CHEM 211 Chapter Notes - Chapter 7.7: Primary Alcohol, Lewis Acids And Bases, Elimination Reaction
8 Dec 2016
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Dehydration = loss of a water molecule: dehydration forms an alkene when heated with a strong acid. The conditions required: 1. temperature and concentration required to dehydrate an alcohol depends on the structure of the alcohol. Primary alcohol: hard to dehydrate, ex. needs concentrated h2so4 and 180 c. Secondary alcohol: easier to dehydrate than primary, ex. needs 85% h3po4 and 165-170 c. Tertiary alcohol: easily dehydrated, ex. needs 20% h2so4 and 85 c, 2. some secondary and primary alcohols undergo rearrangements of their carbon skeletons during dehydration. This occurs through the migration of a methyl group forming a more stable carbocation. Secondary and tertiary alcohol dehydration mechanism - e1: an e1 reaction with the substrate being a protonated alcohol, steps: 1. proton is transferred from the acid to one of the unshared electron pairs on the alcohol: when h2so4 is used: If not concentrated, h o is the donor.
