Received 12 February 2004
Accepted 23 February 2004
Online 20 March 2004
(Cyclohexylideneamino)oxyacetic acid and [chloro(phenyl)methyleneamino]oxyacetic acid: hydrogen-bonded R(8) dimers and aromatic - stacking interactions
aSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland,bDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and cInstituto de Química, Departamento de Química Inorgânica, Universidade Federal do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil
Correspondence e-mail: firstname.lastname@example.org
Persulfate oxidation of iminooxyacetic acids, R(R')C=NOCH2COOH, provides a useful route to iminyl radicals (Forrester et al., 1979). The subsequent reactions of the iminyl radicals thus generated depend greatly on the substituents, and important species including nitrogen-containing heterocycles can result. We report here the molecular and supramolecular structures of two representative examples of such
(cyclohexylideneamino)oxyacetic acid, (I
), and [chloro(phenyl)methyleneamino]oxyacetic acid, (II
In both (I) and (II) (Figs. 1 and 2), the C-O distances in the carboxy groups (Tables 1 and 3) are consistent with the fully ordered locations of the carboxy H atoms as deduced from difference maps. In the side chains of (I) and (II), the corresponding distances show very similar values, apart from the O3-N4 distances, which are significantly different; for comparison, the mean value for the -O-N= bond in oximes is 1.416 Å (Allen et al., 1987). The other distances are typical for bonds of their types.
The conformations of the side chains both exhibit near-planar fragments, viz. O1-C1-C2-O3 and C2-O3-N4-Cn [n = 11 in (I) and n = 5 in (II); see Figs. 1 and 2], but while the intervening C1-C2-O3-N4 torsion angles have similar magnitudes in (I) and (II), they have opposite signs, and it is this difference that determines the different overall conformations of these two molecules. For the cyclohexylidene ring in (I), the ring-puckering parameters (Cremer & Pople, 1975) corresponding to the atom sequence C11-C16 [ = 174.0 (2)° and = 12 (2)°] indicate a conformation close to the chair form (Evans & Boeyens, 1989), despite the planarity at atom C11.
In the structures of both (I) and (II), the molecules are linked into centrosymmetric R22(8) (Bernstein et al., 1995) dimers (Figs. 3 and 4) by paired O-HO hydrogen bonds, which are fairly short and effectively linear (Tables 2 and 4). In each structure, the reference molecule has been selected so that the hydrogen-bonded dimer in which this molecule participates is centred at (, , ). In the structure of (I), there are no further direction-specific interactions between the molecules, but in (II), the R22(8) dimers are weakly linked into chains by a single aromatic - stacking interaction. The aryl rings in the molecules at (x, y, z) and (2 - x, 1 - y, 2 - z) are parallel, with an interplanar spacing of 3.422 (2) Å; the ring-centroid separation is 3.856 (2) Å, corresponding to a centroid offset of 1.777 (2) Å. The molecules at (x, y, z) and (2 - x, 1 - y, 2 - z) are components of hydrogen-bonded dimers centred at (, , ) and (1, , 1), respectively, and propagation by inversion of the two intermolecular interactions generates a chain running parallel to the  direction (Fig. 5).
In neither (I) nor (II) do atoms O3 and N4 act as acceptors of C-HX (X = O or N) hydrogen bonds; there are no intermolecular HX contact distances involving O3 or N4 that are less than 2.60 Å in (I), and none of less than 2.70 Å in (II).
| Figure 1 |
The molecule of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
| Figure 2 |
The molecule of (II), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
| Figure 3 |
Part of the crystal structure of (I), showing the formation of an R22(8) dimer centred at (, , ). For clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*) are at the symmetry position (1 - x, 1 - y, 1 - z).
| Figure 4 |
Part of the crystal structure of (II), showing the formation of an R22(8) dimer centred at (, , ). For clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*) are at the symmetry position (1 - x, 1 - y, 1 - z).
| Figure 5 |
A stereoview of part of the crystal structure of (II), showing the formation of a -stacked  chain of hydrogen-bonded dimers. For clarity, H atoms bonded to C atoms have been omitted.
Benzhydroxamoyl chloride, Cl(Ph)C=NOH, was prepared from H(Ph)C=NOH according to the method of Baruah et al. (1988). Compounds (I) and (II) were prepared by reaction of chloroacetic acid with either cyclohexanone oxime [for (I)] or Cl(Ph)C=NOH [for (II)], using the following modification of the procedure of Forrester et al. (1979). A solution of the oxime (0.10 mol), chloroacetic acid (0.20 mol) and sodium hydroxide (0.40 mol) in a mixture of water (100 ml) and ethanol (50 ml) was heated under reflux overnight. The cooled solution was poured on to ice and acidified with dilute hydrochloric acid. The precipitate was collected, washed with water and dissolved in NaHCO3 solution (100 ml of 1 mol dm-3). This solution was extracted with diethyl ether and acidified with dilute hydrochloric acid. The resulting solid was collected, washed with water and recrystallized from ethanol, yielding crystals suitable for single-crystal X-ray diffraction; m.p: (I) 365-367 K, (II) 381-383 K.
Nonius KappaCCD diffractometer
scans, and scans with offsets
Absorption correction: multi-scan (SORTAV; Blessing, 1995, 1997) Tmin = 0.922, Tmax = 0.981
3988 measured reflections
2133 independent reflections
1980 reflections with I > 2(I)
Rint = 0.031
max = 27.4°
h = -8 8
k = -9 9
l = -13 13
|C5-Cl1 ||1.738 (2) |
|C1-O1 ||1.311 (2) |
|C1-O2 ||1.226 (2) |
|O3-N4 ||1.405 (2) |
|N4-C5 ||1.273 (2) |
|O1-C1-O2 ||124.64 (16) |
|O1-C1-C2 ||112.36 (14) |
|O2-C1-C2 ||123.00 (16) |
|C2-O3-N4 ||107.45 (13) |
|O3-N4-C5 ||113.12 (14) |
|O1-C1-C2-O3 ||-171.61 (14) |
|C1-C2-O3-N4 ||75.87 (17) |
|C2-O3-N4-C5 ||-173.61 (14) |
|D-HA ||D-H ||HA ||DA ||D-HA |
|O1-H1O2i ||0.84 ||1.79 ||2.6329 (17) ||176 |
|Symmetry code: (i) 1-x,1-y,1-z. |
Crystals of (I) and (II) are triclinic; space group was selected for each and confirmed in both cases by the subsequent analyses. All H atoms were located from difference maps and then treated as riding atoms, with C-H distances of 0.95 (aromatic) or 0.99 Å (CH2), and O-H distances of 0.84 Å.
For both compounds, data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).
Supplementary data for this paper are available from the IUCr electronic archives (Reference: GG1209 ). Services for accessing these data are described at the back of the journal.
X-ray data were collected at the EPSRC X-ray Crystallographic Service, University of Southampton, England; the authors thank the staff for all their help and advice. JNL thanks NCR Self-Service, Dundee, for grants that have provided computing facilities for this work. JLW thanks CNPq and FAPERJ for financial support.
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