Cycloalkanes dimethylcyclohexanes

Cycloalkanes can be oxygenated when irradiated in the presence of nitrobenzene.196 A 50% yield of cyclohexanol and cyclohexanone is achieved from cyclohexane. Since the product ratio is independent of reaction time, the alcohol is not an intermediate in ketone formation. Isomeric 1,2-dimethylcyclohexanes give an identical mixture of the isomeric tertiary alcohols, indicative of conformational equilibration and the presence of a radical intermediate. 

CHAPTER 4 Organic Compounds Cycloalkanes and Their Stereochemistry trans- , 2-Dimethylcyclohexane... 

A systematic study of the mechanism of the hydroisomerization reaction has been undertaken in our laboratories in order to elucidate the various steps involved in such reactions. Ethylcyclohexane has been chosen as a model compound for the study of cycloalkanes, inasmuch as it may form a variety of isomers, of which the alkylcyclohexanes can be readily investigated. In order to determine the path through which such reactions may proceed, ethylcyclohexane having a labeled carbon atom in the a position of the side chain has been hydroisomerized. It was reasoned that if the hydroisomerization to dimethylcyclohexanes proceeds by rearrangement... 

The stereochemistry of cycloalkanes is discussed extensively in the chapter by Anderson, and it is important for an understanding of the analyses offered for these compounds to distinguish between isomers and conformers. Because of the low energetic barrier for equilibration between axial and equatorial conformers, only low-temperature HNMR or CNMR as well as IR will freeze the equilibration and allow the spectral analysis of the conformers. However, disubstituted cycloalkanes will exhibit, in addition to structural isomerism, also cis, trans isomerism. Both cis and trans isomers of 1,4-dimethylcyclohexane undergo, at room temperature, a conformer equilibration. In the case of the trans isomer the conformer with two equatorial CH3 groups is more stable, while for the cis isomer both conformers are equally stable and cannot be separated. 

Two ds—trans isomers in substituted cycloalkanes, it is adequate to draw the cycloalkane ring as a planar polygon, as is done in the following disubstituted cyclohexanes ... 

When two or more substitutions appear in a cycloalkane, their locations are determined by number. The ring carbon to which one substituent is bonded is number 1. Other numbers are assigned to give the lowest numbers possible to the other locations. Thus, the following compound is 1,3-dimethylcyclohexane, not 1,5-dimethylcy-clohexane ... 

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