1849
V O L U M E 2 6 , NO. 11, N O V E M B E R 1 9 5 4 Density. 1.519 (flotation in aqueous zinc chloride); 1.525 (x-ray). OPTICALPROPERTIES Refractive Indices (5893 A.; 25' C.). a = 1.442 & 0.002. p = 1.764 & 0.002. y = 1.775 & 0.005. Optic Axial Angles (5893 A.; 25" C.). 2V = 21" (measured). 2E = 37". Dispersion. r > 21. Optic Axial Plane. 010. Sign of Double Refraction. Xegative. Acute Bisectrix. a. Extinction. a A c = 32' in obtuse p. = 1.653. Molecular Refraction ( R ) (5893 il.; 25" (2.). R (calcd.) = 43.3; R (obsd.) = 43.8. FIWONDATA. 2,4-Dinitrotoluene melts a t 70" C. with sublimation (condenses as a liquid) but no decomposition. The melt supercools readily to room temperature. Crystal growth is rapid a t room temperature and the crystals are very small. .4 melt-
back leaving seed material results in slow growth of large highly birefringement rods. These crystals usually show oblique extinction, although occasional crystals show parallel extinction and an optic axial plane just inside the field of an NA 1.30 objective. The optic axial plane is parallel to the length of the rods, r > u, 2 E = (-)37O. ACKNOWLEDGMENT
Much of the m-ork described was performed under a contract between Cornell University and the Office of Scientific Research and Development during World War 11. Alfred T. Blomquist waa technical representative of OSRD Section B-2-A supervising progress of this n-ork. COXTRIBUTIOK~ of crystallographic data for this section should be sent to Walter C. McCrone, Analytical Section, Armour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill.
SCIENTIFIC C O M M U N I C A T I O N
An Approach to the Correlation of Rf Value with Structure in the Paper Chromatography of Carbohydrate Compounds to find a correlation between R, value and structure I in theeffortpaper strip chromatography of carbohydrates, the N AU
work of Isherwood and Jermyn (2) wae examined. Theqe workers employed the solvent system ethyl acetate-pyridinewater, in determining the Rj values of the aldohexoses and the corresponding aldomethgloses. For the aldohexuronic acids they used ethyl acetate-acetic acid-water ( 3 ) . They state that a certain regularity is observed when homomorphous compounds are compared-Le., mannose with mannomethylose and with mannohexuronic acid. I t was felt that if this qualitative statement could be put into more quantitative terms, a step would have been made toward correlating structure with R, value. This communication proposes a method for seeking such correlations. The pyranose configuration is assumed to be the preferred one for the three series: the aldoses, the aldomethgloses, and the aldohexuronic acids, an assumption also made by Isherwood and Jermyn (2). All of these compounds can then be represented by the general formula:
R
much from that obtained ]Then the corresponding altro- compounds are similarly treated. This K would then be characteristic of the transition: aldose +. aldomethyloee. The functions tried in establishing this relation were (R,)", (l/ROn, and ( 1 / R f - l)", where n is probably a function of the solvent system and the position of the R- substituent. Various values of n were assigned to each of these functions and the relation was tested in the transition. aldose -+ aldomethylose. In each case the K's were averaged, and the deviations and average deviations calculated. The average deviations were taken to be a measure of the constancy of K .
Table I. .4ldohexose, R = - CHzOH Allose Altrose Glucose Gulose Mannose Idose Galactose Talose
R0.47Values
R/ 0.22
0.27 0.195 0.23
0.24 0.31
0.178 0.285
Ro.47
for Aldohexose or
ARo.47 for
Nucleus Alone 1.779 1.596 1.947 1.765 1.719
1.456
2.072
1.541
I
\-
If -R is -CH,OH, the formula represents the aldohexoses; if -CH3, the aldomethyloses; and if -COOH, the aldohexuronic acids. The further assumption is then made that the various nuclei-allc-, altrc-, gluco-, etc.-as well as the several R groups mentioned, will make contributions to some mathematical function of theRjvalue, characteristic of each nucleus and R group, and further that these contributions will be practically independent of each other. Expressed in mathematical terms, the problem is to find a function, f(Rf), such that
for homoniorphous pairs, K being constant for all such pairs and dependent on the R group change in going from one member of the pair t o the other. If E,(,, refers to allose and Rf(b)to allomethylose, a K should be obtained which does not differ very
When (R,)" was so examined, there was no minimum in the average deviation of K , it being approximately proportional to n. The reciprocal of the Rfvalue, on the other hand, did exhibit a minimum. The average deviation of K a t this point n a s 3.6% at n = 0.45. The values at points adjacent to this one were average deviation of 4% a t n = 0 35 and 4yo a t n = 0.lj. Finally, nhen ( l / R y - 1)" was given the same treatment, it was found to exhibit a minimum average deviation of 3 0% a t n = 0.47, and as this seemed to be the function of choice, both because of its smallest percentage deviation and because 1/Rf - 1 is directly related to the partition coefficient, it was defined as Ro 47. The closest points to this one examined were n = 0.45, having an average deviation of 4.5%, and n = 0 5, having an average deviation of 3.7%. If the R- group -CH,OH is arbitrarily assigned the AR0.47 value of zero, the contribution of any of the eight pyranoee nuclei to the total Eo 4, value in any particular compound may be considered to be the RO47 value of the appropriate aldohexose itself.
1850
ANALYTICAL CHEMISTRY Table 11.
Aldomethylose, R = - CHa Allomethylose Altromethylose Gulomethylose Rlannomethylose Idomethylose Galactoniethylose Talomethylose
R/
MEETING REPORTS
Ro.4, Values ARo.47
Dev.
-0.468 -0,498
0.000 0.030
-0,454
0.014 0.007 0.005 0,011
R0.47
0.36 0.45
1.311 1.098
0.36 0.38 0.51 0.265
1.311 1.258 0.983 1,615 1.103
0,48
-0.461 -0,473 -0.457 -0,438 Mean -0.408
0.030 0.014
Tables I to IV show the several R0.47 and ARO.~;. assignments as well as the individual deviations for the two sets of compounds. When this treatment is extended t o the aldoheptoses ( R = -CHOHCH,OH) and to the methyl furanosides and pyranosides of the aldohexoses, the results are not nearly so good as those shown. Apparently groups giving rise to new centers of asymmetry cause complications which cannot be resolved by the simple treatment given here. When the aldopentoses ( R = H ) are compared with either of their homomorphous aldohexoses, no constancy in K is obtained. Likewise, when series of epimeric pairs are treated in this manner, little or no regularity is observed.
Southwest Regional Meeting Southwest Regional Meeting of the AMERICAS T Tenth SOCIETY is to be held in Fort Worth, Tex., DeHE
CHEMICAL
cember 2 t,o 4. Secretary of the General Committee is A. F. Rhipple, Globe Laboratories, Fort Worth, Tex. Abstracts of the papers to be presented before the Analytical Division are printed here.
Nonaqueous Titration of Dilute Acids a n d Bases in Acrylonitrile. M. L. OWENS,JR., AND ROBERTL. MAUTE,Monsanto Chemical Co., Texas City, Tex.
It became necessary t o devise precise methods for the determination of small amounts of weak and strong acids and bases in acrylonitrile which would he rapid, hut free of interference from atmospheric carbon dioxide. Application of nonaqueous techniques has made possible the titration of low (0.002 weight %) concentrations of choline hydroxide and benzyl trimethyl ammonium hydroxide as well as acetic and arrylic acids with a precision of 0.001 weight %. The procedures do not require blank corrections or special equipment, and thus results are more rapidly obtained and are more reliable t h a n those ohtained by the usual procedures.
*
Rapid Automatic Combustion Method for Sulfur Analysis. L. M. hl. 0. GERN.WD,Esso Laboratories, Baton Rouge, La.
. ~ D D I S O S AKD
Table 111. .4ldohexuronic Acid, R = -COOH R/ Gluco-
MannoGalacto-
0.15 0.18 0.13
5-CH20H 5-CHa
5-coon
Values
Ro.47
ARo.47
2.260
0.313 0.320 0.371 Mean 0.335
2.039 2.443
Table IV. -R
R0.47
AR0.a;
0 -0.468 0.335
ARo
-
47
Dev. 0.022 0.015
0.036 0.027
Values Dev. % Dev. Arbitrary assignment
0.014 0.027
3.0% 8 . 1%
Within the carbohydrate field no other sets of data approach the completeness of Isherwood and Jermyn's ( 2 ) . However, a regularity in the I f f values of certain aromatic compounds was observed by Bate-Smith and Kestall ( 1 ) as additional groups were added to the molecule. These workers found that when hydroxy-carbosy substituted benzenes were chromatographed in m-cresol-acetic acid solvent the Rj decreased as the number of hydrophilic groups was increased. The same situation prevailed with the flavones, anthocyanins, and related compounds when series having the same carbon skeleton were compared. Furthermore when log (1/ R j - 1)was plotted against the number of groups of one kind in the molecule, approximately straight lines were obtained. ACKNOWLEDGMENT
The author would like to express his appreciation to James English, Jr., and Harold G. Cassidy for their encouragement, suggestions, and criticism of the manuscript. 11. FRANK LEVY Sterling Chemistry Laboratory Yale University Kew Haven, Conn. LITERATURE CITED
(1) Bate-Smith, E. C . , and lJ7estall, R . G., Biochem. et Biophys. Acta, 4, 427 (1950). (2) Isherwood, F. A . , and Jermyn, 11.A., Biochem. J . , 48, 515 (1951). (3) Jermyn, M. A., and Isherwood, F. d.,Ibid., 44, 402 (1949).
RECEIVED for review, July 1. 1954. Accepted September 27, 1954. Work supported, in part, by a grant from the Research Corp
-4completely automatic sulfur determination has been developed based on converting the sulfur in the sample t o sulfur dioxide, which is estimated iodometrically. T h e sample is burned a t 2400' F. in a stream of oxygen t o produce theoretical conversion t o sulfur dioxide. This sulfur dioxide ih absorbed in an aqueous hydrochloric acid solution where it is titrated, as it is evolved, with iodine generated from a standard iodate solution. The titration is performed by a n automatic potentiometric Titrimeter which maintains a definite small excess of iodine in the absorber a t all times. The sample, contained in a boat, is advanced into progressively hotter sections of the furnace by a motor-driven push rod. The Titrimeter controls the rate of sample advance through a suitable electronic circuit t o produce sulfur dioxide evolution a t a constant rate. The sample moves intermittently t o allow a t least 30 seconds' heat-up time after each half-inch advance into the furnace. This prevents uncontrolled burning. The use of this device in a n analytical inspection laboratory h w doubled the daily output per analyst. The automatic, procedure is more precise t h a n manual operation, as the potentiometric Titrimeter neither allows sulfur dioxide t o escape unreacted, owing t o insuffirient iodine, nor allows iodine loss by rolatilization such as occurs if an excess is present. Determination of Thiophene Sulfur by M a s s Spectrometry. S. H. HASTINGS, Refining Technical and Research Divisions, Humble Oil and Refining Co., Baytown. Tex. -4 method is described for the determination of thiophenes in petroleum stocks boiling in t h e naphtha range (150' t o 430' F.) employing a combination of adsorption and mass spectrometric techniques. This method was required t o provide researchers in the field of gasoline quality improvement ~ v i t hpertinent information on a major wlfur compound type present in cracked naphthas. There is a significant concentration of thiophenes in virgin distillates and d a t a are presented which indicate strongly the presence of thiophenes in a crude petroleum (West Texas). The method should he of considerable utility t o others working on analyses for sulfur compounds. Recent Improvements in t h e Modified Lamp Sulfur Apparatus of Skelly Oil Co. Research Laboratory. C . HOR.ARDHOPKINS,Skelly Oil Co., Pawhuska, Okla. Two types of petroleum products have proved troublesome during sulfur determinations by the lamp method: t h e highly volatile liquid samples and the heavy distillate% .I refrigerated lamp has been designed t o handle the former materials, and a novel wick tube heater and flame-propagating tip have adequately solved the combustion of t h e heavier distillates. The effective range of this apparatus has thus been extended t o include distillates up through medium gas oils. Spectrophotometric Method of Analysis for Ketene. ROBERTC . WILKERSOK, Celanese Corp. of America, Clarkwood, Tex.
A continuous spectrophotometric method for determining ketene in hot or cold gaseous streams has been developed. Furnace outlet gases froin acetic acid pyrol a t temperatures up t o 1300'F. have been
