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Search Results: 1 - 10 of 153436 matches for " Steven F. Watkins "
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1-(Adamantan-1-yl)-3-(4-methoxyphenyl)prop-2-en-1-oneCAS 174315-56-1.
Thy M. Nguyen,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812032400
Abstract: The title molecule, C20H24O2, is a chalconoid derivative in which the keto–enone group is slightly distorted from planarity; the O=C—C=C torsion angle is 12.24 (13)°.
1,2-Bis{2-[2-(trimethylsilyl)ethynyl]phenyl}ethane-1,2-dione
Christopher R. Sparrow,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s160053681203663x
Abstract: The title compound, C24H26O2Si2, has C2 crystallographic symmetry. The dihedral angle between the aromatic rings is 84.5 (2)°. The acetylene group is slightly non-linear, with angles at the acetylene C atoms of 175.7 (2) and 177.0 (2)°. In the crystal structure, only van de Waals interactions occur.
(2R,4R)-4-(2-Ethoxy-2-oxoethyl)-2,6,6-trimethyl–2-oxo-1,3,6,2λ5-dioxazaphosphocan-6-ium iodide
Bradford W. Fulfer,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812018466
Abstract: The title compound, C11H23NO5P+·I , consists of an eight-membered cationic heterocyclic ring in a boat–chair conformation. The ring features a tetraalkylammonium N and a methylphosphonate P atom. A –CH2(CO)OC2H5 ester side chain at the C adjacent to oxygen produces two chiral centers at that substituted C atom and the P atom, both of which were determined to have absolute R,R configurations. A previously determined racemic bromide analog has exactly the same ring but with a –C15H31 side chain. In that structure, both chiral centers show the same relative R/S,R/S configurations, but the ring in the bromide analog is in a boat conformation.
Orthorhombic polymorph of (2E)-2-(2,3-dihydro-1H-inden-1-ylidene)-2,3-dihydro-1H-inden-1-oneCAS 17563-12-1.
Hairong Li,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812035994
Abstract: The title compound, C18H14O, is polymorphic at 123 K. The orthorhombic form reported herein has two independent molecules in the asymmetric unit, with molecular volume 313.5 3. The previously reported triclinic (P-1) form [Raston & Scott (2000). Green Chem., 2, 49–52] has molecular volume 309.6 3 at the same temperature. All three molecules deviate significantly and systematically from the putative Cs symmetry (δr.m.s. = 0.0265, 0.0256, 0.0497 ). Comparison of the two molecules in the orthorhombic polymorph shows that 16 of the 19 equivalent pairs of framework atoms have a mirror-image pattern of deviations (above/below plane), suggesting that the two are quasi-enantiomorphs. The pattern of deviations in the triclinic form is nearly the same (13 of 19 atom pairs) as the orthorhombic form.
1,2,3,4,5,6,7,8,13,13,14,14-Dodecachloro-1,4,4a,4b,5,8,8a,12b-octahydro-1,4:5,8-dimethanotriphenylene at 90 KCAS 147730-93-6.
Brandon W. Jenkins,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812032540
Abstract: The previously reported room-temperature crystal structure [Jaud Baldy, Negrel, Poite & Chanon (1993). Z. Kristallogr. 204, 289–291] of the title compound, C20H8Cl12, is monoclinic with Z′ = 1, whereas the 90 K structure reported herein is triclinic with Z′ = 2 and shows a 2% volume contraction. The crystallographically independent unit chosen consists of both enantiomers (Λ and Δ) of this propeller-like molecule. Both enantiomers display quasi-twofold symmetry, with average bond-length/bond-angle deviations of 0.0018 (4) and 0.41 (2)° for Λ, and 0.0026 (4) and 0.50 (2)° for Δ.
syn-5,10,15-Tris(dichloromethyl)-5,10,15-trihydroxy-5H-diindeno[1,2-a:1′,2′-c]fluorene dichloromethane 0.82-solvate
Gregory W. Morrison,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812020703
Abstract: The title compound, C30H18Cl6O3·0.82CH2Cl2, consists of a slightly cup-shaped seven-ring truxene nucleus with hydroxy and dichloromethyl substituents at stereocenters 5R/S, 10R/S and 15R/S. C—Cl distances are in the range 1.759 (4)–1.783 (3) . Solvent channels parallel to the b axis appear to be partially occupied by highly disordered dichloromethane solvent molecules, the contribution of which were removed from the refinement with the SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65, 148–155]. Only one of the OH groups forms a hydrogen bond, which is intermolecular to another OH group, forming centrosymmetric dimers in the crystal.
N-[2-(Phenylsulfonyl)ethyl]benzylamineCAS 550350-59-9.
David A. Aubry,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s160053681203886x
Abstract: The title compound, C15H17NO2S, exhibits intramolecular hydrogen bonding between the amine H atom and a sulfonyl O atom. The conformation of the molecule is described by the four PhCH2—NH—CH2—CH2—SO2Ph torsion angles of 79.6 (2), 166.21 (14), 70.29 (17) and 58.93 (13)°.
(S)-2-Oxotetrahydrofuran-3-aminium bromideCAS 15295-77-9.
Jace D. Sandifer,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812032552
Abstract: In the title HBr salt of (S)-homoserine lactone, C4H8NO2+·Br , the five-membered ring has an envelope conformation, with the –CH2– C atom adjacent to the N-substituted C atom at the flap position. The four-atom mean plane (r.m.s. deviation = 0.005 ) of the envelope forms a dihedral angle of 32.12 (9)° with the three-atom flap plane. The distorted square-pyramidal coordination about the anion involves five surrounding cations, with the square base defined by three N—H...Br hydrogen bonds [Br...N = 3.3046 (10), 3.3407 (12) and 3.3644 (13) ] and near-contact with an H atom attached to C [Br...C = 3.739 (1) ]. Another Br...C contact of 3.427 (1) defines the apex. There is also an N—H...O hydrogen bond present linking the cations.
tert-Butyl (2S)-2-{3-[(R)-bis(tert-butoxycarbonyl)amino]-2-oxopiperidin-1-yl}-3-methylbutanoateCAS Registry Number 500222-63-9.
Michael J. Kangas,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811043212
Abstract: The title compound, C24H42N2O7, is a chiral lactam-constrained amino acid with a six-membered ring backbone and isopropyl and tert-butyl ester side chains. The conformation of the six-membered ring can be described as a half chair, with two CH2 C atoms lying 0.443 (1) and 0.310 (1) out of the best plane of the other four atoms (mean deviation = 0.042 ). Both N atoms are sp2 hybridized, lying 0.0413 (9) and 0.067 (1) out of the planes defined by the three C atoms bonded to them. The absolute configuration was determined, based on resonant scattering of light atoms in Cu Kα radiation.
2,9,16,23-Tetrakis(1-methylethyl)-5,6,11,12,13,14,19,20,25,26,27,28-dodecadehydrotetrabenzo[a,e,k,o]cycloeicoseneCAS 186494-88-2.
Theshini Perera,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811048604
Abstract: The title compound, C48H40, is a tetraisopropyl-substituted polyannulenoenyne. The unsubstituted polyannulenoenyne, C36H16 (CSD: RICVEE; CAS: 186494-87-1), has quasi-D2 (222) symmetry, as determined by least-squares fit (excluding H atoms) to a model optimized in D2 symmetry by molecular mechanics (r.m.s. deviation = 0.239 ). The least-squares fits of 36 common C atoms of the title compound (at 90 K) to the parent (at 295 K) and to the optimized model show r.m.s. deviations of 0.419 and 0.426 , respectively.
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