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1.  Crystal structure of 1-(3-chloro­phen­yl)piperazin-1-ium picrate–picric acid (2/1) 
The title salt {systematic name: bis­[1-(3-chloro­phen­yl)piperazinium 2,4,6-tri­nitro­phenolate]–picric acid (2/1)}, 2C10H14ClN2 +·2C6H5N3O7 −·C6H6N3O7, crystallized with two independent 1-(3-chloro­phen­yl)piperazinium cations, two picrate anions and a picric acid mol­ecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid mol­ecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid mol­ecule inter­acts with the picrate anion through a trifurcated O—H⋯O four-centre hydrogen bond involving an intra­molecular O—H⋯O hydrogen bond and a weak C—H⋯O inter­action. Weak inter­molecular C—H⋯O inter­actions are responsible for the formation of cation–anion–cation trimers resulting in a chain along [010]. In addition, weak C—H⋯Cl and weak π–π inter­actions [centroid–centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing.
doi:10.1107/S1600536814023654
PMCID: PMC4257327  PMID: 25484834
crystal structure; piperazin-1-ium; picrate; picric acid; salt
2.  Crystal structures of 4-(pyrimidin-2-yl)piperazin-1-ium chloride and 4-(pyrimidin-2-yl)piperazin-1-ium nitrate 
The title salts, C8H13N4 +·Cl−, (I), and C8H13N4 +·NO3 −, (II), contain linked pyridinium–piperazine heterocycles. In the crystal of (I), weak N—H⋯Cl inter­actions lead to zigzag chains along [100] while in the crystal of (II), bifurcated N—H⋯(O,O) hydrogen bonds and weak C—H⋯O inter­actions collectively link the components into infinite chains along [100].
The title salts, C8H13N4 +·Cl−, (I), and C8H13N4 +·NO3 −, (II), contain linked pyridinium–piperazine heterocycles. In both salts, the piperazine ring adopts a chair conformation with protonation at the N atom not linked to the other ring. In the crystal of (I), weak N—H⋯Cl inter­actions are observed, leading to zigzag chains along [100]. In the crystal of (II), both H atoms on the NH2 + group form bifurcated N—H⋯(O,O) hydrogen bonds. Weak C—H⋯O inter­actions are also observed. These bonds collectively link the components into infinite chains along [100].
doi:10.1107/S1600536814020169
PMCID: PMC4257175  PMID: 25484652
crystal structure; pyrimidine–piperazine heterocyclic salts; chloride salt; nitrate salt; bifurcated hydrogen bonds
3.  Crystal structure of 3-[4-(pyrimidin-2-yl)piperazin-1-ium-1-yl]butano­ate 
The title compound, C12H18N4O2, crystallizes in the zwitterionic form with protonation at the N atom of the piperazine ring bearing the carboxylate group. The piperazine ring adopts a slightly distorted chair conformation. In the crystal, N—H⋯O hydrogen bonds are observed, forming chains along [010]. The packing is consolidated by C—H⋯O inter­actions, which generate a three-dimensional network.
doi:10.1107/S1600536814018972
PMCID: PMC4186175  PMID: 25309227
crystal structure; 3-(piperazin-1-ium-1-yl)butano­ate; zwitterionic form; fused heterocyclic derivatives; aza-Michael reactions
4.  Two tautomers in the same crystal: 3-(4-fluoro­phen­yl)-1H-pyrazole and 5-(4-fluoro­phen­yl)-1H-pyrazole 
The title co-crystal, 3-(4-fluoro­phen­yl)-1H-pyrazole–5-(4-fluoro­phen­yl)-1H-pyrazole (1/1), C9H7FN2, crystallizes with four independent mol­ecules (A, B, C and D) in the asymmetric unit exhibiting two tautomeric forms (A and D; B and C) due to N—H proton exchange between the two N atoms of the pyrazole ring. The dihedral angles between the mean planes of the pyrazole and benzene rings are 15.6 (1), 19.8 (9), 14.0 (1) and 10.7 (7)° in mol­ecules A, B, C and D, respectively. In the crystal, N—H⋯N hydrogen bonds link the four mol­ecules in the asymmetric unit into a ring with an R 4 4(12) motif. Furthermore, weak C—H⋯F inter­actions link the mol­ecules into a three-dimensional network.
doi:10.1107/S160053681401695X
PMCID: PMC4186127  PMID: 25309273
crystal structure; pyrazole derivative; tautomeric forms; hydrogen bonds
5.  Crystal structure of N-(3-benzoyl-4,5,6,7-tetra­hydro-1-benzo­thio­phen-2-yl)benzamide 
In the title compound, C22H19NO2S, the cyclo­hexene ring adopts a half-chair conformation. The dihedral angles between the plane of the thio­phene ring and those of its amide- and carbonyl-bonded benzene rings are 7.1 (1) and 59.0 (2)°, respectively. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, very weak aromatic π–π stacking inter­actions [centroid–centroid separation = 3.9009 (10) Å] are observed.
doi:10.1107/S1600536814016948
PMCID: PMC4186148  PMID: 25309274
crystal structure; hydrogen bonding; π–π stacking inter­actions; benzamide; 1-benzo­thio­phene; 2-amino­thio­phene derivatives
6.  {2-[(4-Nitro­benzyl­idene)amino]-4,5,6,7-tetrahydro-1-benzo­thio­phen-3-yl}(phen­yl)methanone 
In the title compound, C22H18N2O3S, disorder is found in the benzoyl group (A and B), as well as for four C atoms of the cyclo­hexene ring. Two orientations were modeled in a 0.583 (5):0.417 (5) ratio. The cyclo­hexene ring is in a distorted chair conformation. The dihedral angles between the mean plane of the thio­phene ring and the 4-nitro­benzene and phenyl rings are 30.9 (8) and 64.8 (3) (A) and 62.4 (7)° (B). The mean planes of the 4-nitro­benzene and the phenyl rings are almost perpendicular to each other, with dihedral angles of 85.4 (1) (A) and 83.9 (8)° (B). An extensive array of weak C—H⋯O inter­actions consolidate mol­ecules into a three-dimensional architecture, forming chains along [001] and [010] and layers parallel to (011).
doi:10.1107/S1600536814012185
PMCID: PMC4051066  PMID: 24940302
7.  4-(Pyrimidin-2-yl)piperazin-1-ium (E)-3-carb­oxy­prop-2-enoate 
In the cation of the title salt, C8H13N4 +·C4H3O4 −, the piperazinium ring adopts a slightly distorteded chair conformation. In the crystal, a single strong O—H⋯O inter­molecular hydrogen bond links the anions, forming chains along the c-axis direction. The chains of anions are linked by the cations, via N—H⋯O hydrogen bonds, forming sheets parallel to (100). These layers are linked by weak C—H⋯O hydrogen bonds, forming a three-dimensional structure. In addition, there are weak π–π inter­actions [centroid–centroid distance = 3.820 (9) Å] present involving inversion-related pyrimidine rings.
doi:10.1107/S1600536814011489
PMCID: PMC4051061  PMID: 24940275
8.  4-(Furan-2-carbon­yl)piperazin-1-ium 3,5-di­nitro­benzoate 
In the cation of the title salt, C9H13N2O2 +·C7H3N2O6 −, the piperazine ring adopts a slightly distorted chair conformation. Twofold rotational disorder is exhibited by the furan ring in a 0.430 (4):0.570 (4) ratio. In the crystal, N—H⋯O hydrogen bonds link the ions into chains along [010]. Additional weak C—H⋯O inter­actions are observed, leading to a supra­molecular layer parallel to (011).
doi:10.1107/S160053681401126X
PMCID: PMC4051063  PMID: 24940274
9.  Pyrimethaminium 2-{[4-(tri­fluoro­meth­yl)phen­yl]sulfan­yl}benzoate dimethyl sulfoxide monosolvate 
In the cation of the title solvated mol­ecular salt, C12H14ClN4 +·C14H8F3O2S−·C2H6OS [systematic name of the cation: 2,4-di­amino-5-(4-chloro­phen­yl)-6-ethyl­pyrimidin-1-ium], the dihedral angle between the planes of the pyrimidinium and 4-chloro­phenyl rings is 77.2 (5)°. In the anion, the planes of the benzene rings are twisted with respect to each other by 71.5 (5)°. Disorder was modelled for the dimethyl sulfoxide solvent mol­ecule over two set of sites in a 0.7487 (13):0.2513 (13) ratio. In the crystal, the cations are linked by inversion-generated pairs of N—H⋯N hydrogen bonds, with an R 2 2(8) graph-set motif. The cation donates two N—H⋯O hydrogen bonds to the anion, also generating an R 2 2(8) loop. These inter­actions, along with cation–solvent N—H⋯O hydrogen bonds, and cation–anion C—H⋯F, solvent–anion C—H⋯O and C—H⋯F inter­actions, result in a three-dimensional network.
doi:10.1107/S1600536814010411
PMCID: PMC4051059  PMID: 24940262
10.  Flunarizinium isonicotinate 
In the cation of the title salt {systematic name: 4-[bis­(4-fluoro­phen­yl)meth­yl]-1-[(2E)-3-phenyl­prop-2-en-1-yl]piperazin-1-ium pyridine-4-carboxyl­ate}, C26H27F2N2 +·C6H4NO2 −, the piperazine ring is in a slightly distorted chair conformation. The dihedral angle between the mean planes of the fluoro-substituted benzene rings is 81.9 (1)° and these benzene rings form dihedral angles of 6.5 (1) and 87.8 (1)° with the phenyl ring. In the crystal, a single N—H⋯O hydrogen bond links the cation and the anion. In addition, weak C—H⋯O hydrogen bonds and π–π stacking inter­actions involving one of the fluoro-substituted benzene rings and the phenyl ring, with a centroid–centroid distance of 3.700 (7) Å, link mol­ecules along [100].
doi:10.1107/S1600536814010423
PMCID: PMC4051108  PMID: 24940261
11.  N-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-di­hydro-1H-pyrazol-4-yl)-2-(4-nitro­phen­yl)acetamide 
In the title compound, C19H18N4O4, the nitro­phenyl and phenyl rings are twisted by 67.0 (6) and 37.4 (4)°, respectively, with respect to the pyrazole ring plane [maximum deviation = 0.0042 (16) Å]. The dihedral angle between the mean planes of the phenyl rings is 59.3 (3)°. The amide group, with a C—N—C—C torsion angle of 177.54 (13)°, is twisted away from the plane of the pyrazole ring in an anti­periplanar conformation. In the crystal, N—H⋯O hydrogen bonds involving the carbonyl group on the pyrazole ring and the amide group, together with weak C—H⋯O inter­actions forming R 2 2(10) graph-set motifs, link the mol­ecules into chains along [100]. Additional weak C—H⋯O inter­actions involving the nitro­phenyl rings further link the mol­ecules along [001], also forming R 2 2(10) graph-set motifs, thereby generating (010) layers.
doi:10.1107/S1600536814009738
PMCID: PMC4051092  PMID: 24940224
12.  {2-[(2-Bromo-5-meth­oxy­benzyl­idene)amino]-4,5,6,7-tetra­hydro­benzo[b]thiophen-3-yl}(phen­yl)methanone 
In the title compound, C23H20BrNO2S, disorder was modeled for the outer two C atoms of the cyclo­hexene ring over two sets of sites with an occupancy ratio of 0.580 (11):0.420 (11). Both rings have a half-chair conformation. The dihedral angles between the mean plane of the thio­phene ring and the benzene and phenyl rings are 9.2 (2) and 66.1 (2)°, respectively. The benzene and phenyl rings are inclined to each other by 74.8 (8)°. In the crystal, mol­ecules are linked by pairs of C—H⋯O hydrogen bonds, forming inversion dimers.
doi:10.1107/S1600536814008290
PMCID: PMC4011278  PMID: 24860382
13.  (4-Methyl­piperazin-1-yl)(2,3,4-tri­meth­oxy­benzyl­idene)amine 
In the title compound, C15H23N3O3, the piperazine ring is in a slightly distorted chair conformation and is twisted from the mean plane of the benzene ring making a dihedral angle of 14.94 (6)°. The 4-meth­oxy substituent is almost co-planar with the benzene ring [C—C—O—C torsion angle = 5.4 (1)°], while the meth­oxy groups at positions 2 and 3 [C—C—O—C torsion angles of 122.6 (4) and −66.1 (4)°, respectively] are twisted away from the mean plane of the benzene ring in anti­clinical and synclinical conformations, respectively. No classical hydrogen bonds or any weak inter­molecular inter­actions are observed in the crystal structure.
doi:10.1107/S1600536814006291
PMCID: PMC3998554  PMID: 24826188
14.  {2-[(1H-Indol-3-yl­methyl­idene)amino]-4,5,6,7-tetra­hydro­benzo[b]thio­phen-3-yl}(phen­yl)methanone 
The title compound, C24H20N2OS, crystallizes with two independent mol­ecules (A and B) in the asymmetric unit, in each of which the cyclo­hexene rings adopt half-chair conformations. The mean plane of the indole ring is twisted from those of the phenyl and thio­phene rings by 69.0 (7) and 8.3 (5)°, respectively, in mol­ecule A and by 65.4 (9) and 6.7 (5)°, respectively, in mol­ecule B. The dihedral angles between the mean planes of the phenyl and thio­phene rings are 63.0 (4) and 58.8 (9)° in mol­ecules A and B, respectively. In the crystal, N—H⋯O hydrogen bonds lead to the formation of an infinite chain along [101]. In addition, π–π stacking inter­actions are observed involving the thio­phene and pyrrole rings of the two mol­ecules, with a shortest inter­centroid distance of 3.468 (2) Å.
doi:10.1107/S1600536814006345
PMCID: PMC3998588  PMID: 24826189
15.  {2-[(2-Hy­droxy­benzyl­idene)amino]-4,5,6,7-tetra­hydro-1-benzo­thio­phen-3-yl}(phen­yl)methanone 
In the title compound, C22H19NO2S, the cyclo­hexene ring adopts a slightly distorted half-chair conformation. The dihedral angles between the mean planes of the thio­phene ring and the phenyl and 2-hy­droxy­phenyl rings are 70.4 (5) and 12.1 (9)°, respectively. The phenyl and 2-hy­droxy­phenyl rings are twisted with respect to one another by 81.0 (6)°. A short intra­molecular O—H⋯N hydrogen bond is observed. In the crystal, weak C—H⋯O inter­actions link the mol­ecules into zigzag chains diagonally along [100] .
doi:10.1107/S1600536814006199
PMCID: PMC3998550  PMID: 24826172
16.  5-(4-Fluoro­phen­yl)-2H-pyrazol-1-ium 2,2,2-tri­fluoro­acetate 
The title salt, C9H8FN2 +·C2F3O2 −, crystallizes with two independent cations (A and B) and two independent anions (C and D) in the asymmetric unit. In the cations, the dihedral angles between the benzene and pyrazolium rings are 23.7 (3)° in cation A and 1.8 (8)° in cation B. In the crystal, each anion links to the two cations via N—H⋯O hydrogen bonds, forming a U-shaped unit with an R 4 4(14) ring motif. These U-shaped units stack along the a axis and are linked via C—H⋯O and C—H⋯F hydrogen bonds, forming slabs lying parallel to (100). Within the slabs there are π–π inter­actions between the pyrazolium rings [inter-centroid distance = 3.6326 (15) Å] and between the benzene rings [inter-centroid distance = 3.7244 (16) Å]. In the anions, the F atoms of the tri­fluoro­methyl groups are disordered over two sets of sites, with refined occupancy ratios of 0.58 (3):0.42, 0.540 (14):0.46 (14), and 0.55 (2):0.45 (2) for anion C, and 0.73 (5):0.27 (5), 0.63 (5):0.37 (5), and 0.57 (8):0.43 (8) for anion D.
doi:10.1107/S1600536814005200
PMCID: PMC3998555  PMID: 24826138
17.  3-(1H-Imidazol-1-yl)propanaminium 2-carb­oxy-4,6-di­nitro­phenolate 
In the title salt, C6H12N3 +·C7H3N2O7 −, the imidazole ring is planar, with a maximum deviation of 0.0013 (14) Å for the N attached to the propanaminium group. In the anion, a single intra­molecular O—H⋯O hydrogen bond is observed. The mean planes of the nitro groups in the anion are twisted from the benzene ring mean plane making dihedral angles of 24.7 (9) and 3.9 (6)°. In the crystal, the ammonium H atoms form N—H⋯N and N—H⋯O hydrogen bonds, resulting in an infinite chain along [111]. In addition to the classical hydrogen bonds, weak C—H⋯O and π–π [centroid–centroid distance = 3.7124 (9) Å] inter­actions are also observed, which lead to the formation a three-dimensional supramolecular structure that links the chains into layers along the bc plane.
doi:10.1107/S1600536814003146
PMCID: PMC3998440  PMID: 24765018
18.  1-Piperonylpiperazinium 4-chloro­benzoate 
In the title salt {systematic name: 1-[(1,3-benzodioxol-5-yl)meth­yl]piperazin-1-ium 4-chloro­benzoate}, C12H17N2O2 +·C7H4ClO2 −, the piperazine ring adopts a slightly disordered chair conformation. The dioxole ring is in a flattened envelope conformation with the methyl­ene C atom forming the flap. The relative orientation of the piperonyl ring system and the piperazine rings is reflected in the N—C—C C torsion angle of 132.3 (1)°. In the anion, the mean plane of the carboxyl­ate group is twisted from that of the benzene ring by 14.8 (9)°. In the crystal, the components are linked by N—H⋯O and weak C—H⋯O hydrogen bonds, forming chains along [010].
doi:10.1107/S1600536814002037
PMCID: PMC3998456  PMID: 24764993
19.  1-Piperonylpiperazinium 4-nitro­benzoate monohydrate 
In the title hydrated salt [systematic name: 1-(1,3-benzodioxol-5-ylmeth­yl)piperazin-1-ium 4-nitro­benzoate monohydrate], C12H17N2O2 +·C7H4NO4 −·H2O, the piperazinium ring of the cation adopts a slightly distorted chair conformation. The piperonyl and piperazine rings are rotated with respect to each other with an N—C—C—C torsion angle of 45.6 (2)°. In the anion, the nitro group is almost coplanar with the adjacent benzene ring, forming a dihedral angle of only 3.9 (4)°. In the crystal, the cations, anions and water mol­ecules are linked through N—H⋯O and O—H⋯O hydrogen bonds into chains along the a axis. In addition, weaker inter­molecular C—H⋯O inter­actions are also observed within the chains. The anions form centrosymmetric couples through π-stacking inter­actions, with an inter­centroid distance of 3.681 (4) Å between the benzene rings.
doi:10.1107/S160053681400261X
PMCID: PMC3998489  PMID: 24764985
20.  Flupentixol tartrate 
In the title salt, C23H26F3N2OS+·C4H5O6 − [systematic name: 1-(2-hy­droxy­eth­yl)-4-[3-(2-(tri­fluoro­meth­yl)thioxanthen-9-yl­idene)prop­yl]piperazin-1-ium 3-carb­oxy-2,3-di­hydroxy­pro­pion­ate], the monoprotonated piperazine ring in the cation adopts a chair conformation, while the thio­pyran ring of the thioxanthene group has a boat conformation. The dihedral angle between the mean planes of the two outer aromatic rings of the thioxanthene groups is 31.6 (2)°. In the crystal, the cations and anions are linked via O—H⋯O, N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, forming chains propagating along [100]. In addition, R 2 2(7), R 2 2(11), R 2 2(10) and R 2 2(12) graph-set ring motifs involving the anions, and R 2 2(9) graph-set ring motifs involving both the cations and anions are observed. The three F atoms of the tri­fluoro­methyl group are disordered over two sets of sites and the individual atoms were refined with occupancy ratios of 0.54 (6):0.46 (6), 0.72 (2):0.28 (2) and 0.67 (3):0.33 (3).
doi:10.1107/S1600536814001536
PMCID: PMC3998353  PMID: 24764914
21.  1-Piperonylpiperazinium picrate 
In the cation of the title salt [systematic name: 4-(2H-1,3-benzodioxol-5-ylmeth­yl)piperazin-1-ium 2,4,6-tri­nitro­phen­o­late], C12H17N2O2 +·C6H2N3O7 −, the piperazine ring adopts a slightly disordered chair conformation. The piperonyl ring system and the piperazine ring are twisted with respect to each other with an N—C—C—C torsion angle of 40.7 (2)°. In the anion, the dihedral angles between the mean planes of the nitro substituents ortho to the phenolate O atom and the mean plane of the phenyl ring are 28.8 (9) and 32.2 (8)°. In contrast, the nitro group in the para position lies much closer to the aromatic ring plane, subtending a dihedral angle of 3.0 (1)°. In the crystal, the cations and anions inter­act through N—H⋯O hydrogen bonds and a weak C—H⋯O inter­action. Weak C—H⋯O inter­actions are also observed between the anions, forming R 2 2(10) graph-set ring motifs. In addition, a weak centroid–centroid π–π stacking inter­action between the aromatic rings of the cation and the anion, with an inter­centroid distance of 3.7471 (9) Å, contributes to the crystal packing, resulting in a two-dimensional network along (10-1).
doi:10.1107/S1600536814001524
PMCID: PMC3998354  PMID: 24764915
22.  5-Amino-1H-pyrazol-2-ium hydrogen succinate 
In the cation of the title salt, C3H6N3 +·C4H5O4 −, the protonated pyrazolium ring is planar (r.m.s. deviation = 0.012 Å). An intra­molecular C—H⋯O hydrogen bond occurs in the anion. In the crystal, N—H⋯O hydrogen bonds and a weak C—H⋯O inter­action between the cations and anions form two sets of R 2 2(8) graph-set ring motifs. Inter­molecular O—H⋯O hydrogen bonds between these lead to a criss-cross pattern along the b axis. In addition to the classical hydrogen bonds, a weak C—H⋯π(pyrazolium) inter­action is observed and contributes to crystal packing. All of these inter­actions link the mol­ecules into a two-dimensional supra­molecular framework parallel to (10-1).
doi:10.1107/S1600536814001615
PMCID: PMC3998361  PMID: 24764922
23.  Enrofloxacinium oxalate 
The title salt, 2C19H23FN3O3 +·C2O4 2− {systematic name: bis-[4-(3-carb­oxy-1-cyclo­propyl-6-fluoro-4-oxo-1,4-di­hydro­quino­lin-7-yl)-1-ethyl­piperazin-1-ium] oxalate}, crystallizes with two independent monocations (A and B) and an oxalate dianion (C) in the asymmetric unit. The piperazinium ring in both the cations adopts a slightly disordered chair conformation. The dihedral angles between the mean planes of the cyclo­propyl ring and the 10-membered quinoline ring are 50.6 (5)° (A) and 62.2 (5)° (B). In each of the cations, a single O—H⋯O intra­molecular hydrogen bond is observed. In the crystal, the oxalate anions inter­act with the cations through N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions, forming R 2 2(8) graph-set ring motifs. Weak C—H⋯F inter­actions along with further C—H⋯O inter­actions are observed between the cations, forming zigzag chains along [001]. In addition, π–π stacking inter­actions are observed with centroid–centroid distances of 3.5089 (13), 3.5583 (13), 3.7900 (13) and 3.7991 (13) Å.
doi:10.1107/S1600536814001421
PMCID: PMC3998349  PMID: 24764910
24.  Ethyl 6-(4-chloro­phen­yl)-4-(4-fluoro­phen­yl)-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate 
The asymmetric unit of the title compound, C21H18ClFO3, contains two independent mol­ecules. In one mol­ecule (A), the 4-chloro­phenyl, oxo­cyclo­hex-3-ene, carboxyl­ate, and ethyl groups were refined as disordered over two sets of sites with a 0.684 (5):0.316 (5) ratio. The cyclo­hexene ring in the disordered mol­ecule is in a slightly distorted envelope conformation for the major component (with the C atom bound to the carboxylate group being the flap atom) and in a screw-boat conformation for the minor component. In the ordered mol­ecule (B), the cyclo­hexene ring is in a half-chair conformation. The dihedral angles between the mean planes of the fluoro- and chloro-substituted benzene rings are 89.9 (7) (only the major component is considered for A) and 76.4 (7)° (B). In the crystal, inversion dimers are observed along with weak C—H⋯O hydrogen bonds, which form chains along [100].
doi:10.1107/S1600536813031851
PMCID: PMC3885083  PMID: 24454259
25.  4-(3-Fluoro-4-methyl­anilino)-2-methyl­idene-4-oxo­butanoic acid 
The title compound, C12H12FNO3, crystallizes with two independent mol­ecules (A and B) in the asymmetric unit. The dihedral angle between the mean planes of the 3-fluoro-4-methyl­phenyl ring and the oxo­amine group is 25.7 (7)° in mol­ecule A and 71.3 (7)° in mol­ecule B, while the mean plane of the 2-methyl­idene-4-oxo­butanoic acid group is twisted by 76.2 (1)° from that of the oxo­amine group in mol­ecule A and by 76.2 (4)° in mol­ecule B. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds [the latter forming an R 2 2(8) graph-set motif] link the mol­ecules into a two-dimensional network parallel to the ac plane.
doi:10.1107/S160053681302998X
PMCID: PMC3885031  PMID: 24454206

Results 1-25 (266)