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Predict the major product of acid catalysed dehydration of (i) 1 - methylcyclohexanol and (ii) Butan-1-ol |
Answer» Solution :(i) Acid - catalysed dehydration of 1 - methylcyclohexanol can give tow products, VIZ, I and II. According to Saytzeff rule, I is the major product since it is more highly substituted.  (ii) Acid - catalysed dehydration of butan-1-ol produces but-2-ene as the major product and but-1-ene as the minor product. Now butan-1-ol being a `1^(@)` alcohol upon protonation and elimination of `H_(2)O` first gives a `1^(@)` carbocation (I) which is less stable rearranges to form the more stable `2^(@)` carbocation (II). This can then LOSE a proton in two DIFFERENT ways to form either but -2- ene or but-1- ene. According to Saytzeff rule, the preferred alkene is ONE which is more highly substituted (i.e., contains more alkyl GROUPS linked to the carbon - carbon double bond). Thus, but -2- ene is the major product. 
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