- Email: [email protected]
Crystal and molecular structure of 3-carboxy-1-(carboxymethyl)pyridinium hydroxide inner salt, C5H4(COO)NCH2COOH
Journal ofMolecular Structure, 249 (1991) 135-140 Elsevier Science Publishers B.V., Amsterdam
135
Crystal and molecular structure of 3-carboxy-l(carboxymethyl)pyridinium hydroxide inner salt, C,H,(COO)NCH,COOH Xiao-Ming Chen and Thomas C.W. Makl Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories [Hong Kong) (Received 3 April 1991)
Abstract A new betaine derivative, 3-carboxy-l- (carboxymethyl)pyridinium hydroxide inner salt, C,H,(COO)NCH,COOH (I!, crystallizes in space group F’2,2,2 (No. 18) with a=9.659(2), b=16.071(2), c=4.9028(4) A and 2~4. The structure has been refined the RF=0.042 for 871 observed ( (F, ( > 6al F, ( ) MoKa data. In I the acidic proton reosidingonthe carboxymethyl group forms a very strong donor hydrogen bond of length 2.449 (3) A with the carboxylate group of an adjacent molecule, giving rise to a polymeric zigzag chain in the direction of the b axis.
INTRODUCTION
Betaine compounds are zwitterions containing a carboxylate group and a quaternary ammonium group. Several betaine compounds have been structurally characterized as their hydrates and/or hydrohalides, including betaine hydrochloride, (Me,NCH,COOH)Cl, in two modifications [ 1,2], betaine monohydrate, Me,NCH,COO*H,O [ 3],1-carboxy-N,N,iV-triethylmethanaminium chloride dihydrate, (Et,NCH,COOH)Cl-2H20 [4], bis(pyridine betaine) hydrochloride monohydrate [ ( C5HSNCH2COO)zH] C1*H20 (II) [ 51, bis(betaine) hydrochloridemonohydrate [ (Me,NCHzCOO)zH]C1*HzO (III) [6] and 2-carboxy-N,N,N-trimethylethanaminium bromide monohydrate, ( Me,NCH,CH,COOH)Br*HzO [ 71. Recently we have found the geometry of the carboxyl group of betaines is significantly affected by the positively-charged nitrogen, and such an effect can be reducedby the introduction of an additional methylene group as a spacer [ 71. In the context of the interaction of protons with the carboxy group of betaine derivatives, very strong hydrogen-bonded dimeric cations were found in the crystal structures of the hydrated acid ad‘Author to whom correspondence should be addressed.
0022-2860/91/$03.50
0 1991 Elsevier Science Publishers B.V. All rights reserved.
136
ducts of the prototype betaine” (III) [6] and its pyridine analogue (II) [5]. All the above-mentioned betaine compounds are monocarboxylic derivatives. In this work, we report the synthesis and crystal structure of the nicotinic acid derivative, 3-carboxy-l- (carboxymethyl)pyridinium hydroxide inner salt, which is a dicarboxylic acid analogue of betaine. EXPERIMENTAL
Synthesis
Nicotinic acid (10.0 g) and chloroacetic acid (9.5 g) were mixed in methanol ( 150 cm”), and sodium bicarbonate (14.0 g) was added. The mixture was stirred at room temperature for one day. After filtration the solvent was evaporated under reduced pressure. The residue was redissolved in dilute hydrochloric acid (2.0 N, 50 cm3) and slow evaporation produced prismatic colourless crystals (8.1 g, 55% yield). Crystal data
C,H,(COO)NCH,COOH, FW =181.15, monoclinic, space group P21212 (No. 18), a=9.659(2), b=16.071(2), c=4.9028(4) A, V=761.0(2) A3, 2=4, DexP= 1.572 g cmm3 (flotation in BrCH,CH2Br/CC1,), Dcalc= 1.581 g cmm3, F(OOO) =376, MoKa! radiation (AzO.71073 A), ~=0.12 mm-l. Diffraction intensities (crystal size 0.30 x 0.36 x 0.40 mm3; a@,,,,= 55’) 1057 unique data) were collected at 21 ‘C on a Nicolet R3m/V diffractometer using the o-scan (2.93-14.65 deg min-‘) mode [8]. The raw data were processed with the learnt-profile procedure [9] and absorption corrections (,~=0.021, transmission factors 0.937-0.9,44) were applied by fitting a pseudo-ellipsoid to the y/-scan data of eight selected strong reflections over a range of 28 angles
[lOI*
The structure was solved by the direct method and all the non-hydrogen atoms were refined anisotropically. All the hydrogen atoms were located from a difference map, assigned isotropic thermal parameters, held stationary and included in structure factor calculations in the last stage of full-matrix leastsquares refinement. All computations were performed on a DEC MicroVax-II computer with the SHELXTL-PLUS program package [ 11,121. Analytic expressions of neutralatom scattering factors were employed [ 131. Convergence for 871 (n) observed data (I F,I >6a( F,,I ) and 118 variables (p) was reached at R= CA/ CIF,I ~0.041 andR,= [C wA”/C w]F,,]2]1~2=0.051,whereA= 1IF01 - lFcl I “Common name, betaine; IUPAC name, I-carboxy-N,N,N-trimethylmethanaminium inner salt.
hydroxide
137
and w = [ ~9( 1F, I) + 0.0004 ]F,, I”] - ‘. The goodness-of-fit index S = [ CWA”/ (n-p) ] 1 has the value 1.725 and the residue extrema in the final difference map lie between + 0.24 and - 0.20 e A-“. Structure factors upon request from the corresponding author. RESULTS AND DISCUSSION
The fractional atomic coordinates and thermal parameters are listed in Table 1, and bond lengths and angles in Table 2. The molecule consists of two different asymmetric carboxy fragments with very similar geometric parame ters, although both the C-O and C=O bond lengths (1.286 (4) and 1.231(3) A) in the carboxylate that is conjugated with the pyridine ring are slightly longer than the respective ones ( 1.278 (3 ) and 1.220 (4 ) A) in the carboxymethyl group. The geometry of the carboxymethyl group is similar to that found in the strongly hydrogen-bonded dimeric cation in II [ 5 1. As illustrated in Fig. 1, the different carboxy fragments of two adjacent molecules are bridged by a proton, resulting in a hydrogen bond of length 2.449 (4) A which is very similar to those found in both of the very strongly hydrogenTABLE 1 Atomic coordinates ( x 104) and thermal parameters* (AZ X 104)
O(1) O(2) C(1) C(2) C(3) C(4) C(5) N(1) C(6) C(7) C(8) O(3) C(4) I-I(l) B(3) I-I(4) I-I(5) B(6) H(7A) B(7B)
x
Y
3432(2) 5637(2) 4551(3) 4486(3) 5585(3) 5483(3) 4273(3) 3236(2) 3310(3) 2027 (3) 2249(3) 3133(2) 1412(2) 1419 6422 6153 4233 2486 1134 1838
3016(l) 3293(l) 2897(2) 2192(2) 2035(2) 1425(2) 972(2) 1103(l) 1703(2) 543(2) -203(2) -191(l) -798(l) - 1315 2340 1308 466 1800 826 391
2
UIU,,
u22
u33
u23
G3
u,2
10565(5) 9410(5) 9199(7) 7157(6) 5460(7) 3454(7) 3278(6) 5048(5) 6973(6) 4981(7) 6842(6) 8619(5) 6315(5) 7688 5715 2052 1974 8054 5272 3102
35(l) 37(l) 34(Z) 27(l) 29(l) 34(l) 40(2) 27(l) 26(l) 30(l) 29(l) 56(l) 42(l) 50 50 50 50 50 50 50
38(l) 37(l) 23(l) 23(l) 29(l) 35(2) 26(l) 22(l) 26(l) 29(l) 29(l) 39(l) 34(l)
53(l) 53(l) 34(2) 27(l) 36(2) 31(2) 28(2) 30(l) 26(l) 38(2) 27(l) 40(l) 50(l)
-17(l) -4(l) 2(l) 2(l) 3(l) 3(l) l(1) 4(l) 3(l) 5(l) O(1) 7(l) 15(l)
7(l) -6(l) -6(l) -3(l) 2(l) 5(l) -l(l) -2(l) -l(l) -8(2) -l(l) -21(l) -14(l)
-2(l) -9(l) 2(l) 2(l) -2(l) 6(l) 7(l) l(1) 3(l) -8(l) l(1) -10(l) -14(l)
“The exponents of the isotropic and anisotropic temperature factors take the forms -8n2Usin%/ 1’ and - 2x12 U,hihj.at -a: respectively.
138 TABLE 2 Bond lengths (8) and bond angles (deg.)
0(1)-C(l) C(l)-C(2) C(2)-C(6) C(4)-C(5) N(l)-C(6) C(7)-C(8) C(8)-O(4) O(l)-C(l)-O(2) O(2)-C(l)-C(2) C(l)-C(2)-C(6) C(2)-C(3)-C(4) C(4)-C(5)-N(1) C(5)-N(l)-C(7) C(2)-C(6)-N(1) C(7)-C(8)-O(3) O(3)-C(8)-O(4) Hydrogen bonding 0(4)-H(l) O.*.O(la) Symmetry code: a; 1/2-x,
1.286(4) 1.513(4) 1.385(4) 1.379(4) 1.351(4) 1.522(4) 1.278(3) 126.6(3) 118.5(3) 120.1(2) 120.2(3) 120.6(3) 118.8(2) 119.6(2) 120.9(2) 126.8(3)
1.069(3) 2.449 (4)
0(2)-C(l) C(2)-C(3) C(3)-C(4) C(5)-N(1) N(l)-C(7) C(8)-O(3)
O(l)-C(l)-C(2) C(l)-C(2)-C(3) C(3)-C(2)-C(6) C(3)-C(4)-C(5) C(5)-N(l)-C(6) C(6)-N(l)-C(7) N(l)-C(7)-C(8) C(7)-C(8)-O(4)
O(la).*.H(l) O(4)-H(la)**.O(la)
1.231(3) 1.371(4) 1.393(4) 1.342(4) 1.475(3) 1.220(4)
114.9(2) 120.5(2) 119.4(3) 118.4(3) 121.6(2) 119.5(2) 110.8(2) 112.3(2)
1.383(3) 174(l)
- 1/2+y, 2-2.
Fig. 1. Perspective view showing the molecular structure and hydrogen bonding scheme in I, with atom numbering. Symmetry code a; l/2 - x, - l/2 - y, 2 -2.
bonded dimeric structures of II (2.436 (6) A) and III (2.454 (5 ) A ), qualifying it as a “very strong” hydrogen bond [ 141. The hydrogen bond is virtually linear with O(4)-H(1)=1.069(3) A, O(la)...H(1)=1.383(3) A and 0(4)H (1) **-0 (la) = 174 (1) ’ in an ordered proton arrangement. Strong hydrogen bonds of this type link the molecules into a polymeric zigzag chain in the direction of the b axis, as illustrated in Fig. 2. Although the proton lies closer to the carboxymethyl group indicating asymmetry of the hydrogen bond, the geo-
Fig. 2. Stereoview of the crystal structure of 3-carboxy-1-(carboxymethyl)pyridinium hydroxide inner salt. The origin of the unit cell lies at the upper right corner, with a pointing towards the reader, b from right to left and c downward.
metric similarity of the two carboxy fragments implies that compound I is more similar to type AZ than type B2 acid salts of dicarboxylic acids [ 141. Similar infinite chains of strongly hydrogen-bonded dicarboxylic acid salts are known to exist in alkali salts of hydrogen oxydiacetate [ 15,161. It is noteworthy that the two carboxy fragments participating in the hydrogen bond are not coplanar, the dihedral angle between 0 (3)-C (8)-O (4) and 0 (la)-C (la)-0 (2a) being about 61’. The carboxymethyl group lies in a plane that is almost perpendicular to the aromatic ring (dihedral angle x 84 ’ ); in contrast, the aromatic carboxylate group in the same molecule is nearly coplanar with the pyridine ring (dihedral angle z 5 o ). The conformation of the hydrogen bond in I is thus different from the coplanar configuration commonly found in II [5], III [6] and a variety of mono- and dicarboxylic acid salts [14,17].
REFERENCES
9 10 11 12
13
M.S. Fischer, D.H. Templeton and A. Zalkin, Acta Crystallogr., Sect. B, 26 (1970) 1392. W.H. Yip, R.-J. Wang and T.C.W. Mak, Acta Crystallogr., Sect. C, 46 (1990) 717. T.C.W. Mak, J. Mol. Struct., 220 (1990) 13. W.-Y. Huang, X.-M. Du, B.-H. Yang and T.C.W. Mak, J. Mol. Struct., 222 (1990) 479. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 221 (1990) 256. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 240 (1990) 69. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 245 (1991) 301. R.A. Sparks, in F.R. Ahmed (Ed. ), Crystallographic Computing Techniques, Munksgaard, Copenhagen, 1976, p. 452. R. Diamond, Acta Crystallogr., Sect. A, 25 (1969) 43. G. Kopfmann and R. Huber, Acta Crystallogr., Sect. A, 24 (1968) 348. G.M. Sheldrick, in D. Sayre (Ed. ), Computational Crystallography, Oxford University Press, New York, 1982, p. 506. G.M. Sheldrick, in G.M. Sheldrick, C. Kruger and R. Goddard (Eds.), Crystallographic Computing 3: Data Collection, Structure Determination, Proteins, and Databases, Oxford University Press, New York, 1985, p. 175. J.A. Ibers and W.C. Hamilton (Eds.), International Tables for X-ray Crystallography, Vol. IV, Kynoch Press, Birmingham, 1973, pp. 55,99,149. (Now distributed by Kluwer Academic Publishers, Dordrecht, The Netherlands.)
140 14 15 16 17
J.C. Speakman, Struct. Bonding (Berlin), 12 (1972) 141. J. Albertsson, I. Grenthe and H. Herbertsson, Acta Crystallogr., Sect. B, 29 (1973) 1855. J. Albertsson, I. Grenthe and H. Herbertsson, Acta Crystallogr., Sect. B, 29 (1973) 2839. J. Emsley, Chem. Sot. Rev., 9 (1980) 91.
135
Crystal and molecular structure of 3-carboxy-l(carboxymethyl)pyridinium hydroxide inner salt, C,H,(COO)NCH,COOH Xiao-Ming Chen and Thomas C.W. Makl Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories [Hong Kong) (Received 3 April 1991)
Abstract A new betaine derivative, 3-carboxy-l- (carboxymethyl)pyridinium hydroxide inner salt, C,H,(COO)NCH,COOH (I!, crystallizes in space group F’2,2,2 (No. 18) with a=9.659(2), b=16.071(2), c=4.9028(4) A and 2~4. The structure has been refined the RF=0.042 for 871 observed ( (F, ( > 6al F, ( ) MoKa data. In I the acidic proton reosidingonthe carboxymethyl group forms a very strong donor hydrogen bond of length 2.449 (3) A with the carboxylate group of an adjacent molecule, giving rise to a polymeric zigzag chain in the direction of the b axis.
INTRODUCTION
Betaine compounds are zwitterions containing a carboxylate group and a quaternary ammonium group. Several betaine compounds have been structurally characterized as their hydrates and/or hydrohalides, including betaine hydrochloride, (Me,NCH,COOH)Cl, in two modifications [ 1,2], betaine monohydrate, Me,NCH,COO*H,O [ 3],1-carboxy-N,N,iV-triethylmethanaminium chloride dihydrate, (Et,NCH,COOH)Cl-2H20 [4], bis(pyridine betaine) hydrochloride monohydrate [ ( C5HSNCH2COO)zH] C1*H20 (II) [ 51, bis(betaine) hydrochloridemonohydrate [ (Me,NCHzCOO)zH]C1*HzO (III) [6] and 2-carboxy-N,N,N-trimethylethanaminium bromide monohydrate, ( Me,NCH,CH,COOH)Br*HzO [ 71. Recently we have found the geometry of the carboxyl group of betaines is significantly affected by the positively-charged nitrogen, and such an effect can be reducedby the introduction of an additional methylene group as a spacer [ 71. In the context of the interaction of protons with the carboxy group of betaine derivatives, very strong hydrogen-bonded dimeric cations were found in the crystal structures of the hydrated acid ad‘Author to whom correspondence should be addressed.
0022-2860/91/$03.50
0 1991 Elsevier Science Publishers B.V. All rights reserved.
136
ducts of the prototype betaine” (III) [6] and its pyridine analogue (II) [5]. All the above-mentioned betaine compounds are monocarboxylic derivatives. In this work, we report the synthesis and crystal structure of the nicotinic acid derivative, 3-carboxy-l- (carboxymethyl)pyridinium hydroxide inner salt, which is a dicarboxylic acid analogue of betaine. EXPERIMENTAL
Synthesis
Nicotinic acid (10.0 g) and chloroacetic acid (9.5 g) were mixed in methanol ( 150 cm”), and sodium bicarbonate (14.0 g) was added. The mixture was stirred at room temperature for one day. After filtration the solvent was evaporated under reduced pressure. The residue was redissolved in dilute hydrochloric acid (2.0 N, 50 cm3) and slow evaporation produced prismatic colourless crystals (8.1 g, 55% yield). Crystal data
C,H,(COO)NCH,COOH, FW =181.15, monoclinic, space group P21212 (No. 18), a=9.659(2), b=16.071(2), c=4.9028(4) A, V=761.0(2) A3, 2=4, DexP= 1.572 g cmm3 (flotation in BrCH,CH2Br/CC1,), Dcalc= 1.581 g cmm3, F(OOO) =376, MoKa! radiation (AzO.71073 A), ~=0.12 mm-l. Diffraction intensities (crystal size 0.30 x 0.36 x 0.40 mm3; a@,,,,= 55’) 1057 unique data) were collected at 21 ‘C on a Nicolet R3m/V diffractometer using the o-scan (2.93-14.65 deg min-‘) mode [8]. The raw data were processed with the learnt-profile procedure [9] and absorption corrections (,~=0.021, transmission factors 0.937-0.9,44) were applied by fitting a pseudo-ellipsoid to the y/-scan data of eight selected strong reflections over a range of 28 angles
[lOI*
The structure was solved by the direct method and all the non-hydrogen atoms were refined anisotropically. All the hydrogen atoms were located from a difference map, assigned isotropic thermal parameters, held stationary and included in structure factor calculations in the last stage of full-matrix leastsquares refinement. All computations were performed on a DEC MicroVax-II computer with the SHELXTL-PLUS program package [ 11,121. Analytic expressions of neutralatom scattering factors were employed [ 131. Convergence for 871 (n) observed data (I F,I >6a( F,,I ) and 118 variables (p) was reached at R= CA/ CIF,I ~0.041 andR,= [C wA”/C w]F,,]2]1~2=0.051,whereA= 1IF01 - lFcl I “Common name, betaine; IUPAC name, I-carboxy-N,N,N-trimethylmethanaminium inner salt.
hydroxide
137
and w = [ ~9( 1F, I) + 0.0004 ]F,, I”] - ‘. The goodness-of-fit index S = [ CWA”/ (n-p) ] 1 has the value 1.725 and the residue extrema in the final difference map lie between + 0.24 and - 0.20 e A-“. Structure factors upon request from the corresponding author. RESULTS AND DISCUSSION
The fractional atomic coordinates and thermal parameters are listed in Table 1, and bond lengths and angles in Table 2. The molecule consists of two different asymmetric carboxy fragments with very similar geometric parame ters, although both the C-O and C=O bond lengths (1.286 (4) and 1.231(3) A) in the carboxylate that is conjugated with the pyridine ring are slightly longer than the respective ones ( 1.278 (3 ) and 1.220 (4 ) A) in the carboxymethyl group. The geometry of the carboxymethyl group is similar to that found in the strongly hydrogen-bonded dimeric cation in II [ 5 1. As illustrated in Fig. 1, the different carboxy fragments of two adjacent molecules are bridged by a proton, resulting in a hydrogen bond of length 2.449 (4) A which is very similar to those found in both of the very strongly hydrogenTABLE 1 Atomic coordinates ( x 104) and thermal parameters* (AZ X 104)
O(1) O(2) C(1) C(2) C(3) C(4) C(5) N(1) C(6) C(7) C(8) O(3) C(4) I-I(l) B(3) I-I(4) I-I(5) B(6) H(7A) B(7B)
x
Y
3432(2) 5637(2) 4551(3) 4486(3) 5585(3) 5483(3) 4273(3) 3236(2) 3310(3) 2027 (3) 2249(3) 3133(2) 1412(2) 1419 6422 6153 4233 2486 1134 1838
3016(l) 3293(l) 2897(2) 2192(2) 2035(2) 1425(2) 972(2) 1103(l) 1703(2) 543(2) -203(2) -191(l) -798(l) - 1315 2340 1308 466 1800 826 391
2
UIU,,
u22
u33
u23
G3
u,2
10565(5) 9410(5) 9199(7) 7157(6) 5460(7) 3454(7) 3278(6) 5048(5) 6973(6) 4981(7) 6842(6) 8619(5) 6315(5) 7688 5715 2052 1974 8054 5272 3102
35(l) 37(l) 34(Z) 27(l) 29(l) 34(l) 40(2) 27(l) 26(l) 30(l) 29(l) 56(l) 42(l) 50 50 50 50 50 50 50
38(l) 37(l) 23(l) 23(l) 29(l) 35(2) 26(l) 22(l) 26(l) 29(l) 29(l) 39(l) 34(l)
53(l) 53(l) 34(2) 27(l) 36(2) 31(2) 28(2) 30(l) 26(l) 38(2) 27(l) 40(l) 50(l)
-17(l) -4(l) 2(l) 2(l) 3(l) 3(l) l(1) 4(l) 3(l) 5(l) O(1) 7(l) 15(l)
7(l) -6(l) -6(l) -3(l) 2(l) 5(l) -l(l) -2(l) -l(l) -8(2) -l(l) -21(l) -14(l)
-2(l) -9(l) 2(l) 2(l) -2(l) 6(l) 7(l) l(1) 3(l) -8(l) l(1) -10(l) -14(l)
“The exponents of the isotropic and anisotropic temperature factors take the forms -8n2Usin%/ 1’ and - 2x12 U,hihj.at -a: respectively.
138 TABLE 2 Bond lengths (8) and bond angles (deg.)
0(1)-C(l) C(l)-C(2) C(2)-C(6) C(4)-C(5) N(l)-C(6) C(7)-C(8) C(8)-O(4) O(l)-C(l)-O(2) O(2)-C(l)-C(2) C(l)-C(2)-C(6) C(2)-C(3)-C(4) C(4)-C(5)-N(1) C(5)-N(l)-C(7) C(2)-C(6)-N(1) C(7)-C(8)-O(3) O(3)-C(8)-O(4) Hydrogen bonding 0(4)-H(l) O.*.O(la) Symmetry code: a; 1/2-x,
1.286(4) 1.513(4) 1.385(4) 1.379(4) 1.351(4) 1.522(4) 1.278(3) 126.6(3) 118.5(3) 120.1(2) 120.2(3) 120.6(3) 118.8(2) 119.6(2) 120.9(2) 126.8(3)
1.069(3) 2.449 (4)
0(2)-C(l) C(2)-C(3) C(3)-C(4) C(5)-N(1) N(l)-C(7) C(8)-O(3)
O(l)-C(l)-C(2) C(l)-C(2)-C(3) C(3)-C(2)-C(6) C(3)-C(4)-C(5) C(5)-N(l)-C(6) C(6)-N(l)-C(7) N(l)-C(7)-C(8) C(7)-C(8)-O(4)
O(la).*.H(l) O(4)-H(la)**.O(la)
1.231(3) 1.371(4) 1.393(4) 1.342(4) 1.475(3) 1.220(4)
114.9(2) 120.5(2) 119.4(3) 118.4(3) 121.6(2) 119.5(2) 110.8(2) 112.3(2)
1.383(3) 174(l)
- 1/2+y, 2-2.
Fig. 1. Perspective view showing the molecular structure and hydrogen bonding scheme in I, with atom numbering. Symmetry code a; l/2 - x, - l/2 - y, 2 -2.
bonded dimeric structures of II (2.436 (6) A) and III (2.454 (5 ) A ), qualifying it as a “very strong” hydrogen bond [ 141. The hydrogen bond is virtually linear with O(4)-H(1)=1.069(3) A, O(la)...H(1)=1.383(3) A and 0(4)H (1) **-0 (la) = 174 (1) ’ in an ordered proton arrangement. Strong hydrogen bonds of this type link the molecules into a polymeric zigzag chain in the direction of the b axis, as illustrated in Fig. 2. Although the proton lies closer to the carboxymethyl group indicating asymmetry of the hydrogen bond, the geo-
Fig. 2. Stereoview of the crystal structure of 3-carboxy-1-(carboxymethyl)pyridinium hydroxide inner salt. The origin of the unit cell lies at the upper right corner, with a pointing towards the reader, b from right to left and c downward.
metric similarity of the two carboxy fragments implies that compound I is more similar to type AZ than type B2 acid salts of dicarboxylic acids [ 141. Similar infinite chains of strongly hydrogen-bonded dicarboxylic acid salts are known to exist in alkali salts of hydrogen oxydiacetate [ 15,161. It is noteworthy that the two carboxy fragments participating in the hydrogen bond are not coplanar, the dihedral angle between 0 (3)-C (8)-O (4) and 0 (la)-C (la)-0 (2a) being about 61’. The carboxymethyl group lies in a plane that is almost perpendicular to the aromatic ring (dihedral angle x 84 ’ ); in contrast, the aromatic carboxylate group in the same molecule is nearly coplanar with the pyridine ring (dihedral angle z 5 o ). The conformation of the hydrogen bond in I is thus different from the coplanar configuration commonly found in II [5], III [6] and a variety of mono- and dicarboxylic acid salts [14,17].
REFERENCES
9 10 11 12
13
M.S. Fischer, D.H. Templeton and A. Zalkin, Acta Crystallogr., Sect. B, 26 (1970) 1392. W.H. Yip, R.-J. Wang and T.C.W. Mak, Acta Crystallogr., Sect. C, 46 (1990) 717. T.C.W. Mak, J. Mol. Struct., 220 (1990) 13. W.-Y. Huang, X.-M. Du, B.-H. Yang and T.C.W. Mak, J. Mol. Struct., 222 (1990) 479. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 221 (1990) 256. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 240 (1990) 69. X.-M. Chen and T.C.W. Mak, J. Mol. Struct., 245 (1991) 301. R.A. Sparks, in F.R. Ahmed (Ed. ), Crystallographic Computing Techniques, Munksgaard, Copenhagen, 1976, p. 452. R. Diamond, Acta Crystallogr., Sect. A, 25 (1969) 43. G. Kopfmann and R. Huber, Acta Crystallogr., Sect. A, 24 (1968) 348. G.M. Sheldrick, in D. Sayre (Ed. ), Computational Crystallography, Oxford University Press, New York, 1982, p. 506. G.M. Sheldrick, in G.M. Sheldrick, C. Kruger and R. Goddard (Eds.), Crystallographic Computing 3: Data Collection, Structure Determination, Proteins, and Databases, Oxford University Press, New York, 1985, p. 175. J.A. Ibers and W.C. Hamilton (Eds.), International Tables for X-ray Crystallography, Vol. IV, Kynoch Press, Birmingham, 1973, pp. 55,99,149. (Now distributed by Kluwer Academic Publishers, Dordrecht, The Netherlands.)
140 14 15 16 17
J.C. Speakman, Struct. Bonding (Berlin), 12 (1972) 141. J. Albertsson, I. Grenthe and H. Herbertsson, Acta Crystallogr., Sect. B, 29 (1973) 1855. J. Albertsson, I. Grenthe and H. Herbertsson, Acta Crystallogr., Sect. B, 29 (1973) 2839. J. Emsley, Chem. Sot. Rev., 9 (1980) 91.