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In summary, our structure results show that the metal ions are completely disordered in A12TiOs. The differences between our room temperature and 600°C structures explain the anisotropic thermal expansion behavior of the single crystal. Furthermore, the importance of cleavage planes resulting from edge-shared octahedra in the hysteresis of the thermal expansion of the ceramic is pointed out. Sayre's relations were used to determine the structure of 3',5,5',6-tetramethoxyflavone. The flavone was extracted from the fruit of Sargentia greggii, a citrus plant found in Mexico. The space group is P2Jc and the cell dimensions are a= 7.335 (5), b = 11.304 (5), c = 20.249 (6) A and fl= 104.5 (4) °. 2511 independent reflections were collected by counter methods. The observed density is 1.42 g.cm -3 which is consistent with four molecules per unit cell, de= 1.40 g.cm -3. The model was refined by least-squares techniques to a conventional R value of 0-086 for 1249 of the largest intensities. The heterocyclic ring, which is fused to the benzene ring to form the y-benzopyrone portion of the molecule, is slightly puckered and planes fitted to the two rings make an angle of 4 °. The phenyl ring is planar and makes an angle of 28 ° with the y-benzopyrone portion of the molecule. Three of the methoxyl groups are essentially coplanar with the benzene rings while the fourth is forced from the plane due to intramolecular crowding.

The reaction of ethyl 2-formyl-2-phenylpropionate with FSO3H yields the unique compound diethylThe compound crystallizes in space group PI with a = 26.486 (10), b = 8.543 (3), c = 9.467 (8) A, a = 104.38 (5), fl = 102.45 (5), y = 90.35 (3) °, V = 2022 (2) A 3 and Z = 4. Counter techniques were used to collect 5620 independent reflections. The structure was solved by application of direct-method techniques, and the model was refined by least-squares procedures to an R factor of 0.076. The eight-membered cyclooctadiene ring exhibits a conformation intermediate between the tub and boat forms. The distortion is imposed by the 1,5-epoxy bridge and the 2,6-diene moieties. The conformations of the two independent molecules are identical except for a twist of one ethoxycarbonyl group.

The single-crystal X-ray structures of the sulfonium ylides 9,9-dideuteriothioxanthenium bis(carboethoxy)methylide and thioxanthonium bis(carbomethoxy)methylide reveal that both molecules are folded about an imaginary line connecting C(9) and S (138°and 169°, respectively). Like the corresponding sulfoxides, the methylide carbon is pseudoequatorial (e') in both ylides. The malonylide fragment resides in the plane which bisects the "angle of the fold" of the heterocycle. The oxygen of one carbonyl group ("endo") is arrayed essentially trans to the nonbonding electron pair on sulfur. Dimethyl 9-(l,4-dimethylthioxanthenyl)malonate exists with the malonyl fragment in the pseudoaxial (a') position. 13C resonances of a' methylide carbons in these thioxanthenium ylides occur downfield of corresponding e' methylide carbons (67 vs. 54 ppm). The methylide carbons of related thioxanthonium ylides resonate near 60 ppm, reflecting their intermediate geometry. Both *H and 13C NMR spectra indicate a relatively high rotational barrier about the S+-C~bond in bis(carbomethoxy)methylides derived from thioxanthone, 2-chlorothioxanthone, and 2,4-dimethylthioxanthone. Infrared spectra can be used to distinguish isomeric ylides and thioxanthenes. S(10)-C( 12) 1.770 (3) S(10)-C( 13) 1.755 (3) C(l)-C(2) 1.401 (4) C(1)-C(U) 1.410 (3) C(l)-C(15) 1.496 (4) C(2)-C(3)1.366 (4) C(3)-C(4) 1.384 (4) C(4)-C( 12) 1.393 (4) C(4)-C( 16) 1.497 (4) C(5)-C( 13) 1.402 (5) C( 5)-C( 6) 1.368 (5) C( 6)-C( 7) 1.373 (4) C( 7)-C( 8) 1.388 (6) C(8)-C( 14) 1.388 (15) C( 9)-C(ll)1.513(4) C(9)-C( 14) 1.510(5) C(9)-C(17) 1.556(4) C(ll)-C(12) 1.403 (3) C(13)-C(14) 1.385 (3) C(17)-C(18) 1.513(5) C(18)-0(19) 1.201(3) C(18)-O(20) 1.327 (4) O(20)-C(21) 1.436(6) C(17)-C(22) 1.518(4) C(22)-0(23) 1.194(4) C(22)-0(24) 1.322(3) 0(24)-C(25) 1. 440(5) ylide [thioxanthonium bis(carbomethoxy)methylide ( 5)].Recently,6 we prepared thioxanthenium methylides which, because of peri substitution at C(4),2 must exist with the methylide carbon in the a' position. Using these as model compounds, and not making any other assumptions, it was possible to demonstrate that simple ylides of thioxanthene (i.e., those lacking substituents at C(4)/C(5) and C( 9)) exist in the e' conformation. Our 9,9-Dideuteriothioxanthenium Bis(carboethoxy)methylide