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Microcrystallographic Descriptions of Some Crystalline Anticonvulsants†
SCIENTIFIC EDITION The discrepancies in the melting point values reported for both 3015 RP and Phenergan cannot be explained. In the case of Phenergan, we tested a sample produced in France as well as one produced in this country and found their melting points in agreement. Furthermore, our results with Pyrrolazote are within the range reported in the literature so that the apparatus and method used cannot be at fault.
215 REFERENCES
(1) Halpern, Bernard N., Compf. rend. sac. bid. 140, 363(1946). (2) Halpern B. N. and Ducrot R. O i d . 140 361(1946). 3) Halpern: B. N.:Bull. SOC. chlm. biol., >9, 3b9(1947). 4) Hal-, B. N., Arch. infern. pharmacodynamie, 74, 314 1947). 5 ) Vallery-Radot, P., Halpern, B. N., and Mauric, G., Acfa Allcugologica, 1. 85(1948). (6) Halpern, B. N., ibid., 1, 3(1948). (7) Halpern, B. N.,and Cruchard, S., Ezperienfia, 4,
i
-.(8) Halpern, Bernard N., Comfit.rend. SOC.biol., 140, 830
84(394X\ - - .-_, . I\-l-l,. lQARI
SUMMARY
(9) Reuse, J. J., ibid.. 140,1237(1946). (10) Reuse, J. J. &if.1.Pharmacol. 3,174(1948). . .(11) Winter, C. 'A,, J . Pharmacol. i z p t l . Therap., 90, 224
Microchemical data covering colorimetric and precipitation reactions and optical crystallographic properties of six antihistaminics of the thiodiphenylamine series have been presented. Buckingham's reagent is the best colorimetric one for identifying and differentiating these drugs. The best means for identifying Phenergan and Pyrrolazote is by optical crystallographic methods.
(1947).
(12) Vander Brook, E,.J., Olson, K. J., Richmond, M. T., and Kuizenga, M. H., rbad., 94, 197(1948). (13) Keenan. G.L.,THISJOURNAL, 36,281(1947). (14) Haley, T. J., ibid., 37,294(1948). (15) Haley, T.J., and Keenan, G.L., ibid., 38, 85(1949). (16) Haley, T. J., and Keenan, G.L., ibrd., in press. (17) Thienea C. H. and Haley T. J. "Clinical Toxicology," Lea aAd Febiier, Philadelp'hia, Pehnsylvania, 1948, p. 208. (18) Thienes, C. H., and Haley, T. J.. 09. cit., p. 353. (19) British Patent 608,208, September 10, 1948. (20) Reid, W. B., Jr., Wright, J. B., Kolloff, H. G., and Hunter, J. H., J . A m . Chem. Soc., 70,3100(1948). (21) Collier, H. B., Con. J . Research, 18D, 272(1940).
Microcrystallographic Descriptions of Some Crystalline Anticonvulsants"J By GEORGE L. KEENAN$ Microcrystallographic characteristics of diphenylhydantoin sodium (Dilantin Sodium), 3 - methyl - 6,5 phenyl ethylhydantoin (Mesantoin), and phenobarbital have been determined and are reported. The microcrystallographic data recorded are useful in establishing the identity of the three cornpounds either separately or in combination.
-
-
anticonvulsants, Dilantin Sodium, Mesantoin, and phenobarbital, used in combination in the treatment of epilepsy, have been found to reveal distinctive microscopic features that are of analytical interest in establishing their identity. Chemically, Dilantin Sodium and Mesantoin are both derivatives of the condensation product of urea and acetic acid, while phenobarbital is a derivative of the condensation product of urea and malonic acid. These three substances are crystalline and well adapted for microscopic study, with the possible exception of Dilantin Sodium. The latter is somewhat hygroscopic and
'
gradually absorbs carbon dioxide when exposed to the air, thereby liberating diphenylhydantoin. This behavior precludes a microscopic study of the substance per se, but, as will be shown later, diphenylhydantoin may be readily prepared from it and the optical constants of the Iatter determined.
HE THREE
*
Received August 22, 1949, from Strongsville, Ohio. t Acknowledgment is made for samples of Mesantoin supplied by Sandoz Chemical Works, New York, N. Y., and use of instruments by Baldwin-Wallace College, Berea, Ohio. f Formerly, Microanalyst, Food and Drug Administration; present address, Strongsville. Ohio.
EXPERIMENTAL.
This microscopic study includes general observations and those readily revealed with the polarizing microscope. Principal emphasis is placed upon significant features that can be observed in ordinary light, parallel polarized light (crossed nicols), and the conoscopic examination, when applicable. The description for each substance first will be given, followed by a summation of the distinctive features of the three compounds. (For brevity, the shorter names of the substances will be used in these descriptions.) Mesantoin.-QZH1~N~Oz. In ordinary light the habit is characterized as thin, colorless rhombs and some six-sided forms, also plates tipped on edge, in this orientation suggesting fibrous fragments. I n parallel polarized light (crossed nicols), the thin plates show low-order whites. On the elongated plates, the extinction is parallel and the sign of elongation positive. Many of the thin plates do not
216
JOURNAL OF THE
AMERICAN PHARMACEUTICAL ASSOCIATION
extinguish sharply with crossed nicols. I n convergent polarized light (crossed nicols) the thin plates not extinguishing sharply show a biaxial interference figure with the acute bisectrix and negative optic sign. 2E is small (50 rt: 5” obs.). Refractive indices: a = 1.570, = 1.600, y = 1.605, all * 0.002. j3 and y can be measured on plates showing the plane of the optic axes and with negative optic sign. CY and y are frequently shown on plates tipped on edge (having the appearance of small fibers). Mesantoin readily crystallizes from 95% alcohol and water on a n object slide. To a very small amount of the material on the slide, a drop of 95% alcohol is added. The substance quickly dissolves and then a drop of water is introduced. Short, numerous, thin rhombs will crystallize out. T o hasten the crystallization, the test drop can be reseeded by stirring. Under these conditions, these rhombs will also quickly form from powdered tablet material (containing starch) as well as from the undiluted substance.
1. The ease with which crystalline diphenylhydantoin may be prepared from it on the slide by the addition of 95% alcohol and 5% hydrochloric acid, resulting in the formation of colorless rodlike plates and needles. 2. The frequent occurrence of the minimum and maximum refractive index values of diphenylhydantoin in the orientations indicated. Phenobarbital.-C1*H1*N208. In ordinary light the substance consists largely of colorless rhombs, frequently elongated, and six-sided forms. In paraEle1 pdarized light (crossed nicols) the extinction is parallel on the elongated forms and sign of elongation negative. Many of the plates do not extinguish sharply. In convergent polarized light (crossed nicols) partial biaxial interference figures are observed with negative optic sign. Refractive indices: a = 1.557, p = 1.620, y = 1.667, all *0.002. The a and j3 values are most commonly found.
Diagnostic Microscopic Features.-The following are the outstanding microscopic characters of Mesantoin: 1. The habit, consisting of thin, colorless rhombs, readily formed from 95% alcohol and water. 2. The frequent occurrence of plates tipped on edge and resembling small fibers (similar t o talc in this respect). 3. The low-order whites shown on plates when examined with crossed nicols. 4. The acute bisectrix interference figures showing small axial angle with negative optic sign. 5. The close similarity of the p and y refractive index values. If the powdered substance is immersed in either the p or y liquid and observed in ordinary light, the margins of the plates will have essentially disappeared on the greater proportion of the crystals. I n fact, in tablet material, only the starch grains will be visible, but upon crossing the nicols, the thin, colorless plates will be observed.
TABLE I.-sUMMARY
Dilantin Sodium.-Cl6H1lN202Na. For reasons already given, the monosodium salt of 5,5-diphenylhydantoin is not suitable for microscopic examination by the immersion method. However, for the purpose of characterizing the substance microscopically, it is convenient t o dissolve a small amount in a drop of 95% alcohol on an object slide, then adding a drop of 5% hydrochloric acid. Rodlike plates and fine needles of diphenylhydantoin separate out, readily dry on the slide a t room temperature and may be subsequently examined with the polarizing microscope. In parallel polarized light (crossed nicols) the extinction is parallel and the sign of elongation negative. Low-order whites are shown on the very thin plates. In convergent polarized light (crossed nicols) no interference figures are observed. Refractive indices: a = 1.600 (commonly shown lengthwise), y = 1.635 (commonly shown crosswise) ; both +0.002. (3 was not determined due t o lack of interference figures. Diagnostic Microscopic Features.-The most significant microscopic characters of Dilantin Sodium are:
OF
MICROSCOPIC CHARACTERS
Mesantoin
Dilantin Na“
Habit
Rhombs
Rods, needles
Extinction Elongation Class Sign 2E Indices
Parallel Positive Biaxial Negative 50 5’
Parallel Negative Biaxial ? ?
1.570 1.600 1.605
1.600
a
B Y
f
?
1.635
Phenobarbital
Rhombs, parallelograms Parallel Negative Biaxial Negative ?
1.557 1.620 1.667
0 These data refer to diphenylhydantoin prepared as described from Dilantin Sodium.
To facilitate the orientation of the crystals in respect t o the most commonly occurring refractive indices, it is convenient t o dissolve a small amount of phenobarbital in a drop of 95% alcohol on a n object slide, followed by a drop of water. Soon the edge of the drop will become “milky” in appearance and eventually a copious crop of parallelograms will come out. The preparation may be allowed t o dry at room temperature and examination subsequently made with the polarizing microscope. In this condition, the parallelograms usually show a refractive index of 1.557 (a)lengthwise and 1.620 (8) crosswise. Plates tipped on edge will show 1.557 (a) lengthwise and 1.667 (y)crosswise. Diagnostic Microscopic Features.-Phenobarbital exhibits the following significant features microscopically: 1. The significant habit of parallelograms when crystallized from 95% alcohol and water. 2. The frequent occurrence of the a and p index values, shown respectively, lengthwise and crosswise. 3. The frequent occurrence of the a and y index values on plates tipped on edge.
215 REFERENCES
(1) Halpern, Bernard N., Compf. rend. sac. bid. 140, 363(1946). (2) Halpern B. N. and Ducrot R. O i d . 140 361(1946). 3) Halpern: B. N.:Bull. SOC. chlm. biol., >9, 3b9(1947). 4) Hal-, B. N., Arch. infern. pharmacodynamie, 74, 314 1947). 5 ) Vallery-Radot, P., Halpern, B. N., and Mauric, G., Acfa Allcugologica, 1. 85(1948). (6) Halpern, B. N., ibid., 1, 3(1948). (7) Halpern, B. N.,and Cruchard, S., Ezperienfia, 4,
i
-.(8) Halpern, Bernard N., Comfit.rend. SOC.biol., 140, 830
84(394X\ - - .-_, . I\-l-l,. lQARI
SUMMARY
(9) Reuse, J. J., ibid.. 140,1237(1946). (10) Reuse, J. J. &if.1.Pharmacol. 3,174(1948). . .(11) Winter, C. 'A,, J . Pharmacol. i z p t l . Therap., 90, 224
Microchemical data covering colorimetric and precipitation reactions and optical crystallographic properties of six antihistaminics of the thiodiphenylamine series have been presented. Buckingham's reagent is the best colorimetric one for identifying and differentiating these drugs. The best means for identifying Phenergan and Pyrrolazote is by optical crystallographic methods.
(1947).
(12) Vander Brook, E,.J., Olson, K. J., Richmond, M. T., and Kuizenga, M. H., rbad., 94, 197(1948). (13) Keenan. G.L.,THISJOURNAL, 36,281(1947). (14) Haley, T. J., ibid., 37,294(1948). (15) Haley, T.J., and Keenan, G.L., ibid., 38, 85(1949). (16) Haley, T. J., and Keenan, G.L., ibrd., in press. (17) Thienea C. H. and Haley T. J. "Clinical Toxicology," Lea aAd Febiier, Philadelp'hia, Pehnsylvania, 1948, p. 208. (18) Thienes, C. H., and Haley, T. J.. 09. cit., p. 353. (19) British Patent 608,208, September 10, 1948. (20) Reid, W. B., Jr., Wright, J. B., Kolloff, H. G., and Hunter, J. H., J . A m . Chem. Soc., 70,3100(1948). (21) Collier, H. B., Con. J . Research, 18D, 272(1940).
Microcrystallographic Descriptions of Some Crystalline Anticonvulsants"J By GEORGE L. KEENAN$ Microcrystallographic characteristics of diphenylhydantoin sodium (Dilantin Sodium), 3 - methyl - 6,5 phenyl ethylhydantoin (Mesantoin), and phenobarbital have been determined and are reported. The microcrystallographic data recorded are useful in establishing the identity of the three cornpounds either separately or in combination.
-
-
anticonvulsants, Dilantin Sodium, Mesantoin, and phenobarbital, used in combination in the treatment of epilepsy, have been found to reveal distinctive microscopic features that are of analytical interest in establishing their identity. Chemically, Dilantin Sodium and Mesantoin are both derivatives of the condensation product of urea and acetic acid, while phenobarbital is a derivative of the condensation product of urea and malonic acid. These three substances are crystalline and well adapted for microscopic study, with the possible exception of Dilantin Sodium. The latter is somewhat hygroscopic and
'
gradually absorbs carbon dioxide when exposed to the air, thereby liberating diphenylhydantoin. This behavior precludes a microscopic study of the substance per se, but, as will be shown later, diphenylhydantoin may be readily prepared from it and the optical constants of the Iatter determined.
HE THREE
*
Received August 22, 1949, from Strongsville, Ohio. t Acknowledgment is made for samples of Mesantoin supplied by Sandoz Chemical Works, New York, N. Y., and use of instruments by Baldwin-Wallace College, Berea, Ohio. f Formerly, Microanalyst, Food and Drug Administration; present address, Strongsville. Ohio.
EXPERIMENTAL.
This microscopic study includes general observations and those readily revealed with the polarizing microscope. Principal emphasis is placed upon significant features that can be observed in ordinary light, parallel polarized light (crossed nicols), and the conoscopic examination, when applicable. The description for each substance first will be given, followed by a summation of the distinctive features of the three compounds. (For brevity, the shorter names of the substances will be used in these descriptions.) Mesantoin.-QZH1~N~Oz. In ordinary light the habit is characterized as thin, colorless rhombs and some six-sided forms, also plates tipped on edge, in this orientation suggesting fibrous fragments. I n parallel polarized light (crossed nicols), the thin plates show low-order whites. On the elongated plates, the extinction is parallel and the sign of elongation positive. Many of the thin plates do not
216
JOURNAL OF THE
AMERICAN PHARMACEUTICAL ASSOCIATION
extinguish sharply with crossed nicols. I n convergent polarized light (crossed nicols) the thin plates not extinguishing sharply show a biaxial interference figure with the acute bisectrix and negative optic sign. 2E is small (50 rt: 5” obs.). Refractive indices: a = 1.570, = 1.600, y = 1.605, all * 0.002. j3 and y can be measured on plates showing the plane of the optic axes and with negative optic sign. CY and y are frequently shown on plates tipped on edge (having the appearance of small fibers). Mesantoin readily crystallizes from 95% alcohol and water on a n object slide. To a very small amount of the material on the slide, a drop of 95% alcohol is added. The substance quickly dissolves and then a drop of water is introduced. Short, numerous, thin rhombs will crystallize out. T o hasten the crystallization, the test drop can be reseeded by stirring. Under these conditions, these rhombs will also quickly form from powdered tablet material (containing starch) as well as from the undiluted substance.
1. The ease with which crystalline diphenylhydantoin may be prepared from it on the slide by the addition of 95% alcohol and 5% hydrochloric acid, resulting in the formation of colorless rodlike plates and needles. 2. The frequent occurrence of the minimum and maximum refractive index values of diphenylhydantoin in the orientations indicated. Phenobarbital.-C1*H1*N208. In ordinary light the substance consists largely of colorless rhombs, frequently elongated, and six-sided forms. In paraEle1 pdarized light (crossed nicols) the extinction is parallel on the elongated forms and sign of elongation negative. Many of the plates do not extinguish sharply. In convergent polarized light (crossed nicols) partial biaxial interference figures are observed with negative optic sign. Refractive indices: a = 1.557, p = 1.620, y = 1.667, all *0.002. The a and j3 values are most commonly found.
Diagnostic Microscopic Features.-The following are the outstanding microscopic characters of Mesantoin: 1. The habit, consisting of thin, colorless rhombs, readily formed from 95% alcohol and water. 2. The frequent occurrence of plates tipped on edge and resembling small fibers (similar t o talc in this respect). 3. The low-order whites shown on plates when examined with crossed nicols. 4. The acute bisectrix interference figures showing small axial angle with negative optic sign. 5. The close similarity of the p and y refractive index values. If the powdered substance is immersed in either the p or y liquid and observed in ordinary light, the margins of the plates will have essentially disappeared on the greater proportion of the crystals. I n fact, in tablet material, only the starch grains will be visible, but upon crossing the nicols, the thin, colorless plates will be observed.
TABLE I.-sUMMARY
Dilantin Sodium.-Cl6H1lN202Na. For reasons already given, the monosodium salt of 5,5-diphenylhydantoin is not suitable for microscopic examination by the immersion method. However, for the purpose of characterizing the substance microscopically, it is convenient t o dissolve a small amount in a drop of 95% alcohol on an object slide, then adding a drop of 5% hydrochloric acid. Rodlike plates and fine needles of diphenylhydantoin separate out, readily dry on the slide a t room temperature and may be subsequently examined with the polarizing microscope. In parallel polarized light (crossed nicols) the extinction is parallel and the sign of elongation negative. Low-order whites are shown on the very thin plates. In convergent polarized light (crossed nicols) no interference figures are observed. Refractive indices: a = 1.600 (commonly shown lengthwise), y = 1.635 (commonly shown crosswise) ; both +0.002. (3 was not determined due t o lack of interference figures. Diagnostic Microscopic Features.-The most significant microscopic characters of Dilantin Sodium are:
OF
MICROSCOPIC CHARACTERS
Mesantoin
Dilantin Na“
Habit
Rhombs
Rods, needles
Extinction Elongation Class Sign 2E Indices
Parallel Positive Biaxial Negative 50 5’
Parallel Negative Biaxial ? ?
1.570 1.600 1.605
1.600
a
B Y
f
?
1.635
Phenobarbital
Rhombs, parallelograms Parallel Negative Biaxial Negative ?
1.557 1.620 1.667
0 These data refer to diphenylhydantoin prepared as described from Dilantin Sodium.
To facilitate the orientation of the crystals in respect t o the most commonly occurring refractive indices, it is convenient t o dissolve a small amount of phenobarbital in a drop of 95% alcohol on a n object slide, followed by a drop of water. Soon the edge of the drop will become “milky” in appearance and eventually a copious crop of parallelograms will come out. The preparation may be allowed t o dry at room temperature and examination subsequently made with the polarizing microscope. In this condition, the parallelograms usually show a refractive index of 1.557 (a)lengthwise and 1.620 (8) crosswise. Plates tipped on edge will show 1.557 (a) lengthwise and 1.667 (y)crosswise. Diagnostic Microscopic Features.-Phenobarbital exhibits the following significant features microscopically: 1. The significant habit of parallelograms when crystallized from 95% alcohol and water. 2. The frequent occurrence of the a and p index values, shown respectively, lengthwise and crosswise. 3. The frequent occurrence of the a and y index values on plates tipped on edge.