L,?-Dimethylcyclohexane

Amines, thiols, eOH (p. 226), etc., will also add to the 0-carbon atom of 0-unsaturated carbonyl compounds and esters, but the most important reactions of C=C—C=0 systems are in Michael reactions with carbanions reactions in which carbon-carbon bonds are formed. A good example is the synthesis of l,l-dimethylcyclohexan-3,5-dione (dimedone, 100) starting from 2-methylpent-2-ene-4-one (mesityl oxide, 101) and the carbanion 0CH(CO2Et)2 ... 

Draw the structure of ( , )-3-chloro-4-fluoro-l,l-dimethylcyclohexane as a Newman projection formula viewed along the C6-C1 and C4-C3 bonds. (The chlorine and fluorine atoms should be drawn antiperiplanar to each other.)... 

Propose a Williamson synthesis of 3-butoxy-l,l-dimethylcyclohexane from 3,3-dimethyl-cyclohexanol and butan-l-ol. 

Use the principles of conformational analysis to predict the difference in heats of combustion of cis- and fr ns-l dimethylcyclohexane. How does your calculated value compare with the data in Table 3.3 ... 

Briefly discuss what changes would occur in the product if 2 chloro-l,l-dimethylcyclohexane were heated with KI in aqueous THF. Draw the product. 

On the other hand, compound I, (2S,6S)-2,6-dibromo-l,l-dimethylcyclohexane, contains no mirror plane The molecule is chiral, enantiomerically pure, and, hence, optically active. In other words, the reaction leaves the stereochemical integrity and identity of C2 intact, generating only one enantiomer of the product, which is nonsuperimposable with its mirror image, the (2R,6R) diastereomer (Section 5-5). 

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