Organic Chemistry: Aromatic Reactions, Alcohols, Ethers, Epoxides, and Sulfur Compounds

Comprehensive vocabulary flashcards covering electrophilic aromatic substitution, nucleophilic aromatic substitution, benzylic functionalizations, alcohols, ethers, epoxides, thiols, sulfides, and the Claisen rearrangement.

Benzylic Total Oxidation

The complete oxidation of toluene, primary alkylbenzenes, or secondary alkylbenzenes to benzoic acid ($\text{Ph-COOH}$) using strong oxidants such as $\text{Na}_2\text{Cr}_2\text{O}_7, \text{H}_2\text{SO}_4$ or $\text{KMnO}_4, \text{H}_2\text{O}, \Delta$.

Benzylic Radical Halogenation

A free-radical substitution reaction converting benzylic $\text{C-H}$ bonds into benzylic bromides using $\text{NBS}$ in the presence of peroxides or light ($h\nu$).

Wolff-Kishner Reduction

A downstream reduction of aryl ketones to alkyl groups ($\text{Aryl-CH}_2\text{R}$) using $\text{NH}_2\text{NH}_2$ and $\text{KOH}$, leaving nitro groups ($-\text{NO}_2$), alkenes, and benzene rings unaffected (SAFE).

Clemmensen Reduction

An acidic reduction utilizing $\text{Zn}(\text{Hg}), \text{HCl}$ (or $\text{Zn}, \text{HCl}$) that reduces aryl ketones to alkyl chains while simultaneously reducing aromatic nitro groups ($-\text{NO}_2$) to amino groups ($-\text{NH}_2$), leaving alkenes and benzene rings unaffected.

Iron Reduction ($\text{Fe}, \text{HCl}$)

A selective functional group transformation that reduces aromatic nitro groups ($-\text{NO}_2$) to amino groups ($-\text{NH}_2$) while keeping aryl ketones, alkenes, and benzene rings intact.

Exhaustive Catalytic Hydrogenation ($\text{H}_2, \text{Rh/C}$)

Strong catalytic reduction conditions that reduce aromatic nitro groups to amines, aryl ketones to alkyl chains, alkenes to alkanes, and aromatic benzene rings to cyclohexane rings.

Williamson Ether Synthesis

An $\text{S}_\text{N}2$ substitution method for synthesizing asymmetrical or symmetrical ethers by reacting an alkoxide (formed via deprotonation of an alcohol with $\text{NaH}$) with an alkyl halide, wherein the less hindered partner must serve as the electrophile.

Alkoxymercuration-Demercuration

A two-step Markovnikov ether synthesis where an alkene reacts with an alcohol ($\text{ROH}$) in the presence of $\text{Hg}(\text{O}_2\text{CCF}_3)_2$, followed by reductive demercuration using $\text{NaBH}_4$.

Acidic Ether Cleavage

An $\text{S}_\text{N}2$ cleavage reaction of ethers via treatment with strong hydrohalic acids ($\text{HI}$ or $\text{HBr}$), transforming methoxybenzene into phenol and methyl iodide ($\text{H}_3\text{C-I}$).

Epoxidation via Halohydrin

An intramolecular ether formation wherein an alcohol bearing a neighboring halogen is treated with $\text{NaH}$ to form an alkoxide that displaces the bromide leaving group to generate an epoxide ring.

Epoxide Ring Opening

The nucleophilic cleavage of an oxirane ring by attack of nucleophiles (such as $\text{NaN}_3$, $\text{NaOR}$, $\text{NaSR}$, or $\text{RMgX}$) followed by aqueous protonation with $\text{H}_2\text{O}$ to form functionalized alcohols.

Thiourea Thiol Synthesis

A two-step preparation of thiols ($\text{R-SH}$) from alkyl halides ($\text{R-X}$) by heating with thiourea followed by basic hydrolysis with $\text{NaOH}$ and $\text{H}_2\text{O}$.

Sulfide Synthesis

The conversion of a thiol ($\text{R-SH}$) into a sulfide ($\text{R-S-R}'$) by deprotonation with $\text{NaH}$ followed by nucleophilic substitution on an alkyl halide ($\text{R}'\text{-X}$).

Claisen Rearrangement

A thermal [3,3]-sigmatropic pericyclic rearrangement requiring an allyl vinyl ether minimum unit in the starting material, which produces a $\gamma,\delta$-unsaturated carbonyl product (identifiable by an alkene located two $\text{sp}^3$ atoms away from the carbonyl).

Nucleophilic Aromatic Substitution ($\text{S}_\text{N}\text{Ar}$)

An aromatic substitution mechanism involving the addition of an electron-rich nucleophile to an electron-deficient aromatic ring to generate an anionic intermediate, followed by elimination of a halide leaving group.

Anionic $\sigma$-Complex (Meisenheimer Complex)

The resonance-stabilized carbanionic intermediate formed during an $\text{S}_\text{N}\text{Ar}$ reaction following nucleophilic addition to the ipso carbon bearing the leaving group.

$\text{S}_\text{N}\text{Ar}$ Substrate Requirements

Structural criteria for nucleophilic aromatic substitution requiring a leaving group ($\text{F}$, $\text{Cl}$, or $\text{Br}$) positioned ortho or para to a strong electron-withdrawing group ($-\text{NO}_2$, $-\text{CN}$, $-\text{SO}_2\text{R}$), OR positioned directly adjacent to a ring nitrogen in a heteroaromatic system such as pyridine.

Alcohol Water Solubility Threshold

The solubility trend where alcohols with fewer than 4 carbons ($< 4$ carbons) are miscible with water, while alcohols with greater than 4 carbons ($> 4$ carbons) are soluble with decreasing solubility as carbon chain length increases.

Sodium Borohydride ($\text{NaBH}_4$)

A mild hydride reducing agent capable of reducing aldehydes to primary ($1^\circ$) alcohols and ketones to secondary ($2^\circ$) alcohols, leaving esters and carboxylic acids unreduced (SAFE).

Lithium Aluminum Hydride ($\text{LiAlH}_4$)

A strong hydride reducing agent capable of reducing aldehydes to $1^\circ$ alcohols, ketones to $2^\circ$ alcohols, and both esters and carboxylic acids to $1^\circ$ alcohols.

Grignard Addition to Esters

The nucleophilic addition of two equivalents of an organomagnesium reagent ($\text{R-MgBr}$) to an ester, forming a tertiary ($3^\circ$) alcohol containing two identical alkyl additions after workup.

Dess-Martin Periodinane (DMP)

A selective, non-acidic hypervalent iodine oxidant that oxidizes primary alcohols to aldehydes and secondary alcohols to ketones, leaving tertiary alcohols unaffected.

Jones Reagent ($\text{CrO}_3, \text{H}_2\text{SO}_4$)

A strong aqueous chromium oxidant that completely oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones.

Thionyl Chloride with Pyridine ($\text{SOCl}_2, \text{pyr}$)

A reagent system that substitutes primary and secondary alcohols to give alkyl chlorides with inversion of configuration, while being unreactive ($\text{N/A}$) toward tertiary alcohols.

Phosphorus Tribromide ($\text{PBr}_3$)

A selective halogenating agent that converts primary and secondary alcohols into alkyl bromides without carbocation rearrangements, and does not react ($\text{N/A}$) with tertiary alcohols.

Phosphorus Oxychloride ($\text{POCl}_3$)

A mild dehydrating reagent used with pyridine to induce elimination of primary, secondary, and tertiary alcohols to yield alkenes without skeletal carbocation rearrangement.

Acid-Catalyzed Alcohol Dehydration ($\text{H}_2\text{SO}_4$)

An elimination reaction of primary, secondary, or tertiary alcohols under concentrated sulfuric acid that proceeds via carbocation intermediates, requiring vigilance for carbocation rearrangements.

Electrophilic Aromatic Substitution ($\text{EAS}/\text{S}_\text{E}\text{Ar}$)

A two-step reaction wherein an aromatic ring donates pi electrons to attack an electrophile ($E^+$) forming a cationic $\sigma$-complex intermediate, followed by proton loss to re-aromatize.

Cationic $\sigma$-Complex (Arenium Ion)

The resonance-stabilized, non-aromatic carbocation intermediate formed after the pi system of an aromatic ring attacks an incoming electrophile in an $\text{EAS}$ mechanism.

Aromatic Nitration

An electrophilic aromatic substitution introducing a nitro group ($-\text{NO}_2$) onto a benzene ring using a mixture of concentrated $\text{HNO}_3$ and $\text{H}_2\text{SO}_4$.

Aromatic Sulfonylation

An electrophilic aromatic substitution that attaches a sulfonic acid group ($-\text{SO}_3\text{H}$) onto benzene using sulfur trioxide and sulfuric acid ($\text{SO}_3, \text{H}_2\text{SO}_4$).

Aromatic Desulfonylation

A reversible reaction that removes a sulfonic acid group ($-\text{SO}_3\text{H}$) from an arene to restore a $\text{C-H}$ bond by heating in dilute aqueous acid ($\text{H}_3\text{O}^+, \Delta$).

Friedel-Crafts Alkylation

An $\text{EAS}$ substitution adding an alkyl group ($-\text{R}$) to an aromatic ring using an alkyl chloride ($\text{R-Cl}$) activated by a Lewis acid catalyst such as $\text{AlCl}_3$ or $\text{FeCl}_3$.

Friedel-Crafts Acylation

An $\text{EAS}$ transformation coupling an acyl chloride ($\text{R-COCl}$) to an aromatic ring in the presence of $\text{AlCl}_3$ or $\text{FeCl}_3$ to form an aryl ketone without carbocation rearrangement.

Halogen Directing Effect in EAS

The unique directing property of halogens ($-\text{F}$, $-\text{Cl}$, $-\text{Br}$, $-\text{I}$), which act as deactivating groups due to strong inductive electron withdrawal while remaining ortho, para-directors due to resonance lone-pair donation into the cationic $\sigma$-complex.

Meta-Directing Deactivators

Strongly electron-withdrawing substituents (e.g., $-\text{NH}_3^+$, $-\text{NO}_2$, $-\text{CN}$, $-\text{SO}_3\text{H}$, $-\text{COR}$, $-\text{CHO}$) that pull electron density from the aromatic ring and direct electrophiles to the meta position by severely destabilizing ortho and para arenium ions.