Alcohols feature a hydroxyl group (-OH) bonded to an \(sp^3\) carbon and are named with the suffix -ol (ethanol, propanol). They are classified as primary (1°), secondary (2°), or tertiary (3°) by the number of carbons attached to the carbinol carbon. Hydrogen bonding through the -OH group gives alcohols unusually high boiling points relative to ethers or alkanes of similar mass, and IR spectra show a characteristic broad O–H stretch around 3200–3550 cm\(^{-1}\). Primary alcohols oxidize to aldehydes with mild oxidants like PCC, while stronger oxidants such as \(K_2Cr_2O_7/H_2SO_4\) or Jones reagent (\(CrO_3/H_2SO_4\)) carry the oxidation to carboxylic acids; secondary alcohols oxidize to ketones, while tertiary alcohols resist oxidation because they lack a hydrogen on the carbinol carbon. The Lucas test (\(ZnCl_2/HCl\)) distinguishes these classes: tertiary alcohols cloud immediately, secondary react slowly, and primary do not react at room temperature. Acid-catalyzed dehydration of an alcohol produces an alkene by an E1 mechanism following Zaitsev's rule, while reaction with \(SOCl_2\) substitutes -OH with -Cl to give an alkyl chloride with loss of \(SO_2\) and HCl. Phenols are aromatic compounds with -OH directly bonded to a benzene ring (Ar-OH); they are more acidic than typical alcohols because the resulting phenoxide anion is resonance-stabilized by delocalization of the negative charge into the aromatic ring.
Ethers contain an oxygen bonded to two carbon groups (R-O-R′) and are named by the two alkyl groups followed by 'ether' (common) or with the 'alkoxy-' prefix in IUPAC nomenclature (methoxy-, ethoxy-, etc.). Ethers are relatively unreactive because they lack an acidic O–H and resist oxidation and reduction, although they are cleaved by strong acids such as HI or HBr to give alkyl iodides (or an alkyl iodide plus an alcohol, depending on conditions). Their inertness, combined with the ability to solvate cations without acting as proton donors, makes ethers valuable as aprotic polar solvents for reactions such as Grignard reagent formation.
Epoxides are cyclic ethers with a three-membered ring (oxirane). Substantial ring strain makes them far more reactive than ordinary ethers and susceptible to ring-opening by nucleophiles. Under basic conditions a nucleophile attacks the less hindered carbon via a classic \(S_N2\) backside attack; under acidic conditions the oxygen is protonated and the nucleophile attacks the more substituted carbon where partial carbocation character develops. Epoxides can be formed from alkenes by reaction with a peracid such as mCPBA through a concerted oxygen transfer, or from halohydrins by intramolecular \(S_N2\) cyclization in which an alkoxide displaces the halide—both routes driven by ring-strain relief.