ance of the solution is determined against a reagent blank at the wave length of maximum absorption. RESULTS
T o illustrate the method, data obtained with benzimidazolone, its N methyl, N,N’-dimethyl, and 5-chloro derivatives, as well as with 5-tert-butylbenzimidazolone, which is an antimitotic compound (7), are presented. The wave length of maximum absorption was 505 mp for benzimidazolone, the monomethyl, and 5-tert-butyl compounds, 515 mp for the 5-chloro derivative, and 525 mp for the dimethyl derivative. Figure 1 shows that the alcohol requirement for maximal color development varies widely-Le., from 0.1 to 0.9 ml., depending upon the derivative under examination. The data of Figure 2 show that the color develops rapidly, then slowly fades. It is apparent that while no great error will result from minor differences in the timing of absorbance determinations, for precise results the reaction should be closely timed. This is particularly true for the dimethyl derivative, the color of which fades more rapidly. A 3-minute interval was allowed bet m e n addition of dichromate and absorbance determinations in establishing standard curves for the five compounds. Beer’s law was obeyed with concentra-
tions ranging from 0.02 to 0.3 mmole per liter. Absorbances a t the wave lengths of maximum absorption are shown in Table I. Qualitative observations with a number of other compounds are recorded in Table II.
Color Reaction with Various Compounds”
Compound o-Phenylenediamine p-Phenylenediamine Isatin 1,3-Diphenylbenzimidazolone 1-Phenyl-3-acetylbenzimidazolone Diacetyl-o-phenylenediamine 2,3-Ureylene-4methylpyridine 1,2-Ureylenenaphthalene
+ + -
Reactions and Remarks Brown-pink color Good pink color
-
Table 11. The reaction does not appear to be general for benzimidazolones, as the 1,3-diphenyl and diacetyl derivatives did not yield a color. Because ophenylenediamine, as well as the p isomer, produced color under the conditions of this method, some of their derivatives might also be expected to interfere. However, neither diacetyl ophenylenediamine nor o-phenylenemalonamide gave a colored product. Some compounds-e.g., 1,Bureylenenaphthalene-although chromogenic, will not interfere in the method as described because of the ephemeral nature of the color produced. LITERATURE CITED
Light pink
- Bright color,
fades rapidly
1-Phenylbenzimidazolone 3-Methyloxindole 5-Carboxvmethvlbenzoxazoione ” Benzoxazolone o-Phenylenemalonamide Benzimidazole a Reaction mixtures contained 100 y of compound and 0.5 ml. ethyl alcohol in 3ml. final volume.
+
(1) Fischer, O., Dischinger, .4.,Ber. 29, 1602 (1896). (2) Fischer, O., Heiler, O., Ibid., 26, 378 (1893). (3) Fischer, O., Hepp, E., Ibid., 22, 356 (1889). (4) Griess, P., J. prakt. Chem. 3, 143
118711. (5j Niemontowski, St. von, Ber. 43, 3012 (1910). (6) Pellizzari, G. B., Gazz. chim. ital. 48, 173 (1918). (7) Stoerk, H.C., .4rison, R. N., Hawkins, J. E., Jr., Nature 180, 1428 (1957). (8) Ullman, F., Mauthner, F., Ber. 35, 4302 (1902). CURTC. PORTER Merck Sharp & Dohme Research Laboratories West Point, Pa. RECEIVEDfor review April 16, 1958. Accepted October 14, 1958.
The Nomenclature of Thermochemical Titrimetry SIR: Interest in thermochemical titration methods has developed rapidly in the past few years and the number of publications on this subject has been growing steadily. Indicative of the trend has been the appearance of a chapter devoted to the subject in the current edition of a widely read textbook on instrumental analysis (10). The program of the 132nd National Meeting of the American Chemical Society (New York, September 1957) included a one-day Symposium on Thermoanalytical Titrimetry ( 1 ) . L’nfortunately, a multiplicity of terms has been used in the literature to describe a essentially the same method-viz., titration is an adiabatic system yielding a plot of temperature cs. volume of titrant. Prior to 1954, the designation “thermometric titration” appears to have been used exclusively. The relevant literature has been reviewed b y Linde, Rogers, and Hume (9). I n its 1952 report, the Committee on Nomenclature of the Division of Analytical Chemistry of the American Chemical 2064
ANALYTICAL CHEMISTRY
Society stated “the term thermometric is not recommended” (4). This statement is neither amplified nor elaborated. Since then, terms such as “thermal titration” (S), “calorimetric titration” (%’), and “enthalpy titration” (6, 7 , 10) have been introduced by various authors. I n other papers ( 1 , 6, 8, 9, 11) the term “thermometric titration” has continued to be used. I n order to avoid unnecessary proliferation of terms and with a view to minimizing confusion regarding nomenclature, a round-table discussion on terminology was held a t the 1957 Symposium on Thermoanalytical Titrimetry. Various views were presented by the panel, which included L. T. Hallett (Chairman), D . N. Hume, Joseph Jordan, and M. G. Mellon; a lively discussion ensued with much participation from the floor. While no vote was taken and no formal minutes of the discussion were kept, the consensus of opinion was that the term “thermometric titration” should be adhered to in the future. We
wish to place these conclusions on record for the guidance of interested persons. It is hoped that appropriate committees of the International Union of Pure and Applied Chemistry, and similar bodies, may consider this matter. We feel that official action is desirable to standardize the nomenclature a t an early date and prevent further multiplication of terms.
D.
N. HUME
Department of Chemistry Massachusetts Institute of Technology Cambridge 39, Mass.
JOSEPH JORDAN Department of Chemistry Pennsylvania State University University Park, Pa. LITERATURE CITED
(1) -4bstracts of Papers, 132nd Meeting, ACS, pp. 5B-l3B, New York, N. Y.,
September 1957.
(2) Bjerrum, J., Acta Chens. S c a n d . 9, 1407 (1955). (3) Ewing, G. W., “Instrumental Methods of Chemical Analysis,” pp. 311-13, McGraw-Hill, New York, 1954. (4)Hallett, L. T., Graham, R. P., Furman, N. H., Diehl, H. C., Ashley, S. E. Q., Churchill, H. V., ANAL. CHEU. 24, 1348 (1952).
( 5 ) Jordan, J., hlleman, T. G., Zhid., 29,
9 (1957). (6) Jordan, J., Ben-Yair, hl. P., Abstracts of Papers, XIIth International Congress of Pure and Applied Chemistry, pp. 42-3, Xew York, N. Y., September 1951. (7) Jordan, J., Ben-Yair, M. P., Brkiv Kemi 11, 239 (1957).
(8) Keily, H. J., Hume, D. CHESI.
28, 1294 (1956).
K.,ANAL.
(9) Linde, H. W.,Rogers, L. B., Hume, D. N.,Zbid., 2 5 , 404 (1953). (10) Willard. H. H.. Merritt. L. L.. ’ Dean, J. i., “Instrimental kfethods or Analysis,” pp. 594-8, Van Nostrand, Princeton, 1958. (11) Zenchelsky, S. T., Periale, J., Cobb, J. c., A N A L . CHEM. 28, 67 (1957).
176. ,Copper Etioporphyrin II PETER K. IBER, The Johns Hopkins University, Baltimore, Md.
C
OPPER etioporphyrin
I1 (C32H36N4C~) containing the reflections (h01), (Okl),
was synthesized and crystals were grown in dimethyl formamide. They are very soft needles, about 5 mm. long and 0.5 mm. thick. They are opaque, violet in reflected light; the smallest crystals (0.1 mm. thick) are clear and red in transmitted light. The material decomposes in the solid state a t approximately 350’ C. The crystal structure of the related compound nickel etioporphyrin I has been described (1). Precession photographs (CuK, radiation) n’ere taken of the reciprocal nets
and ( h l l ) . They show the crystals to be monoclinic, with the following cell dimensions: a = 14.23, b = 20.31, c = 4.76 A. (all &0.3%), p = 90’0’. The space group PZ1/n is uniquely determined by the systematic omissions (h01 observed only with h 1 even and OkO only with k even), which also confirm the holohedral point group 2/m, indicated b y the morphological development. Tlyinning on (101) is fairly common; occasionally three crystals occur in one t x i n related as follows: I to I1 by
Table 1. hkl
110 020 120 200 210 220 040
Za
&obsd.b
8 8
0,00759 0,01006 0.01504 0.02017 0.02274 0 02932 0 03916
5 5
5 4
4
0.04753 0.05963
+
Powder Data for Copper Etioporphyrin II
&o.led.’
0.00736 0.00968 0.01462 0.01976 0 02218 0 02944 0 03872 0.04688 0.04663 0.05883
0.14607 0.16783
{ {0.05848
0.17539
0.06643 0.07167 0.08228
:1 {
(0.08867
0.24528
350 260)
O ’‘0407
E:)
0 11089
25 1 0,12606 510
E\ 450J
3
{
i::;;:$! 0.12592 0.13627 0.13954
0.31518 0.31959
1
262 3 10 0 391. 571 70 1 ill,
0.20643 (0,22821 0 22447 0 22372 0 24228 0.24549 0.24734 30 24335 0.24308 0 24383 0 24463 (0.26396 10.26031
I I
0.26496 0.26399 (0.28661
0 10 1‘
0,28372
3
0.28610
0.30036 i[0.30271 0.30276
{
0.31635 0.31877 0.32144 0,32212
0.32739
0.18949 , O . 18752 0.20725
(0.00624 0.07365 0.07093 0.08026 0.08318
0.08787 0,10471 0.10269 /0.1041)6 10,10688 0.10965 0.11045 (0.12447
0.30184
0.17784
410 060 141)
0.14917 0.14503 0,14528 0.16773 0.16616 0.17684 0.17464 0.17579 0,17739 0.18652 0.18420
0 06599
330 221 131)
reflection in (101), and I to I11 by reflection in (ioi), where I1 and I11 have parallel orientations. A crystal Iyas measured on the twocircle goniometer ( 2 ) . The quality of the signals was fair in the prism zone and poor in (101). The best averaged value for m:m’ = (110):(170) is 74’24’, which gives a:b = 0.7054 (morph.), as coinpared to 0.7006 (x-rays). The angle plol, between the c axis and the normal t o (101), is 16’28’, which gives a n approximate ralue c:a = 0.2956 (morph.), as compared to 0.3345 (x-rays). This
0.28686 0.28501 0.28629 0.28642 .O ,28884
0.34088
1.10,2’ 133 930 223. 722 2.13.0 4.12.0,
2
0.42649
I\
;
0.32933 0.32603 0.34245 0.34300 0.34063 0.36565
I
0.36298 0.42418 0,42461 0.42216 0,42733 0.42873 0.42942 0.42810 0.44155 0.44477
0.44083 0.44590 Z. Relative intensities estimated visually on a scale of 8. b &,,bed. = 4 sin28/k2 = l/daObsd. c Qcald. = l/d2(hki) = h ’ ~ * ~ k2h*’ Pc*2 2lhc*a* cos @*. 5
+
VOL. 30, NO. 12, DECEMBER 1958
+
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2065
