Both cis- and trans-2-methylcyclohexanol undergo dehydration in warm sulfuric acid to give 1-methylcyclohexene as the major alkene product. These alcohols can also be converted to alkenes by tosylation using TsCland pyridine, followed by elimination using KOC(CH₃)₃as a strong base. Under these basic conditions, the tosylate of cis-2-methylcyclohexanol eliminates to give mostly 1-methylcyclohexene, but the tosylate of trans-2-methylcyclohexanol eliminates to gives only 3-methylcyclohexene. Explain how this stereochemical difference in reactants controls a regiochemical difference in the products of the basic elimination, but not in the acid-catalyzed elimination.

An elimination reaction is carried out when the substituents such as hydrogen/halogen atoms are removed from the compound to form the desired product either by a one/ two-step mechanism.

In cis and trans isomers, we get more substituted alkene due to stability. Here abstract proton of leaving group are anti-periplanar to each other, which is favorable condition for elimination reaction.

Here both cis and trans-2-methyl cyclohexanol is treated with sulfuric acid forming 1-methylcyclohexene. In this reaction, an acidic condition is used.

Formation of 1-methylcyclohexene

Cis-2-methyl cyclohexanol is treated to form a compound. Then nucleophile attack the proton to form 1-methyl cyclohexane.

Formation of 1-methyl cyclohexene

Trans-2-methylcyclohexanol has been treated to form a compound the nucleophile attack the proton as it is anti to leaving group. Hence form 3-methyl cyclohexane.

Formation of 3-methyl cyclohexene