Alcohols and Phenols Review

Flashcards covering the classification, naming, properties, acidity, preparation, reactions, protection, industrial uses, and spectroscopy of alcohols and phenols from the lecture notes.

Primary Alcohol (1°)

An alcohol classification where the hydroxyl-bearing carbon is bonded to one organic group.

Secondary Alcohol (2°)

An alcohol classification where the hydroxyl-bearing carbon is bonded to two organic groups.

Tertiary Alcohol (3°)

An alcohol classification where the hydroxyl-bearing carbon is bonded to three organic groups.

IUPAC Naming (Alcohols)

Rules include selecting the longest carbon chain containing the hydroxyl group, using the suffix '-ol', numbering the chain from the end nearer the hydroxyl group, and listing substituents alphabetically.

Phenol Naming

Named using '-phenol' as the parent name for aromatic compounds with a hydroxyl group directly attached to the benzene ring.

Hydrogen-Bonding (Alcohols/Phenols)

A weak intermolecular force resulting from the attraction between a positively polarized –OH hydrogen atom of one molecule and a lone pair of electrons on the electronegative oxygen atom of another molecule, leading to higher boiling points.

Oxonium Ions (ROH₂⁺)

Formed when alcohols or phenols act as weak bases and are reversibly protonated by strong acids.

Alkoxide Ion (RO⁻)

Formed when an alcohol acts as a weak acid and dissociates slightly in aqueous solution by donating a proton to water.

Phenoxide Ion (ArO⁻)

Formed when a phenol acts as a weak acid, which is resonance-stabilized by delocalization of the negative charge over the aromatic ring, making phenols more acidic than alcohols.

Acidity Constant (Ka)

A measure of the strength of an acid; a larger Ka indicates a more acidic compound.

pKa

The negative logarithm of the acidity constant (pKa = -log Ka); a smaller pKa indicates a more acidic compound.

Solvation of Alkoxide Ion

The stabilization of an alkoxide ion by water molecules, which increases its stability and the acidity of the parent alcohol.

Inductive Effects

Electronic effects where electron-withdrawing substituents stabilize an alkoxide ion by spreading the charge, thus increasing the alcohol's acidity.

Alkoxides as Bases

The conjugate bases of alcohols (RO⁻), which are strong bases frequently used as reagents in organic chemistry and are named by adding the '-ate' suffix to the alcohol name.

Hydroboration–Oxidation

An indirect method for hydrating alkenes, yielding the syn, non-Markovnikov hydration product (an alcohol).

Oxymercuration–Demercuration

An indirect method for hydrating alkenes, yielding the Markovnikov hydration product (an alcohol).

1,2-Diols (Glycols)

Compounds with two hydroxyl groups on adjacent carbons, which can be prepared by direct hydroxylation of an alkene with OsO₄ (cis diol) or acid-catalyzed hydrolysis of an epoxide (trans diol).

Reduction of Aldehydes

Formation of primary alcohols from aldehydes using reducing agents like sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄).

Reduction of Ketones

Formation of secondary alcohols from ketones using reducing agents like NaBH₄ or LiAlH₄.

Sodium Borohydride (NaBH₄)

A safe and easy-to-handle reducing agent for aldehydes and ketones, usable in water or alcohol solutions.

Lithium Aluminum Hydride (LiAlH₄)

A more reactive, but dangerous, reducing agent that reduces all carbonyl groups (aldehydes, ketones, carboxylic acids, esters) to alcohols.

Grignard Reagents (RMgX)

Organomagnesium compounds that react with carbonyl compounds (formaldehyde, aldehydes, ketones, esters) to yield alcohols by adding a carbanion nucleophile.

Sₙ1 Mechanism (Alcohol Conversion)

The mechanism by which tertiary alcohols react with strong acids (e.g., HCl or HBr) to form alkyl halides, involving a carbocation intermediate.

Sₙ2 Mechanism (Alcohol Conversion)

The mechanism by which primary and secondary alcohols are converted into halides by treatment with reagents like SOCl₂ or PBr₃, where the -OH group is converted into a better leaving group.

Alkyl Tosylates (ROTos)

Compounds formed by the reaction of alcohols with p-toluenesulfonyl chloride (tosyl chloride), behaving similarly to alkyl halides in substitution reactions and useful for stereochemical control.

Acid-Catalyzed Dehydration of Alcohols

An E1 reaction where tertiary alcohols lose water in the presence of acid to form the more stable alkene, following Zaitsev's rule and involving a carbocation intermediate.

POCl₃ in Pyridine Dehydration

An E2 mechanism used for the dehydration of secondary and tertiary alcohols under mild, basic conditions, where the –OH group is converted into a good leaving group.

Esterification

The reaction of alcohols with carboxylic acids (or their derivatives like acid chlorides) to produce esters, catalyzed by strong acid in the lab or mediated by thioesters/acyl adenosyl phosphates in biology.

Oxidation of Primary Alcohols

Can yield either aldehydes (e.g., with Dess–Martin periodinane) or carboxylic acids (e.g., by heating with KMnO₄ in basic aqueous solution).

Oxidation of Secondary Alcohols

Yields ketones using oxidizing agents like Dess–Martin periodinane.

Dess–Martin Periodinane

An iodine-containing reagent used for the mild oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in dichloromethane solution.

Protecting Group

A chemical modification used to temporarily block an interfering functional group during a multi-step synthesis, requiring introduction and removal steps.

Trialkylsilyl Ethers (R'–O–SiR₃)

Common protecting groups for alcohols, formed by reaction with chlorotrialkylsilanes (e.g., TBS or TMS) and later removed by aqueous acid or fluoride ion.

Cumene Process

An industrial method for manufacturing phenol and acetone from isopropylbenzene (cumene) through benzylic oxidation and acid-catalyzed rearrangement of cumene hydroperoxide.

Electrophilic Aromatic Substitution (Phenols)

Reactions where the hydroxyl group on a phenol ring acts as a strongly activating, ortho- and para-directing substituent, making phenols highly reactive.

Quinone

A 2,5-cyclohexadiene-1,4-dione formed by the oxidation of a phenol, known for its oxidation–reduction (redox) properties.

Ubiquinones (Coenzyme Q)

Quinones that act as biochemical oxidizing agents in living cells, mediating electron-transfer processes in energy production (e.g., respiration in mitochondria).

IR Spectroscopy (Alcohols)

Shows a strong C–O stretching absorption near 1050 cm⁻¹ and a characteristic O–H stretching absorption at 3300 to 3600 cm⁻¹ (broad for hydrogen-bonded, sharp for unassociated).

IR Spectroscopy (Phenols)

Shows a characteristic broad IR absorption at 3500 cm⁻¹ due to the –OH group, as well as typical aromatic bands at 1500 and 1600 cm⁻¹.

¹³C NMR Spectroscopy (Alcohols)

Carbon atoms bonded to electron-withdrawing –OH groups are deshielded and absorb at a lower field, typically in the range of 50 to 80 δ.

¹H NMR Spectroscopy (Alcohols)

Hydrogens on the oxygen-bearing carbon atom are deshielded (3.4 to 4.5 δ); the O–H proton often undergoes rapid exchange, leading to no spin-spin splitting with neighboring protons.

Alpha Cleavage (Mass Spectrometry, Alcohols)

A fragmentation pathway in alcohols where a C–C bond nearest the hydroxyl group is broken, yielding a neutral radical and a resonance-stabilized, oxygen-containing cation.

Dehydration Pathway (Mass Spectrometry, Alcohols)

A fragmentation pathway in alcohols where water is eliminated from the molecular ion, yielding an alkene radical cation.