5-Iodouracil: structure of a reflection twin
Lutz, Martin; de Klein, Thomas J. S.; Huijben, Jeroen; Acta Crystallographica Section C 71 (2015) 912–915; doi:10.1107/S2053229615017167

data_2020129
_publ_section_title
;
 5-Iodouracil: structure of a reflection twin
;
_journal_coeditor_code           SK3601
_journal_issue                   10
_journal_name_full               'Acta Crystallographica Section C'
_journal_page_first              912
_journal_page_last               915
_journal_paper_doi               10.1107/S2053229615017167
_journal_volume                  71
_journal_year                    2015
_chemical_formula_iupac          'C4 H3 I N2 O2'
_chemical_formula_moiety         'C4 H3 I N2 O2'
_chemical_formula_sum            'C4 H3 I N2 O2'
_chemical_formula_weight         237.98
_chemical_name_common            5-Iodouracil
_chemical_name_systematic
;
5-Iodo-1<i>H</i>-pyrimidine-2,4-dione
;
_space_group_crystal_system      monoclinic
_space_group_IT_number           4
_space_group_name_Hall           'P 2yb'
_space_group_name_H-M_alt        'P 1 21 1'
_symmetry_space_group_name_Hall  'P 2yb'
_symmetry_space_group_name_H-M   'P 1 21 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     heavy
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-2014/7
_cell_angle_alpha                90
_cell_angle_beta                 92.721(3)
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   4.8929(3)
_cell_length_b                   4.4195(2)
_cell_length_c                   14.1348(7)
_cell_measurement_reflns_used    4649
_cell_measurement_temperature    150(2)
_cell_measurement_theta_max      30.02
_cell_measurement_theta_min      4.17
_cell_volume                     305.31(3)
_computing_cell_refinement
;
PEAKREF (Schreurs, 2013)
;
_computing_data_collection
;
APEX2 (Bruker, 2007)
;
_computing_data_reduction
;
EVAL15 (Schreurs <i>et al.</i>,  2010) and TWINABS (Sheldrick,
2012)
;
_computing_molecular_graphics
;
PLATON (Spek, 2009)
;
_computing_publication_material
;
SHELXL2014 (Sheldrick, 2015)
;
_computing_structure_refinement
;
SHELXL2014 (Sheldrick, 2015)
;
_computing_structure_solution
;
coordinates from the literature (Sternglanz <i>et al.</i>,  1975)
;
_diffrn_ambient_temperature      150(2)
_diffrn_measured_fraction_theta_full 0.998
_diffrn_measured_fraction_theta_max 0.995
_diffrn_measurement_device_type  'Bruker Kappa APEXII'
_diffrn_measurement_method       '\f and \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0226
_diffrn_reflns_limit_h_max       6
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       6
_diffrn_reflns_limit_k_min       -6
_diffrn_reflns_limit_l_max       19
_diffrn_reflns_limit_l_min       -19
_diffrn_reflns_number            13501
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         30.087
_diffrn_reflns_theta_min         2.885
_exptl_absorpt_coefficient_mu    5.163
_exptl_absorpt_correction_T_max  0.4326
_exptl_absorpt_correction_T_min  0.3129
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
(TWINABS; Sheldrick, 2012)
;
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    2.589
_exptl_crystal_description       needle
_exptl_crystal_F_000             220
_exptl_crystal_size_max          0.24
_exptl_crystal_size_mid          0.05
_exptl_crystal_size_min          0.04
_refine_diff_density_max         0.928
_refine_diff_density_min         -0.541
_refine_ls_abs_structure_details
;
Flack <i>x</i> determined using 728 quotients [(I+)-(I-)]/[(I+)+(I-)]
(Parsons <i>et al.</i>,  2013)
;
_refine_ls_abs_structure_Flack   -0.021(12)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.087
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     83
_refine_ls_number_reflns         3122
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      1.087
_refine_ls_R_factor_all          0.0211
_refine_ls_R_factor_gt           0.0189
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0254P)^2^+0.0706P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0449
_refine_ls_wR_factor_ref         0.0455
_reflns_number_gt                2932
_reflns_number_total             3122
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            sk3601sup1.cif
_cod_data_source_block           I
_cod_database_code               2020129
_cod_database_fobs_code          2020129
_shelx_hkl_checksum              79092
_shelx_res_checksum              31920