Nitration of 3-hydroxyacetophenone gives 2,6-dinitro-3-hydroxyacetophenone, C8H6N206, in which the nitro groups have entered the sterically least favourable positions in the aromatic nucleus. None of the expected
substitution in the 4-position was observed. The two nitro groups flanking the carbonyl side chain are different in that one is in the plane of the aryl ring but the other
is twisted well out of the plane

Cristiano, Maria Lurdes Santos

Johnstone, Robert A. W.

Pratt, M. J.

Acta Crystallographica Section C Crystal Structure Communications

Sapientia

C. L. L. CHAI AND D. C. R. HOCKLESS 2581 Hooker, T. M., Bayley, P. M., Radding, W. & Schellman, J. A. (1974). Biopolymers, 13, 549-566. IUPAC-IUB Commission on Biochemical Nomenclature (1970). Biochemistry, 9, 3471-3479. Kopple, K. D. & Marr, D. H. (1967). J. Am. Chem. Soc. 89, 6193- 6200. Kopple, K. D. & Ohnishi, M. (1969). J. Am. Chem. Soc. 91,962-970. Lin, C. F. & Webb, L. E. (1973). J. Am. Chem. Soc. 95, 6803--6811. Molecular Structure Corporation (1988). MSC/AFC Diffractometer Control Software. MSC, 3200 Research Forest Drive, The Wood- lands, TX 77381, USA. Molecular Structure Corporation (1993). TEXSAN. Single Crystal Structure Analysis Software. Version 1.6c. MSC, 3200 Research Forest Drive, The Woodlands, TX 77381, USA. North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359. Acta Cryst. (1995). C51, 2581-2583 3-Hydroxy-2,6-dinitroacetophenone: an Unusual Substitution Pattern Resulting from Nitration of 3-Hydroxyacetophenone M. LURDES S. CRISrIANO AND ROBERT A. W. JOHNSTONE Department of Chemistry, University of Liverpool, Liverpool L69 3BX, England MICHAEL J. PRA'rr Du Pont (UK) Ltd, Coal Road, Leeds LS14 2AL, England (Received 17 October 1994; accepted 6 June 1995) Abstract Nitration of 3-hydroxyacetophenone gives 2,6-dinitro- 3-hydroxyacetophenone, C8H6N206, in which the nitro groups have entered the sterically least favourable po- sitions in the aromatic nucleus. None of the expected substitution i  the 4-position was observed. The two ni- tro groups flanking the carbonyl side chain are different in that one is in the plane of the aryl ring but the other is twisted well out of the plane. Comment During nitration of 3-hydroxyacetophenone to obtain the previously reported 2-nitro-3-hydroxyacetophenone (Butenandt, Hallmann & Beckmann, 1957), a substantial quantity of a new compound was also isolated. 1H NMR spectroscopy showed that there were two ortho H atoms and, by using additivity rules for chemical shifts (Gordon & Ford, 1972), it seemed that the H atoms occupied the 4,5-positions in the aromatic ring indicating that an unexpected substitution had occurred. However, this prediction was not sufficiently clear-cut © 1995 International Union of Crystallography Printed in Great Britain - all rights reserved to distinguish it from the altemative xpected structure with H atoms at the 5,6-positions. X-ray analysis gave the true structure (I) and showed that the NMR prediction had been correct. The relatively high yield of nitration products is unusual in that one nitro group joined the aryl ring ortho to the carbonyl and para to hydroxyl while the other joined ortho to both carbonyl and hydroxyl (a position of sterically restricted access); no nitration was observed in the expected position, ortho to hydroxyl and para to carbonyl, where there is no steric constraint. This substitution pattern violates the normal rules for electrophilic substitution into a simple aromatic ring (March, 1985) since sterically hindered nitration is highly unfavourable. There are a few examples in the literature exhibiting a similar 'ortho' effect of carbonyl (Ingold, 1954; Rubenstein, 1925; Raiford & Wells, 1935; Ginsburg, 1951). The present result is another even more extreme xample of substitution which appears to be governed by transition- state energies rather than the 'normal' ground-state considerations for electrophilic aromatic substitution (Kruse & Cha, 1982). COCH 3 O 2 N ~  NO2 "OH (1) The structure of the title compound is also unusual in that one nitro group alongside the carbonyl ies planar with the aryl ring whilst the other nitro adjacent o the carbonyl is twisted almost at right angles to it. The aromatic ring remains ubstantially planar. C8 H3 °3 H2 H6 O1 Fig. 1. Molecular structure showing 50% probability displacement ellipsoids. Acta Crystallographica Section C ISSN 0108-2701 ©1995 2582 C8H6N206 Experimental Addition of conc. nitric acid (s.g. 1.42; 10 ml) in conc. sulfuric acid (8 ml) to 3-hydroxyacetophenone (20 g) in conc. sulfuric acid (59 ml) at 253 K, followed by stirring for 15 min gave, after chromatography on silica gel, some starting material (5.2 g), 2-nitro-3-hydroxyacetophenone (6.5 g; 33% yield) and 2,6-dinitro-3-hydroxyacetophenone (6.1 g; 25% yield). The latter was recrystallized from ethanol as yellow needles (m.p. 455-456 K). Crystal data CsH6N206 Mo Ka radiation Mr = 226.15 A = 0.7107 Monoclinic Cell parameters from 20 P21/ c reflections a = 7.813 (2) ,~ 0 = 13.10-18.93 ° b = 12.708 (3) /~ # = 0.135 mm - I  c = 9.392 (2) /k  T = 24.0 K /3 = 101.14 (2) ° Prism V = 915.0 (4)/~3 0.450 x 0.300 x 0.300 mm Z = 4 Yellow Dx = 1.641 Mg m -3 Data collection Rigaku AFC-6S diffractom- eter 0,,/20 scans Absorption correction: empirical refined from ~b scan (North, Phillips & Mathews, 1968) Tmin = 0.95, Tmax = 1.00 1815 measured reflections 1688 independent reflections Refinement Refinement on F R = 0.0656 wR = 0.0766 S = 2.982 937 reflections 145 parameters H-atom parameters not refined 937 observed reflections [I > 4o'(/)] Rim = 0.008 0m~ x = 24.98 °h = 0 ---~ 9 k = 0 ---+ 15 l =-11  ~ 11 3 standard reflections monitored every 150 reflections intensity decay: 0.01% Weighting scheme based on measured e.s.d.'s (A/or)max = 0.0408 Apmax = 0.619 e ,~-3 mpmin = -0 .310  e ,~-3 Atomic scattering factors from International Tables for X-ray Crystallography (1974, Vol. IV) Table 1. Fractional atomic coordinates and equivalent isotropic displacement parameters (,~2) Ueq = (1/3)Ei~jUija~aTai.a). x y z Ueq O1 1.0350 (6) 0.7770 (4) 0.1465 (4) 0.0771 02 0.8398 (6) 0.7066 (4) -0.0168 (5) 0.0757 03 0.5906 (4) 0.8915 (3) -0.0453 (4) 0.0512 04 0.5662 (6) 1.0191 (4) -0.3214 (5) 0.0732 05 0.7383 (6) 1.0923 (4) -0.4417 (5) 0.0984 06 1.2748 (5) 0.8441 (4) 0.0055 (5) 0.0709 N 1 0.9482 (6) 0.7750 (4) 0.0263 (5) 0.0455 N2 0.7092 (7) 1.0321 (4) -0.3476 (6) 0.0594 C1 0.8277 (6) 0.9010 (4) -0.1650 (5) 0.0306 C2 0.8557 (7) 0.9764 (4) -0.2632 (5) 0.0387 C3 1.0243 (7) 1.0046 (5) -0.2768 (6) 0.0473 C4 1.1648 (7) 0.9604 (4) -0.1895 (6) 0.0434 C5 1.1429 (6) 0.8883 (4) -0.0858 (6) 0.0394 C6 0.9723 (6) 0.8584 (4) -0.0768 (5) 0.0323 C7 0.6456 (7) 0.8639 (4) -0.1508 (6) 0.0408 C8 0.5505 (7) 0.7907 (5) -0.2638 (7) 0.0603 Table 2. Selected geometric parameters (,~, o) OI--NI 1.200 (6) C1----C2 1.376 (7) O2--NI 1.226 (6) C1----C6 1.376 (6) O3---C7 1.206 (6) C1--C7 1.529 (7) O4--N2 1.200 (6) C2--C3 1.395 (7) O5--N2 1.224 (6) C3---C4 1.358 (8) O6----C5 1.331 (6) C4--C5 1.372 (7) N1---C6 1.472 (7) C5--C6 1.404 (7) N2---C2 1.446 (7) C7---C8 i.497 (8) O1--N 1-----<)2 123.6 (5) C2---C3---C4 120.4 (5) OI--NI--C6 118.9 (5) C3---C4--C5 120.5 (5) O2--N1--C6 117.5 (5) O6---C5---C4 123.5 (5) O4---N2---4)5 122.9 (6) O6---C5----C6 118.2 (5) O4--N2---C2 !19.4 (5) C4--C5---C6 118.2 (5) O5--N2---C2 117.7 (5) N 1------C6------C 1 119.0 (4) C2--C1---C6 117.3 (4) N1------C6------C5 118.5 (5) C2--C1---C7 123.0 (5) C1---C6--425 122.4 (5) C6---C1---C7 119.7 (5) O3---C7---C1 117.9 (5) N2---C2----C1 119.7 (5) O3----C7---428 123.8 (5) N2---C2--C3 119.1 (5) C1--C7--C8 118.2 (5) CI---C2--C3 121.0 (5) O1--N 1~C6~C1 -138.4 (5) O4~N2---C2~C1 7.0 (8) O1--N 1--C6--425 44.4 (7) O4--N2--C2---C3 -169.3 (6) O2--N 1--C6---C1 41.9 (7) C2----CI----C6---C5 -0.9 (7) O2--N1---C6----C5 -135.4 (5) C2----C1----C7---C8 76.1 (7) O3---C7--C1---422 - 107.4 (6) C3----C4--C5---C6 2.7 (8) O3----C7---C 1--C6 72.5 (6) C6---<21----C7---C8 - 104.0 (6) Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1988). Cell refinement: MSC/AFC Diffractometer Control Software. Data reduction: TEXSAN PROCESS (Molecular Structure Corporation, 1989). Program(s) used to refine structure: TEXSAN LS. Software used to prepare material for publication: TEXSAN FINISH. The authors  thank Du Pont ,  the Eschenmoser  Trust  and JN ICT  (Portugal )  for  f inancial  support  (MLSC)  and Mr  James  V. Bark ley  for  exper t  techn ica l  ass istance.  Lists of structure factors, anisotropic displacement parameters, H- atom coordinates and complete geometry have been deposited with the IUCr (Reference: HU1148). Copies may be obtained through The Managing Editor, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. References Butenandt, A., Hallmann, G. & Beckmann, R. (1957). Chem. Ber. 90, 1120-1124. Ginsburg, D. (1951). J. Am. Chem. Soc. 73, 702-704. Gordon, A. J. & Ford, R. A. (1972). The Chemist's Companion, pp. 261-262. New York: Wiley. Ingold, C. K. (1954). Structure and Mechanism in Organic Chemistry, pp. 261-263. Ithaca: Cornell Univ. Press. Kruse, L. I. & Cha, J. K. (1982). J. Chem. Soc. Chem. Commun. pp. 1333-1336. March, J. (1985). Advanced Organic Chemistry, pp. 459-460. New York: Wiley. Molecular Structure Corporation (1988). MSC/AFC Diffractometer Control Software. MSC, 3200 Research Forest Drive, The Wood- lands, TX 77381, USA. CRISTIANO, JOHNSTONE AND PRATT 2583 Molecular Structure Corporation (1989). TEXSAN. Single Crystal Structure Analysis Software. Version 5.0. MSC, 3200 Research Forest Drive, The Woodlands, TX 77381, USA. North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359. Raiford, L. C. & Wells, E. H. (1935). J. Am. Chem. Soc. 57, 2500- 2503. Rubenstein, L. (1925). J. Chem. Soc. 127, 1998-2004. Acta Cryst. (1995). C51, 2583-2584 Homochiral Methyl (S)-2-Benzoyloxy-4- bromo-4-methylpentanoate mosaicity. Despite the fact that there may have been some reflections for which the crystal was not bathed in a uniform beam, the quality of the data does not appear to have been affected, as evidenced by the ex- cellent results. We have previously used similarly large crystals without deleterious effects (Shaw, Tan & Black- man, 1995). Refinement in the orthorhombic space group P212121 showed the presence of only one enantiomer. The stereochemistry at atom C5 was found to be S, with the correct choice of 'handedness' verified by the value of the Flack (1983) parameter [X = -0.01 (2)]. All bond lengths and angles within the identical fragments of (I) and methyl (S)-2-benzenesulfonyloxy-4-bromo- 4-methylpentanoate r the same within three e.s.d.'s, with the exception of the O3--C5--C7 angle [107.2 (3) versus 111.6 (4) ° in the latter] (Shaw, Tan & Blackman, 1995). JOANNE P. SHAW, ENG Wul  TAN AND ALLAN G. BLACK.MAN Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand (Received 24 April 1995; accepted 22 June 1995) Abstract The stereochemistry at position 2 of the title compound, ClaHI7BrO4,  has been confirmed as S. Comment The title compound, methyl (S)-2-benzoyloxy-4-bromo- 4-methylpentanoate, (I), was investigated as part of a study of the regioselective bromination of 2-hydroxy-4- methylpentanoic a id derivatives (Shaw, Tan & Black- man, 1995). X-ray structure analysis was undertaken iorder to confirm that the stereochemistry at the 2 posi- tion (i.e. atom C5) was unaffected by the bromination reaction. Me B r ~ ~  0 OMe (I) CIO C7 C9 04 02 OI C8 03 C5 C13 C6 ~ 1~ Brl C3 C2 Fig. 1. ORTEP (Johnson, 1965) drawing of (I) showing displacement ellipsoids at the 50% probability level. The compound crystallized as large blocks; the small- est of these was used for data collection as, despite re- peated attempts, suitable smaller crystals could not be obtained. Cutting the crystal also destroyed the crystal © 1995 International Union of Crystallography Printed in Great Britain - all rights reserved Experimental A mixture of methyl (S)-2-benzoyloxy-4-methylpentanoate (1.11g, 4.4mmol) and N-bromosuccinimide (1.18g, 6.6mmol) in benzene (100ml) was heated at reflux under Acta Crystallographica Section C ISSN 0108-2701 ©1995 

3-Hydroxy-2,6-dinitroacetophenone: an unusual substitution pattern resulting from nitration of 3-hydroxyacetophenone

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