Cyclohexane, model

Pick up the cyclohexane model and view it from the side of the chair. Visualize the ring around the perimeter of the system perpendicular to the axis through the center. Of the 12 hydrogens, how many are pointed up relative to the plane (4a) How many are pointed down (4b) ... 

Cyclohexane model kits each consisting of the following... 

Suresh AK, Sridhar T, Potter OE. (1988) Autocatalytic oxidation of cyclohexane modelling reaction kinetics. AICHEJ, 34 69-80. 

CY Dg cyclohexane modelled by the lowest energy conformational isomer of cyclohexane. 

AK Suresh, T Sridhar, OE Potter. Autocatalytic oxidation of cyclohexane—modeling reaction kinetics. AIChE J 34 69-80, 1988. 

A solution of 7-bromo-2-(fV-methylanilino)hept-2-enenitrile (145 mg, 0.52 mmol) in cyclohexane (60 ml) was placed in a quartz tube and purged with oxygen. The sample was irradiated for 8h in a Rayonet Model RPR-100 Reactor using 254 nm light. An oxygen atmosphere was maintained during... 

In keeping with the bent bond de scription of Figure 3 10 the carbon-carbon bond distance in cycio propane (151 pm) is slightly shorter than that of ethane (153 pm) and cyclohexane (154 pm) The calculated val ues from molecular models (see Learning By Modeling) reproduce these experimen tal values... 

FIGURE 3 14 (a) A ball and spoke model and (b) a space filling model of the boat confor mation of cyclohexane Torsional strain from eclipsed bonds and van der Waals strain involving the flagpole hydrogens (red) make the boat less stable than the chair... 

The best way to un derstand ring flip ping in cyclohexane IS to view the animation of Figure 3 18 in Learning By Modeling... 

Use molecular models to compare —C=CH —CH=CH2 and —CH2CH3 with respect to their preference for an equatonal onentation when attached to a cyclohexane nng One of these groups IS very much different from the other two Which one" Why" ... 

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 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°. ... 

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

Construct a molecular model of rra i-2-bromocyclohexanol in its most stable conformation. This conformation is ill-suited to undergo epoxide formation on treatment with base. Why What must happen in order to produce 1,2-epoxy cyclohexane from rra i-2-bromocyclohexanol ... 

We ran an SCRF single point energy calculation for gauche dichloroethane conformers in cyclohexane (e=2.0), using the Onsager model at the Hartree-Fock and MP2 levels of theory (flfl=3.65) and using the IPCM model at the B3LYP level. The 6-31+G(d) basis set was used for all jobs. We also ran gas phase calculations for both conformations at the same model chemistries, and an IPCM calculation for the trans conformation (SCRF=Dipole calculations are not necessary for the trans conformation since it has no dipole moment). 

Figure 9-64. Pressure drop at the flood point as a function of ioad-ing. Values are calculated using the Stichimair et al. model and distillation conditions using cyclohexane/n-heptane and Gempak 2A packing. Note ordinate (N/m /m)/3.3853 = in. Hg/m. Reproduced by permission of the American Institute of Chemical Engineers, Fair, J. R. and Bravo, J. L., Chemical Engineering Progress, V. 86, No. 1 (1990) p. 19 ail rights reserved.

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. 

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