The structure of the 2/1 'channel' inclusion compound between deoxycholic acid and pinacolone, 2C24H40O4.C6H12O

Abstract

WER.NINCK, BLAIR., MILBURN, ANDO, BLOOR, MOTEVALLI AND HUR.STHOUSE 229 be a minimum, hence defining a least-motion reaction path. The r.m.s, displacement for MSHD is also large so that it does not provide a critical test of the criteria. The crystal structure data for other diacetylenes suggests, however, that the simple criterion of Schmidt is adequate for the assessment of solid-state reactivity of diacetylenes.The larger monomer separation for MSHD relative to TSHD and BSHD [5.774(2) Abstract. Mr-885.32 , orthorhombic, P212121, a= 27.132 (7), b= 13.543 (2), c= 14.228 (2) A, V= 5228 (2) A 3, Z=4, D x=l.12Mgm -3, CuKa, 2= 1.5418/~,, /z=0.6 mm -1, F(000)= 1952, room temperature, R = 0.078 and R w = 0.079 for 3067 independent reflections with I > 1.5 a(/). The crystal packing is very similar to those found in the deoxycholic acid inclusion compounds with norbornadiene and quadricyclane (tetracyclo[2.2.1.02.6.0a,5]heptane), and is characterized by an assembly of antiparallel pleated bilayers of the steroid molecules, which pack together leaving empty spaces occupied by the guest molecules. The cross section of the channels is almost square. The centers of gravity of pinacolone, which assumes in the channels two different orientations related by a pseudo twofold axis, have coordinates approximately equal to those of norbornadiene and quadricyclane. energy (Hautala, Little & Sweet, 1977). Because of the lack of overlap between the electronic absorption spectrum of NBD and the solar radiance spectrum, the direct conversion NBD--,QDC by sunlight is precluded. However, this conversion is still achievable by means of photosensitizers. Since the quantum efficiency of the reaction and the purity of QDC could be improved inside the channels of an inclusion compound, those of the deoxycholic acid (DCA) were chosen for this purpose.The inclusion compounds between DCA and NBD (DCANBD; D'Andrea, Fedeli, Giglio, Mazza & Pavel, 1981) and QDC (DCAQDC; Coiro, Giglio, Mazza & Pavel, 1984) were studied in order to establish whether the DCA host lattices are nearly equal. Since the DCA host lattice does not change, it is possible to foresee that it can easily tolerate the lattice-controlled photoinduced reaction NBD--,QDC, without destroying the crystal structure of the inclusion compound. Furthermore, the structural information gained from the crystal packing of DCANBD and DCAQDC is useful for the choice of

Singularities in Molecular Conformation

“…In 3 crystals the τ angle is in the 0-5° range, in 3 structures between 5-15º, and in 4 structures in the range from 15 to over 30°. 3,[17][18][19][20][21][22] In the co-crystal with deoxycholic acid angle τ is the highest, of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 7 30.05°, which is considered essential for its photosensitizing effect. 3 The conformation of pinacolone, apart from torsion angle O1=C2-C3-C4 (τ.…”

“…Our survey of the Cambridge Structural Database (Version 5.36) revealed 7 solvate crystals with 11 independent pinacolone molecules. In three crystals the τ angle is in the 0–5° range, in three structures between 5 and 15°, and in four structures in the range from 15 to over 30°. ,− In the cocrystal with deoxycholic acid angle τ is the highest, of 30.05°, which is considered essential for its photosensitizing effect . The conformation of pinacolone, apart from torsion angle O1C2–C3–C4 (τ.…”

“…3 The conformation of pinacolone, apart from torsion angle O1=C2-C3-C4 (τ. Figure 1), involves the rotations of methyl groups C1H 3 , C4H 3 , C5H 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 8 passes through 0°, which implies the rotation of methyl C1H 3 by ∆τ 5 =60° and that this abrupt conformation change is coupled to small abrupt rotations of the methyl hydrogen atoms at the closely located groups C5H 3 (τ 3 ) and C5'H 3 (τ 2 ). These rotations relax the steric hindrances due to the overcrowding of the H-atoms, and they cumulate in the largest rotation (∆τ 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17...…”

“…The minimum of potential energy occurs at 14° ± n ·120°. Red dashes indicate the torsion angles of pinacolone molecules present in cocrystalline compounds. ,− The Δ E p barriers have been indicated and the inset (top) expands the schematic Δ E p to over one full rotation of the tert -butyl group.…”

“…Pinacolone is the product of pinacol rearrangement, one of textbook reactions in organic chemistry. Pinacolone products have manifold applications, including advanced fungicides (e.g., triadimefon and triadimenol) and as a photosensitizer, e.g., inter alia in an inclusion compound with deoxycholic acid, allowing the chemical storage of solar energy . The molecule of pinacolone is flexible; however this structure, conformation, and interactions in the crystalline state have not been investigated.…”