Alcohols, Phenols & Ethers – Core Vocabulary

Vocabulary flashcards covering definitions, reagents, mechanisms, and key facts about alcohols, phenols, and ethers as presented in the lecture notes.

Alcohol (organic chemistry)

A compound in which an alkyl or aryl group is attached to a hydroxyl (–OH) group; general formula R-OH.

Monohydric alcohol

Alcohol containing one hydroxyl group per molecule.

Dihydric alcohol (glycol)

Alcohol containing two hydroxyl groups, e.g., ethane-1,2-diol (ethylene glycol).

Trihydric alcohol

Alcohol containing three hydroxyl groups, e.g., propane-1,2,3-triol (glycerol).

Primary (1°) alcohol

Alcohol in which the –OH-bearing carbon is attached to one other carbon.

Secondary (2°) alcohol

Alcohol whose –OH-bearing carbon is attached to two other carbons.

Tertiary (3°) alcohol

Alcohol whose –OH-bearing carbon is attached to three other carbons.

Methanol (methyl alcohol)

CH3OH; called wood spirit; produced industrially from CO + H2 under 200–300 atm, Cu/ZnO/Cr2O3 catalyst.

Ethanol (ethyl alcohol)

C2H5OH; produced by fermentation of sugars; 95 % solution is rectified spirit.

Denatured alcohol

Industrial ethanol rendered unfit to drink by adding methanol, pyridine, or CuSO4.

Methylated spirit

Denatured alcohol specifically containing added methanol.

Lucas reagent

Conc. HCl + anhydrous ZnCl2; differentiates 1°, 2°, 3° alcohols via turbidity time.

Lucas test result – 3° alcohol

Gives immediate turbidity with Lucas reagent.

Lucas test result – 2° alcohol

Produces turbidity within 5–10 minutes with Lucas reagent.

Lucas test result – 1° alcohol

Shows no turbidity at room temperature with Lucas reagent.

Hydroboration–oxidation

Addition of BH3 to an alkene followed by H2O2/NaOH to give anti-Markovnikov alcohol.

Acid-catalysed hydration of alkenes

Addition of H2O in presence of acid producing Markovnikov alcohol via carbocation intermediate.

Grignard reagent

Organomagnesium halide (RMgX) used to convert carbonyl compounds to alcohols after hydrolysis.

Grignard + formaldehyde

Gives primary alcohol after acidic work-up.

Grignard + other aldehydes

Produces secondary alcohols on hydrolysis.

Grignard + ketones

Yields tertiary alcohols after hydrolysis.

NaBH4 reduction

Selective reagent that reduces aldehydes and ketones to 1° and 2° alcohols, respectively.

LiAlH4 reduction

Strong reducing agent that converts carbonyl compounds, acids, and esters to alcohols.

Catalytic hydrogenation of esters

H2 / Pd reduces esters to give a mixture of two alcohols.

Boiling-point trend in alcohols

Higher than alkanes, halides, or ethers due to intermolecular hydrogen bonding.

Effect of branching on alcohol b.p.

More branching lowers boiling point because of decreased surface area/van der Waals forces.

Water solubility of lower alcohols

Miscible owing to hydrogen bonding with water.

Phenol

A compound where –OH is bonded to an sp2-hybridised carbon of an aromatic ring (Ar-OH).

o-Cresol

2-Methyl phenol; example of a cresol (methyl-substituted phenol).

Picric acid

2,4,6-Trinitrophenol; obtained by nitration of phenol with conc. HNO3/H2SO4.

Kolbe reaction

NaOH-treated phenol reacts with CO2 (200 °C, 4 atm) then acidified to give salicylic acid.

Reimer–Tiemann reaction

Phenoxide treated with CHCl3 and NaOH yields salicylaldehyde (ortho-hydroxybenzaldehyde).

Cumene process

Industrial preparation of phenol from isopropylbenzene via cumene hydroperoxide cleavage.

Benzoquinone

Oxidation product of phenol with Na2Cr2O7/H2SO4.

Acidity order: phenol vs alcohol

Phenol > alcohol because phenoxide ion is resonance-stabilised; alkoxide is not.

Electron-withdrawing groups on phenol

NO2 increases acidity by stabilising the phenoxide ion via –I/–R effects.

Electron-donating groups on phenol

Alkyl (e.g., CH3) decrease acidity via +I effect, destabilising phenoxide ion.

Ortho-nitrophenol volatility

Steam volatile due to intramolecular hydrogen bonding.

Phenoxide ion resonance

Negative charge delocalised to ortho/para positions, enhancing stability.

Ether

Compound with two alkyl/aryl groups bonded to oxygen: R-O-R'. Functional isomer of alcohol.

Symmetrical (simple) ether

Ether with identical alkyl/aryl groups, e.g., diethyl ether.

Unsymmetrical (mixed) ether

Ether with two different alkyl/aryl groups, e.g., ethyl methyl ether.

Williamson synthesis

Preparation of ethers by reacting alkyl halide with sodium alkoxide/phenoxide (SN2).

Limitation of Williamson synthesis

Tertiary halides undergo elimination (E2) instead of substitution, forming alkenes.

Acidic dehydration of alcohols to ethers

Two alcohol molecules react with conc. H2SO4 at 413 K to give symmetrical ether.

Boiling point of ethers

Lower than isomeric alcohols because ethers cannot hydrogen bond with each other.

Peroxide formation in ethers

Old ethers form explosive peroxides on standing in air.

HI cleavage of ethers (excess)

Gives two alkyl iodides and water via protonation and C–O bond cleavage.

HI cleavage of aryl alkyl ethers

Produces phenol + alkyl iodide; C(sp2)–O bond resists cleavage due to resonance.

Anisole

Methoxybenzene; undergoes ortho/para electrophilic substitution due to activating –OCH3.

Ether dipole moment

Non-zero because C–O bonds are polar and lone-pair–lone-pair repulsion creates bent geometry.

Lucas reagent composition

ZnCl2 (anhydrous) + concentrated HCl (conc. HCl).

Propan-1-ol formula

CH3-CH2-CH2-OH; IUPAC name propan-1-ol (n-propyl alcohol).

Isopropyl alcohol

Propan-2-ol (CH3-CHOH-CH3); common secondary alcohol.

tert-Butyl alcohol

2-Methyl-2-propanol; simplest tertiary alcohol.

Glycerol

Propane-1,2,3-triol; viscous trihydric alcohol used in cosmetics, explosives (nitroglycerine).

Ethylene glycol

Ethane-1,2-diol; antifreeze agent in automobiles.

Pyridinium chlorochromate (PCC)

CrO3•HCl•pyridine complex; oxidises 1° alcohols to aldehydes without over-oxidation.

E1 dehydration mechanism

Protonation → carbocation formation → β-H elimination to give alkene.

Acid strength order (given list)

Prop-1-ol < o-Cresol < Phenol < 4-Nitrophenol < 2,4-Dinitrophenol (picric acid strongest).

Rectified spirit

Azeotropic mixture containing 95 % ethanol and 5 % water.

Wood spirit

Common name for methanol obtained from destructive distillation of wood.

Salicylic acid

2-Hydroxybenzoic acid; made via Kolbe reaction; precursor to aspirin.

Aspirin

Acetyl salicylic acid; analgesic prepared by acetylating salicylic acid with acetic anhydride.

Picrate formation in phenols

Electron-withdrawing NO2 groups facilitate formation of 2,4,6-trinitrophenol during nitration.

Halogenation of phenol (no solvent)

Br2 water gives 2,4,6-tribromophenol white precipitate instantly.

Halogenation of phenol in CS2

Br2/CS2 at low temperature yields mixture of ortho- and para-bromophenol.

Nitration of phenol (dil. HNO3)

Gives o- and p-nitrophenol mixture.

Benzoquinone synthesis

Oxidation of phenol with Na2Cr2O7/H2SO4 produces p-benzoquinone.

Clemmensen reduction of carbonyl

Noted Zn/Hg + HCl but here Zn dust reduces phenol to benzene (different context).

Ether nomenclature (IUPAC)

Longest chain used as alkane; shorter +O named as alkoxy substituent (e.g., methoxyethane).

Diphenyl ether

Ph-O-Ph; also called phenoxybenzene in IUPAC.

Anhydrous ZnCl2 role (Lucas)

Acts as Lewis acid to generate more reactive RCl by coordinating to OH group.

Van der Waals forces in b.p.

Increase with molar mass; branching reduces surface area and lowers b.p.

Intramolecular H-bonding

Occurs in o-nitrophenol, lowering b.p. and increasing volatility.

Intermolecular H-bonding

Responsible for high b.p. of phenol and alcohols, low of ethers.

SN2 dependence in Williamson

Requires primary (or methyl) halide for best yield; steric hindrance decreases rate.