Chair conformation molecular model

The stereochemical course of the reaction may be rationalized by assuming a six-mem-bered chelate which presumably exists in a chair-like conformation. Molecular models support the assumption that the nucleophile preferentially attacks from the bottom face of the complex due to the steric hindrance of the axial A-methyl group. 

Make a molecular model of the chair conformation of cy clohexane and turn it so that you can look down one of the C—C bonds... 

Make a molecular model of each chair conformation of methylcyclohexane and compare their energies... 

Make molecular models of the two chair conformations of cis 1 tert butyl 4 phenyl cyclohexane What is the strain energy calculated for each conformation by molecular mechanics Which has a greater preference for the equatorial onentation phenyl or tert butyD... 

The most stable conformation of 1 3 dioxan 5 ol is the chair form that has its hydroxyl group in an axial orientation Suggest a reasonable explanation for this fact Building a molecular model IS helpful... 

Make a molecular model of the chair conformation of 3 D glucopyranose... 

The most stable conformation of cyclohexane is the chair. Electron diffraction studies in the gas phase reveal a slight flattening of the chair compared with the geometry obtained when tetrahedral molecular models are used. The torsion angles are 55.9°, compared with 60° for the ideal chair conformation, and the axial C—H bonds are not perfectly parallel but are oriented outward by about 7°. The length of the C—C bonds is 1.528 A, the length of the C—H bonds is 1.119 A, and the C—C—C angles are 111.05°. ... 

The easiest way to visualize chair cyclohexane is to build a molecular model. (In fact do it now.) Two-dimensional drawings like that in Figure 4.7 are useful, but there s no substitute for holding, twisting, and turning a three-dimensional model in your own hands. The chair conformation of cyclohexane can be drawn in three steps. 

Ketones react with alcohols to yield products called acetals. Why does the all-cis isomer of 4- cvf-butyl-l13-cyclohexanediol react readily with acetone and an acid cataty st to form an acetal while other stereoisomers do not react In formulating your answer, draw the more stable chair conformations of all four stereoisomers and the product acetal. Use molecular models for help. 

Maltose, l- 4- -link in, 998 molecular model of, 998 mutarotation of, 998 structure of, 998 Manicone, synthesis of. 805 Mannich reaction. 915 Mannose, biosynthesis of, 1011 chair conformation of, 126 configuration of, 982 molecular model of, 126 Margarine, manufacture of, 1063 Markovnikov. Vladimir Vassilyevich. 192... 

A half-chair conformation of a crystalline monosaccharide has not been observed. A half-chair conformation for the fourth 2-acetamido-2-deoxy-/3-D-glucopyranosyl residue (residue D) in the lysozyme substrate has not been detected, although, on the basis of model fitting, its presence has been suggested (see p. 96). 2-Acetamido-2-deoxy-/3-D-glucosyl groups were added to a molecular model constructed by use of data obtained from the nature of the enzyme-trisaccharide complex it was implicit that the lifetime of the half-chair conformation would be quite short. 

Two models were proposed to rationalize these interrelationships. One is a molecular motion chain termination model in which it would be presumed that molecular motion would involve orientation involving either coordinated flipping of the ends of the chair conformation trithiane or a rotational motion of the molecule. 

The same distortion, however, is not required for chelation of transA, -cyclohexanediamine (chxn) molecular models show that the two NH2 groups are now ideally situated for bidentate formation to a metal ion (Fig. 8). 7rart -l,2-cyclohexanediamine differs from the ethylenediamine system in that, when it is coordinated, only one chair conformation of the cyclohexane ring is possible. If the other conformer is assumed, the NH2... 

Five-membered ring formation is very favourable as the conformation needed 4 is reasonable and transition state and product are unstrained. If you make a molecular model of a long chain and fold it round you will find that the atoms that approach each other have a 1,5-relationship. Folding a chain 12 to form a six-membered ring takes the nucleophile past the electrophile 12a and only when the chain folds up in a chair-like fashion can cyclisation 13 occur. 

The most basic information that is needed for constructing a global potential energy surface for gas phase MD simulations is the structures and vibrational frequencies. The earliest information about gas-phase RDX molecular structures was obtained from theoretical calculations [54-58]. In 1984 Karpowicz and Brill [59] reported Fourier transform infrared spectra for vapor-phase (and for the a - and p -phase) RDX in 1984, however, their data precluded a complete description of the molecular conformations and vibrational spectroscopy. More recently, Shishkov et al. [60] presented a more complete description based on electron-scattering data and molecular modeling. They concluded that the data were best reproduced by RDX in the chair conformation with all the nitro groups in axial positions. 

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