data_2203174
loop_
_publ_author_name
'Dilovan S. Cati'
'Helen Stoeckli-Evans'
_publ_section_title
;
An orthorhombic polymorph of
N,N'-bis(2-pyridylmethyl)pyrazine-2,3-dicarboxamide
;
_journal_issue                 2
_journal_name_full             'Acta Crystallographica, Section E'
_journal_page_first            o210
_journal_page_last             o212
_journal_volume                60
_journal_year                  2004
_chemical_formula_iupac        'C18 H16 N6 O2'
_chemical_formula_moiety       'C18 H16 N6 O2'
_chemical_formula_structural   ?
_chemical_formula_sum          'C18 H16 N6 O2'
_chemical_formula_weight       348.37
_chemical_melting_point        ?
_chemical_name_common          ?
_chemical_name_systematic      ' ?'
_symmetry_cell_setting         Orthorhombic
_symmetry_space_group_name_Hall '-P 2ac 2ab'
_symmetry_space_group_name_H-M 'P b c a'
_atom_sites_solution_hydrogens difmap
_atom_sites_solution_primary   direct
_atom_sites_solution_secondary difmap
_cell_angle_alpha              90
_cell_angle_beta               90
_cell_angle_gamma              90
_cell_formula_units_Z          8
_cell_length_a                 8.5131(6)
_cell_length_b                 31.862(2)
_cell_length_c                 12.1757(6)
_cell_measurement_reflns_used  15934
_cell_measurement_temperature  153
_cell_measurement_theta_max    25.61
_cell_measurement_theta_min    1.28
_cell_volume                   3302.6(4)
_computing_cell_refinement     X-AREA
_computing_data_collection     'X-AREA (Stoe & Cie, 2003)'
_computing_data_reduction      'X-RED32 Stoe & Cie, 2003)'
_computing_molecular_graphics  'PLATON  (Spek, 1990)'
_computing_publication_material SHELXL97
_computing_structure_refinement 'SHELXL97 (Sheldrick, 1997)'
_computing_structure_solution  'SHELXS97 (Sheldrick, 1990)'
_diffrn_ambient_temperature    153
_diffrn_detector_area_resol_mean ?
_diffrn_measured_fraction_theta_full 0.982
_diffrn_measured_fraction_theta_max 0.982
_diffrn_measurement_device_type 'Stoe IPDS-II'
_diffrn_measurement_method     \w
_diffrn_radiation_monochromator graphite
_diffrn_radiation_source       'fine-focus sealed tube'
_diffrn_radiation_type         MoK\a
_diffrn_radiation_wavelength   0.71073
_diffrn_reflns_av_R_equivalents 0.0450
_diffrn_reflns_av_sigmaI/netI  0.0269
_diffrn_reflns_limit_h_max     7
_diffrn_reflns_limit_h_min     -10
_diffrn_reflns_limit_k_max     38
_diffrn_reflns_limit_k_min     -38
_diffrn_reflns_limit_l_max     14
_diffrn_reflns_limit_l_min     -14
_diffrn_reflns_number          18389
_diffrn_reflns_reduction_process ' ?'
_diffrn_reflns_theta_full      25.53
_diffrn_reflns_theta_max       25.53
_diffrn_reflns_theta_min       1.28
_diffrn_standards_decay_%      0
_diffrn_standards_interval_count ?
_diffrn_standards_interval_time 0
_diffrn_standards_number       0
_exptl_absorpt_coefficient_mu  0.097
_exptl_absorpt_correction_T_max ?
_exptl_absorpt_correction_T_min ?
_exptl_absorpt_correction_type none
_exptl_absorpt_process_details ?
_exptl_crystal_colour          colourless
_exptl_crystal_density_diffrn  1.401
_exptl_crystal_density_meas    ?
_exptl_crystal_density_method  'Not Measured'
_exptl_crystal_description     block
_exptl_crystal_F_000           1456
_exptl_crystal_size_max        0.500
_exptl_crystal_size_mid        0.500
_exptl_crystal_size_min        0.400
_exptl_crystal_size_rad        ?
_refine_diff_density_max       0.171
_refine_diff_density_min       -0.140
_refine_ls_extinction_coef     0.0087(9)
_refine_ls_extinction_expression FC^*^=KFC[1+0.001XFC^2^\L^3^/SIN(2\Q)]^-1/4^
_refine_ls_extinction_method   shelxl97
_refine_ls_goodness_of_fit_ref 1.033
_refine_ls_hydrogen_treatment  refall
_refine_ls_matrix_type         full
_refine_ls_number_constraints  ?
_refine_ls_number_parameters   300
_refine_ls_number_reflns       3034
_refine_ls_number_restraints   0
_refine_ls_restrained_S_all    1.033
_refine_ls_R_factor_all        0.0437
_refine_ls_R_factor_gt         0.0315
_refine_ls_shift/su_max        0.001
_refine_ls_shift/su_mean       0.001
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0478P)^2^+0.1168P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme    calc
_refine_ls_wR_factor_gt        0.0744
_refine_ls_wR_factor_ref       0.0785
_reflns_number_gt              2456
_reflns_number_total           3034
_reflns_threshold_expression   I>2\s(I)
loop_
_symmetry_equiv_pos_as_xyz
x,y,z
1/2-x,-y,1/2+z
1/2+x,1/2-y,-z
-x,1/2+y,1/2-z
-x,-y,-z
1/2+x,y,1/2-z
1/2-x,1/2+y,z
x,1/2-y,1/2+z
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
O1 0.0301(5) 0.0389(5) 0.0304(5) 0.0065(4) -0.0037(4) -0.0014(4)
O2 0.0300(5) 0.0349(4) 0.0336(5) -0.0025(4) 0.0040(4) 0.0027(4)
N1 0.0278(6) 0.0318(5) 0.0352(6) 0.0033(4) -0.0035(5) -0.0004(4)
N2 0.0395(7) 0.0370(6) 0.0275(6) 0.0030(5) -0.0036(5) -0.0007(4)
N3 0.0264(6) 0.0393(6) 0.0297(6) 0.0019(5) -0.0001(5) -0.0068(4)
N4 0.0409(7) 0.0341(5) 0.0428(7) -0.0011(5) 0.0080(6) -0.0040(5)
N5 0.0251(6) 0.0287(5) 0.0303(6) 0.0034(4) 0.0033(5) -0.0007(4)
N6 0.0266(6) 0.0317(5) 0.0290(6) 0.0011(4) 0.0016(5) -0.0004(4)
C1 0.0256(6) 0.0240(5) 0.0297(7) -0.0005(4) 0.0002(5) 0.0010(4)
C2 0.0301(7) 0.0250(5) 0.0265(7) -0.0010(5) -0.0005(5) 0.0008(4)
C3 0.0404(8) 0.0402(7) 0.0311(8) 0.0030(6) -0.0094(7) 0.0007(5)
C4 0.0332(8) 0.0379(7) 0.0378(8) 0.0047(6) -0.0093(6) 0.0007(5)
C5 0.0255(6) 0.0255(5) 0.0285(7) -0.0026(5) 0.0006(5) 0.0003(4)
C6 0.0332(7) 0.0445(7) 0.0257(7) -0.0062(6) 0.0051(6) -0.0047(5)
C7 0.0262(7) 0.0358(6) 0.0300(7) 0.0060(5) -0.0004(6) -0.0042(5)
C8 0.0429(9) 0.0441(7) 0.0329(8) 0.0091(6) -0.0017(7) -0.0075(6)
C9 0.0636(11) 0.0402(7) 0.0483(10) 0.0137(7) -0.0163(9) -0.0153(7)
C10 0.0543(10) 0.0300(7) 0.0661(11) 0.0038(6) -0.0142(9) -0.0062(7)
C11 0.0486(9) 0.0338(7) 0.0610(11) -0.0017(6) 0.0050(8) 0.0003(7)
C12 0.0301(7) 0.0307(6) 0.0207(6) 0.0022(5) 0.0023(5) -0.0028(4)
C13 0.0296(7) 0.0324(6) 0.0272(7) 0.0050(5) 0.0003(5) 0.0001(5)
C14 0.0235(6) 0.0298(6) 0.0246(6) 0.0038(5) -0.0018(5) 0.0021(4)
C15 0.0336(7) 0.0295(6) 0.0390(8) -0.0005(5) 0.0051(6) -0.0002(5)
C16 0.0301(7) 0.0424(7) 0.0356(8) -0.0026(6) 0.0082(6) 0.0040(5)
C17 0.0264(7) 0.0409(6) 0.0259(7) 0.0066(5) -0.0001(5) -0.0018(5)
C18 0.0287(7) 0.0329(6) 0.0299(7) 0.0009(5) 0.0006(6) -0.0040(5)
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
_atom_site_thermal_displace_type
_atom_site_calc_flag
_atom_site_refinement_flags
_atom_site_occupancy
_atom_site_type_symbol
O1 0.48512(11) 0.11895(3) 0.67140(7) 0.0331(3) Uani . . 1.000 O
O2 0.66545(11) 0.11705(3) 0.44520(8) 0.0328(3) Uani . . 1.000 O
N1 0.15489(13) 0.14818(3) 0.51065(9) 0.0316(3) Uani . . 1.000 N
N2 0.33433(14) 0.11150(3) 0.34397(9) 0.0347(4) Uani . . 1.000 N
N3 0.27131(14) 0.15786(3) 0.71466(9) 0.0318(3) Uani . . 1.000 N
N4 0.47626(15) 0.22332(3) 0.76079(11) 0.0393(4) Uani . . 1.000 N
N5 0.55206(13) 0.05570(3) 0.49747(9) 0.0280(3) Uani . . 1.000 N
N6 0.76169(13) -0.02198(3) 0.42001(9) 0.0291(3) Uani . . 1.000 N
C1 0.29800(15) 0.13237(3) 0.53071(10) 0.0264(3) Uani . . 1.000 C
C2 0.38618(15) 0.11353(3) 0.44781(10) 0.0272(4) Uani . . 1.000 C
C3 0.19148(18) 0.12732(4) 0.32535(12) 0.0372(4) Uani . . 1.000 C
C4 0.10223(17) 0.14503(4) 0.40816(12) 0.0363(4) Uani . . 1.000 C
C5 0.36065(15) 0.13594(3) 0.64586(10) 0.0265(3) Uani . . 1.000 C
C6 0.31589(17) 0.16569(4) 0.82746(11) 0.0345(4) Uani . . 1.000 C
C7 0.39115(15) 0.20801(4) 0.84357(11) 0.0307(4) Uani . . 1.000 C
C8 0.37539(19) 0.22895(4) 0.94271(12) 0.0400(5) Uani . . 1.000 C
C9 0.4489(2) 0.26717(4) 0.95676(15) 0.0507(5) Uani . . 1.000 C
C10 0.5344(2) 0.28365(4) 0.87083(15) 0.0501(5) Uani . . 1.000 C
C11 0.5456(2) 0.26067(4) 0.77576(16) 0.0478(5) Uani . . 1.000 C
C12 0.54885(15) 0.09581(4) 0.46547(10) 0.0272(4) Uani . . 1.000 C
C13 0.70008(16) 0.03740(4) 0.53576(11) 0.0297(4) Uani . . 1.000 C
C14 0.79668(15) 0.01783(3) 0.44534(10) 0.0260(3) Uani . . 1.000 C
C15 0.91649(16) 0.03958(4) 0.39401(11) 0.0340(4) Uani . . 1.000 C
C16 1.00657(17) 0.01966(4) 0.31531(12) 0.0360(4) Uani . . 1.000 C
C17 0.97450(16) -0.02165(4) 0.29072(11) 0.0311(4) Uani . . 1.000 C
C18 0.85102(15) -0.04081(4) 0.34334(11) 0.0305(4) Uani . . 1.000 C
H3 0.157(2) 0.1258(5) 0.2487(16) 0.051(4) Uiso . . 1.000 H
H3N 0.182(2) 0.1687(5) 0.6879(14) 0.051(5) Uiso . . 1.000 H
H4 -0.002(2) 0.1566(5) 0.3932(13) 0.044(4) Uiso . . 1.000 H
H5N 0.456(2) 0.0453(4) 0.5211(13) 0.042(4) Uiso . . 1.000 H
H6A 0.221(2) 0.1630(4) 0.8713(13) 0.046(4) Uiso . . 1.000 H
H6B 0.3944(19) 0.1431(4) 0.8504(12) 0.038(4) Uiso . . 1.000 H
H8 0.313(2) 0.2173(5) 0.9989(15) 0.049(5) Uiso . . 1.000 H
H9 0.442(2) 0.2812(6) 1.0290(16) 0.064(5) Uiso . . 1.000 H
H10 0.592(2) 0.3114(5) 0.8761(14) 0.058(5) Uiso . . 1.000 H
H11 0.608(2) 0.2717(5) 0.7115(15) 0.058(5) Uiso . . 1.000 H
H13A 0.7658(19) 0.0597(4) 0.5710(12) 0.035(4) Uiso . . 1.000 H
H13B 0.6723(17) 0.0151(4) 0.5890(12) 0.029(3) Uiso . . 1.000 H
H15 0.9327(19) 0.0685(5) 0.4141(12) 0.038(4) Uiso . . 1.000 H
H16 1.093(2) 0.0350(5) 0.2808(14) 0.048(4) Uiso . . 1.000 H
H17 1.0368(19) -0.0376(4) 0.2376(13) 0.037(4) Uiso . . 1.000 H
H18 0.8215(18) -0.0698(5) 0.3263(12) 0.038(4) Uiso . . 1.000 H
loop_
_atom_type_symbol
_atom_type_description
_atom_type_scat_dispersion_real
_atom_type_scat_dispersion_imag
_atom_type_scat_source
O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
N N 0.0061 0.0033 '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'
C C 0.0033 0.0016 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
loop_
_diffrn_standard_refln_index_h
_diffrn_standard_refln_index_k
_diffrn_standard_refln_index_l
? ? ?
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_2
_geom_angle_site_symmetry_3
_geom_angle
_geom_angle_publ_flag
C1 N1 C4 . . . 116.68(11) yes
C2 N2 C3 . . . 116.20(11) yes
C5 N3 C6 . . . 122.59(11) yes
C7 N4 C11 . . . 117.46(13) yes
C12 N5 C13 . . . 119.41(11) yes
C14 N6 C18 . . . 117.17(11) yes
C6 N3 H3N . . . 120.1(11) no
C5 N3 H3N . . . 117.3(11) no
C13 N5 H5N . . . 121.2(9) no
C12 N5 H5N . . . 114.5(9) no
C2 C1 C5 . . . 121.10(11) no
N1 C1 C5 . . . 117.61(11) yes
N1 C1 C2 . . . 121.28(11) yes
N2 C2 C12 . . . 114.71(11) yes
C1 C2 C12 . . . 123.47(11) no
N2 C2 C1 . . . 121.76(11) yes
N2 C3 C4 . . . 122.04(13) yes
N1 C4 C3 . . . 121.99(13) yes
O1 C5 N3 . . . 124.38(12) yes
O1 C5 C1 . . . 120.52(11) yes
N3 C5 C1 . . . 115.09(11) yes
N3 C6 C7 . . . 112.94(11) yes
N4 C7 C8 . . . 122.33(12) yes
C6 C7 C8 . . . 120.23(12) no
N4 C7 C6 . . . 117.40(12) yes
C7 C8 C9 . . . 119.28(14) no
C8 C9 C10 . . . 118.79(15) no
C9 C10 C11 . . . 118.26(13) no
N4 C11 C10 . . . 123.87(16) yes
O2 C12 C2 . . . 120.46(11) yes
N5 C12 C2 . . . 114.68(11) yes
O2 C12 N5 . . . 124.74(12) yes
N5 C13 C14 . . . 113.65(11) yes
N6 C14 C13 . . . 115.99(11) yes
N6 C14 C15 . . . 122.34(11) yes
C13 C14 C15 . . . 121.65(10) no
C14 C15 C16 . . . 119.52(12) no
C15 C16 C17 . . . 118.67(13) no
C16 C17 C18 . . . 118.35(12) no
N6 C18 C17 . . . 123.91(12) yes
N2 C3 H3 . . . 114.6(10) no
C4 C3 H3 . . . 123.4(10) no
N1 C4 H4 . . . 116.9(9) no
C3 C4 H4 . . . 121.1(9) no
N3 C6 H6A . . . 106.8(10) no
N3 C6 H6B . . . 108.1(8) no
C7 C6 H6A . . . 111.2(8) no
C7 C6 H6B . . . 108.5(8) no
H6A C6 H6B . . . 109.4(12) no
C7 C8 H8 . . . 119.8(10) no
C9 C8 H8 . . . 120.9(10) no
C8 C9 H9 . . . 118.9(11) no
C10 C9 H9 . . . 122.3(11) no
C9 C10 H10 . . . 122.7(10) no
C11 C10 H10 . . . 119.0(10) no
N4 C11 H11 . . . 115.8(10) no
C10 C11 H11 . . . 120.3(10) no
N5 C13 H13A . . . 109.6(8) no
N5 C13 H13B . . . 106.8(8) no
C14 C13 H13A . . . 107.5(9) no
C14 C13 H13B . . . 108.1(8) no
H13A C13 H13B . . . 111.2(12) no
C14 C15 H15 . . . 118.1(9) no
C16 C15 H15 . . . 122.4(9) no
C15 C16 H16 . . . 119.1(10) no
C17 C16 H16 . . . 122.2(10) no
C16 C17 H17 . . . 122.2(8) no
C18 C17 H17 . . . 119.5(8) no
N6 C18 H18 . . . 115.0(9) no
C17 C18 H18 . . . 121.1(9) no
loop_
_geom_bond_atom_site_label_1
_geom_bond_atom_site_label_2
_geom_bond_site_symmetry_1
_geom_bond_site_symmetry_2
_geom_bond_distance
_geom_bond_publ_flag
O1 C5 . . 1.2299(15) yes
O2 C12 . . 1.2265(16) yes
N1 C1 . . 1.3408(16) yes
N1 C4 . . 1.3298(18) yes
N2 C2 . . 1.3407(17) yes
N2 C3 . . 1.3358(19) yes
N3 C5 . . 1.3297(16) yes
N3 C6 . . 1.4466(17) yes
N4 C7 . . 1.3337(18) yes
N4 C11 . . 1.3409(17) yes
N5 C12 . . 1.3363(16) yes
N5 C13 . . 1.4647(17) yes
N6 C14 . . 1.3389(14) yes
N6 C18 . . 1.3453(17) yes
N3 H3N . . 0.896(17) no
N5 H5N . . 0.928(16) no
C1 C2 . . 1.3938(17) no
C1 C5 . . 1.5044(17) no
C2 C12 . . 1.5109(18) no
C3 C4 . . 1.383(2) no
C6 C7 . . 1.5057(18) no
C7 C8 . . 1.3857(19) no
C8 C9 . . 1.3798(19) no
C9 C10 . . 1.379(2) no
C10 C11 . . 1.373(2) no
C13 C14 . . 1.5090(18) no
C14 C15 . . 1.3824(18) no
C15 C16 . . 1.382(2) no
C16 C17 . . 1.3772(18) no
C17 C18 . . 1.3741(19) no
C3 H3 . . 0.980(19) no
C4 H4 . . 0.978(17) no
C6 H6A . . 0.972(17) no
C6 H6B . . 1.021(15) no
C8 H8 . . 0.942(18) no
C9 H9 . . 0.99(2) no
C10 H10 . . 1.013(16) no
C11 H11 . . 1.009(18) no
C13 H13A . . 1.001(14) no
C13 H13B . . 0.990(14) no
C15 H15 . . 0.963(16) no
C16 H16 . . 0.978(17) no
C17 H17 . . 0.979(15) no
C18 H18 . . 0.980(16) no
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
N3 H3N N1 . 0.896(17) 2.267(17) 2.6921(16) 108.7(13) yes
N3 H3N N4 6_456 0.896(17) 2.547(17) 3.2785(16) 139.2(14) yes
N5 H5N N6 5_656 0.928(16) 2.122(16) 3.0493(16) 178.3(13) yes
C3 H3 O2 6_455 0.980(19) 2.378(19) 3.3178(18) 160.5(14) yes
C6 H6A O1 6_456 0.972(17) 2.505(16) 3.1855(17) 127.0(11) yes
C6 H6B O1 . 1.021(15) 2.437(15) 2.8114(16) 100.7(9) yes
C10 H10 O2 8_555 1.013(16) 2.509(16) 3.4749(17) 159.2(13) yes
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
C4 N1 C1 C2 . . . . -0.16(16) no
C4 N1 C1 C5 . . . . 179.44(10) no
C1 N1 C4 C3 . . . . -1.57(18) no
C3 N2 C2 C1 . . . . -2.09(16) no
C3 N2 C2 C12 . . . . -179.31(10) no
C2 N2 C3 C4 . . . . 0.37(18) no
C6 N3 C5 O1 . . . . 2.93(18) no
C6 N3 C5 C1 . . . . -177.86(10) no
C5 N3 C6 C7 . . . . 97.34(13) no
C11 N4 C7 C6 . . . . -178.86(13) no
C11 N4 C7 C8 . . . . -1.1(2) no
C7 N4 C11 C10 . . . . 0.3(2) no
C13 N5 C12 O2 . . . . 14.69(19) no
C13 N5 C12 C2 . . . . -169.22(11) no
C12 N5 C13 C14 . . . . -89.76(13) no
C18 N6 C14 C13 . . . . -176.90(11) no
C18 N6 C14 C15 . . . . 1.56(18) no
C14 N6 C18 C17 . . . . 0.15(19) no
N1 C1 C2 N2 . . . . 2.08(16) no
C5 C1 C2 C12 . . . . -0.54(16) no
N1 C1 C2 C12 . . . . 179.05(10) no
C5 C1 C2 N2 . . . . -177.51(10) no
C2 C1 C5 O1 . . . . -6.56(16) no
C2 C1 C5 N3 . . . . 174.20(10) no
N1 C1 C5 O1 . . . . 173.85(10) no
N1 C1 C5 N3 . . . . -5.40(14) no
C1 C2 C12 O2 . . . . -95.14(15) no
N2 C2 C12 O2 . . . . 82.03(14) no
N2 C2 C12 N5 . . . . -94.24(13) no
C1 C2 C12 N5 . . . . 88.60(14) no
N2 C3 C4 N1 . . . . 1.5(2) no
N3 C6 C7 N4 . . . . -32.27(17) no
N3 C6 C7 C8 . . . . 149.91(13) no
C6 C7 C8 C9 . . . . 178.23(14) no
N4 C7 C8 C9 . . . . 0.5(2) no
C7 C8 C9 C10 . . . . 0.8(2) no
C8 C9 C10 C11 . . . . -1.6(2) no
C9 C10 C11 N4 . . . . 1.0(3) no
N5 C13 C14 N6 . . . . -85.59(13) no
N5 C13 C14 C15 . . . . 95.95(14) no
C13 C14 C15 C16 . . . . 176.92(12) no
N6 C14 C15 C16 . . . . -1.5(2) no
C14 C15 C16 C17 . . . . -0.4(2) no
C15 C16 C17 C18 . . . . 1.9(2) no
C16 C17 C18 N6 . . . . -1.9(2) no