Dibenzo-15-crown-5 ether and its sodium thiocyanate complex. X-ray crystallographic and NMR studies in the solid phase and in solution

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. Can. J . Chem. 70, 981 (1992) The structures of the title materials have been determined via X-ray crystallography. In the free crown ether, there is effectively a plane of symmetry that bisects the molecule. In the NaNCS complex, ring inversion of one of the cyclohexane moieties has occurred, giving a distorted pentagonal pyramidal coordination geometry about the sodium ion. For the free crown, two conformers, whose free energies differ by ca. 0.5 kJ/mol in solution can be detected via I3C NMR at 168 K. Limiting low-temperature solution spectra are compared to those which have been obtained in the solid phase using the I3c CPMAS technique.Key words: crown ethers, stereochemistry, X-ray, NMR.G . W. BUCHANAN, S . MA.~HIAS, C. BENSIMON et J. P. CHARLAND. Can. J. Chem. 70, 98 1 (1992). On a dCterminC les structures des produits mentionnks dans le titre par diffraction des rayons X. Dans 1'Cther couronne h 1'Ctat libre, il existe un plan de symCtrie qui bissecte la molCcule. Dans le complexe NaNCS, il se produit une inversion des cycles des portions cyclohexaniques; il s'ensuit que la coordination autour du sodium est de type pyramide pentagonale dCformCe. Pour la couronne libre, h 168 K , la RMN du permet de dCtecter deux conformkres dont les Cnergies libres different par environ 0,5 kJ/mol, en solution. On a comparC les spectres obtenus ii la limite infkrieure de tempkrature supportCe par la solution avec ceux qui ont Ct C obtenus en phase solide h I'aide de la technique du CPMAS du "C.

Section: Introductionmentioning

confidence: 99%

“…In the case of 2, the lack of symmetry in the crystal structure is reflected in the appearance of the solid phase I3c Cyclohexyl rings C+C 1-C2-C3 58.1 (4) One notable difference in the chemical shifts for solid 1 vs. 2 concerns the CH,-0 carbons. In 2, the resonances for C8, 9, 10, and 1 1 are all shielded by at least 3.6 ppm relative to C8 and C9 of 1.…”

mentioning

confidence: 99%

Stereochemistry of crown ethers, X-ray crystallographic structures, solid phase ¹³C NMR, and solution conformational equilibria in cis-syn-cis dicyclohexano-15-crown-5 ether and its sodium thiocyanate complex

Buchanan¹,

Mathias²,

Bensimon³

et al. 1992

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“…Conformational equilibria in cis-syn-cis-and cis-anti-cis-dicyclohexano-12-crown-4-ethers (1 and 2 below) as well as their 18-crown-6 and 24-crown-8 analogs are amenable to examination via 13c NMR spectroscopy at low temperature (1)(2)(3)(4).…”

Section: Introductionmentioning

confidence: 99%

“…Acetic acid (0.5 mL) and rhodium-on-alumina catalyst (0.3 g) were added to the solution and hydrogenation was performed at 40°C using a pressure of 600 psi for 8 h. Following filtration, the solvent was removed at reduced pressure and the crude product was dissolved in 100 mL of CH,Cl, and washed with saturated NaCl (2 x 10 mL) and water (20 mL). After drying over sodium sulfate and solvent removal, the resultant oil was purified by column chromatography to yield 1.2 g (88%) of 1,5-dicyclohexoxy-3-oxapentane 4 Compound 6 was prepared according to the following procedure. Phenol (5.0 g, 0.053 mol) was dissolved in 200 mL of anhydrous acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

Dicyclohexylethyleneglycol, -diethyleneglycol, -triethyleneglycol, and related monosubstituted cyclohexanes. Conformational analysis using low-temperature ¹³C and ¹H NMR spectroscopy

Buchanan¹,

Moghimi²,

Reynolds³

et al. 1995

Two conformations of each of the title molecules have been detected by 100 MHz I3C NMR at 210 K. For the dicyclohexyl systems, the conformations are related via a single ring inversion. In each case the equatorial-axial conformer is 4.7 ? 0.4 kJ/mol less stable than the diequatorially substituted form in CD2CI2 solution. For monosubstituted models, the conformational free energy (-AGO) values of the -0-CH,-CH2-0CH3, -OCH,-CH2-0-CH,-CH,, and -0-CH2-CH2-0-CH-(CH,), groups have been determined to be 5.4.6.1, and 6.1 + 0.2 kJ/mol, respectively. In methanol, the latter equilibria are slightly more biased towards the axially substituted conformers.Key words: substituted ethylene glycols, conformational equilibria.

“…tions between solid state ' 3~ Nh4R behaviour and X-ray crystallographic structures of benz-annelated crown ethers with a variety of structures. This has included the benzo-and dibenzo-15-crown-5 systems depicted below (1,5).…”

Section: Introductionmentioning

confidence: 99%

Solid state and solution stereochemistry of crown ethers and models. ortho-Dimethoxydiphenyl ether and related dibenzo-15-crown-5 and tetrabenzo-30-crown-10 ethers as studied by X-ray crystallography and ¹H and ¹³C NMR spectroscopy

Buchanan¹,

Rodrigue²,

Bourque³

et al. 1994

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Introduction trends with X-ray derived structural features are presented. Following the early of Tmter and co-workers (I), a Solution 13c chemical shift assignments are made on the basis number of recent publications (2-6) have dealt with correlaof NOESY and l43TCOR results. tions between solid state ' 3~ Nh4R behaviour and X-ray crystallographic structures of benz-annelated crown ethers with a variety of structures. This has included the benzo-and dibenzo-15-crown-5 systems depicted below (1, 5).