Cycloalkane representation

Cycloalkanes are alkanes that are cyclic with the general formula C H2 . The simplest members of this class consist of a single, unsuhstituted carhon ring, and these form a homologous series similar to the unbranched alkanes. The C3 to Ce cycloalkanes with their structural representations are shown below. 

Cycloalkanes having three to six carbon atoms are shown in the accompanying figure. They are most often drawn in skeletal representations. 

The cyclic saturated hydrocarbons, or cychalkanes, have the general formula C 2n-cycloalkanes (and other ring compounds that we will encounter later) are often shown in simplified skeletal form in which each intersection of two lines represents a C atom we mentally add enough H atoms to give each carbon atom four bonds. The first four unsubstituted cycloalkanes and their simplified representations are... 

Alkanes that form rings, or cycles, are called cycloalkanes. As T Figure 24.5 illustrates, cycloalkane structures are sometimes drawn as line structures, which are polygons in which each corner represents a CH2 group. This method of representation is similar to that used for benzene rings, ono (Section 8.6) (Remember from our benzene discussion that in aromatic structures each vertex represents a CH group, not a CH2 group.)... 

Configuration of cycloalkanes is based on the combinations of tetrahedrons, similarly to the case of alkanes. However, in some cases the ring structure requires that the angles between C-C bonds deviate from the normal tetrahedral values (109°28 ). Almost ideal tetrahedral angles are present in the molecule of cyclohexane. For the pictorial representation of three dimensional molecular structures of cyclic molecules special descriptive projection is used. Let us analyse the structure of cyclohexane molecule in more detail. 

Alkanes all have the molecular formula C H.2 +2- The simplest alkane is methane, CH4. Vast numbers of related molecules can be constructed from methane by replacing one or more of its hydrogens with other carbons and their attendant hydrogens. Linear arrays can be made, as well as branched structures and even rings (ring compounds called cycloalkanes, have a slightly different formula C H2 ). Figure 2.1 shows a few schematic representations for these molecules. 

Cycloalkanes are alkanes in which the carbon atoms are arranged in a ring, or cyclic, structure. The structural formulas for cycloalkanes are often drawn in a simplified form. In these skeletal representations, such as the one below on the right, it is understood that there is a carbon atom at each corner and enough hydrogen atoms to complete the four bonds to each carbon atom. 

The line-angle representations shown at the bottom of page 1221 might lead you to believe that the carbon atoms in cycloalkanes all lie in the same plane. However, this is not generally the case. As we will soon see, cyclopropane is the only cycloalkane in which the carbon atoms form a planar ring. 

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