Cyclohexane point group

Even a single molecule is not usually a completely defined object because it is not rigid. An example is provided by cA-1,2-disubstituted cyclohexanes such as dimethyl c/. r-l,2-cyclohcxanedi-carboxylatc. A detailed physicochemical investigation by low-temperature spectroscopy or a detailed mechanistic study (e.g., enzyme-catalyzed semi-saponification of the diesteij, would require an analysis in terms of equilibrating enantiomers 1 of point group C. However, for most practical purposes, e.g.. a manufacturer s catalog, the Haworth-type formula 2 of a Cs-symmetric species would suffice. 

Exercise 1.1. As an exercise, let us locate all of the symmetry elements of the Did point group as they pertain to cyclohexane. The effect of these on the cyclohexane skeleton are shown in Figure 1.2. 

Figure 2.26 Decoration of vertices in the diamond lattice to illustrate the possibility of growing the lattice by decoration about a single point using the orbits of the point group Tj (a) within the conventional unit cell (b) about the larger circle, O, in the extended lattice of interlocked cyclohexane chairs .

The cyclohexane ring has a unique property that is familiar to everyone who has handled molecular models. There is one form, the chair form (point group >3 ), that appears to be rigid, and there is a family of flexible forms that includes the... 

Solution, (a) PF5 is nonpolar (trigonal bipyramidal, 031, point group), (b) Co(en)3 + is nonpolar (D3 point group), (c) c/s-Dichloroethene is polar (C2V point group), (d) The boat form of cyclohexane is polar (C2V point group). 

Determine the point groups of the following molecules. (a) Hydrogen selenide, H2Se (b) Partially deuterated hydrogen sulfide, or HDS (c) The chair conformer of cyclohexane, CgH,2 (d) The boat conformer of cyclohexane, CgH,2... 

Example Point Group Assignments 3.11.1 Example 1 Conformations of Cyclohexane... 

These heat of formation parameters may be considered as shifting the zero point of Fpp to a common origin. Since corrections from larger moieties are small, it follows that energy differences between systems having the same groups (for example methyl-cyclohexane and ethyl-cyclopentane) can be calculated directly from differences in steric energy. 

Petroleum contains hydrocarbons other than the open-chain alkanes considered to this point. These include cycloalkanes in which 3 to 30 CH2 groups are bonded into closed rings. The structures of the two most common hydrocarbons of this type are shown in Figure 22.5 (p. 585). Cyclopentane and cyclohexane, where the bond angles are close to the ideal tetrahedral angle of 109.5°, are stable liquids with boiling points of 49°C and 81°C, respectively. 

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