2,5-Dihydroxy­benzaldehyde

The title compound, C₇H₆O₃, features a planar mol­ecule (r.m.s. deviation for all non-H atoms = 0.019 Å). Geometric parameters are in the usual ranges. Whereas one hydroxyl group forms an intra­molecular hydrogen bond with the carbonyl group, the other forms an inter­molecular hydrogen bond with the carbonyl group of a symmetry-equivalent mol­ecule. The mol­ecules crystallize in planes parallel to the bc plane.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.032
• wR factor = 0.084
• Data-to-parameter ratio = 8.5

checkCIF/PLATON results

No syntax errors found



Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.29
           From the CIF: _reflns_number_total                843
           Count of symmetry unique reflns          851
           Completeness (_total/calc)             99.06%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Recently, we have extended our studies to redox-active ligands which can be used to influence the electrochemical reactivity of transition metals since their redox activity is expanded upon complexation (Lerner et al., 2006; Kretz et al., 2007). The resulting complexes can undergo multi-electron transfer reactions which are the sum of the oxidation state changes of the metal center and the ligand (Margraf et al., 2006; Kretz et al., 2006). Due to their electrochemical reversibility, hydroquinone / quinone derivatives are candidates for redox-active ligands (Lerner et al., 2006; Kretz et al., 2007). In our studies we have used Schiff-Base derivatives which can conveniently be achieved by reaction of amines and aldehyde derivatives (Margraf et al., 2006; Kretz et al., 2007). Thereby 2,5-dihydroxybenzaldehyde represents one of the starting materials. Single crystals of 2,5-dihydroxybenzaldehyde were obtained by recrystallization from toluene.

The title compound, C₇H₆O₃, features a planar molecule (r.m.s. deviation for all non-H atoms 0.019 Å). Geometric parameters are in the usual ranges. Whereas one hydroxyl group forms an intramolecular hydrogen bond with the carbonyl group, the other one forms an intermolecular hydrogen bond with the carbonyl group of a symmetry equivalent molecule. The molecules crystallize in planes parallel to the bc plane.

Related literature

For related literature, see: Kretz et al. (2006, 2007); Lerner et al. (2006); Margraf et al. (2006).

S2. Experimental

Commercially available 2,5-dihydroxybenzaldehyde (1.38 g) was recrystallized from toluene (20 ml).

S3. Refinement

H atoms bonded to C were refined with fixed individual displacement parameters [U(H) = 1.2 U_eq(C)] using a riding model with C—H = 0.93 Å. The H atoms bonded to O were refined isotropically. In the final cycles of refinement, in the absence of significant anomalous scattering effects, Friedel pairs were merged and Δf" set to zero.

Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997 and PLATON (Spek, 2003).

Figures

Fig. 1. Perspective view of the title compound with the atom numbering; displacement ellipsoids are at the 50% probability level.

2,5-Dihydroxybenzaldehyde

Crystal data

C7H6O3	F(000) = 288
Mr = 138.12	Dx = 1.448 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 11598 reflections
a = 6.7544 (7) Å	θ = 3.8–27.4°
b = 8.2240 (9) Å	µ = 0.12 mm^−1
c = 11.4040 (13) Å	T = 173 K
V = 633.47 (12) Å^3	Block, yellow
Z = 4	0.49 × 0.32 × 0.29 mm

Data collection

Stoe IPDS II two-circle diffractometer	797 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.064
Graphite monochromator	θmax = 27.3°, θmin = 3.9°
ω scans	h = −8→8
7904 measured reflections	k = −10→10
843 independent reflections	l = −14→14

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)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.084	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0573P)^2 + 0.0216P] where P = (Fo^2 + 2Fc^2)/3
843 reflections	(Δ/σ)max < 0.001
99 parameters	Δρmax = 0.23 e Å^−3
0 restraints	Δρmin = −0.13 e Å^−3

Special details

Experimental. ;

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
C1	0.1189 (2)	0.78697 (16)	0.40573 (13)	0.0313 (3)
C2	0.11078 (18)	0.80898 (15)	0.52767 (12)	0.0291 (3)
C3	0.1003 (2)	0.67401 (16)	0.60198 (12)	0.0303 (3)
H3	0.0964	0.6895	0.6845	0.036*
C4	0.0956 (2)	0.51869 (15)	0.55672 (12)	0.0306 (3)
C5	0.1033 (2)	0.49826 (15)	0.43446 (12)	0.0324 (3)
H5	0.0997	0.3916	0.4025	0.039*
C6	0.1159 (2)	0.62973 (16)	0.36011 (12)	0.0335 (3)
H6	0.1225	0.6133	0.2777	0.040*
O1	0.13038 (18)	0.91338 (14)	0.32977 (10)	0.0418 (3)
H1	0.119 (3)	1.005 (3)	0.384 (2)	0.064 (7)*
O4	0.0787 (2)	0.39039 (12)	0.63213 (10)	0.0435 (3)
H4	0.097 (4)	0.301 (3)	0.581 (2)	0.070 (7)*
C21	0.1097 (2)	0.97036 (17)	0.57875 (14)	0.0350 (3)
H21	0.1055	0.9793	0.6618	0.042*
O21	0.11390 (18)	1.09707 (11)	0.52045 (11)	0.0424 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0284 (6)	0.0292 (6)	0.0363 (7)	−0.0003 (6)	−0.0025 (5)	0.0039 (5)
C2	0.0263 (5)	0.0247 (6)	0.0363 (7)	0.0001 (6)	−0.0010 (5)	−0.0004 (5)
C3	0.0330 (6)	0.0271 (6)	0.0307 (6)	0.0008 (5)	−0.0015 (5)	−0.0021 (5)
C4	0.0320 (6)	0.0243 (6)	0.0356 (6)	0.0006 (5)	−0.0012 (5)	0.0025 (5)
C5	0.0341 (6)	0.0262 (6)	0.0371 (6)	0.0005 (5)	−0.0014 (5)	−0.0061 (5)
C6	0.0346 (6)	0.0351 (7)	0.0306 (6)	−0.0011 (6)	0.0001 (6)	−0.0032 (5)
O1	0.0508 (6)	0.0349 (5)	0.0396 (5)	−0.0017 (5)	−0.0021 (5)	0.0118 (4)
O4	0.0649 (8)	0.0240 (5)	0.0416 (5)	0.0002 (5)	−0.0014 (5)	0.0041 (4)
C21	0.0347 (6)	0.0252 (6)	0.0449 (7)	0.0011 (6)	0.0012 (6)	−0.0036 (5)
O21	0.0462 (5)	0.0231 (5)	0.0580 (7)	0.0010 (4)	0.0009 (5)	0.0017 (5)

Geometric parameters (Å, º)

C1—O1	1.3554 (16)	C4—C5	1.405 (2)
C1—C6	1.3941 (17)	C5—C6	1.3766 (19)
C1—C2	1.4034 (18)	C5—H5	0.9500
C2—C3	1.3982 (19)	C6—H6	0.9500
C2—C21	1.4494 (17)	O1—H1	0.98 (2)
C3—C4	1.3781 (17)	O4—H4	0.95 (3)
C3—H3	0.9500	C21—O21	1.2364 (18)
C4—O4	1.3660 (16)	C21—H21	0.9500
O1—C1—C6	118.28 (12)	C6—C5—C4	121.30 (11)
O1—C1—C2	122.45 (12)	C6—C5—H5	119.4
C6—C1—C2	119.27 (12)	C4—C5—H5	119.4
C3—C2—C1	120.01 (12)	C5—C6—C1	119.97 (12)
C3—C2—C21	118.89 (12)	C5—C6—H6	120.0
C1—C2—C21	121.10 (12)	C1—C6—H6	120.0
C4—C3—C2	120.66 (12)	C1—O1—H1	100.7 (14)
C4—C3—H3	119.7	C4—O4—H4	101.5 (16)
C2—C3—H3	119.7	O21—C21—C2	123.75 (13)
O4—C4—C3	118.82 (12)	O21—C21—H21	118.1
O4—C4—C5	122.37 (12)	C2—C21—H21	118.1
C3—C4—C5	118.79 (12)
O1—C1—C2—C3	−179.61 (11)	O4—C4—C5—C6	178.53 (12)
C6—C1—C2—C3	0.2 (2)	C3—C4—C5—C6	0.2 (2)
O1—C1—C2—C21	1.4 (2)	C4—C5—C6—C1	−0.7 (2)
C6—C1—C2—C21	−178.79 (12)	O1—C1—C6—C5	−179.65 (12)
C1—C2—C3—C4	−0.8 (2)	C2—C1—C6—C5	0.5 (2)
C21—C2—C3—C4	178.24 (13)	C3—C2—C21—O21	−178.30 (13)
C2—C3—C4—O4	−177.85 (12)	C1—C2—C21—O21	0.7 (2)
C2—C3—C4—C5	0.6 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4···O21^i	0.95 (3)	1.82 (3)	2.7382 (15)	163 (2)
O1—H1···O21	0.98 (2)	1.73 (3)	2.6501 (16)	155 (2)

Symmetry code: (i) x, y−1, z.