Chapter 12: Alcohols and Phenols

Alcohols are characterized by an OH group bonded to a saturated carbon atom, while phenols feature a hydroxyl group directly attached to an aromatic ring, a structural difference that produces dramatically different chemical properties and reactivity patterns. The chapter explores the classification of alcohols as primary, secondary, or tertiary based on the number of carbon groups attached to the hydroxyl-bearing carbon, which fundamentally influences their susceptibility to oxidation and their reactivity in substitution and elimination reactions. Students learn how hydrogen bonding involving the polar OH group explains the relatively high boiling points of alcohols compared to analogous hydrocarbons and their solubility in water. The distinction between alcohol and phenol reactivity is emphasized, particularly regarding acidity; phenols are significantly more acidic than aliphatic alcohols due to the electron-withdrawing effects of the aromatic ring and the resonance stabilization of the resulting phenoxide anion. The chapter covers major reactions including oxidation of primary alcohols to aldehydes and carboxylic acids, oxidation of secondary alcohols to ketones, and substitution reactions facilitated by converting the OH group into a better leaving group through protonation or protection strategies. Dehydration reactions that form alkenes from alcohols under acidic conditions are analyzed with attention to Zaitsev's rule and carbocation rearrangement mechanisms. Protection and deprotection strategies for alcohol functional groups are introduced as practical synthetic techniques. The unique properties of polyols and their commercial applications are discussed alongside the synthesis and characteristic reactions of phenols, including electrophilic aromatic substitution at the ortho and para positions and formation of ethers and esters.