organic compounds
2-Carboxyanilinium chloride monohydrate
aInstitute of Chemistry, University of the Punjab, Lahore 54590, Pakistan, bDepartment of Physics, University of Sargodha, Sagrodha, Pakistan, and cDepartment of Chemistry, F.C. College & University, Lahore, Pakistan
*Correspondence e-mail: dmntahir_uos@yahoo.com
In the molecule of the title compound, C7H8NO2+·Cl−·H2O, an intramolecular N—H⋯O hydrogen bond results in the formation of a non-planar six-membered ring adopting a flattened boat conformation. In the intermolecular O—H⋯O and N—H⋯Cl hydrogen bonds link the molecules. There is a C=O⋯π contact between the carbonyl unit and the centroid of the benzene ring. There is a C=O⋯π contact [C⋯Cg = 3.5802 (18), C—O⋯Cg = 89 (1)°] between the carbonyl unit and the centroid of the benzene ring.
Related literature
For applications of anthranilic acid derivatives, see: Congiu et al. (2005); Nittoli et al. (2005). For a related structure, see: Bahadur et al. (2007); For bond-length data, see: Allen et al. (1987). For ring puckering parameters, see: Cremer & Pople (1975).
Experimental
Crystal data
|
Refinement
|
Data collection: APEX2 (Bruker, 2007); cell APEX2; data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999) and PLATON.
Supporting information
10.1107/S1600536808029267/hk2527sup1.cif
contains datablocks text, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808029267/hk2527Isup2.hkl
For the preparation of the title compound, 2-aminobenzoic acid (4.11 g, 3 mmol) and trichloroacetic acid (1.64 g, 1 mmol) were neutrilized with Na2CO3 separately in H2O, and then mixed together. Na2CO3 (3.18 g) was added to the resulting mixture and refluxed for 4 h. The refluxed solution was cooled, and concenterated HCl was added to get PH = 1. The solution was kept in open air for 3 d to get the suitable crystals.
H atoms were located in difference syntheses and refined as [O-H = 0.82 (2) Å (for OH); O-H = 0.76 (3) and 0.78 (3) Å (for H2O); N-H = 0.88 (2)-0.958 (19) Å, ( for NH3) and C-H = 0.93 (2)-0.96 (2) Å (for CH)] and constrained to ride on their parent atoms with Uiso(H) = xUeq(C,N,O), where x = 1.5 for NH3 H and x = 1.2 for all other H atoms.
Data collection: APEX2 (Bruker, 2007); cell
APEX2 (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999) and PLATON..Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are shown as dashed lines. | |
Fig. 2. A packing diagram of the title compound. Hydrogen bonds are shown as dashed lines. |
C7H8NO2+·Cl−·H2O | F(000) = 800 |
Mr = 191.61 | Dx = 1.407 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2238 reflections |
a = 23.094 (4) Å | θ = 2.5–28.3° |
b = 4.7833 (8) Å | µ = 0.39 mm−1 |
c = 16.381 (3) Å | T = 296 K |
β = 91.605 (9)° | Prism, brown |
V = 1808.8 (5) Å3 | 0.28 × 0.10 × 0.06 mm |
Z = 8 |
Bruker Kappa APEXII CCD diffractometer | 2238 independent reflections |
Radiation source: fine-focus sealed tube | 1749 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.025 |
Detector resolution: 7.5 pixels mm-1 | θmax = 28.3°, θmin = 2.5° |
ω scans | h = −30→30 |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | k = −6→3 |
Tmin = 0.975, Tmax = 0.985 | l = −21→20 |
9747 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.101 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0476P)2 + 1.0872P] where P = (Fo2 + 2Fc2)/3 |
2238 reflections | (Δ/σ)max < 0.001 |
139 parameters | Δρmax = 0.30 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
C7H8NO2+·Cl−·H2O | V = 1808.8 (5) Å3 |
Mr = 191.61 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 23.094 (4) Å | µ = 0.39 mm−1 |
b = 4.7833 (8) Å | T = 296 K |
c = 16.381 (3) Å | 0.28 × 0.10 × 0.06 mm |
β = 91.605 (9)° |
Bruker Kappa APEXII CCD diffractometer | 2238 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | 1749 reflections with I > 2σ(I) |
Tmin = 0.975, Tmax = 0.985 | Rint = 0.025 |
9747 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 0 restraints |
wR(F2) = 0.101 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.30 e Å−3 |
2238 reflections | Δρmin = −0.22 e Å−3 |
139 parameters |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Cl1 | 0.05634 (2) | 0.81018 (10) | 0.08328 (3) | 0.0425 (2) | |
O1 | 0.24332 (5) | 0.7928 (3) | 0.36801 (9) | 0.0551 (5) | |
O2 | 0.17708 (5) | 0.9236 (3) | 0.45555 (8) | 0.0493 (4) | |
O3 | 0.18909 (7) | 0.6690 (4) | 0.07558 (14) | 0.0796 (7) | |
N1 | 0.07438 (6) | 0.6617 (3) | 0.45470 (9) | 0.0340 (4) | |
C1 | 0.19199 (7) | 0.7781 (3) | 0.39900 (10) | 0.0338 (5) | |
C2 | 0.15328 (6) | 0.5699 (3) | 0.35784 (9) | 0.0304 (4) | |
C3 | 0.17259 (8) | 0.4219 (4) | 0.29012 (10) | 0.0408 (5) | |
C4 | 0.13710 (9) | 0.2318 (4) | 0.25017 (11) | 0.0462 (6) | |
C5 | 0.08157 (8) | 0.1841 (4) | 0.27706 (12) | 0.0466 (6) | |
C6 | 0.06160 (7) | 0.3269 (4) | 0.34388 (11) | 0.0398 (5) | |
C7 | 0.09727 (6) | 0.5188 (3) | 0.38354 (9) | 0.0300 (4) | |
H1 | 0.2619 (10) | 0.922 (5) | 0.3885 (14) | 0.0661* | |
H1A | 0.0991 (9) | 0.802 (4) | 0.4684 (12) | 0.0510* | |
H1B | 0.0399 (10) | 0.732 (4) | 0.4423 (13) | 0.0510* | |
H1C | 0.0724 (9) | 0.534 (4) | 0.4996 (12) | 0.0510* | |
H3 | 0.2113 (9) | 0.452 (4) | 0.2717 (11) | 0.0489* | |
H3A | 0.1584 (14) | 0.692 (7) | 0.0892 (19) | 0.0955* | |
H3B | 0.1945 (14) | 0.777 (6) | 0.041 (2) | 0.0955* | |
H4 | 0.1511 (9) | 0.133 (5) | 0.2061 (13) | 0.0554* | |
H5 | 0.0582 (9) | 0.052 (4) | 0.2493 (12) | 0.0558* | |
H6 | 0.0245 (9) | 0.298 (4) | 0.3628 (12) | 0.0477* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.0314 (2) | 0.0499 (3) | 0.0463 (3) | −0.0004 (2) | 0.0035 (2) | −0.0055 (2) |
O1 | 0.0320 (7) | 0.0668 (9) | 0.0673 (9) | −0.0189 (6) | 0.0174 (6) | −0.0255 (7) |
O2 | 0.0401 (7) | 0.0554 (8) | 0.0531 (7) | −0.0144 (6) | 0.0133 (6) | −0.0206 (6) |
O3 | 0.0408 (8) | 0.0837 (13) | 0.1153 (15) | 0.0249 (8) | 0.0207 (9) | 0.0514 (11) |
N1 | 0.0255 (7) | 0.0362 (8) | 0.0406 (8) | −0.0012 (6) | 0.0081 (5) | −0.0030 (6) |
C1 | 0.0283 (8) | 0.0362 (8) | 0.0372 (8) | −0.0030 (6) | 0.0049 (6) | 0.0006 (7) |
C2 | 0.0279 (7) | 0.0312 (8) | 0.0323 (7) | −0.0017 (6) | 0.0041 (6) | 0.0009 (6) |
C3 | 0.0357 (9) | 0.0456 (10) | 0.0416 (9) | −0.0040 (8) | 0.0111 (7) | −0.0063 (8) |
C4 | 0.0512 (11) | 0.0487 (10) | 0.0391 (9) | −0.0031 (8) | 0.0077 (8) | −0.0135 (8) |
C5 | 0.0445 (10) | 0.0462 (10) | 0.0486 (10) | −0.0088 (8) | −0.0048 (8) | −0.0109 (8) |
C6 | 0.0292 (8) | 0.0435 (10) | 0.0466 (9) | −0.0053 (7) | 0.0018 (7) | −0.0030 (8) |
C7 | 0.0278 (7) | 0.0307 (8) | 0.0315 (7) | 0.0005 (6) | 0.0031 (6) | 0.0014 (6) |
O1—C1 | 1.304 (2) | C2—C3 | 1.399 (2) |
O2—C1 | 1.216 (2) | C2—C7 | 1.393 (2) |
O1—H1 | 0.82 (2) | C3—C4 | 1.377 (3) |
O3—H3B | 0.78 (3) | C4—C5 | 1.387 (3) |
O3—H3A | 0.76 (3) | C5—C6 | 1.380 (3) |
N1—C7 | 1.463 (2) | C6—C7 | 1.383 (2) |
N1—H1B | 0.88 (2) | C3—H3 | 0.96 (2) |
N1—H1C | 0.958 (19) | C4—H4 | 0.93 (2) |
N1—H1A | 0.91 (2) | C5—H5 | 0.94 (2) |
C1—C2 | 1.487 (2) | C6—H6 | 0.93 (2) |
Cl1···O3 | 3.1452 (18) | N1···O2 | 2.6820 (19) |
Cl1···N1i | 3.3227 (16) | C1···C3iv | 3.581 (2) |
Cl1···N1ii | 3.1464 (16) | C1···O3vi | 3.339 (2) |
Cl1···N1iii | 3.1231 (16) | C1···C4iv | 3.477 (3) |
Cl1···H5iv | 2.96 (2) | C3···C1x | 3.581 (2) |
Cl1···H3A | 2.42 (3) | C3···O1viii | 3.338 (2) |
Cl1···H6v | 3.13 (2) | C4···C1x | 3.477 (3) |
Cl1···H1Bii | 2.28 (2) | C1···H1A | 2.46 (2) |
Cl1···H1Ai | 2.84 (2) | H1···H3Bvi | 2.27 (4) |
Cl1···H1Ciii | 2.181 (19) | H1···H3Avi | 2.27 (4) |
O1···C3vi | 3.338 (2) | H1···O3vi | 1.73 (2) |
O1···O3vi | 2.539 (2) | H1A···C1 | 2.46 (2) |
O2···O3vii | 2.777 (3) | H1A···O2 | 1.91 (2) |
O2···N1 | 2.6820 (19) | H1A···Cl1vii | 2.84 (2) |
O3···O2i | 2.777 (3) | H1B···Cl1ii | 2.28 (2) |
O3···O1viii | 2.539 (2) | H1B···H6 | 2.47 (3) |
O3···C1viii | 3.339 (2) | H1C···Cl1ix | 2.181 (19) |
O3···Cl1 | 3.1452 (18) | H3···O1 | 2.372 (19) |
O1···H4vi | 2.86 (2) | H3···O1viii | 2.655 (19) |
O1···H3vi | 2.655 (19) | H3A···O2i | 2.90 (3) |
O1···H3 | 2.372 (19) | H3A···H1viii | 2.27 (4) |
O2···H3Avii | 2.90 (3) | H3A···Cl1 | 2.42 (3) |
O2···H3Bvii | 2.04 (3) | H3B···H1viii | 2.27 (4) |
O2···H1A | 1.91 (2) | H3B···O2i | 2.04 (3) |
O3···H1viii | 1.73 (2) | H4···O1viii | 2.86 (2) |
N1···Cl1ix | 3.1231 (16) | H5···Cl1x | 2.96 (2) |
N1···Cl1vii | 3.3227 (16) | H6···Cl1xi | 3.13 (2) |
N1···Cl1ii | 3.1464 (16) | H6···H1B | 2.47 (3) |
C1—O1—H1 | 110.7 (16) | C3—C4—C5 | 120.07 (17) |
H3A—O3—H3B | 107 (3) | C4—C5—C6 | 120.20 (17) |
C7—N1—H1C | 109.9 (12) | C5—C6—C7 | 119.54 (15) |
H1A—N1—H1B | 109.5 (18) | N1—C7—C2 | 121.21 (13) |
H1B—N1—H1C | 110.9 (19) | C2—C7—C6 | 121.35 (14) |
C7—N1—H1A | 107.7 (13) | N1—C7—C6 | 117.43 (13) |
H1A—N1—H1C | 109.0 (17) | C2—C3—H3 | 119.5 (11) |
C7—N1—H1B | 109.8 (14) | C4—C3—H3 | 119.7 (11) |
O1—C1—O2 | 123.05 (15) | C5—C4—H4 | 120.6 (13) |
O1—C1—C2 | 113.64 (14) | C3—C4—H4 | 119.3 (13) |
O2—C1—C2 | 123.31 (15) | C4—C5—H5 | 118.7 (13) |
C3—C2—C7 | 118.04 (14) | C6—C5—H5 | 121.1 (13) |
C1—C2—C7 | 122.14 (13) | C5—C6—H6 | 121.5 (12) |
C1—C2—C3 | 119.82 (14) | C7—C6—H6 | 119.0 (12) |
C2—C3—C4 | 120.80 (17) | ||
O1—C1—C2—C3 | −2.8 (2) | C3—C2—C7—N1 | 178.91 (14) |
O1—C1—C2—C7 | 178.32 (14) | C3—C2—C7—C6 | 0.3 (2) |
O2—C1—C2—C3 | 176.32 (16) | C2—C3—C4—C5 | −0.3 (3) |
O2—C1—C2—C7 | −2.5 (2) | C3—C4—C5—C6 | 0.1 (3) |
C1—C2—C3—C4 | −178.82 (16) | C4—C5—C6—C7 | 0.3 (3) |
C7—C2—C3—C4 | 0.1 (2) | C5—C6—C7—N1 | −179.16 (16) |
C1—C2—C7—N1 | −2.2 (2) | C5—C6—C7—C2 | −0.5 (3) |
C1—C2—C7—C6 | 179.17 (15) |
Symmetry codes: (i) x, −y+2, z−1/2; (ii) −x, y, −z+1/2; (iii) x, −y+1, z−1/2; (iv) x, y+1, z; (v) −x, y+1, −z+1/2; (vi) −x+1/2, y+1/2, −z+1/2; (vii) x, −y+2, z+1/2; (viii) −x+1/2, y−1/2, −z+1/2; (ix) x, −y+1, z+1/2; (x) x, y−1, z; (xi) −x, y−1, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O3vi | 0.82 (2) | 1.73 (2) | 2.539 (2) | 171 (2) |
N1—H1A···O2 | 0.91 (2) | 1.91 (2) | 2.6820 (19) | 142.1 (18) |
N1—H1B···Cl1ii | 0.88 (2) | 2.28 (2) | 3.1464 (16) | 166.6 (18) |
N1—H1C···Cl1ix | 0.958 (19) | 2.181 (19) | 3.1231 (16) | 167.5 (18) |
O3—H3A···Cl1 | 0.76 (3) | 2.42 (3) | 3.1452 (18) | 160 (3) |
O3—H3B···O2i | 0.78 (3) | 2.04 (3) | 2.777 (3) | 159 (3) |
C1—O2···Cgiv | 1.22 (1) | 3.40 (1) | 3.5802 (18) | 89 (1) |
Symmetry codes: (i) x, −y+2, z−1/2; (ii) −x, y, −z+1/2; (iv) x, y+1, z; (vi) −x+1/2, y+1/2, −z+1/2; (ix) x, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C7H8NO2+·Cl−·H2O |
Mr | 191.61 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 296 |
a, b, c (Å) | 23.094 (4), 4.7833 (8), 16.381 (3) |
β (°) | 91.605 (9) |
V (Å3) | 1808.8 (5) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.39 |
Crystal size (mm) | 0.28 × 0.10 × 0.06 |
Data collection | |
Diffractometer | Bruker Kappa APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2005) |
Tmin, Tmax | 0.975, 0.985 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9747, 2238, 1749 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.667 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.101, 1.05 |
No. of reflections | 2238 |
No. of parameters | 139 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.30, −0.22 |
Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003), WinGX publication routines (Farrugia, 1999) and PLATON..
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O3i | 0.82 (2) | 1.73 (2) | 2.539 (2) | 171 (2) |
N1—H1A···O2 | 0.91 (2) | 1.91 (2) | 2.6820 (19) | 142.1 (18) |
N1—H1B···Cl1ii | 0.88 (2) | 2.28 (2) | 3.1464 (16) | 166.6 (18) |
N1—H1C···Cl1iii | 0.958 (19) | 2.181 (19) | 3.1231 (16) | 167.5 (18) |
O3—H3A···Cl1 | 0.76 (3) | 2.42 (3) | 3.1452 (18) | 160 (3) |
O3—H3B···O2iv | 0.78 (3) | 2.04 (3) | 2.777 (3) | 159 (3) |
C1—O2···Cgv | 1.216 (2) | 3.3988 (16) | 3.5802 (18) | 88.5 (1) |
Symmetry codes: (i) −x+1/2, y+1/2, −z+1/2; (ii) −x, y, −z+1/2; (iii) x, −y+1, z+1/2; (iv) x, −y+2, z−1/2; (v) x, y+1, z. |
Acknowledgements
The authors acknowledge the Higher Education Commission, Islamabad, Pakistan, for funding the purchase of the diffractometer at GCU, Lahore.
References
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Bahadur, S. A., Kannan, R. S. & Sridhar, B. (2007). Acta Cryst. E63, o2722–o2723. Web of Science CSD CrossRef IUCr Journals Google Scholar
Bruker (2005). SADABS. Bruker AXS Inc. Madison, Wisconsin, USA. Google Scholar
Bruker (2007). APEX2 and SAINT. Bruker AXS Inc. Madison, Wisconsin, USA. Google Scholar
Congiu, C., Cocco, M. T., Lilliu, V. & Onnis, V. (2005). J. Med. Chem. 48, 8245–8252. Web of Science CrossRef PubMed CAS Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Nittoli, T., Curran, K., Insaf, S., DiGrandi, M., Orlowski, M., Chopra, R., Agarwal, A., Howe, A. Y. M., Prashad, A., Floyd, M. B., Johnson, B., Sutherland, A., Wheless, K., Feld, B., O'Connell, J., Mansour, T. S. & Bloom, J. (2005). J. Med. Chem. 48, 7560–7581. Web of Science PubMed Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Anthranilic acid is widely used for various purposes such as production of dyes, pigments and saccharin. Its derivatives also have importance in medicinal chemistry and are used as antiinflammatory and anticancer agents (Congiu et al., 2005) and for inhibition of Hepatitis C NS5B polymerase (Nittoli et al., 2005). The title compound has been prepared to see its bioactivity with hope that it will be a good antibactarial agent at the economical cost and to utilize for preparing further derivatives. Crystal structures of proton transfer compound of 2-aminobenzoic acid with nitric acid (Bahadur et al., 2007) has been reported, where the intramolecular N-H···O hydrogen bond has also been observed.
In the molecule of the title compound (Fig. 1), the bond lengths (Allen et al., 1987) and angles are within normal ranges. Ring A (C2-C7) is, of course, planar. The intramolecular N-H···O hydrogen bond (Table 1) results in the formation of a nonplanar six-membered ring B (N1/O2/C1/C2/C7/H1A) having total puckering amplitude, QT, of 0.127 (3) Å, and flattened boat conformation [ϕ = -21.25 (3)°, θ = 44.41 (3)°] (Cremer & Pople, 1975).
In the crystal structure, intermolecular O-H···O and N-H···Cl hydrogen bonds (Table 1) link the molecules (Fig. 2), in which they may be effective in the stabilization of the structure. The C=O···π contact (Table 1) between the carbonyl moiety and the centroid of the benzene ring may further stabilize the structure.