Isomers of cycloalkanes

Q Draw and name the isomers of cycloalkanes, and explain ring strain. 

Skeletal Isomers of Cycloalkanes Five cyclic compounds of C5H10. Start with a five-membered ring. Then use a four-membered ring with a one-carbon side chain. Finally, draw a three-membered ring with either one two-carbon side chain or two one-carbon side chains. 

In Section 11.3, we observed that the rotation around the carbon-carbon bonds of cycloalkanes was restricted. The consequence of the absence of free rotation was the formation of geometric or cis-trans isomers. The cis isomers of cycloalkanes had substituent groups on the same side of the ring (L., cis, "on the same side"). The trans isomers of cycloalkanes had substituent groups located on opposite sides of the ring (L., trans, "across from"). 

Name and draw structural formulas for geometric isomers of cycloalkanes. (Section 1.9)... 

Cis and trans isomers of cycloalkanes furnish us with another example of stereoisomers that are diastereomers. Consider the following two compounds ... 

Cis-trans isomers of cycloalkanes are a type of stereoisomer, also called geometric stereoisomers, in which substituents are on the same side ids) or on the opposite sides trans) of the ring. 

These stereoisomers are not readily interconverted by rotation around the double bond at room temperature. Like cis-trans isomers of cycloalkanes, they are configurational stereoisomers and can be separated from one another by distillation, taking advantage of the difference in their boiling points. 

Stereoisomers (Section 4.2) are compounds whose atoms are connected in the same order hut with a different arrangement in space. Among the kinds of stereoisomers we ve seen are enantiomers, diastereomers, and cis-trans isomers of cycloalkanes. Actually, cis-trans isomers are just one class of diastereomers because they are non-mirror-image stereoisomers ... 

Since cycloalkanes do not have isomers, the heat evolved has been calculated per CH2 group. First we find the heat of combustion of cyclohexane which is most stable and then the heat of combustion per CH2 group. It comes to 157.4 K cals/mole. Now to calculate the ring strain for other cycloalkanes, we multiply 157.4 K cal/mole by n and then subtract it from the heat of combustion of cycloalkane. 

Review Chapter 5. The inability of atoms in rings to rotate completely about their [Pg.167]

The isomerization of cycloalkanes over SbF5-intercalated graphite can be achieved at room temperature without the usual ring opening and cracking reactions, which occur at higher temperatures and lower acidities.110 In the presence of excess hydrocarbon after several hours, the thermodynamic equilibrium is reached for the isomers. Interconversion between cyclohexane (20) and methylcyclopentane (21) yields the thermodynamic equilibrium mixture [Eq. (5.46)]. 

Recognize, draw, and name cis-trans isomers of substituted cycloalkanes. 

Table 2.12.13C chemical shifts (5C) and relative configurations of cycloalkanes, pyranoses and alkenes (application of y-effects)4 8. The shifts which are printed in boldface reflect y-effects on C atoms in the corresponding --------------------------------------------------isomer pairs---------------------------------------------------... 

Draw isomers of alkanes and cycloalkanes, and use the IUPAC rules to name alkanes, cycloalkanes, and bicyclic alkanes. Problems 3-32,33,37, and 41... 

Balaban, A.T. (1978). Chemical Graphs. XXXII. Constitutional and Steric Isomers of Substituted Cycloalkanes. Croat. Chem.Acta, 51,35-42. 

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