantities of pentaerythritol and dipentaerythritol were refluxed for 6 hours with five times their weight of acetic anhydride and 1.5 times their weight of anhydrous sodium acetate. The reaction mixture was cautiously diluted with water (ten times the weight of the initial mixture) and, after the excess anhydride had been hydrolyzed, extracted repeatedly with carbon tetrachloride. The solution was filtered through a dry fluted filter and the final volume noted.
1
2-mm. cell
d X 100 - 17.1 cXlX35
1.47 X d X v a x 1
V
X I X 6
- ,19.7
where a = weight of sample, grams u = final volume of solution in carbon tetrachloride, ml. 1 = length of cell, mm. d = optical density of solution a t 1115 cm.-l 1.99 = ratio of molecular weights of (11) (506) and dipentaerythritol (254) 2.24 = ratio of molecular nclights of (I) (304) and pentaerythritol (136) LITERATURE CITED
72. 2274 (1950). . , (2) Friedrich and Brun, Ber., 63, 2681 (1930). (3) Kraft, J . Chem. Ind. (U.S.S.R.), 8, 507 (1931). (4) Lew, B. W., Wolfrom, AI. L., and Goepp, R. M.,J . A m . Chem. Soc., 68, 1449 (1946). (5) JTilliams, V. Z . , Rec. Sci. Instruments, 19, 135 (1948). (6) Wyler, J. A , , ISD. ENG.CHEM.,AXAL.ED.,18, 777 (1946). ( 1 ) -Roerachov. Sac.. . -_~~- ,~E..,~.J. A m . Chem. \-,
In calculating the percentage of I1 in the mixtures it is assumed that no other compound was present and the absorption of I at 1115 em.-* is taken into account. The following equation therefore obtains, according to Beer's lax:
~~
RECEIVED December 12, 1949. Investigation carrled o u t under t h e auspices of t h e Scientific Department. Iqraell Ministry of Defence, a n d published with its approval.
