Organic Chemistry: Carbonyl Preparations, Aromatic Reactions, and Synthetic Strategies

Vocabulary practice flashcards covering aromatic substitution mechanisms, Birch reduction regioselectivity, aldehyde and ketone preparation methods, protecting group chemoselectivity, and multistep synthetic strategies.

Elimination-Addition Mechanism

A nucleophilic aromatic substitution pathway occurring on unactivated aryl halides under forcing conditions, proceeding via a strained benzyne intermediate that undergoes subsequent nucleophilic addition.

Dow Process Conditions

Forced elimination-addition conditions using sodium hydroxide ($\text{NaOH}$) at $350^\circ\text{C}$ followed by acid workup ($\text{H}_3\text{O}^+$) to convert chlorobenzene to phenol.

Benzyne Intermediate Regiochemical Outcome

The generation of a mixture of regioisomers (such as meta- and para-toluidine from 4-chlorotoluene) because the incoming nucleophile can attack either carbon atom of the formal triple bond in the benzyne ring.

Birch Reduction

The dissolving metal reduction of an aromatic ring using sodium ($\text{Na}$), methanol ($\text{CH}_3\text{OH}$), and liquid ammonia ($\text{NH}_3$) to produce an unconjugated 1,4-cyclohexadiene.

Birch Reduction Regiochemistry with an EDG

An electron-donating group directs the 1,4-reduction such that the ring carbon bearing the substituent is not reduced and retains a $\text{C}=\text{C}$ double bond ($sp^2$ carbon).

Birch Reduction Regiochemistry with an EWG

An electron-withdrawing group directs the 1,4-reduction such that the ring carbon bearing the substituent is reduced and becomes an $sp^3$-hybridized carbon with a $\text{C}-\text{H}$ bond.

Mild Oxidizing Agents for Aldehydes

Reagents such as pyridinium chlorochromate ($\text{PCC}$ in $\text{CH}_2\text{Cl}_2$), Dess-Martin periodinane ($\text{DMP}$), or Swern oxidation conditions ($\text{DMSO}, (\text{COCl})_2, \text{Et}_3\text{N}$) that convert primary alcohols into aldehydes without over-oxidation to carboxylic acids.

Ozonolysis of Alkenes to Aldehydes

The oxidative cleavage of an alkene using ozone ($\text{O}_3$) followed by dimethyl sulfide ($\text{DMS}$), producing an aldehyde whenever at least one alkene carbon bears a hydrogen atom.

Hydroboration-Oxidation of Terminal Alkynes

A two-step reaction using a sterically hindered borane ($\text{R}_2\text{B-H}$) followed by basic hydrogen peroxide ($\text{H}_2\text{O}_2, \text{NaOH}$) that achieves anti-Markovnikov hydration of an alkyne to form an enol, which tautomerizes into an aldehyde.

Oxidation of Secondary Alcohols

The oxidation of a secondary alcohol to a ketone using either strong oxidizing agents ($\text{Na}_2\text{Cr}_2\text{O}_7, \text{H}_2\text{SO}_4, \text{H}_2\text{O}$) or mild agents ($\text{PCC}$), without risk of over-oxidation.

Acid-Catalyzed Hydration of Terminal Alkynes

A Markovnikov addition of water across a terminal alkyne catalyzed by sulfuric acid ($\text{H}_2\text{SO}_4$), water ($\text{H}_2\text{O}$), and mercuric sulfate ($\text{HgSO}_4$), yielding an enol that tautomerizes into a methyl ketone.

Friedel-Crafts Acylation

An electrophilic aromatic substitution in which an acyl halide reacts with an aromatic ring in the presence of an aluminum trichloride ($\text{AlCl}_3$) Lewis acid catalyst to form an aryl ketone.

Wolff-Kishner Reduction

A method to reduce a ketone or aldehyde carbonyl to a methylene ($-\text{CH}_2-$) group using hydrazine ($\text{H}_2\text{NNH}_2$) and potassium hydroxide ($\text{KOH}$) under elevated heat ($\Delta$).

Wolff-Kishner Alkyl Halide Incompatibility

The side reactions caused by potassium hydroxide ($\text{KOH}$) during Wolff-Kishner reductions, where the strongly basic conditions trigger competitive $\text{S}_\text{N}2$ substitution (e.g., converting alkyl bromides to alcohols) and/or $\text{E}2$ elimination.

Chemoselective Acetal Protection

The preferential protection of an aldehyde over a ketone by treatment with ethylene glycol ($\text{HO-CH}_2\text{CH}_2\text{-OH}$) under acid catalysis ($[\text{H}^+]$) with removal of water ($-\text{H}_2\text{O}$), taking advantage of the aldehyde's higher electrophilicity and lesser steric hindrance.

Radical Bromination of Alkylcycloalkanes

A free-radical functionalization using bromine and light ($\text{Br}_2, h\nu$) to selectively substitute bromine at the most substituted, tertiary position of a saturated ring system.

Cycloalkene Ring Cleavage

The synthetic sequence of cleaving a cycloalkene with ozone ($\text{O}_3$) followed by dimethyl sulfide ($\text{DMS}$) to unroll the carbocyclic framework into an open-chain dicarbonyl compound.

Benzylic Bromination with NBS

The selective introduction of a bromine atom at a benzylic position using $N$-bromosuccinimide ($\text{NBS}$) with heat ($\Delta$) via a radical pathway without brominating the aromatic ring.

Dehydrohalogenation via Potassium tert-Butoxide

An $\text{E}2$ elimination carried out with the bulky, non-nucleophilic base potassium tert-butoxide ($t\text{-BuOK}$) on an alkyl or benzylic halide to form a conjugated alkene.

Elimination-Addition Mechanism

A nucleophilic aromatic substitution pathway occurring on unactivated aryl halides under forcing conditions (such as $\text{NaOH}$ at $350^\circ\text{C}$ or $\text{NaNH}_2$ in liquid $\text{NH}_3$) that proceeds through an unstable benzyne intermediate.

Benzyne Intermediate Regiochemical Outcome

The elimination step creates a formal triple bond across two adjacent aromatic carbons, allowing nucleophilic attack to take place at either carbon and resulting in a mixture of regioisomeric products (such as para- and meta-substituted anilines from 4-chlorotoluene).

Birch Reduction

The dissolving metal reduction of benzene to 1,4-cyclohexadiene using sodium metal ($\text{Na}$) in liquid ammonia ($\text{NH}_3$) with methanol ($\text{CH}_3\text{OH}$).

Birch Reduction Regiochemistry (EDG vs. EWG)

Substituents direct the placement of double bonds during reduction: an electron-donating group (EDG) yields a product where the substituted carbon retains a double bond, whereas an electron-withdrawing group (EWG) directs reduction so the substituted carbon becomes $sp^3$-hybridized and lacks a double bond.

Oxidation of Primary Alcohols (Aldehyde Formation)

The selective conversion of primary alcohols to aldehydes using mild oxidizing agents such as PCC, DMP, or Swern conditions ($\text{DMSO}, (\text{COCl})_2$, followed by $\text{Et}_3\text{N}$) that prevent over-oxidation to carboxylic acids.

Ozonolysis of Alkenes to Aldehydes

The cleavage of a $\text{C}=\text{C}$ double bond using ozone ($\text{O}_3$) followed by dimethyl sulfide ($\text{DMS}$); aldehydes are formed if either carbon atom of the double bond bears a hydrogen atom.

Hydroboration-Oxidation of Terminal Alkynes

An anti-Markovnikov addition of water across a $\pi$ bond using a sterically hindered borane ($\text{R}_2\text{B-H}$) followed by alkaline peroxide ($\text{H}_2\text{O}_2, \text{NaOH}$), followed by tautomerization of the intermediate enol to form an aldehyde.

Oxidation of Secondary Alcohols

The oxidation of secondary alcohols to ketones using strong agents (such as $\text{Na}_2\text{Cr}_2\text{O}_7$ with $\text{H}_2\text{SO}_4$ and $\text{H}_2\text{O}$) or mild agents (such as PCC); the resulting ketones are resistant to further oxidation.

Ozonolysis of Tetrasubstituted Alkenes

The reaction of tetrasubstituted alkenes with $\text{O}_3$ followed by $\text{DMS}$, cleaving the double bond to yield two ketone fragments because neither alkene carbon bears a hydrogen atom.

Acid-Catalyzed Hydration of Terminal Alkynes

The Markovnikov addition of water across the triple bond catalyzed by $\text{H}_2\text{SO}_4, \text{H}_2\text{O}$, and $\text{HgSO}_4$, which produces an enol intermediate that tautomerizes into a methyl ketone.

Friedel-Crafts Acylation

The electrophilic aromatic substitution reaction between an aromatic ring (that is not strongly deactivated) and an acyl halide in the presence of an $\text{AlCl}_3$ Lewis acid catalyst to synthesize an aryl ketone.

Side Reactivity of Alkyl Halides in Wolff-Kishner Reduction

When subjected to Wolff-Kishner conditions ($\text{H}_2\text{NNH}_2, \text{KOH}, \Delta$), the basic and nucleophilic hydroxide ion ($\text{KOH}$) simultaneously promotes $S_N2$ displacement (e.g., converting benzylic bromides into alcohols) and/or E2 elimination on any alkyl halide functionality present.

Chemoselective Acetal Formation

The preferential reaction of ethylene glycol ($\text{HOCH}_2\text{CH}_2\text{OH}$) with an aldehyde in the presence of a sterically hindered ketone under acidic catalysis ($[\text{H}^+], -\text{H}_2\text{O}$) to form a cyclic dioxolane acetal while leaving the ketone unreacted.

Functionalization and Ring Opening of tert-Butylcyclohexane

A multistep transformation relying on radical bromination ($\text{Br}_2, h\nu$) at the tertiary ring carbon, E2 elimination using potassium tert-butoxide ($t\text{-BuOK}$) to install a double bond, and ozonolysis ($\text{O}_3, \text{DMS}$) to cleave the cyclohexane ring into a dicarbonyl compound.

Alkene Installation via Benzylic Bromination and Elimination

A synthetic strategy where cumene is first para-brominated ($\text{Br}_2, \text{FeBr}_3$), then brominated specifically at the benzylic position using $\text{NBS}, \Delta$, followed by base-mediated E2 elimination with $t\text{-BuOK}$ to form 1-bromo-4-(prop-1-en-2-yl)benzene.