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2-Methylpiperidinium hydrogen bis(pchlorobenzoate), C6HIaN +C14H9C1204, Mr = 412.29. Form 1, monoclinic, C2/c, a = 21.746 (3), b = 8.404 (3), c = 23-777 (3) A, /3= 110.84 (1) °, V = 4061 (2) A 3, Z = 8, D~ = 1-349 Mg m -3, /z = 3-13 mm -~, F(000)= 1728, final R=0.055 for 2363 reflections with IFol larger than 3o(Fo); Form 2, monoclinic, C2/c, a = 19.084 (4), b = 9.689(3), c = 11.465 (4)A, /3=90.56(2) °, V= 2120 (1) A3, Z = 4 , D~ = 1.292 Mg m3, /~ = 3.00 mm~, F(000) = 864, final R = 0-081 for 975 reflections with IFol larger than 3o(Fo). Cu Ket, h = 1-54178 A, T = 295 K. In the crystal of Form 1 the 2-methylpiperidinium cation and hydrogen bis(p-chlorobenzoate) anion occupy general positions. The anion is composed of neutral and ionized benzoate residues which are held together through an asymmetric O--H.. .O hydrogen bond of O...O 2.469 (3)A. In Form 2 the cation is disordered around a twofold axis, and the benzoate residues in the anion are linked by a short crystallographically symmetric O---H..-O hydrogen bond of O...O 2-437 (9) A. Introduction. As part of a study on short hydrogen bonds (Misaki, Kashino & Haisa, 1986, 1989a,b), the relationship between the symmetry of the hydrogen bond and the crystal structure is examined in the dimorphic structures of 2-methylpiperidinium hydrogen bis(p-chlorobenzoate). Experimental. Experimental details are listed in Table 1. Crystals of Forms 1 and 2 were grown in the same batch by slow evaporation from a xylene solution. The intensities were collected on a Rigaku AFC-5 four-circle diffractometer equipped with a rotating anode with to--20-scan method [scan speed 4 ° m i n -! in to, scan range (1.2+0.15tan0) ° in to, Ni-filtered C u K a ( a = 1.54178A) at 40kV, 200 mA]. Background was measured for 4 s on either side of peak. Three standard reflections were recorded after every 97 reflections. Lorentz and polarization corrections were applied, but no absorp* Part III: Misaki, Kashino & Haisa (1989b). I" To whom correspondence should be addressed. 0108-2701/89/101574-04503.00 tion correction. Non-zero reflections within 28max were used for the refinements. The structure of Form 1 was solved by MULTAN78, and refined by block-diagonal leastsquares method. The value minimized was Y.w(iFolIFcl) 2, where w = 1/[o(Fo) 2 0"03671Fol + 0.00161Fo12]. All the H atoms were located on a difference Fourier map. The non-H atoms were refined anisotropically and the H atoms isotropically. Correction for the secondary-extinction effect was applied for the strongest five reflections [Ico= = Io(1 + 8-11 x 10-5Ic)]. The structure of Form 2 was solved by MULTAN78. The non-H atoms of the cation were found by successive Fourier and difference syntheses. The cation was disordered around a twofold axis. The structure was refined by full-matrix least-squares method. All the non-H atoms were refined anisotropically. The value minimized was Ew(igol-Igcl) 2 with w = 1/o(Fo) 2. The conformation, bond lengths and bond angles involving the non-H atoms, of the cation were restrained to the same values as those in Form 1. The positional parameters of the H atoms attached to the cation ring were calculated by assuming a usual geometry and were fixed; their thermal parameters were assumed to be identical with B~q of the non-H atoms to which they were attached. The H atoms of the methyl group were not included in the refinement. The positional parameters of the H atoms attached to the phenylene ring were calculated by assuming a usual geometry and were fixed; only their thermal parameters were refined isotropicaUy. The H atom participating in the O..-H..-O hydrogen |
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