CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 4 1343-1349
Articles 3-Aminobenzenesulfonic Acid: A Disappearing Polymorph J. M. Rubin-Preminger1 and J. Bernstein*,2 Department of Chemistry and Doctoral Program for Interdisciplinary Studies, Ben Gurion University of the Negev, Beer Sheva 84105 Israel Received September 22, 2004;
Revised Manuscript Received April 14, 2005
ABSTRACT: We have identified and characterized the existence of two new polymorphic forms (orthorhombic needles and monoclinic plates) of 3-aminobenzenesulfonic acid, one of which was a previously unrecognized polymorphic form. The circumstances and events indicate that Form I may be considered a disappearing crystal form. The production of Form III was a serendipitous occurrence in an attempt to use the strategy of tailor-made additives to reobtain Form I; although unsuccessful, it has once more shown the need to explore as much of the chemical potential surface as possible even in a system as seemingly simple as this one. Introduction
Table 1. Crystal Data of the Two Polymorphs of 3-Aminobenzenesulfonic Acid
Disappearing polymorphs or disappearing crystal forms are a fairly commonly observed polymorphic phenomenon.3-11 Here, a known crystal form is supplanted by another, usually more stable, crystal form. In many of these cases, experimental methods that originally yielded the earlier known forms no longer do so, and the first form is only reobtained with difficulty if at all thereafter.3 This does not imply that it is impossible to reproduce the initial metastable crystal form, only that the conditions under which this form can be reobtained need to be found.3,6,12 3-Aminobenzenesulfonic acid (3ABSA), also known as m-sulfanilic acid, aniline-m-sulfonic acid, and metanilic acid (C6H7NO3S), is a zwitterionic material (1) often used as a reagent in the manufacture of azo dyes and in certain sulfa drugs.13a It possesses the ability to confer solubility in water to otherwise insoluble materials, leading to a wide range of applications in dyes, detergents, and oil additives for engine protection.14 Most recently, it has been used in the manufacture of copolymers.15
The Merck Index (1996)13b reports that 3ABSA exists as anhydrous orthorhombic needles [with a solubility * To whom correspondence
[email protected].
should
be
addressed.
E-mail:
form system space group a (Å) b (Å) c (Å) β (°) Z Z′ volume (Å3) density (calc)
Form I (ANISAC) orthorhombic Pnam 8.5 11.944 6.756
Form II orthorhombic Pca21 15.997(3) 7.503(1) 11.207(2)
4 1 685.9 1.677
8 2 1345.1(4) 1.710
Form III monoclinic Pc 7.492(6) 7.970(6) 11.47(1) 97.71(3) 4 2 678.4(1) 1.696
in water of 0.79% (w/w) at 0 °C and 6.50% at 85 °C] and sesquihydrated triclinic prisms [with a solubility in water of 2.37% (w/w) at 16.8 °C]. The CRC Handbook13a reports only needles of the sesquihydrate. In 1965, Hall and Maslen16 reported the crystal structure of the anhydrate (Refcode ANISAC) as “colorless orthorhombic needles elongated in the c direction” (Table 1), with no mention of the sesquihydrate. In our continuing investigation of the various crystal forms of the mono- and diaminobenzenesulfonic acids,17 we have isolated two new polymorphic forms (Form II and Form III) of the 3-aminobenzenesulfonic acid anhydrate. Form II was grown using the same method described by Hall and Maslen,16 and Form III was grown by using a structurally similar additive (m-toluenesulfonic acid, 2) in an effort to prevent the growth of Form II and to reobtain Form I.18 However, we have been unable to grow crystals of Form I according to the methods earlier described, indicating that this may be another example of a disappearing crystal form.6
10.1021/cg049680y CCC: $30.25 © 2005 American Chemical Society Published on Web 06/02/2005
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Figure 1. Needles of (a) Form II taken under a microscope at ×20 magnification and (b) Form III at the same magnification but between crossed polarizers.
Figure 2. The stereoviews of (a) Form I14, (b) Form II, and (c) Form III. For ease of comparison, all three structures are plotted on the plane of the benzene ring of the reference molecule colored red.
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Figure 3. Hydrogen bonds of Form I as calculated by PLUTO.26 The literal designators correspond to the first-order graph sets (diagonal elements) in Table 2. Figure 5. Hydrogen bonds of 3ABSA3 as calculated by PLUTO.26 The literal designators correspond to the first-order graph sets (diagonal elements) in Table 4. Table 2. Graph Set Matrix of Form I a R22(14) C22(6) C22(14)
a b c
b
c C22(6)
C(7)
C(7)
Table 3. Graph Set Matrix of Form II a b c d e f g h
a D(2) C22(14) C22(6) D33(12) D33(12) R22(14) D33(12) D33(12)
b
c
d
e
f
C(7)
C22(6) C(7)
g
h
C(7)
C22(6) C(7)
D(2) D(2) D32(10) D33(12) C22(14) D33(12) D33(12)
C22(14) D33(12)
D32(10)
D(2) D32(10) D33(12)
C22(14)
Table 4. Graph Set Matrix of Form III
Figure 4. Hydrogen bonds of 3ABSA2 as calculated by PLUTO.26 The literal designators correspond to the first-order graph sets (diagonal elements) in Table 3.
Experimental Details Crystal Preparation. 3-Aminobenzenesulfonic acid was obtained commercially from the Aldrich Chemical Co. and was used without further purification. Using the growth conditions specified by Hall and Maslen,16 we obtained colorless needles of 3ABSA. Single-crystal X-ray analysis showed that we had obtained a new polymorphic form of the material (Figure 1). A series of experiments have not yielded the form (Form I) reported by Hall and Maslen, instead producing a new form, Form II, even though a variety of growth conditions (temperatures in the range 13-70 °C and a pH between 3 and 9) were used as well as the growth procedure specified by Hall and Maslen;16 Form II was obtained in all cases. These circumstances (i.e., crystallization conditions that previously yielded a particular crystal form and now yield a different form) are typical of a disappearing crystal form.6 Previous reports18-20 have shown how the addition of structurally similar molecules to a solution can influence the habit and/or polymorph obtained. Therefore, in our attempts
a a C(7) b D3(10) 2 c C2(14) 2 d C2(14) 2 e D3(12) 3 f g D3(12) 3 h D3(12) 3 i
B D(2) D33(12) D33(12) C22(6) D33(12) R22(14) C22(14) D33(12)
c C22(6)
d C22(6)
C(7)
R12(4) C(7)
C22(14) D33(12)
e
f
D33(12) D(2) D32(10) D32(10) D33(12) C22(14) D33(12) D32(10) R22(14) D33(12)
g
h
i
C(7)
C22(6) D33(12) D(2) D33(12) C22(6) D(2) C22(14) D33(12) D32(10) C(7)
Table 5. Hydrogen-Bond Lengths in the Three Forms of 3ABSA form Form I Form II Form III
range of hydrogen-bond lengths (Å) 1.86-1.90 1.97-2.46 1.95-2.36
to obtain Form I, we attempted to inhibit the growth of Form II by adding molecules of similar molecular size and structure but with different functional groups that could inhibit the development of hydrogen-bonded networks. To this end, 5-7% of m-toluenesulfonic acid (2) or m-toluidine (3) was added to
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Figure 6. Experimental diffractogram of Aldrich material (blue) and the calculated powder diffraction patterns of Form I, Form II, and Form III; all are plotted on the same scale. The red lines indicate the peak positions of the Aldrich material obtained experimentally. aqueous solutions of 3ABSA at a variety of temperatures in the range 13-70 °C. In many cases, the growth of Form II was inhibited, but Form I was not obtained. Recrystallization from distilled water with 5% m-toluenesulfonic acid monohy-
drate at 45 °C produced colorless plates of a new form, Form III. The other solutions either failed to produce crystals or produced Form II. The two new forms were characterized by a variety of analytical methods.
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Figure 7. The experimental spectra (blue) of the Aldrich-supplied sample of 3ABSA and the literature34 FT-IR spectra of Form II. Analytical Methods Used. Hot stage microscopy was carried out on a Kofler hot stage microscope (Wagner and Muntz) with crossed polarizers and heating range of 20-400 °C. In all experiments, a heating rate of 4 °C/min was used. DSC measurements were performed using Rheometric Scientific Plus V v5.42 software on a Polymer Laboratories PL-DSC differential scanning calorimeter. The reported measurements were all run with a heating rate of 10 °C/min and an ambient cooling rate in sealed Al-pans. FT-IR experiments were run as pellets in dry KBr on a Nicolet Impact 410 also using Opus software with a resolution of 8.0 cm-1. Single-crystal data were collected at on a Bruker SMART 1000K or 6000K diffractometer using Mo KR radiation with a graphite monochromator at 293 K. All the atoms (including the hydrogen atoms) were located from the difference maps. The data were reduced by SAINT,21 and absorption corrections were applied using SADABS,22 solved using SHELXS,23 and then refined with SHELXL24 in SHELXTL.25
Single-Crystal Analysis Single-crystal X-ray analysis confirmed that we have obtained two new polymorphic forms of the material. The relationship of unit cell parameters and the space groups of the new polymorphic forms (Table 1) suggests some similarity of the structures. A check for misassigned or additional symmetry carried out with the program PLATON26 confirms that each of the structures is unique, and more convincingly, the packing arrangements of the molecules in the two structures are clearly different (Figure 2). The space group Pc for Form III is rather rare, occurring in less than 0.4% of cases listed in the CCDC (November 2003 edition). Of these cases, less than half occur in organic molecules. Application of Burger’s Density Rule27 using the calculated densities of the three polymorphic forms (Table 1) indicates that Form II is the thermodynamically favored form, followed by Form III, and then by Form I. This relative order of discovery and stability
(at least regarding the appearance of Forms II and III after Form I) is consistent with Ostwald’s Rule of Stages28,29 for crystal forms and may in part explain why Form I has gone unobserved (at least in our hands) once Form II was formed. Hot stage microscopy experiments were also undertaken, and in two instances a phase transformation from what is believed to be Form I to Form II was observed. This was only observed in these two cases, and only for the first batch of crystals obtained from the mother liquors. Subsequent batches proved to be Form II on examination by XRD. Unfortunately, the initial batches of crystals were not of sufficient quality for XRD analysis. This too indicated that Form II is the preferred form. The packing diagrams of the three forms are very different (Figure 2). In Form I, centrosymmetrically related plane-to-plane pairs of 3ABSA molecules lie head to tail, forming stacks parallel to the c axis (consistent with the morphology described by Hall and Maslen) with both their amino and sulfate groups on opposite sides. These columns form the basis of sheets along the b axis. Neighboring columns of the sheets are held together by strong charge-assisted hydrogen bonding between adjacent NH3+ and SO3- groups. In Form II, the pairs of 3ABSA molecules lie head to tail but with the sulfate group of one molecule directly above the amino group of the second molecule. This pair of molecules comprises the asymmetric unit. The pairs of molecules are tilted with respect to each other and with respect to the a axis. In Form III, the asymmetric unit consists of a pair of 3ABSA molecules side by side, with their dipoles orientated in the same direction but tilted with respect to each other, and with respect to the b axis. The rows of molecules pack in layers, with all the dipoles in one layer being orientated in the same direction and the molecules in the layers above and below it as head-to-
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Figure 8. A portion of the FT-IR spectra of Form II (blue) and Form III (pink), exhibiting some spectral differences between the structures of the two forms. Table 6. Several Characteristic Peaks of the Three Forms of 3-Aminobenzenesulfonic Acid
Table 7. Comparison of FT-IR Spectra of Form II and Form III of 3ABSA
Form I (°)
Form II (°)
Form III (°)
Form II (cm-1)
12.9 14.9 15.1 24.8 28.1
15.9 19.3 22.8 24.4 38.5
17.4 18.9 21.5 26.7 26.8
1380, 667 1297, 1184, 619 1164, 1103, 1027, 998, 555 885, 873
tail pairs with dipoles in the opposite direction. The hydrogen bonds form an interlinked 3-D network. Graph set notation30,31 can be used to aid in characterizing and comparing the nature of the hydrogenbonding patterns in the two polymorphs. The graph set description of Form I with Z′ ) 1 (Figure 3 and Table 2) is far less complex than that of Form II (Z′ ) 2) (Figure 4 and Table 3) or Form III (Z′ ) 2) (Figure 5 and Table 4). All of the hydrogen-bond motifs of Form I, except for the first-order motif R22(14), appear in the graph set matrix of Form II and Form III. All of the hydrogen-bond motifs of Form II appear in the graph set matrix of Form III, but Form III possesses an additional first-order motif and several additional secondorder motifs, attesting to the complexity of the 3-D hydrogen-bond network in this structure. The presence of many “discrete” (D) motifs is typical of structures with Z′ > 1; more extended motifs (R or C) appear at higher levels. The hydrogen-bond lengths in Form I are on average shorter than those in Form II and Form III (Table 5), with the smallest range of values. Form II possesses the largest range of hydrogen-bond lengths. The relative shortness of the hydrogen bonds is an indication of the effect of charge-assisted hydrogen bonding in organic molecules.32,33 Powder X-ray Diffraction. The experimental powder X-ray diffraction pattern of the Aldrich supplied material does not agree with the calculated powder diffraction pattern (PLATON26) of Form I nor of Form III (Figure 6) and is in best agreement with that of Form II. Minor deviations can be accounted for by preferred orientation of the needle-shaped powdered crystallites.
Form III (cm-1)
assignment
1338, 646 622 1045, 1010
benzylic amino group sulfonic acid group vicinal trisubstituted aromatic
865 831
one aromatic CH group two neighboring aromatic CH groups
In Figure 6, the peaks of the Aldrich material are demarcated in red to permit a ready comparison with the patterns calculated from the structures of the three known polymorphs. Several characteristic peaks for each form of 3ABSA are also listed in Table 6. Spectroscopic Analysis. The FT-IR spectrum of the material obtained from Aldrich agrees well with that found in the literature34 for 3ABSA (Figure 7). Unfortunately, it is not known when this reference spectrum was run. An early IR spectrum (run by Evans in 197435) does not differ from the spectrum measured for Form II, which may be further evidence of the previous existence and subsequent disappearance of Form I, even prior to 1974. The prominent peaks from the FT-IR spectra of Form II and Form III (Figure 8) were compared and assigned36 (Table 7) and found to differ significantly despite some similarities in their molecular packing arrangements and the rigidity of the molecular structure, which might have been expected to have shown common stretches and bends of the intramolecular bonds. Conclusions We have identified and characterized the existence of two new polymorphic forms of 3ABSA, one of which was a previously unrecognized polymorphic form (although perhaps the credit for the preparation of this form should go to the Aldrich Chemical Co.). We have not been able to obtain the crystal form of this material whose structure was described by Hall and Maslen,14
3-Aminobenzenesulfonic Acid
possibly due to the presence of seeds of Form II in our laboratory from the Aldrich material. The circumstances and events indicate that Form I may be considered a disappearing crystal form. The production of Form III was the serendipitous result of an attempt to use the strategy of tailor-made additives to obtain Form I. Although unsuccessful, it has once more shown the need to explore as much of the chemical potential surface as possible even in a system as seemingly simple as this one. Acknowledgment. We are grateful to the Kreitman Foundation for a doctoral fellowship to J.R.-P. References (1) Doctoral Program for Interdisciplinary Studies, Ben-Gurion University of the Negev, P.O. Box 635, Beer-Sheva, Israel, 84105. (2) Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 635, Beer-Sheva, Israel, 84105. (3) Henck, J. O.; Bernstein, J.; Ellern, A.; Boese, R. J. Am. Chem. Soc. 2001, 123, 1834-1841. (4) Chemburkar, S. R.; Bauer, J.; Deming, K.; Spiwek, H.; Patel, K.; Morris, J.; Henry, R.; Spanson, S.; Dziki, W.; Porter, W.; Quick, J.; Bauer, P.; Donaubauer, J.; Narayanan, B. A.; Soldani, M.; Riley, D.; Farland, K. Org. Proc. Res. Dev. 2000, 4, 413-417. (5) Lommerse, J. P. M.; Motherwell, W. D. S.; Ammon, H. L.; Dunitz, J. D.; Gavezzotti, A.; Hofmann, D. W. M.; Leusen, F. J. J.; Mooij, W. T. M.; Price, S. L.; Schweizer, B.; Schmidt, M. U.; van Eijck, B. P.; Verwer, P.; Williams, D. Acta Crystallogr. 2000, B56, 697-714. (6) Dunitz, J. D.; Bernstein, J. Acc. Chem. Res. 1995, 28, 193200. (7) Czugler, M.; Kalman, A.; Kovacs, J.; Pinter, I. Acta Crystallogr. 1981, B37, 172-177. (8) Webb, J.; Anderson, B. J. Chem. Educ. 1978, 55, 644. (9) Bavin, P. M. G. Can. J. Chem. 1960, 38, 882-889. (10) Dewar, J.; Morrison, D. R.; Read, J. J. Chem. Soc. 1936, 1598-1600. (11) Levene, P. A. J. Biol. Chem. 1935, 108, 419-420. (12) Jacewicz, V. W.; Nayler, J. H. C. J. Appl. Crystallogr. 1979, 12, 396-397. (13) (a) Weast, R. C. CRC Handbook of Chemistry and Physics, 55th ed.; CRC Press: Cleveland, 1974-1975; p C172. (b) Merck Index, 12th ed.; Chapman and Hall: New York, 1996; pp 5988, 7010, 9096.
Crystal Growth & Design, Vol. 5, No. 4, 2005 1349 (14) Bickerton, J.; MacNab, J. I.; Skinner, H. A.; Pilcher, G. Thermochim. Acta, 1993, 222, 69-77. (15) Lee, Jim Y.; Cui, C. Q. J. Electroanal. Chem. 1996, 403, 109-116. (16) Hall, S. R.; Maslen, E. N. Acta Crystallogr. 1965, 18, 301306. (17) Rubin-Preminger, J. M.; Bernstein, J. Helv. Chim. Acta 2003, 86, 303-307. (18) He, X.; Stowell, J. G.; Morris, K. R.; Pfeiffer, R. R.; Li, H.; Stahly, P.; Byrn, S. R. Cryst. Growth Des. 2001, 1, 305312. (19) Blagden, N.; Davey, R. J. Cryst. Growth Des. 2003, 3, 873885. (20) Weissbuch, I.; Lahav, M.; Leiserowitz, L. Cryst. Growth Des. 2003, 3, 125-150. (21) SAINT+, Release 6.22; Bruker Analytical Systems: Madison, Wisconsin, USA, 1997-2001. (22) Sheldrick, G. M. SADABS, version 2.03, Program for area detector absorption and other corrections; University of Gottingen: Germany, 2001. (23) Sheldrick, G. M. SHELXS-97, Program for the solution of crystal structures; University of Gottingen: Germany, 1997. (24) Sheldrick, G. M.; Schneider, T. R. SHELXL-97, Program for the refinement of crystal structures; University of Gottingen: Germany, 1997. (25) Sheldrick, G. M. SHELXTL-Plus, Release 6.10; Bruker Analytical Systems: Madison, Wisconsin, USA, 2000. (26) PLATON - Spek, A. L. Acta Crystallogr. 1990, A46, C34. (27) Burger, A.; Ramberger, R. Mikrochim. Acta 1979, II, 259272. (28) Blagden, N.; Davey, R. J.; Rowe, R.; Roberts, R. Int. J. Pharm. 1998, 172, 169-177. (29) Brittain, H. G. Polymorphism in Pharmaceutical Solids; Marcel Dekker: New York, 1999. (30) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N.-L. Angew. Chem. Int. Ed. Engl. 1995, 34, 1555-1573. (31) Etter, M. C. Acc. Chem. Res. 1990, 23, 120-126. (32) Gilli, G.; Gilli, P. J. Mol. Struct. 2000, 552, 1-15. (33) Gilli, P.; Bertolasi, V.; Ferretti, V.; Gilli, G. J. Am. Chem. Soc. 1994, 116, 909-915. (34) SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/14.9.03. (35) Evans, W. H. Spectrochim. Acta 1974, 30A, 543-547. (36) Shriner, R. L.; Fuson, R. C.; Curtin, D. Y. The Systematic Identification of Organic Compounds: A Laboratory Manual, 5th ed.; John Wiley and Sons: New York, 1964; pp 182-183.
CG049680Y
