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Identification of 1-, 2-, 3-, and 4-Chlorophenothiazine Isomers
734
Jozirnal of Pharnzaceztlical Sciences
fcrcd with the hexachlorophene absorbance. The wavelength of hexachlorophene absorbance is pH dependent. In the system reported here (pH 0.8/11.5), the absorbancc was a t 320 mp. Using the U.S.P. XVII buffer-acid system, the absorbance is a t 312 mp, causing slight interferencc with the p-bydroxybenzoate absorbance. RESULTS
(3) Clements. J. Is., and Newhurgcr, S. H., J . Assoc. Ofic. Agr. Chemists, 37, lYO(1983). ()! Dean, D. E., Sufis, I t . , and Levy, A,, Soap, Chem. Specialtzcs, 37, 87, 89, lOl(lYG1). (5) Elvidae, U. A., and Peutrell, B., J . Phnrm. Pharmacol., 13, l l l T ( 1 0 6 1 ) . (6) Gottlieb, S., and Marsh, P. B., Ind. Eng. Chenz. (Anal. Ed.), 18. lti(1946). (7) Johnson, C. A . , and Savidge, R. A,, J . Pharm. Pharmacol., 10, 171T(1958). ( 8 ) Johnston, V. D., and Porcaro, P. J., Anal. Chem., 36, 124(1964). - (9). Klinge, K., Seifen, O l e , Fefte, Wachse, 85, 61, 87 I_
The recovery of standard hcxachlorophene carried through this method was 99 f 2%. The accuracy and reproducibility of the spectrophotometric “difference” method have already been well documcnted ( 5 ) . KEFEKENCES (1) Achmeteli, H. I., J . Assoc. Ofic. Agr. Chemisls, 43, 278(1960). ( 2 ) Childs, R. F.. and Parks, L. M., J . A m . Pharm. Assoc., Sci. Ed., 45,313(1966).
(IYWJ.
(10) Laison A. L. J . A m . Oil Chemisls S O C . 28 301(1931). W., hchdarn, 1. A , and Jones, k. B., Soag (11) Lord, Pevfnmery Cosmetics, 26, 788(1953). (12) Van der Pol, H. J., Pharm. Weekblad, 93, 881(1958). (is) Technzcal Bullelm, Sindar Corp., H-7, New Yurk,
i.
__
N. Y.
(14) Singer, A. J., and Stern, E. R., Anal. Chem., 2 3 , 1511 (19-51). . (15j Tamura, T., and Totani, T., T o k y o Toritsu Bisei Kenykujo Nenpo, (KO. 8) 1956, 5 2 , through Chem. Abstr., 52, 20903(1958). (16) “United Statcs Pharmacopeia,” 17th rev., Mack Publishitis Co., Easton, Pa., 1965, p. 281.
Identification of 1-, 2-, 3-, and 4-Chlorophenothiazine Isomers By I. B. EISDORFER, R. J. WARREN, W. E. THOMPSON, and J. E. ZAREMBO T h e infrared and ultraviolet spectral data for four monochloroisomers of phenothiazine are presented and discussed. From these data it is possible to make a positive and rapid identification of any of the isomers with a minimum amount of sample. T h e method can be used to identify the isomers alone or i n combination.
T
of isomers in the preparation of chlorinatcd phenothiazines is always a possibility. The problem of determining the presence of an isomer and identifying the specific isomer present is a frequent analytical problem. A simplc, rapid method for identifying the 1-, 2-, 3-, and 4-chlorophenothiazine isomers is presented. HE PRESENCE
EXPERIMENTAL
Reagents. - 1 - Chlorophenotliiazine, 2-chlorophcnothiazinc, 3-chlorophenothiazine, and 4-chlorophenotliiazine. All chemicals are of analytical gradc as prcparcd at Smith Kline & Frcnch Laboratories. Spectrophotometers.-The infrared spectra were recorded with a Perkin-Elmer model 21 double beam spectrophotometer with a sodium chloride prism. The phenothiazines studied were prepared as mineral oil mulls. The ultraviolet spectra were recorded with a Cary model 14 recording spectrophotometer using matched fused silica cells with a 1-cni. light path. RESULTS A N D DISCUSSION
Infrared Spectra.-Figure 1 shows the infrared spectra obtained for the four chlorophenothiazine isomcrs. Thc arca of greatest intcrcst is the region between 1000 and 650 cm.-I. This is the regioii which contains absorption bands due to C-H out-ofplane deformations in aromatic ring systcms. Each of the isomers has its own unique pattern in this area owing to the particular position of the chlorine atom Received February 21, 1066, from Smith Kline & F1-ench Laboratoi-ies, Philadelphia, Pa. Accepted for publication May 10, 1966. The authors are grateful t o MI. Alex Pavloff and Mr. Arnold Krog of these laboratories for the samples of the phenothiazines discussed here.
on the ring. The infrared pattern here is specific enough to distinguish one isomer from another, and the absorption bands are so located as to yerrnit detection of one or more isomers in the presencc of another. Spectrum .I,which is that of the 1-chloro isomer, shows strong absorption bands betweeri 770 and 700 cm.-l which are assignable to 3 and 4 adjacent free hydrogeii atoms in an aromatic ring (1). Spectrum B is that of the 2-chloro isomer with absorption !no 80 60 $0
W
2
c
5 (0
z
a LL
Fig. 1.-Key: A, 1-chloroplieiiotliiazine; B, 2clilorophenotliiazine; C, 3-cliloroplienothiaziiic; D, 4chlorophenotliiazine.
1701.
55, N o . 7, JULY 1966
735
bands a t 750, 800, 825, and 920 cni.-l which are assignablc to a 2-substituted phenothiazine (2). Spectrum C is the 3-chloro isomer with absorption bands a t 750,810, 850, 875, and 925 cm. -l which are all assignable to 4 arid 2 adjacent free hydrogen atoms and one free hydrogen atom on an aromatic ring (1). Spectrum D is the 4chloro isomer with strong absorption bands at 740 and '765 c m - l which are in agreement with out-of-plane bending vibrations of 3 and 4 adjacent free hydrogen atoms on an aromatic ring system (1). From these infrared datait is possible not only to identify each isomer alone but also in cornbiriation with the other three isomers. An illustration of how thcsc data may be used to identify the isomers in combination is shown in Fig. 2. Spectrum A is that of 2-chlorophcnothiazine. Spectrum B is a mixture containing 67, of 3-chlorophenothiazirie. Spectrum C is the spectrum of a 10% mixture of the 3-isomer in 2-chlorophcnothiazine. Thcrc is no absorption whatever at 11.45 p in the 2-cliloro isomer but in the spectra of both mixtures an absorption band a t 11.45 pis noted. This band is due to the presence of the 3-chloro isomer (see spcctruni C in Fig. 1). Prcparation of a series of standards or mixtures of known concentrations makes i t possible to prcparc a calibration curve from which quantitative data and minor components could bc derived. The infrared spectra of the four isomers complements the ultraviolet data which follow and is very valuable indeed in identifying chromatographic fractions from gas Chromatography or spots from thin-layer or paper cliromatography. It also pro-
vides a rapid means of idcntification of isomers in a given preparation of chlorinatcd phcnothiazines. Ultraviolet Spectra.-Table I lists the ultraviolet maxima and corresponding log e values for the four
TABLE I.-U.V. SPECTRAL DATAFOR CHL~ROPHENOTHIAZINES~ Compd.
A, nw
Log
320
3.69
256
4.71
1-C hlorophenothiazine
c1
H
2- Chlorophenothiazine
H
323
3.67
258
4.68
3-Chlorophenothiazine
c1
4-Chlorophenothiazine U. V. spectra run in 95% ethanol.
chloro isomers, The effect of the position of the chlorinc on the ring can readily bc seen in the various wavelength shifts. The infrared data complcmented by these ultraviolet data for the isomers make possible a quantitative estimation of the amount of various isomers present in a given preparation. SUMMARY
Data are given t o show t h a t 1-, 2-, 3-, and 4-chloroplienothiazines each possess a uniquc infrared and ultraviolet spectrtlm. This information provides a basis for determining the presence or absence of isomers in a given preparation nf chlorinated phenoI 1
3
4
5
b
7
8
B
1D
1 1 1 2
13
14
l i t 6
Fig. 2.-Kcy: A, 2-chloroplie1iothiazine; B, 6% ~-clilorophenoiliiadtiein 2-chlorophe11otliia7ine; C , 10c/h 3-chlorophenothiazi1ie in Z-chlorophmothi:17111e.
thiazitw. REFERENCES (1) Bellamy, L. J . , "Infrared Spectra of Complex Molecules," 2nd ed., John Wiley & Sons, Inc., New York, N . Y.,
19.58. (2) Warren, R. J., Eisdorfer, I . R . , Thompson, W. E., and Zarembo, J. I:., J. Pharnz. Scz., 5 5 , 144(19803.
Jozirnal of Pharnzaceztlical Sciences
fcrcd with the hexachlorophene absorbance. The wavelength of hexachlorophene absorbance is pH dependent. In the system reported here (pH 0.8/11.5), the absorbancc was a t 320 mp. Using the U.S.P. XVII buffer-acid system, the absorbance is a t 312 mp, causing slight interferencc with the p-bydroxybenzoate absorbance. RESULTS
(3) Clements. J. Is., and Newhurgcr, S. H., J . Assoc. Ofic. Agr. Chemists, 37, lYO(1983). ()! Dean, D. E., Sufis, I t . , and Levy, A,, Soap, Chem. Specialtzcs, 37, 87, 89, lOl(lYG1). (5) Elvidae, U. A., and Peutrell, B., J . Phnrm. Pharmacol., 13, l l l T ( 1 0 6 1 ) . (6) Gottlieb, S., and Marsh, P. B., Ind. Eng. Chenz. (Anal. Ed.), 18. lti(1946). (7) Johnson, C. A . , and Savidge, R. A,, J . Pharm. Pharmacol., 10, 171T(1958). ( 8 ) Johnston, V. D., and Porcaro, P. J., Anal. Chem., 36, 124(1964). - (9). Klinge, K., Seifen, O l e , Fefte, Wachse, 85, 61, 87 I_
The recovery of standard hcxachlorophene carried through this method was 99 f 2%. The accuracy and reproducibility of the spectrophotometric “difference” method have already been well documcnted ( 5 ) . KEFEKENCES (1) Achmeteli, H. I., J . Assoc. Ofic. Agr. Chemisls, 43, 278(1960). ( 2 ) Childs, R. F.. and Parks, L. M., J . A m . Pharm. Assoc., Sci. Ed., 45,313(1966).
(IYWJ.
(10) Laison A. L. J . A m . Oil Chemisls S O C . 28 301(1931). W., hchdarn, 1. A , and Jones, k. B., Soag (11) Lord, Pevfnmery Cosmetics, 26, 788(1953). (12) Van der Pol, H. J., Pharm. Weekblad, 93, 881(1958). (is) Technzcal Bullelm, Sindar Corp., H-7, New Yurk,
i.
__
N. Y.
(14) Singer, A. J., and Stern, E. R., Anal. Chem., 2 3 , 1511 (19-51). . (15j Tamura, T., and Totani, T., T o k y o Toritsu Bisei Kenykujo Nenpo, (KO. 8) 1956, 5 2 , through Chem. Abstr., 52, 20903(1958). (16) “United Statcs Pharmacopeia,” 17th rev., Mack Publishitis Co., Easton, Pa., 1965, p. 281.
Identification of 1-, 2-, 3-, and 4-Chlorophenothiazine Isomers By I. B. EISDORFER, R. J. WARREN, W. E. THOMPSON, and J. E. ZAREMBO T h e infrared and ultraviolet spectral data for four monochloroisomers of phenothiazine are presented and discussed. From these data it is possible to make a positive and rapid identification of any of the isomers with a minimum amount of sample. T h e method can be used to identify the isomers alone or i n combination.
T
of isomers in the preparation of chlorinatcd phenothiazines is always a possibility. The problem of determining the presence of an isomer and identifying the specific isomer present is a frequent analytical problem. A simplc, rapid method for identifying the 1-, 2-, 3-, and 4-chlorophenothiazine isomers is presented. HE PRESENCE
EXPERIMENTAL
Reagents. - 1 - Chlorophenotliiazine, 2-chlorophcnothiazinc, 3-chlorophenothiazine, and 4-chlorophenotliiazine. All chemicals are of analytical gradc as prcparcd at Smith Kline & Frcnch Laboratories. Spectrophotometers.-The infrared spectra were recorded with a Perkin-Elmer model 21 double beam spectrophotometer with a sodium chloride prism. The phenothiazines studied were prepared as mineral oil mulls. The ultraviolet spectra were recorded with a Cary model 14 recording spectrophotometer using matched fused silica cells with a 1-cni. light path. RESULTS A N D DISCUSSION
Infrared Spectra.-Figure 1 shows the infrared spectra obtained for the four chlorophenothiazine isomcrs. Thc arca of greatest intcrcst is the region between 1000 and 650 cm.-I. This is the regioii which contains absorption bands due to C-H out-ofplane deformations in aromatic ring systcms. Each of the isomers has its own unique pattern in this area owing to the particular position of the chlorine atom Received February 21, 1066, from Smith Kline & F1-ench Laboratoi-ies, Philadelphia, Pa. Accepted for publication May 10, 1966. The authors are grateful t o MI. Alex Pavloff and Mr. Arnold Krog of these laboratories for the samples of the phenothiazines discussed here.
on the ring. The infrared pattern here is specific enough to distinguish one isomer from another, and the absorption bands are so located as to yerrnit detection of one or more isomers in the presencc of another. Spectrum .I,which is that of the 1-chloro isomer, shows strong absorption bands betweeri 770 and 700 cm.-l which are assignable to 3 and 4 adjacent free hydrogeii atoms in an aromatic ring (1). Spectrum B is that of the 2-chloro isomer with absorption !no 80 60 $0
W
2
c
5 (0
z
a LL
Fig. 1.-Key: A, 1-chloroplieiiotliiazine; B, 2clilorophenotliiazine; C, 3-cliloroplienothiaziiic; D, 4chlorophenotliiazine.
1701.
55, N o . 7, JULY 1966
735
bands a t 750, 800, 825, and 920 cni.-l which are assignablc to a 2-substituted phenothiazine (2). Spectrum C is the 3-chloro isomer with absorption bands a t 750,810, 850, 875, and 925 cm. -l which are all assignable to 4 arid 2 adjacent free hydrogen atoms and one free hydrogen atom on an aromatic ring (1). Spectrum D is the 4chloro isomer with strong absorption bands at 740 and '765 c m - l which are in agreement with out-of-plane bending vibrations of 3 and 4 adjacent free hydrogen atoms on an aromatic ring system (1). From these infrared datait is possible not only to identify each isomer alone but also in cornbiriation with the other three isomers. An illustration of how thcsc data may be used to identify the isomers in combination is shown in Fig. 2. Spectrum A is that of 2-chlorophcnothiazine. Spectrum B is a mixture containing 67, of 3-chlorophenothiazirie. Spectrum C is the spectrum of a 10% mixture of the 3-isomer in 2-chlorophcnothiazine. Thcrc is no absorption whatever at 11.45 p in the 2-cliloro isomer but in the spectra of both mixtures an absorption band a t 11.45 pis noted. This band is due to the presence of the 3-chloro isomer (see spcctruni C in Fig. 1). Prcparation of a series of standards or mixtures of known concentrations makes i t possible to prcparc a calibration curve from which quantitative data and minor components could bc derived. The infrared spectra of the four isomers complements the ultraviolet data which follow and is very valuable indeed in identifying chromatographic fractions from gas Chromatography or spots from thin-layer or paper cliromatography. It also pro-
vides a rapid means of idcntification of isomers in a given preparation of chlorinatcd phcnothiazines. Ultraviolet Spectra.-Table I lists the ultraviolet maxima and corresponding log e values for the four
TABLE I.-U.V. SPECTRAL DATAFOR CHL~ROPHENOTHIAZINES~ Compd.
A, nw
Log
320
3.69
256
4.71
1-C hlorophenothiazine
c1
H
2- Chlorophenothiazine
H
323
3.67
258
4.68
3-Chlorophenothiazine
c1
4-Chlorophenothiazine U. V. spectra run in 95% ethanol.
chloro isomers, The effect of the position of the chlorinc on the ring can readily bc seen in the various wavelength shifts. The infrared data complcmented by these ultraviolet data for the isomers make possible a quantitative estimation of the amount of various isomers present in a given preparation. SUMMARY
Data are given t o show t h a t 1-, 2-, 3-, and 4-chloroplienothiazines each possess a uniquc infrared and ultraviolet spectrtlm. This information provides a basis for determining the presence or absence of isomers in a given preparation nf chlorinated phenoI 1
3
4
5
b
7
8
B
1D
1 1 1 2
13
14
l i t 6
Fig. 2.-Kcy: A, 2-chloroplie1iothiazine; B, 6% ~-clilorophenoiliiadtiein 2-chlorophe11otliia7ine; C , 10c/h 3-chlorophenothiazi1ie in Z-chlorophmothi:17111e.
thiazitw. REFERENCES (1) Bellamy, L. J . , "Infrared Spectra of Complex Molecules," 2nd ed., John Wiley & Sons, Inc., New York, N . Y.,
19.58. (2) Warren, R. J., Eisdorfer, I . R . , Thompson, W. E., and Zarembo, J. I:., J. Pharnz. Scz., 5 5 , 144(19803.