Triethyl benzene-1,3,5-tri­carboxyl­ate

The title compound, C₁₅H₁₈O₆, first synthesized in 1868, has previously been analysed by single-crystal X-ray diffraction, but only the unit-cell dimensions and space group have been published. Here we present the full low-temperature structure determination and show that the title compound crystallizes in the chiral space group P6₅ (or P6₁), despite its inherent non-chirality.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.043
• wR factor = 0.122
• Data-to-parameter ratio = 18.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_031  Alert C Refined Extinction Parameter within Range ....       2.50 Sigma

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           28.84
         From the CIF: _reflns_number_total               3515
         Count of symmetry unique reflns         1972
         Completeness (_total/calc)            178.25%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured      1543
         Fraction of Friedel pairs measured     0.782
         Are heavy atom types Z>Si present           no
          ALERT: MoKa measured Friedel data cannot be used to
                 determine absolute structure in a light-atom
                 study EXCEPT under VERY special conditions.
                 It is preferred that Friedel data is merged in such cases.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

S1. Comment

The title compound, (I), was first synthesized in 1868 (Fittig & Furtenbach, 1868) and is the second simplest member of the known family of trimesic acid (benzene-1,3,5-tricarboxylic acid) alkyl triesters, which spans methyl (Karabinos et al., 1946) through to tetracosyl (C₂₄) chains (Breusch & Ulusoy, 1961). None of these alkyl esters has been fully structurally characterized, although the more elaborate 1,3,5-tris[(triallylsilyl)phenylester]benzene (Cambridge Structural Database, Version 5.24, April 2003 update; Allen, 2002; refcode GUCQOK; Gossage et al., 1999) has been analysed using the single-crystal X-ray technique. The trimethyl ester has been used as a ligand for such metals as Ti, Al and Re, for which the structures of the complexes are known (Sobota et al., 1993; Utko et al., 1993; Adams et al., 1993).

The unit-cell dimensions and space group of (I) have been previously determined (Hertel & Dumont, 1935), but here the full low-temperature structure analysis is presented.

The initial solution, provided by SIR92 (Altomare et al., 1994), in space group P3₂ indicated two molecules in the asymmetric unit (Z'=2); however, PLATON (Spek, 2003) identified additional missed symmetry, yielding the space group P6₅ (or P6₁; the absolute configuration was not determined) and hence Z' = 1.

The three independent carboxyl groups deviate little from coplanarity with the aromatic ring [dihedral angles with respect to ring C1–C6: C7 O1 O2 3.76 (3)°; C10 O3 O4 4.38 (4)°; C13 O5 O6 0.56 (2)°]; furthermore, the C—O and C═O bond lengths (Table 1) are in the expected ranges.

In the crystal structure, molecules of (I) form sheets, extending in the a and b directions.

S2. Experimental

Catalytic H₂SO₄ was added to a refluxing ethanolic solution (25 ml) of trimesic acid (500 mg, 2.38 mmol). After 60 h, the solution was allowed to cool and the solvent removed in vacuo. The residue was dissolved in dichloromethane (10 ml) and washed with saturated aqueous NaHCO₃ (3 × 10 ml). The organic layer was then dried (Na₂SO₄), filtered and evaporated to dryness, yielding (I) (602 mg, 80%) as a white solid. X-ray quality crystals were grown by slow evaporation of a dichloromethane solution of (I). M.p. 405–407 K (literature 407 K; Ghosh et al., 1999); analysis calculated for C₁₅H₁₈O₆: C 61.22, H 6.16%; found: C 61.08; H 6.18%. IR, ¹H NMR and ¹³C NMR spectroscopy data agree with those previously reported (Ghosh et al., 1999).

S3. Refinement

All H atoms were placed in geometrically calculated positions, and were refined using a riding model (aromatic C—H distance = 0.95 Å; methylene and methyl C—H distances = 0.99 and 0.98 Å, respectively). U_iso values were set to 1.2U_eq for aryl H (1.5U_eq for methyl H and methylene H). 1543 Friedel pairs were measured but these were not merged prior to refinement.

Computing details

Data collection: SMART (Siemens, 1994); cell refinement: SAINT (Siemens, 1994); data reduction: SAINT; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXTL (Bruker, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Figures

Fig. 1. View of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented by circles of arbitrary radii.

Triethyl benzene-1,3,5-tricarboxylate

Crystal data

C15H18O6	Dx = 1.338 Mg m^−3
Mr = 294.29	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P65	Cell parameters from 4977 reflections
a = 11.3438 (17) Å	θ = 2.3–27.9°
c = 19.665 (4) Å	µ = 0.10 mm^−1
V = 2191.5 (6) Å^3	T = 150 K
Z = 6	Block, colourless
F(000) = 936	0.37 × 0.25 × 0.09 mm

Data collection

Bruker SMART 1000 CCD diffractometer	3515 independent reflections
Radiation source: sealed tube	2448 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ω scans	θmax = 28.8°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	h = −14→14
Tmin = 0.910, Tmax = 0.991	k = −14→14
19450 measured reflections	l = −26→26

Refinement

Refinement on F^2	Secondary atom site location: direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.043	H-atom parameters constrained
wR(F^2) = 0.122	w = 1/[σ^2(Fo^2) + (0.0469P)^2 + 1.115P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
3515 reflections	Δρmax = 0.27 e Å^−3
194 parameters	Δρmin = −0.24 e Å^−3
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0005 (2)

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
C1	0.2827 (2)	0.2794 (2)	0.48183 (14)	0.0221 (5)
C2	0.2420 (2)	0.3761 (2)	0.48402 (14)	0.0241 (5)
H2	0.3084	0.4702	0.4838	0.029*
C3	0.1043 (2)	0.3362 (2)	0.48652 (14)	0.0222 (5)
C4	0.0069 (2)	0.1977 (2)	0.48731 (13)	0.0236 (5)
H4	−0.0871	0.1698	0.4900	0.028*
C5	0.0476 (2)	0.1008 (2)	0.48414 (13)	0.0222 (5)
C6	0.1853 (2)	0.1410 (2)	0.48142 (13)	0.0239 (5)
H6	0.2130	0.0746	0.4793	0.029*
C7	0.4319 (2)	0.3279 (2)	0.48111 (14)	0.0253 (5)
O1	0.51962 (17)	0.44676 (17)	0.47984 (12)	0.0362 (5)
O2	0.45666 (15)	0.22437 (16)	0.48303 (10)	0.0280 (4)
C8	0.5996 (2)	0.2602 (2)	0.48419 (18)	0.0319 (5)
H8A	0.6479	0.3232	0.5223	0.048*
H8B	0.6450	0.3051	0.4411	0.048*
C9	0.6014 (3)	0.1297 (3)	0.49311 (17)	0.0348 (6)
H9A	0.5595	0.0883	0.5368	0.052*
H9B	0.6956	0.1487	0.4923	0.052*
H9C	0.5502	0.0671	0.4561	0.052*
C10	0.0542 (2)	0.4355 (2)	0.48695 (14)	0.0263 (5)
O3	−0.06424 (18)	0.40346 (18)	0.49229 (12)	0.0392 (5)
O4	0.15618 (15)	0.56416 (16)	0.48140 (10)	0.0275 (4)
C11	0.1159 (3)	0.6686 (2)	0.47950 (17)	0.0338 (6)
H11A	0.0780	0.6740	0.5240	0.051*
H11B	0.0459	0.6465	0.4441	0.051*
C12	0.2416 (3)	0.8010 (3)	0.4636 (2)	0.0467 (9)
H12A	0.3106	0.8208	0.4986	0.070*
H12B	0.2194	0.8741	0.4626	0.070*
H12C	0.2771	0.7948	0.4191	0.070*
C13	−0.0534 (2)	−0.0480 (2)	0.48425 (14)	0.0236 (5)
O5	−0.02254 (18)	−0.13599 (16)	0.48252 (13)	0.0358 (4)
O6	−0.18161 (16)	−0.07265 (15)	0.48634 (11)	0.0277 (4)
C14	−0.2880 (2)	−0.2150 (2)	0.48817 (18)	0.0322 (6)
H14A	−0.2700	−0.2632	0.5251	0.048*
H14B	−0.2912	−0.2598	0.4445	0.048*
C15	−0.4198 (3)	−0.2188 (3)	0.5004 (2)	0.0501 (10)
H15A	−0.4181	−0.1808	0.5454	0.075*
H15B	−0.4947	−0.3132	0.4984	0.075*
H15C	−0.4331	−0.1649	0.4655	0.075*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0211 (11)	0.0208 (10)	0.0249 (11)	0.0108 (9)	0.0004 (10)	0.0003 (10)
C2	0.0225 (11)	0.0169 (10)	0.0297 (12)	0.0074 (9)	−0.0026 (11)	−0.0021 (11)
C3	0.0227 (11)	0.0198 (11)	0.0244 (12)	0.0109 (9)	−0.0006 (11)	−0.0016 (10)
C4	0.0202 (11)	0.0224 (11)	0.0278 (12)	0.0105 (10)	0.0001 (10)	−0.0001 (11)
C5	0.0212 (11)	0.0185 (11)	0.0240 (12)	0.0078 (9)	0.0007 (10)	0.0003 (10)
C6	0.0253 (11)	0.0217 (11)	0.0260 (12)	0.0127 (9)	−0.0001 (11)	−0.0013 (11)
C7	0.0218 (11)	0.0242 (11)	0.0309 (13)	0.0123 (10)	−0.0006 (11)	−0.0002 (11)
O1	0.0216 (9)	0.0211 (8)	0.0626 (13)	0.0081 (7)	−0.0001 (10)	0.0012 (9)
O2	0.0190 (8)	0.0256 (9)	0.0405 (10)	0.0120 (7)	0.0003 (8)	−0.0010 (9)
C8	0.0185 (11)	0.0302 (12)	0.0484 (15)	0.0132 (10)	−0.0017 (12)	−0.0028 (13)
C9	0.0250 (13)	0.0342 (14)	0.0501 (16)	0.0185 (11)	−0.0002 (12)	0.0013 (13)
C10	0.0246 (12)	0.0217 (11)	0.0335 (13)	0.0122 (10)	−0.0017 (11)	−0.0017 (12)
O3	0.0235 (9)	0.0281 (10)	0.0680 (14)	0.0145 (8)	0.0007 (10)	−0.0027 (10)
O4	0.0240 (8)	0.0200 (8)	0.0409 (10)	0.0128 (7)	−0.0002 (8)	0.0012 (8)
C11	0.0346 (14)	0.0253 (12)	0.0488 (17)	0.0206 (11)	0.0010 (13)	0.0031 (13)
C12	0.0457 (18)	0.0249 (14)	0.074 (3)	0.0211 (13)	0.0140 (15)	0.0044 (14)
C13	0.0212 (11)	0.0229 (12)	0.0243 (11)	0.0092 (9)	0.0011 (11)	−0.0001 (10)
O5	0.0289 (9)	0.0226 (9)	0.0559 (12)	0.0127 (8)	0.0022 (10)	−0.0006 (10)
O6	0.0201 (8)	0.0192 (8)	0.0403 (9)	0.0072 (6)	−0.0011 (8)	−0.0007 (8)
C14	0.0236 (12)	0.0173 (12)	0.0488 (15)	0.0050 (10)	−0.0004 (13)	0.0017 (12)
C15	0.0225 (14)	0.0281 (14)	0.087 (3)	0.0029 (11)	0.0055 (14)	−0.0146 (15)

Geometric parameters (Å, º)

C1—C2	1.387 (3)	C10—O3	1.208 (3)
C1—C6	1.397 (3)	C13—O5	1.212 (3)
C1—C7	1.495 (3)	C7—O2	1.338 (3)
C2—C3	1.392 (3)	C10—O4	1.339 (3)
C2—H2	0.9500	O4—C11	1.468 (3)
C3—C4	1.397 (3)	C11—C12	1.499 (4)
C3—C10	1.494 (3)	C11—H11A	0.9900
C4—C5	1.391 (3)	C11—H11B	0.9900
C4—H4	0.9500	C12—H12A	0.9800
C5—C6	1.393 (3)	C12—H12B	0.9800
C5—C13	1.493 (3)	C12—H12C	0.9800
C6—H6	0.9500	C13—O6	1.337 (3)
C7—O1	1.211 (3)	O6—C14	1.455 (3)
O2—C8	1.462 (3)	C14—C15	1.494 (4)
C8—C9	1.500 (3)	C14—H14A	0.9900
C8—H8A	0.9900	C14—H14B	0.9900
C8—H8B	0.9900	C15—H15A	0.9800
C9—H9A	0.9800	C15—H15B	0.9800
C9—H9B	0.9800	C15—H15C	0.9800
C9—H9C	0.9800
C2—C1—C6	120.0 (2)	H9B—C9—H9C	109.5
C2—C1—C7	118.21 (19)	O3—C10—O4	124.0 (2)
C6—C1—C7	121.7 (2)	O3—C10—C3	124.0 (2)
C1—C2—C3	120.4 (2)	O4—C10—C3	111.99 (19)
C1—C2—H2	119.8	C10—O4—C11	115.73 (18)
C3—C2—H2	119.8	O4—C11—C12	106.9 (2)
C2—C3—C4	119.6 (2)	O4—C11—H11A	110.3
C2—C3—C10	122.8 (2)	C12—C11—H11A	110.3
C4—C3—C10	117.52 (19)	O4—C11—H11B	110.3
C5—C4—C3	119.95 (19)	C12—C11—H11B	110.3
C5—C4—H4	120.0	H11A—C11—H11B	108.6
C3—C4—H4	120.0	C11—C12—H12A	109.5
C4—C5—C6	120.3 (2)	C11—C12—H12B	109.5
C4—C5—C13	121.54 (19)	H12A—C12—H12B	109.5
C6—C5—C13	118.2 (2)	C11—C12—H12C	109.5
C5—C6—C1	119.6 (2)	H12A—C12—H12C	109.5
C5—C6—H6	120.2	H12B—C12—H12C	109.5
C1—C6—H6	120.2	O5—C13—O6	124.1 (2)
O1—C7—O2	124.1 (2)	O5—C13—C5	123.8 (2)
O1—C7—C1	124.0 (2)	O6—C13—C5	112.10 (18)
O2—C7—C1	111.90 (19)	C13—O6—C14	116.39 (18)
C7—O2—C8	116.57 (18)	O6—C14—C15	107.4 (2)
O2—C8—C9	106.71 (19)	O6—C14—H14A	110.2
O2—C8—H8A	110.4	C15—C14—H14A	110.2
C9—C8—H8A	110.4	O6—C14—H14B	110.2
O2—C8—H8B	110.4	C15—C14—H14B	110.2
C9—C8—H8B	110.4	H14A—C14—H14B	108.5
H8A—C8—H8B	108.6	C14—C15—H15A	109.5
C8—C9—H9A	109.5	C14—C15—H15B	109.5
C8—C9—H9B	109.5	H15A—C15—H15B	109.5
H9A—C9—H9B	109.5	C14—C15—H15C	109.5
C8—C9—H9C	109.5	H15A—C15—H15C	109.5
H9A—C9—H9C	109.5	H15B—C15—H15C	109.5
C6—C1—C2—C3	0.6 (4)	C1—C7—O2—C8	−178.6 (3)
C7—C1—C2—C3	−178.4 (3)	C7—O2—C8—C9	174.6 (3)
C1—C2—C3—C4	0.5 (4)	C2—C3—C10—O3	−176.4 (3)
C1—C2—C3—C10	−178.2 (3)	C4—C3—C10—O3	4.9 (4)
C2—C3—C4—C5	−1.4 (4)	C2—C3—C10—O4	3.0 (4)
C10—C3—C4—C5	177.4 (2)	C4—C3—C10—O4	−175.7 (3)
C3—C4—C5—C6	1.2 (4)	O3—C10—O4—C11	−2.2 (4)
C3—C4—C5—C13	−179.5 (2)	C3—C10—O4—C11	178.4 (2)
C4—C5—C6—C1	0.0 (4)	C10—O4—C11—C12	−172.3 (3)
C13—C5—C6—C1	−179.5 (2)	C4—C5—C13—O5	−178.9 (3)
C2—C1—C6—C5	−0.9 (4)	C6—C5—C13—O5	0.5 (4)
C7—C1—C6—C5	178.1 (2)	C4—C5—C13—O6	1.2 (3)
C2—C1—C7—O1	−2.8 (4)	C6—C5—C13—O6	−179.4 (2)
C6—C1—C7—O1	178.2 (3)	O5—C13—O6—C14	1.4 (4)
C2—C1—C7—O2	176.3 (2)	C5—C13—O6—C14	−178.7 (2)
C6—C1—C7—O2	−2.7 (4)	C13—O6—C14—C15	172.0 (3)
O1—C7—O2—C8	0.5 (4)