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###                                                                        ###
###        Electronic paper (Acta Crystallographica Section E)             ###
###                                                                        ###
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#                                                                            #
# This CIF contains the data in a paper accepted for publication in Acta     #
# Crystallographica Section E. It conforms to the requirements of Notes      #
# for Authors for Section E, and has been peer reviewed under the auspices   #
# of the IUCr Commission on Journals.                                        #
#                                                                            #
# Full details of the Crystallographic Information File format               #
# are given in the paper "The Crystallographic Information File (CIF):       #
# a New Standard Archive File for Crystallography" by S. R. Hall, F. H.      #
# Allen and I. D. Brown [Acta Cryst. (1991), A47, 655-685].                  #
#                                                                            #
# The current version of the core CIF dictionary is obtainable from          #
# ftp://ftp.iucr.org/pub/cif_core.dic. The current version number is 2.4.    #
#                                                                            #
# Software is freely available for graphical display of the structure(s) in  #
# this CIF.  For information consult the CIF home page http://www.iucr.org/  #
# cif/home.html                                                              #
#                                                                            #
# This file may be used for bona fide research purposes within the           #
# scientific community so long as proper attribution is given to the journal # 
# article from which it was obtained.                                        #
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data_global
_audit_creation_method     'form.cif (version 2.0)'
_journal_data_validation_number     ?
_journal_date_recd_electronic     2010-07-17
_journal_date_accepted     2010-07-19
_journal_name_full     'Acta Crystallographica, Section E'
_journal_year     2010
_journal_volume     66
_journal_issue      8
_journal_page_first     o2109
_journal_page_last     o2109
_journal_paper_category     QO
_journal_coeditor_code     HB5558
_publ_contact_author_name     'Prof. Fun, Hoong-Kun'
_publ_contact_author_address
;
      X-ray Crystallography Unit
      School of Physics
      Universiti Sains Malaysia
      11800 USM, Penang
      MALAYSIA
;
_publ_contact_author_email     'hkfun@usm.my'
_publ_contact_author_fax     '6 04 6579150'
_publ_contact_author_phone     '6 04 6533652'
_publ_section_title
;
2,6-Difluorobenzoic acid
;
loop_
    _publ_author_name
    _publ_author_footnote
    _publ_author_address
    'Mohammad T. M. Al-Dajani' ?
;
      School of Pharmaceutical Sciences
      Universiti Sains Malaysia
      11800 USM, Penang
      Malaysia
;
    'Habibah A Wahab' ?
;
Malaysian Institute of Pharmaceuticals and Nutraceuticals
Ministry of Science, Technology and Innovation
Blok A, 10 Persiaran Bukit Jambul
11900 Bayan Lepas, Penang
Malaysia
;
    'Nornisah Mohamed' ?
;
      School of Pharmaceutical Sciences
      Universiti Sains Malaysia
      11800 USM, Penang
      Malaysia
;
    'Chin Sing Yeap'
;
      Thomson Reuters ResearcherID: A-5523-2009.
;
;
      X-ray Crystallography Unit
      School of Physics
      Universiti Sains Malaysia
      11800 USM, Penang
      Malaysia
;
    'Hoong-Kun Fun'
;
      Thomson Reuters ResearcherID: A-3561-2009.
;
;     X-ray Crystallography Unit
      School of Physics
      Universiti Sains Malaysia
      11800 USM, Penang
      Malaysia
;
data_I
_audit_creation_method     SHELXL-97
_chemical_name_systematic
;
2,6-Difluorobenzoic acid
;
_chemical_name_common     ?
_chemical_formula_moiety     'C7 H4 F2 O2'
_chemical_formula_sum     'C7 H4 F2 O2'
_chemical_formula_iupac     'C7 H4 F2 O2'
_chemical_formula_weight     158.10
_chemical_melting_point     ?
_symmetry_cell_setting     monoclinic
_symmetry_space_group_name_H-M     'P 21/c'
_symmetry_space_group_name_Hall     '-P 2ybc'
loop_
    _symmetry_equiv_pos_as_xyz
    'x, y, z'
    '-x, y+1/2, -z+1/2'
    '-x, -y, -z'
    'x, -y-1/2, z-1/2'
_cell_length_a     3.6517(4)
_cell_length_b     14.1214(15)
_cell_length_c     12.2850(13)
_cell_angle_alpha     90.00
_cell_angle_beta     95.651(3)
_cell_angle_gamma     90.00
_cell_volume     630.42(12)
_cell_formula_units_Z     4
_cell_measurement_reflns_used     3166
_cell_measurement_theta_min     3.33
_cell_measurement_theta_max     32.07
_cell_measurement_temperature     100.00(10)
_exptl_crystal_description     'needle'
_exptl_crystal_colour     'colourless'
_exptl_crystal_size_max     0.73
_exptl_crystal_size_mid     0.19
_exptl_crystal_size_min     0.09
_exptl_crystal_density_diffrn     1.666
_exptl_crystal_density_meas     ?
_exptl_crystal_density_method     'not measured'
_exptl_crystal_F_000     320
_exptl_absorpt_coefficient_mu     0.159
_exptl_absorpt_correction_type     multi-scan
_exptl_absorpt_process_details     '(<i>SADABS</i>; Bruker, 2009)'
_exptl_absorpt_correction_T_min     0.841
_exptl_absorpt_correction_T_max     0.986
_exptl_special_details
;
The crystal was placed in the cold stream of an Oxford Cryosystems Cobra
open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
;
_diffrn_ambient_temperature     100
_diffrn_radiation_type     MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_radiation_source     'fine-focus sealed tube'
_diffrn_radiation_monochromator     graphite
_diffrn_measurement_device_type     'Bruker APEXII DUO CCD'
_diffrn_measurement_method     '\f and \w scans'
_diffrn_detector_area_resol_mean     ?
_diffrn_reflns_number     6112
_diffrn_reflns_av_R_equivalents     0.0290
_diffrn_reflns_av_sigmaI/netI     0.0338
_diffrn_reflns_theta_min     2.20
_diffrn_reflns_theta_max     32.14
_diffrn_reflns_theta_full     32.14
_diffrn_measured_fraction_theta_max     0.983
_diffrn_measured_fraction_theta_full     0.983
_diffrn_reflns_limit_h_min     -5
_diffrn_reflns_limit_h_max     5
_diffrn_reflns_limit_k_min     -20
_diffrn_reflns_limit_k_max     20
_diffrn_reflns_limit_l_min     -18
_diffrn_reflns_limit_l_max     18
_diffrn_standards_number     0
_diffrn_standards_interval_count     .
_diffrn_standards_interval_time     .
_diffrn_standards_decay_%     ?
_refine_special_details
;
Refinement of <i>F</i>^2^ against ALL reflections. The weighted <i>R</i>-factor
<i>wR</i> and goodness of fit <i>S</i> are based on <i>F</i>^2^, conventional
<i>R</i>-factors <i>R</i> are based on <i>F</i>, with <i>F</i> set to zero for
negative <i>F</i>^2^. The threshold expression of <i>F</i>^2^ >
\s(<i>F</i>^2^) is used only for calculating <i>R</i>-factors(gt) <i>etc</i>.
and is not relevant to the choice of reflections for refinement.
<i>R</i>-factors based on <i>F</i>^2^ are statistically about twice as large
as those based on <i>F</i>, and <i>R</i>- factors based on ALL data will be
even larger.
;
_reflns_number_total     2190
_reflns_number_gt     1895
_reflns_threshold_expression     I>2\s(I)
_refine_ls_structure_factor_coef     Fsqd
_refine_ls_matrix_type     full
_refine_ls_R_factor_all     0.0548
_refine_ls_R_factor_gt     0.0488
_refine_ls_wR_factor_gt     0.1369
_refine_ls_wR_factor_ref     0.1430
_refine_ls_goodness_of_fit_ref     1.118
_refine_ls_restrained_S_all     1.118
_refine_ls_number_reflns     2190
_refine_ls_number_parameters     116
_refine_ls_number_restraints     0
_refine_ls_hydrogen_treatment     refall
_refine_ls_weighting_scheme     calc
_refine_ls_weighting_details
         'calc w=1/[\s^2^(Fo^2^)+(0.0668P)^2^+0.3079P] where P=(Fo^2^+2Fc^2^)/3'
_atom_sites_solution_hydrogens     geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary     difmap
_refine_ls_shift/su_max     0.000
_refine_ls_shift/su_mean     0.000
_refine_diff_density_max     0.467
_refine_diff_density_min     -0.314
_refine_ls_extinction_method     none
_refine_ls_extinction_coef     ?
loop_
    _atom_type_symbol
    _atom_type_description
    _atom_type_scat_dispersion_real
    _atom_type_scat_dispersion_imag
    _atom_type_scat_source
    'C' 'C' 0.0033 0.0016
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'H' 'H' 0.0000 0.0000
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'O' 'O' 0.0106 0.0060
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'F' 'F' 0.0171 0.0103
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
_computing_data_collection     'APEX2 (Bruker, 2009)'
_computing_cell_refinement     'SAINT (Bruker, 2009)'
_computing_data_reduction     'SAINT (Bruker, 2009)'
_computing_structure_solution     'SHELXTL (Sheldrick, 2008)'
_computing_structure_refinement     'SHELXTL (Sheldrick, 2008)'
_computing_molecular_graphics     'SHELXTL (Sheldrick, 2008)'
_computing_publication_material
;
SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009)
;
loop_
    _atom_site_type_symbol
    _atom_site_label
    _atom_site_fract_x
    _atom_site_fract_y
    _atom_site_fract_z
    _atom_site_U_iso_or_equiv
    _atom_site_adp_type
    _atom_site_calc_flag
    _atom_site_refinement_flags
    _atom_site_occupancy
    _atom_site_disorder_assembly
    _atom_site_disorder_group
    F F1 0.0410(3) -0.01635(6) 0.16839(7) 0.0312(2) Uani d . 1 . .
    F F2 0.2348(3) 0.26707(6) 0.36896(7) 0.0285(2) Uani d . 1 . .
    O O2 0.2287(3) 0.09843(7) 0.46658(7) 0.0238(2) Uani d . 1 . .
    O O3 0.4751(3) -0.00746(7) 0.35958(8) 0.0222(2) Uani d . 1 . .
    C C1 0.0163(4) 0.07830(9) 0.17659(9) 0.0194(2) Uani d . 1 . .
    C C2 -0.1413(4) 0.12763(10) 0.08679(10) 0.0228(3) Uani d . 1 . .
    C C3 -0.1734(4) 0.22519(10) 0.09441(10) 0.0234(3) Uani d . 1 . .
    C C4 -0.0482(4) 0.27250(10) 0.19005(11) 0.0230(3) Uani d . 1 . .
    C C5 0.1044(4) 0.22003(9) 0.27793(9) 0.0184(2) Uani d . 1 . .
    C C6 0.1398(3) 0.12160(8) 0.27576(9) 0.0160(2) Uani d . 1 . .
    C C7 0.2939(3) 0.06665(8) 0.37288(9) 0.0156(2) Uani d . 1 . .
    H H2 -0.221(7) 0.0927(16) 0.0182(18) 0.038(6) Uiso d . 1 . .
    H H3 -0.285(6) 0.2599(15) 0.0302(17) 0.035(5) Uiso d . 1 . .
    H H4 -0.074(6) 0.3406(16) 0.1979(18) 0.035(5) Uiso d . 1 . .
    H H1O2 0.341(11) 0.062(3) 0.526(3) 0.098(12) Uiso d . 1 . .
loop_
    _atom_site_aniso_label
    _atom_site_aniso_U_11
    _atom_site_aniso_U_22
    _atom_site_aniso_U_33
    _atom_site_aniso_U_12
    _atom_site_aniso_U_13
    _atom_site_aniso_U_23
    F1 0.0518(6) 0.0183(4) 0.0219(4) 0.0019(4) -0.0044(4) -0.0039(3)
    F2 0.0459(6) 0.0169(4) 0.0210(4) -0.0010(4) -0.0048(4) -0.0018(3)
    O2 0.0340(6) 0.0238(5) 0.0135(4) 0.0038(4) 0.0014(4) 0.0013(3)
    O3 0.0269(5) 0.0179(4) 0.0216(4) 0.0056(4) 0.0012(4) 0.0030(3)
    C1 0.0238(6) 0.0181(5) 0.0162(5) 0.0001(4) 0.0014(4) 0.0003(4)
    C2 0.0242(6) 0.0289(6) 0.0150(5) -0.0002(5) -0.0006(4) 0.0019(4)
    C3 0.0224(6) 0.0289(6) 0.0184(5) 0.0037(5) -0.0001(4) 0.0078(4)
    C4 0.0272(6) 0.0193(6) 0.0225(6) 0.0041(5) 0.0016(5) 0.0062(4)
    C5 0.0210(5) 0.0174(5) 0.0166(5) 0.0004(4) 0.0012(4) 0.0011(4)
    C6 0.0182(5) 0.0160(5) 0.0137(4) 0.0009(4) 0.0014(4) 0.0019(3)
    C7 0.0174(5) 0.0148(5) 0.0148(4) -0.0006(4) 0.0020(4) 0.0012(3)
_geom_special_details
;
All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.
;
loop_
    _geom_bond_atom_site_label_1
    _geom_bond_atom_site_label_2
    _geom_bond_site_symmetry_2
    _geom_bond_distance
    _geom_bond_publ_flag
    F1 C1 . 1.3442(15) ?
    F2 C5 . 1.3467(14) ?
    O2 C7 . 1.2794(14) ?
    O2 H1O2 . 0.96(4) ?
    O3 C7 . 1.2574(15) ?
    C1 C2 . 1.3815(17) ?
    C1 C6 . 1.3976(16) ?
    C2 C3 . 1.387(2) ?
    C2 H2 . 0.99(2) ?
    C3 C4 . 1.3892(19) ?
    C3 H3 . 0.98(2) ?
    C4 C5 . 1.3807(17) ?
    C4 H4 . 0.97(2) ?
    C5 C6 . 1.3965(17) ?
    C6 C7 . 1.4866(15) ?
loop_
    _geom_angle_atom_site_label_1
    _geom_angle_atom_site_label_2
    _geom_angle_atom_site_label_3
    _geom_angle_site_symmetry_1
    _geom_angle_site_symmetry_3
    _geom_angle
    _geom_angle_publ_flag
    C7 O2 H1O2 . . 113(2) ?
    F1 C1 C2 . . 117.86(11) ?
    F1 C1 C6 . . 118.83(11) ?
    C2 C1 C6 . . 123.29(12) ?
    C1 C2 C3 . . 118.58(12) ?
    C1 C2 H2 . . 119.4(13) ?
    C3 C2 H2 . . 122.0(13) ?
    C2 C3 C4 . . 120.79(11) ?
    C2 C3 H3 . . 118.2(13) ?
    C4 C3 H3 . . 121.0(13) ?
    C5 C4 C3 . . 118.49(12) ?
    C5 C4 H4 . . 119.3(13) ?
    C3 C4 H4 . . 122.2(13) ?
    F2 C5 C4 . . 117.84(11) ?
    F2 C5 C6 . . 118.74(10) ?
    C4 C5 C6 . . 123.38(11) ?
    C5 C6 C1 . . 115.44(10) ?
    C5 C6 C7 . . 122.18(10) ?
    C1 C6 C7 . . 122.37(11) ?
    O3 C7 O2 . . 123.76(11) ?
    O3 C7 C6 . . 119.51(10) ?
    O2 C7 C6 . . 116.72(10) ?
loop_
    _geom_torsion_atom_site_label_1
    _geom_torsion_atom_site_label_2
    _geom_torsion_atom_site_label_3
    _geom_torsion_atom_site_label_4
    _geom_torsion_site_symmetry_1
    _geom_torsion_site_symmetry_2
    _geom_torsion_site_symmetry_3
    _geom_torsion_site_symmetry_4
    _geom_torsion
    _geom_torsion_publ_flag
    F1 C1 C2 C3 . . . . 179.13(13) ?
    C6 C1 C2 C3 . . . . 1.2(2) ?
    C1 C2 C3 C4 . . . . 0.3(2) ?
    C2 C3 C4 C5 . . . . -0.9(2) ?
    C3 C4 C5 F2 . . . . 178.01(12) ?
    C3 C4 C5 C6 . . . . 0.0(2) ?
    F2 C5 C6 C1 . . . . -176.65(11) ?
    C4 C5 C6 C1 . . . . 1.31(19) ?
    F2 C5 C6 C7 . . . . 4.12(18) ?
    C4 C5 C6 C7 . . . . -177.92(12) ?
    F1 C1 C6 C5 . . . . -179.87(12) ?
    C2 C1 C6 C5 . . . . -1.92(19) ?
    F1 C1 C6 C7 . . . . -0.65(19) ?
    C2 C1 C6 C7 . . . . 177.31(12) ?
    C5 C6 C7 O3 . . . . -147.25(13) ?
    C1 C6 C7 O3 . . . . 33.57(18) ?
    C5 C6 C7 O2 . . . . 33.33(17) ?
    C1 C6 C7 O2 . . . . -145.84(13) ?
loop_
    _geom_hbond_atom_site_label_D
    _geom_hbond_atom_site_label_H
    _geom_hbond_atom_site_label_A
    _geom_hbond_site_symmetry_A
    _geom_hbond_distance_DH
    _geom_hbond_distance_HA
    _geom_hbond_distance_DA
    _geom_hbond_angle_DHA
    _geom_hbond_publ_flag
    O2 H1O2 O3 3_656 0.95(4) 1.68(4) 2.6318(14) 174(4) yes
    C3 H3 F2 4_465 0.98(2) 2.54(2) 3.3428(16) 138.7(16) yes