1-Ethyl-4-hydroxy-2-oxo-1,2-di­hydro­quinoline-3-carboxyl­ic acid

An X-ray diffraction study of the title compound, C₁₂H₁₁NO₄, has shown that this compound exists in the crystal as the 2-oxo-4-hydroxy tautomer. The formation of two O—H...O=C-type intramolecular hydrogen bonds leads to the elongation of both exocyclic and carboxyl­ic C=O double bonds involved in the hydrogen bonding, causes shortening of the exocyclic C—O single bond, and also affects the C—C bond lengths in the di­hydro­pyridine ring.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.038
• wR factor = 0.116
• Data-to-parameter ratio = 11.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



ABSMU_01  Alert C The ratio of given/expected absorption coefficient lies
          outside the range 0.99 <> 1.01
          Calculated value of mu =     0.108
          Value of mu given      =     0.110

SHFSU_01  Alert C The absolute value of parameter shift to su ratio > 0.05
          Absolute value of the parameter shift to su ratio given   0.085
          Additional refinement cycles may be required.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

---

S1. Comment

The derivatives of 4-hydroxyquinol-2-one can exist in different tautomeric forms depending on the substituent in the 3 position. They provide a relatively rare example of the systems where more than two tautomeric forms are conceivable. These forms differ from each other in the H-atom positions and the location of hydroxy and carbonyl groups. Therefore, these compounds have been the focus of several structural investigations (Ukrainets et al., 1992, 1996; Garsia Ruano et al., 1991). In the present paper, we report the crystal and molecular structure of 1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid, (I) (Fig. 1).

The C2—O13, C4—O17, C14—O16 and C3—C4 bond lengths [1.266 (2), 1.333 (2), 1.239 (3) and 1.381 (2) Å, respectively] indicate that the title compound exists in the crystal as the 2-oxo-4-hydroxy tautomer. This conclusion is also confirmed by the positions of the H atoms of the hydroxy and carboxy groups, which were located in a difference map.

All non-H atoms of this molecule with the exception of the C12 atom lie in one plane. The formation of the O15—H15O···O13 and O17—H17O···O16 hydrogen bonds [H15O···O13 1.67 (3) Å, O15···O13 2.505 (2) Å, O15—H15O···O13 147 (3)°; H17O···O16 1.66 (3) Å, O17···O16 2.548 (2) Å, O17—H17O···O16 151 (3)°] leads to the significant change of bond lengths in the hydroxy, carboxy and carbonyl groups: the O13—C2 and O16—C14 bonds are longer as compared with standard value for the C═O bond of 1.210 Å (Bürgi & Dunitz, 1994) and the O17—C4 bond is shorter than standard value for the Csp²—O (1.362 Å). The presence of intramolecular hydrogen bonds causes noticeable redistribution of the electron density within the dihydropyridine ring. As a result, the C3—C4 and C5—C10 bonds are longer and the C2—C3 and C4—C5 bonds are shorter than the standard values for the C═C (1.334 Å) and Csp²—Csp² (1.455 Å) bonds (Bürgi & Dunitz, 1994), respectively.

The repulsion between the substituent at the N1 atom, carbonyl group and the H atom in the peri-position of the aromatic ring {the shortened intramolecular contacts O13···H11b 2.33 Å [van der Waals radii sum is 2.45 Å according to Zefirov & Zorky (1995)], H9···C11 2.55 Å (2.87 Å), H9···H11a 2.06 Å (2.32 Å)} causes an elongation of the N1—C2, N1—C10 and N1—C11 bonds up to 1.371 (2), 1.403 (2) and 1.488 (2) Å, respectively [standard values for the N—Csp² and N—Csp³ bonds are 1.355 and 1.464%A (Bürgi & Dunitz, 1994)]. The C12 atom of the substituent at the N1 atom is oriented orthogonal with respect to the plane of the dihydrocycle [the C2—N1—C11—C12 torsion angle is -94.2 (2)°].

Molecules of the title compound are linked into infinite chains stretched along the x axis of the crystal due to the C9—H9···O16ⁱ intermolecular hydrogen bond (H···Oⁱ 2.36 Å and C—H···Oⁱ 154°; symmetry code: (i) 1 + x, y, z).

S2. Experimental

The title compound was prepared according to the procedure of Ukrainets et al. (1996).

S3. Refinement

All H atoms, except the H atoms of the hydroxy groups, were placed in calculated positions and included in the refinement as riding, with U_iso constrained to be 1.2U_eq of the carrier atom (1.5U_eq for methyl H atoms). Hydroxy H atoms were located in a difference maps and refined in the isotropic approximation.

Computing details

Data collection: P3 (Siemens, 1989); cell refinement: P3; data reduction: XDISK (Siemens, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1991); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. View of the title compound. The non-H atoms are shown with displacement ellipsoids drawn at the 50% probability level.

1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid

Crystal data

C12H11NO4	F(000) = 488
Mr = 233.22	Dx = 1.426 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.278 (2) Å	Cell parameters from 24 reflections
b = 14.050 (4) Å	θ = 10–11°
c = 8.938 (2) Å	µ = 0.11 mm^−1
β = 111.21 (3)°	T = 293 K
V = 1086.2 (5) Å^3	Needles, colourless
Z = 4	0.40 × 0.20 × 0.20 mm

Data collection

Siemens P3/PC diffractometer	Rint = 0.012
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.3°
Graphite monochromator	h = −11→10
θ–2θ scans	k = 0→16
2133 measured reflections	l = 0→10
1885 independent reflections	2 standard reflections every 98 reflections
1153 reflections with I > 2σ(I)	intensity decay: 5%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.116	H atoms treated by a mixture of independent and constrained refinement
S = 0.97	w = 1/[σ^2(Fo^2) + (0.0812P)^2] where P = (Fo^2 + 2Fc^2)/3
1885 reflections	(Δ/σ)max = 0.085
162 parameters	Δρmax = 0.15 e Å^−3
0 restraints	Δρmin = −0.14 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.59133 (12)	0.83381 (8)	0.03227 (14)	0.0409 (3)
C2	0.43989 (17)	0.80711 (11)	−0.00738 (18)	0.0456 (4)
C3	0.34375 (17)	0.85989 (11)	0.0589 (2)	0.0496 (4)
C4	0.40513 (19)	0.93366 (12)	0.1649 (2)	0.0536 (4)
C5	0.56517 (18)	0.95893 (10)	0.21021 (17)	0.0468 (4)
C6	0.6329 (2)	1.03379 (12)	0.3190 (2)	0.0655 (5)
H6	0.5735	1.0678	0.3649	0.079*
C7	0.7857 (3)	1.05629 (13)	0.3568 (2)	0.0750 (6)
H7	0.8296	1.1058	0.4278	0.090*
C8	0.8748 (2)	1.00548 (13)	0.2898 (2)	0.0675 (5)
H8	0.9784	1.0213	0.3164	0.081*
C9	0.81315 (18)	0.93217 (12)	0.1848 (2)	0.0528 (4)
H9	0.8755	0.8985	0.1420	0.063*
C10	0.65706 (16)	0.90758 (10)	0.14141 (16)	0.0408 (4)
C11	0.68548 (19)	0.78072 (12)	−0.04404 (19)	0.0532 (4)
H11A	0.7574	0.8243	−0.0645	0.064*
H11B	0.6178	0.7556	−0.1464	0.064*
C12	0.7752 (2)	0.69946 (13)	0.0598 (2)	0.0661 (5)
H12A	0.8447	0.7242	0.1601	0.099*
H12B	0.8331	0.6669	0.0056	0.099*
H12C	0.7044	0.6558	0.0795	0.099*
O13	0.38718 (13)	0.73776 (8)	−0.10185 (14)	0.0662 (4)
C14	0.1795 (2)	0.83414 (15)	0.0133 (3)	0.0746 (6)
O15	0.12440 (15)	0.76423 (12)	−0.0903 (2)	0.0885 (5)
H15O	0.201 (4)	0.738 (2)	−0.123 (3)	0.091 (8)*
O16	0.09477 (17)	0.87788 (12)	0.0696 (2)	0.1101 (6)
O17	0.32029 (18)	0.98451 (10)	0.22852 (19)	0.0829 (5)
H17O	0.222 (3)	0.9531 (19)	0.192 (3)	0.121 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0403 (7)	0.0421 (7)	0.0412 (7)	0.0043 (5)	0.0158 (5)	−0.0010 (5)
C2	0.0449 (8)	0.0430 (8)	0.0459 (9)	0.0024 (7)	0.0128 (7)	0.0067 (7)
C3	0.0427 (8)	0.0507 (9)	0.0585 (10)	0.0065 (7)	0.0221 (7)	0.0155 (8)
C4	0.0604 (10)	0.0506 (9)	0.0634 (10)	0.0209 (8)	0.0387 (9)	0.0170 (8)
C5	0.0596 (10)	0.0405 (8)	0.0422 (9)	0.0099 (7)	0.0209 (7)	0.0047 (7)
C6	0.0934 (14)	0.0476 (10)	0.0530 (10)	0.0155 (9)	0.0235 (10)	−0.0006 (8)
C7	0.0901 (15)	0.0486 (10)	0.0629 (12)	−0.0044 (10)	−0.0006 (10)	−0.0086 (9)
C8	0.0580 (11)	0.0567 (11)	0.0689 (12)	−0.0080 (9)	0.0001 (9)	0.0053 (9)
C9	0.0459 (9)	0.0520 (9)	0.0564 (10)	0.0015 (7)	0.0135 (7)	0.0044 (8)
C10	0.0438 (8)	0.0377 (8)	0.0392 (8)	0.0045 (6)	0.0131 (6)	0.0051 (6)
C11	0.0533 (9)	0.0603 (10)	0.0503 (9)	0.0076 (7)	0.0240 (7)	−0.0085 (8)
C12	0.0644 (11)	0.0625 (11)	0.0718 (12)	0.0199 (8)	0.0249 (9)	−0.0054 (9)
O13	0.0608 (7)	0.0593 (7)	0.0683 (8)	−0.0096 (6)	0.0112 (6)	−0.0122 (6)
C14	0.0520 (11)	0.0740 (13)	0.1048 (17)	0.0096 (10)	0.0367 (11)	0.0335 (12)
O15	0.0539 (8)	0.0856 (10)	0.1138 (12)	−0.0165 (7)	0.0156 (8)	0.0185 (9)
O16	0.0656 (10)	0.1137 (13)	0.1771 (17)	0.0137 (9)	0.0755 (11)	0.0292 (12)
O17	0.0919 (10)	0.0780 (10)	0.1055 (11)	0.0259 (8)	0.0678 (10)	0.0038 (8)

Geometric parameters (Å, º)

N1—C2	1.3712 (19)	C5—C10	1.416 (2)
N1—C10	1.4026 (18)	C6—C7	1.370 (3)
N1—C11	1.4885 (19)	C7—C8	1.382 (3)
C2—O13	1.2660 (18)	C8—C9	1.371 (2)
C2—C3	1.442 (2)	C9—C10	1.400 (2)
C3—C4	1.381 (2)	C11—C12	1.516 (2)
C3—C14	1.473 (3)	C14—O16	1.239 (3)
C4—O17	1.333 (2)	C14—O15	1.320 (3)
C4—C5	1.435 (2)	O15—H15O	0.93 (3)
C5—C6	1.416 (2)	O17—H17O	0.96 (3)
C2—N1—C10	121.94 (12)	C10—C5—C4	118.39 (14)
C2—N1—C11	117.44 (12)	C7—C6—C5	120.25 (17)
C10—N1—C11	120.62 (11)	C6—C7—C8	120.08 (17)
O13—C2—N1	119.70 (14)	C9—C8—C7	121.23 (17)
O13—C2—C3	121.51 (14)	C8—C9—C10	120.52 (17)
N1—C2—C3	118.79 (13)	C9—C10—N1	121.38 (14)
C4—C3—C2	120.34 (14)	C9—C10—C5	118.63 (14)
C4—C3—C14	120.17 (17)	N1—C10—C5	120.00 (12)
C2—C3—C14	119.48 (17)	N1—C11—C12	112.32 (13)
O17—C4—C3	122.31 (16)	O16—C14—O15	120.84 (19)
O17—C4—C5	117.21 (17)	O16—C14—C3	120.7 (2)
C3—C4—C5	120.47 (14)	O15—C14—C3	118.42 (19)
C6—C5—C10	119.29 (15)	C14—O15—H15O	111.5 (18)
C6—C5—C4	122.31 (15)	C4—O17—H17O	104.4 (17)
C10—N1—C2—O13	−177.35 (13)	C6—C7—C8—C9	0.1 (3)
C11—N1—C2—O13	2.1 (2)	C7—C8—C9—C10	0.7 (2)
C10—N1—C2—C3	3.32 (19)	C8—C9—C10—N1	179.00 (13)
C11—N1—C2—C3	−177.25 (12)	C8—C9—C10—C5	−1.0 (2)
O13—C2—C3—C4	178.31 (14)	C2—N1—C10—C9	177.95 (13)
N1—C2—C3—C4	−2.4 (2)	C11—N1—C10—C9	−1.5 (2)
O13—C2—C3—C14	−1.3 (2)	C2—N1—C10—C5	−2.05 (19)
N1—C2—C3—C14	178.00 (13)	C11—N1—C10—C5	178.53 (13)
C2—C3—C4—O17	179.75 (15)	C6—C5—C10—C9	0.6 (2)
C14—C3—C4—O17	−0.6 (2)	C4—C5—C10—C9	179.77 (13)
C2—C3—C4—C5	0.2 (2)	C6—C5—C10—N1	−179.38 (12)
C14—C3—C4—C5	179.79 (14)	C4—C5—C10—N1	−0.2 (2)
O17—C4—C5—C6	0.6 (2)	C2—N1—C11—C12	−94.27 (16)
C3—C4—C5—C6	−179.75 (14)	C10—N1—C11—C12	85.17 (17)
O17—C4—C5—C10	−178.49 (13)	C4—C3—C14—O16	−0.2 (3)
C3—C4—C5—C10	1.1 (2)	C2—C3—C14—O16	179.42 (16)
C10—C5—C6—C7	0.1 (2)	C4—C3—C14—O15	178.91 (15)
C4—C5—C6—C7	−179.02 (15)	C2—C3—C14—O15	−1.5 (2)
C5—C6—C7—C8	−0.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H17O···O16	0.96 (3)	1.66 (3)	2.548 (2)	151 (3)
O15—H15O···O13	0.93 (3)	1.67 (3)	2.505 (2)	147 (3)
C9—H9···O16^i	0.93	2.36	3.227 (2)	154

Symmetry code: (i) x+1, y, z.