2-Ethyl 3,4-dimethyl 4′-methyl­biphenyl-2,3,4-tricarboxyl­ate

In the title compound, C₂₀H₂₀O₆, the biphenyl twist angle is 48.2 (1)°. All three ester groups are planar and they make dihedral angles of 63.6 (1), 56.8 (1) and 41.6 (1)° with the attached benzene ring. C—H...O inter­actions contribute to both mol­ecular and crystal stability.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.074
• wR factor = 0.217
• Data-to-parameter ratio = 18.4

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT220_ALERT_2_B Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.56 Ratio
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for        C14

Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.97
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature .        293 K
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.62 Ratio
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C20 H20 O6

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

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

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S1. Comment

Compounds with an aromatic–aromatic bond, i.e. a single bond between aromatic rings such as phenyl rings, and their derivatives with extended structures (oligomers and polymers) have received considerable interest owing to their intriguing structural motifs and unique electroconductive, nonlinear optical and luminescence properties (Kovacic & Jones, 1987; Tour, 1996). The interest in the study of biphenyl derivatives is one of looking for the hydrogen bonding and C—H···O interactions in aromatic compounds (Dobson & Gerkin, 1999c) and the influence of the hydrogen bonding substituents on such interactions. The structural analysis of the title compound, (I), was undertaken in order to look for hydrogen bonds, if any, and the C—H···O interactions that make up for the stability.

The angles in phenyl ring A range from 117.6 (2) to 121.6 (2)° and in B from 117.4 (2) to 121.8 (3)°, deviating from 120°, a feature that is also observed in decachlorobiphenyl (Pedersen, 1975). All other distances and angles fall within normal limits (Table 1). In the ethyl ester, atom C15 deviates from the mean-square ester plane by 1.119 (1) Å. The dihedral angle between the two rings comprising the biphenyl core, the biphenyl twist angle, is 48.2 (1)° (Fig. 1). The deviation from orthogonality could be attributed to the absence of the hydrogen-bonding substituent in the ortho position of the second phenyl ring. For hydrogen-bonding substituents in the ortho position, the twist angles in the literature are 87.3 (1)° (Dobson & Gerkin, 1999a) and 87.5 (2)° (Dobson & Gerkin, 1999b). When there is no hydrogen-bonding substitutent in the ortho position, the twist angle [36.3 (1)°] deviates from orthogonality as evidenced by Sutherland & Rawas (1983). The twist angle of the present compound is comparable to that of the two polymorphic structures with the absence of ortho substitution in the second ring (Subbiah Pandi et al., 2002).

The non-H atoms of the ester group lie very nearly in a plane. The ester planes O1/C13/O2/C14/C15, O3/C16/O4/C17 and O5/C18/O6/C19 are inclined at angles of 63.6 (1)°, 56.8 (1)° and 41.6 (1)°, respectively, to ring A. The two methyl ester planes are very nearly orthogonal [89.1 (1) and 89.0 (1)°] to ring B and are oriented at an angle of 52.5 (1)° to each other. The ethyl ester plane makes a dihedral angle of 68.8 (1)° with ring B, 35.2 (2)° with the first methyl ester and 82.2 (1)° with the second methyl ester.

In addition to the van der Waals forces, the crystal packing is further stabilized by C—H···O hydrogen bonds. Atom C17 of the methoxycarbonyl group interacts with atom O3 at (−1/2 + x, 1/2 − y, −1/2 + z), which generates a C—H···O interaction in a chain motif C(5) along the c axis (Fig. 2).

S2. Experimental

A mixture of DMF (dimethyl formamide)–DMA (dimethyl acetal) (2.5 mmol) and β-phenylethyl crotanate (1 mmol) was refluxed for 4 h and then cooled to 333 K. DMAD (dimethyl acetylene dicarboxilate) (1.5 mmol) was added and the reaction was continued for another 30 min. The compound was recrystallized using an ethyl acetate and hexane mixture (1:1) to afford good quality crystals.

S3. Refinement

The H atoms were positioned geometrically and were treated as riding on their parent C atoms, with C—H distances of 0.93–0.97 Å, and with U_iso(H) values of 1.5U_eq(C) for methyl H and 1.2U_eq(C) for other H atom.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of the title compound showing 30% probability displacement ellipsoids.
	Fig. 2. The molecular packing of (I), viewed down the a axis. Hydrogen bonds are shown as dashed lines, and H atoms not involved in hydrogen bonding have been omitted.

2-Ethyl 3,4-dimethyl 4'-methylbiphenyl-2,3,4-tricarboxylate

Crystal data

C20H20O6	F(000) = 752
Mr = 356.36	Dx = 1.266 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3056 reflections
a = 6.7650 (6) Å	θ = 2.4–27.9°
b = 23.8952 (19) Å	µ = 0.09 mm^−1
c = 12.0094 (10) Å	T = 293 K
β = 105.670 (1)°	Block, colourless
V = 1869.2 (3) Å^3	0.23 × 0.21 × 0.19 mm
Z = 4

Data collection

Bruker SMART APEX CCD area-detector diffractometer	3295 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.025
Graphite monochromator	θmax = 28.0°, θmin = 1.7°
ω scans	h = −8→8
21287 measured reflections	k = −31→30
4398 independent reflections	l = −15→15

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)] = 0.074	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.217	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.1204P)^2 + 0.2698P] where P = (Fo^2 + 2Fc^2)/3
4398 reflections	(Δ/σ)max < 0.001
239 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.20 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
O1	1.2520 (3)	0.20486 (7)	0.75542 (15)	0.0735 (5)
O2	1.1006 (3)	0.13339 (7)	0.64428 (14)	0.0740 (5)
O3	0.9915 (3)	0.23666 (8)	0.96656 (15)	0.0865 (6)
O4	0.8275 (2)	0.20413 (6)	0.79192 (12)	0.0589 (4)
O5	0.9565 (4)	0.12263 (10)	1.19172 (16)	0.0965 (7)
O6	0.7289 (3)	0.15045 (9)	1.03081 (15)	0.0787 (5)
C1	1.2643 (3)	0.07016 (9)	0.86501 (19)	0.0562 (5)
C2	1.1657 (3)	0.12252 (8)	0.84392 (17)	0.0526 (5)
C3	1.0524 (3)	0.14307 (9)	0.91630 (17)	0.0527 (5)
C4	1.0355 (3)	0.11120 (9)	1.01143 (18)	0.0571 (5)
C5	1.1356 (3)	0.06035 (10)	1.0330 (2)	0.0646 (6)
H5	1.1287	0.0396	1.0974	0.077*
C6	1.2453 (3)	0.03998 (10)	0.9609 (2)	0.0644 (6)
H6	1.3085	0.0052	0.9764	0.077*
C7	1.3942 (3)	0.04745 (9)	0.79344 (19)	0.0574 (5)
C8	1.3752 (4)	−0.00794 (10)	0.7560 (2)	0.0688 (6)
H8	1.2760	−0.0307	0.7733	0.083*
C9	1.5020 (4)	−0.02946 (11)	0.6936 (2)	0.0763 (7)
H9	1.4865	−0.0666	0.6699	0.092*
C10	1.6505 (4)	0.00265 (12)	0.6655 (2)	0.0716 (7)
C11	1.6690 (4)	0.05744 (12)	0.7018 (2)	0.0720 (7)
H11	1.7675	0.0801	0.6834	0.086*
C12	1.5440 (3)	0.07979 (10)	0.7652 (2)	0.0647 (6)
H12	1.5609	0.1169	0.7890	0.078*
C13	1.1810 (3)	0.15853 (9)	0.74366 (18)	0.0556 (5)
C14	1.0986 (6)	0.16402 (14)	0.5388 (2)	0.0992 (11)
H14A	1.1464	0.2020	0.5573	0.119*
H14B	1.1875	0.1459	0.4985	0.119*
C15	0.8881 (9)	0.1641 (3)	0.4673 (4)	0.186 (3)
H15A	0.8314	0.1272	0.4658	0.279*
H15B	0.8851	0.1753	0.3901	0.279*
H15C	0.8085	0.1899	0.4988	0.279*
C16	0.9555 (3)	0.20011 (9)	0.89624 (17)	0.0555 (5)
C17	0.7308 (4)	0.25823 (11)	0.7612 (2)	0.0767 (7)
H17A	0.6427	0.2662	0.8099	0.115*
H17B	0.6511	0.2576	0.6818	0.115*
H17C	0.8345	0.2866	0.7715	0.115*
C18	0.9069 (4)	0.12911 (10)	1.0888 (2)	0.0629 (6)
C19	0.5938 (5)	0.17025 (13)	1.0980 (3)	0.0863 (8)
H19A	0.5462	0.1390	1.1339	0.129*
H19B	0.4784	0.1892	1.0480	0.129*
H19C	0.6674	0.1956	1.1566	0.129*
C20	1.7892 (5)	−0.02138 (16)	0.5980 (3)	0.1012 (11)
H20A	1.8809	0.0072	0.5857	0.152*
H20B	1.7076	−0.0349	0.5247	0.152*
H20C	1.8674	−0.0517	0.6407	0.152*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0883 (12)	0.0572 (9)	0.0785 (11)	−0.0153 (8)	0.0285 (9)	0.0105 (8)
O2	0.0986 (13)	0.0649 (10)	0.0539 (9)	−0.0087 (9)	0.0129 (9)	0.0102 (7)
O3	0.1146 (15)	0.0699 (11)	0.0614 (10)	−0.0028 (10)	0.0004 (10)	−0.0107 (8)
O4	0.0630 (9)	0.0591 (9)	0.0490 (8)	0.0046 (7)	0.0056 (6)	0.0052 (6)
O5	0.1218 (17)	0.1114 (17)	0.0569 (11)	0.0112 (13)	0.0251 (11)	0.0199 (10)
O6	0.0628 (10)	0.1073 (14)	0.0641 (10)	−0.0014 (9)	0.0137 (8)	−0.0097 (9)
C1	0.0432 (10)	0.0577 (12)	0.0607 (12)	−0.0073 (8)	0.0023 (9)	0.0123 (9)
C2	0.0464 (10)	0.0535 (11)	0.0514 (11)	−0.0102 (8)	0.0020 (8)	0.0095 (8)
C3	0.0471 (10)	0.0560 (11)	0.0479 (10)	−0.0100 (8)	0.0005 (8)	0.0068 (8)
C4	0.0504 (11)	0.0652 (13)	0.0493 (11)	−0.0144 (9)	0.0025 (9)	0.0087 (9)
C5	0.0559 (12)	0.0716 (14)	0.0593 (13)	−0.0095 (10)	0.0039 (10)	0.0255 (11)
C6	0.0508 (11)	0.0617 (13)	0.0742 (15)	−0.0004 (10)	0.0054 (11)	0.0237 (11)
C7	0.0467 (10)	0.0568 (12)	0.0598 (12)	−0.0016 (9)	−0.0007 (9)	0.0112 (9)
C8	0.0596 (13)	0.0618 (14)	0.0751 (15)	−0.0035 (10)	0.0013 (11)	0.0157 (11)
C9	0.0815 (17)	0.0641 (14)	0.0699 (15)	0.0112 (13)	−0.0023 (13)	0.0015 (11)
C10	0.0604 (13)	0.0893 (18)	0.0549 (13)	0.0139 (12)	−0.0020 (10)	0.0057 (12)
C11	0.0536 (12)	0.0894 (18)	0.0684 (15)	−0.0093 (12)	0.0084 (11)	0.0004 (13)
C12	0.0521 (11)	0.0662 (14)	0.0725 (14)	−0.0106 (10)	0.0113 (11)	−0.0029 (11)
C13	0.0548 (11)	0.0547 (12)	0.0573 (12)	−0.0019 (9)	0.0152 (9)	0.0085 (9)
C14	0.155 (3)	0.089 (2)	0.0556 (15)	0.000 (2)	0.0315 (18)	0.0127 (13)
C15	0.156 (5)	0.291 (8)	0.102 (3)	0.031 (5)	0.017 (3)	0.091 (4)
C16	0.0579 (11)	0.0585 (12)	0.0472 (11)	−0.0092 (9)	0.0092 (9)	0.0032 (9)
C17	0.0837 (17)	0.0708 (15)	0.0722 (15)	0.0205 (13)	0.0154 (13)	0.0156 (12)
C18	0.0693 (14)	0.0611 (13)	0.0557 (13)	−0.0177 (10)	0.0126 (11)	0.0058 (10)
C19	0.0812 (17)	0.0902 (19)	0.093 (2)	−0.0099 (15)	0.0332 (15)	−0.0198 (15)
C20	0.095 (2)	0.133 (3)	0.0725 (18)	0.037 (2)	0.0159 (16)	0.0019 (17)

Geometric parameters (Å, º)

O1—C13	1.200 (3)	C8—H8	0.9300
O2—C13	1.316 (3)	C9—C10	1.377 (4)
O2—C14	1.459 (3)	C9—H9	0.9300
O3—C16	1.193 (3)	C10—C11	1.375 (4)
O4—C16	1.320 (2)	C10—C20	1.509 (4)
O4—C17	1.451 (3)	C11—C12	1.389 (4)
O5—C18	1.200 (3)	C11—H11	0.9300
O6—C18	1.320 (3)	C12—H12	0.9300
O6—C19	1.452 (3)	C14—C15	1.450 (6)
C1—C6	1.394 (3)	C14—H14A	0.9700
C1—C2	1.408 (3)	C14—H14B	0.9700
C1—C7	1.488 (3)	C15—H15A	0.9600
C2—C3	1.395 (3)	C15—H15B	0.9600
C2—C13	1.506 (3)	C15—H15C	0.9600
C3—C4	1.403 (3)	C17—H17A	0.9600
C3—C16	1.504 (3)	C17—H17B	0.9600
C4—C5	1.381 (3)	C17—H17C	0.9600
C4—C18	1.496 (4)	C19—H19A	0.9600
C5—C6	1.373 (4)	C19—H19B	0.9600
C5—H5	0.9300	C19—H19C	0.9600
C6—H6	0.9300	C20—H20A	0.9600
C7—C12	1.387 (3)	C20—H20B	0.9600
C7—C8	1.393 (3)	C20—H20C	0.9600
C8—C9	1.381 (4)
C13—O2—C14	117.6 (2)	O1—C13—O2	125.6 (2)
C16—O4—C17	116.2 (2)	O1—C13—C2	123.0 (2)
C18—O6—C19	117.0 (2)	O2—C13—C2	111.32 (18)
C6—C1—C2	117.6 (2)	C15—C14—O2	107.0 (3)
C6—C1—C7	119.3 (2)	C15—C14—H14A	110.3
C2—C1—C7	123.03 (18)	O2—C14—H14A	110.3
C3—C2—C1	120.94 (18)	C15—C14—H14B	110.3
C3—C2—C13	117.73 (18)	O2—C14—H14B	110.3
C1—C2—C13	121.3 (2)	H14A—C14—H14B	108.6
C2—C3—C4	119.7 (2)	C14—C15—H15A	109.5
C2—C3—C16	120.58 (18)	C14—C15—H15B	109.5
C4—C3—C16	119.6 (2)	H15A—C15—H15B	109.5
C5—C4—C3	119.1 (2)	C14—C15—H15C	109.5
C5—C4—C18	118.21 (19)	H15A—C15—H15C	109.5
C3—C4—C18	122.6 (2)	H15B—C15—H15C	109.5
C6—C5—C4	121.0 (2)	O3—C16—O4	125.1 (2)
C6—C5—H5	119.5	O3—C16—C3	123.6 (2)
C4—C5—H5	119.5	O4—C16—C3	111.34 (17)
C5—C6—C1	121.6 (2)	O4—C17—H17A	109.5
C5—C6—H6	119.2	O4—C17—H17B	109.5
C1—C6—H6	119.2	H17A—C17—H17B	109.5
C12—C7—C8	117.4 (2)	O4—C17—H17C	109.5
C12—C7—C1	121.5 (2)	H17A—C17—H17C	109.5
C8—C7—C1	121.0 (2)	H17B—C17—H17C	109.5
C9—C8—C7	120.8 (2)	O5—C18—O6	123.7 (2)
C9—C8—H8	119.6	O5—C18—C4	123.7 (2)
C7—C8—H8	119.6	O6—C18—C4	112.52 (19)
C10—C9—C8	121.8 (3)	O6—C19—H19A	109.5
C10—C9—H9	119.1	O6—C19—H19B	109.5
C8—C9—H9	119.1	H19A—C19—H19B	109.5
C11—C10—C9	117.6 (2)	O6—C19—H19C	109.5
C11—C10—C20	121.0 (3)	H19A—C19—H19C	109.5
C9—C10—C20	121.4 (3)	H19B—C19—H19C	109.5
C10—C11—C12	121.5 (2)	C10—C20—H20A	109.5
C10—C11—H11	119.2	C10—C20—H20B	109.5
C12—C11—H11	119.2	H20A—C20—H20B	109.5
C7—C12—C11	120.9 (2)	C10—C20—H20C	109.5
C7—C12—H12	119.6	H20A—C20—H20C	109.5
C11—C12—H12	119.6	H20B—C20—H20C	109.5
C6—C1—C2—C3	−0.4 (3)	C8—C9—C10—C20	179.5 (2)
C7—C1—C2—C3	−177.32 (18)	C9—C10—C11—C12	0.5 (4)
C6—C1—C2—C13	178.86 (19)	C20—C10—C11—C12	−179.2 (2)
C7—C1—C2—C13	1.9 (3)	C8—C7—C12—C11	0.2 (3)
C1—C2—C3—C4	−0.2 (3)	C1—C7—C12—C11	177.7 (2)
C13—C2—C3—C4	−179.42 (17)	C10—C11—C12—C7	−0.5 (4)
C1—C2—C3—C16	177.27 (17)	C14—O2—C13—O1	0.5 (4)
C13—C2—C3—C16	−2.0 (3)	C14—O2—C13—C2	178.1 (2)
C2—C3—C4—C5	1.4 (3)	C3—C2—C13—O1	59.1 (3)
C16—C3—C4—C5	−176.08 (19)	C1—C2—C13—O1	−120.2 (2)
C2—C3—C4—C18	−176.49 (18)	C3—C2—C13—O2	−118.6 (2)
C16—C3—C4—C18	6.1 (3)	C1—C2—C13—O2	62.1 (2)
C3—C4—C5—C6	−2.1 (3)	C13—O2—C14—C15	−126.1 (4)
C18—C4—C5—C6	175.9 (2)	C17—O4—C16—O3	2.2 (3)
C4—C5—C6—C1	1.6 (3)	C17—O4—C16—C3	−177.66 (19)
C2—C1—C6—C5	−0.3 (3)	C2—C3—C16—O3	−121.6 (3)
C7—C1—C6—C5	176.75 (19)	C4—C3—C16—O3	55.8 (3)
C6—C1—C7—C12	−129.3 (2)	C2—C3—C16—O4	58.3 (2)
C2—C1—C7—C12	47.6 (3)	C4—C3—C16—O4	−124.3 (2)
C6—C1—C7—C8	48.2 (3)	C19—O6—C18—O5	4.2 (4)
C2—C1—C7—C8	−134.9 (2)	C19—O6—C18—C4	−178.8 (2)
C12—C7—C8—C9	0.2 (3)	C5—C4—C18—O5	40.7 (3)
C1—C7—C8—C9	−177.3 (2)	C3—C4—C18—O5	−141.4 (2)
C7—C8—C9—C10	−0.3 (4)	C5—C4—C18—O6	−136.4 (2)
C8—C9—C10—C11	−0.1 (4)	C3—C4—C18—O6	41.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C17—H17B···O3^i	0.96	2.52	3.473 (3)	171

Symmetry code: (i) x−1/2, −y+1/2, z−1/2.