Classification: Alcohols are 1° ($RCH_{2}OH$), 2° ($R_{2}CHOH$), or 3° ($R_{3}COH$). The degree determines reactivity in oxidation, dehydration, and Lucas test.

Lucas Test ($ZnCl_{2}$/conc. HCl):

• 3° alcohol: immediate turbidity (< 5 min) — stable 3° carbocation forms rapidly via SN1
• 2° alcohol: turbidity in 5-20 min — 2° carbocation forms more slowly
• 1° alcohol: no turbidity at room temperature — 1° carbocation too unstable; SN2 requires heating

The observation is cloudiness (turbidity) from water-insoluble alkyl chloride formed in the reaction. This test is a direct application of carbocation stability: 3° > 2° > 1°.

Oxidation Ladder — The Most Tested OC-05 Concept:

• 1° alcohol + PCC (anhydrous $CH_{2}Cl_{2}$) → aldehyde (STOPPED — no water, no gem-diol)
• 1° alcohol + $KMnO_{4}$ or $K_{2}Cr_{2}O_{7}$ (aqueous) → carboxylic acid (complete oxidation)
• 2° alcohol + PCC or $KMnO_{4}$ → ketone (cannot oxidize further without C-C cleavage)
• 3° alcohol + any standard oxidant → no reaction (no α-H on carbinol C)

PCC is the selective reagent — the single most important reagent distinction in this chapter. "P = Partial; K = Kaput (complete)."

Reduction of Carbonyl Compounds to Alcohols:

• $NaBH_{4}$: reduces aldehydes → 1° alcohols; ketones → 2° alcohols. Cannot reduce carboxylic acids or esters.
• $LiAlH_{4}$: reduces all carbonyl compounds including carboxylic acids (→ 1° alcohol), esters, and amides.

Dehydration (Saytzeff's Rule): With conc. $H_{2}SO_{4}$ at 443 K, alcohols dehydrate to alkenes. The more substituted alkene (more stable, more hyperconjugation) is the major product. Rate of dehydration: 3° >> 2° > 1°, reflecting stability of the carbocation intermediate.

Fischer Esterification:

$\text{RCOOH} + \text{R'OH} \xrightarrow{\text{H}^+, \Delta} \text{RCOOR'} + \text{H}_2\text{O}$

Reversible, acid-catalyzed. Equilibrium driven forward by removing water or using excess of one reactant. Example: acetic acid + ethanol → ethyl acetate (SMILES:CCOC(=O)C).

Preparation Summary:

• Alkene + $H_{2}O$/$H^{+}$ → alcohol (Markovnikov, more substituted C gets -OH)
• Grignard: RMgX + HCHO → 1°; + RCHO → 2°; + $R_{2}CO$ → 3° (after hydrolysis)
• Reduction: $NaBH_{4}$ for RCHO/$R_{2}CO$; $LiAlH_{4}$ for RCOOH