Synthesis, 1H, 13C, and 29Si nuclear magnetic resonance spectra and crystal structure of trans-1,4-diphenyldecamethylcyclohexasilane

1987 ◽  
Vol 65 (2) ◽  
pp. 437-440 ◽  
Author(s):  
Kanta Kumar ◽  
Morton H. Litt ◽  
Raj K. Chadha ◽  
John E. Drake
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Reaction ◽  
Chair Conformation ◽  
Site Symmetry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Phenyl Rings

The coupling reaction between PhMeSiCl2 and Me2SiCl2 in the presence of Na/K alloy resulted in a variety of phenylated permethylcyclohexasilanes of which only trans-1,4-Ph2Me10Si6 could be obtained in pure form by repeated recrystallizations. It was studied by means of nmr (1H, 13C, and 29Si) and X-ray crystallography. The crystals are monoclinic, P21/c with a = 10.105(6), b = 14.77(1), c = 9.973(6) Å, β = 94.08(5)°, V = 1485(2) Å3, and Z = 2 for 1922 unique "observed" reflections and the structure refined to an R index of 0.036. The molecule has site symmetry [Formula: see text] and the chair conformation of cyclohexane, with the two phenyl rings occupying the equatorial positions.

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

Structure and nuclear magnetic resonance spectra of 6-bromo-3,3′,4′,5,7-penta-O-methylcatechin

1985 ◽  
Vol 63 (8) ◽  
pp. 2176-2180 ◽  
Author(s):  
F. W. B. Einstein ◽  
E. Kiehlmann ◽  
E. K. Wolowidnyk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Title Compound ◽  
Bromine Atom ◽  
Heterocyclic Ring ◽  
Equatorial Orientation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ring Conformations

The title compound has been synthesized by selective debromination of 6,8-dibromocatechin and indirect methylation of the resulting 6-bromocatechin via its pentaacetate. The structure of C20H23BrO6 has been determined by X-ray crystallography. The compound crystallizes in the space group P1 with a = 9.589(3) Å, b = 11.576(3) Å, c = 11.326(3) Å, α = 118.80(3)°, β = 93.23(3)°, γ = 111.44(3)°, ρc = 1.481 g cm−3, and Z = 2. Intensities were measured for 2584 independent reflections (2θ < 45°) of which 2213 were observed (I > 3.0σ(I)) and used in subsequent refinement (final R values were R = 0.0268 and Rw = 0.0344). Crystallographic and pmr data confirm the position of the bromine atom at C-6, the trans-diaxial arrangement of H-2/H-3 and the quasi-equatorial orientation of the 3,4-dimethoxyphenyl group (ring B). The two heterocyclic ring conformations are consistent with the expected flexibility of the molecule.

The crystal structure of bis(triphenyltin)telluride and the interpretation of the 119Sn Mössbauer and nuclear magnetic resonance data of the bis(triphenyltin) and bis(trimethyltin) chalcogenides

1983 ◽  
Vol 61 (11) ◽  
pp. 2611-2615 ◽  
Author(s):  
F. W. B. Einstein ◽  
C. H. W. Jones ◽  
T. Jones ◽  
R. D. Sharma
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Solution Nmr ◽  
Fold Axis ◽  
X Ray ◽  
X Ray Crystallography ◽  
Magnetic Resonance Data ◽  
Resonance Data

The structure of (Ph3Sn)2Te has been determined by X-ray crystallography. The compound crystallizes in the space group C2/c with a = 18.578(3) Å, b = 7.731(1) Å, c = 25.272(4) Å, β = 117.17(1)°, ρc = 1.702 g cm−3, ρo(CHCl3/CH2I2) = 1.69 g cm−3, and Z = 4. Intensities were measured for 2853 independent reflections (2θ ≤ 50°) of which 2044 were observed (I ≤ 2.3σ(I)) and used in subsequent refinement (final R values were R = 0.034 and Rw = 0.045). The (Ph3Sn)2Te molecule exhibits a "bent" structure in which Sn—Te—Sn = 103.68(2)° and Te—Sn = 2.7266(6) Å and in which the Te atom lies on a crystallographic two-fold axis. Comparison of the present structure with corresponding selenide and sulphide analogues indicates that in all three cases the environment about tin corresponds to that of sp3 hybridisation. The 119Sn Mössbauer quadrupole splittings of (Ph3Sn)3E and (Me3Sn)2E, where E = S, Se, or Te, show a correlation with the 119Sn solution nmr chemical shifts and this correlation is discussed.

The preferred conformation of 2-fluoro-2-deoxy β-D-mannopyranosyl fluoride. An X-ray crystallographic and 2-dimensional proton nuclear magnetic resonance study

1986 ◽  
Vol 64 (2) ◽  
pp. 232-236 ◽  
Author(s):  
Stephen G. Withers ◽  
Ian P. Street ◽  
Steven J. Rettig
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Direct Methods ◽  
Chair Conformation ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Proton Nuclear Magnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic

The preferred conformation of 2-fluoro-2-deoxy β-D-mannopyranosyl fluoride has been determined in the solid state by X-ray crystallography and in aqueous solution by 2-dimensional J-resolved proton nuclear magnetic resonance. Crystals of 2-fluoro-2-deoxy β-D-mannopyranosyl fluoride are monoclinic, a = 4 10.9150(8), b = 4 4.9079(4), c = 4 6.9902(6) Å, β = 105.158(4)°, Z = 2, space group P21. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.028 and Rw = 0.031 for 797 reflections with I ≥ 3σ(I). The sugar ring was present in an essentially undistorted 4C1 chair conformation. Weak, but significant interactions, presumably hydrogen bonding of the type OH … F and CH … F, are observed within the crystal lattice. Coupling constants observed in the proton nmr were consistent only with a 4C1 chair conformation in solution. These observations are briefly discussed in terms of recent findings concerning the interaction of fluorodeoxy sugars with enzymic binding sites.

Sign in / Sign up

Export Citation Format

Share Document