Organic Chemistry Reactions Flashcards

Flashcards testing knowledge of organic chemistry reaction pathways, reagents, stereochemistry, and mechanisms from the provided lecture notes.

What stereochemical outcome and regioselectivity are observed in the hydroboration-oxidation of an alkene using $1)\,\text{BH}_3/\text{THF}$ followed by $2)\,\text{H}_2\text{O}_2/\text{OH}^-$?

It yields an anti-Markovnikov addition of $\text{OH}$ with syn-planar stereochemistry.

How do dehydration conditions using $\text{H}_2\text{SO}_4$ and heat differ from using $\text{POCl}_3$ and heat regarding the alkene product formed?

$\text{H}_2\text{SO}_4$ with heat is $\text{E1}$-like and cannot give a terminal alkene, whereas $\text{POCl}_3$ with heat dehydrates specifically to form a terminal alkene.

What reagents are used in oxymercuration-demercuration to achieve Markovnikov, anti-planar addition of an alcohol to an alkene to form an ether?

$1)\,\text{Hg(OAc)}_2/\text{CH}_3\text{OH}$ and $2)\,\text{NaBH}_4$.

Which reagents are preferred for the syn-dihydroxylation of an alkene to obtain a high yield despite being toxic and expensive?

$\text{OsO}_4$ with $\text{H}_2\text{O}_2$.

What are the key differences between acidic and basic epoxide ring opening in terms of regioselectivity?

Under acidic conditions, nucleophilic attack occurs at the more substituted carbon; under basic conditions ($\text{S}_\text{N}2$-like), attack occurs at the least substituted carbon.

How does the choice of base dictate whether a terminal or internal alkyne is synthesized from a vicinal dihalide?

$\text{NaNH}_2$ at $100^\circ\text{C}$ followed by $\text{H}_3\text{O}^+$ yields a terminal alkyne, while $\text{KOH}$ at $200^\circ\text{C}$ yields an internal alkyne.

What stereospecific products are obtained when reducing an internal alkyne using Lindlar's catalyst versus dissolving metal conditions?

Lindlar's catalyst ($\text{H}_2/\text{Pd(BaSO}_4\text{)}$, quinoline) performs syn addition to yield a cis-alkene, whereas dissolving metal ($\text{Na}/\text{NH}_3$) performs anti addition to yield a trans-alkene.

What is the product difference when hydrating a terminal alkyne with mercuric ion catalyst versus hydroboration-oxidation?

Mercuric ion hydration ($\text{HgSO}_4/\text{H}_2\text{O},\,\text{H}_2\text{SO}_4$) undergoes Markovnikov addition to form a ketone, while hydroboration-oxidation ($1)\,\text{Sia}_2\text{BH},\,2)\,\text{H}_2\text{O}_2/\text{OH}^-$) undergoes anti-Markovnikov addition to form an aldehyde.

Which reduction reagent selectively reduces aldehydes and ketones while leaving esters and carboxylic acids unreacted?

$\text{NaBH}_4$ in ethanol ($\text{EtOH}$).

What is the specific function of Pyridinium Chlorochromate ($\text{PCC}$) in the oxidation of primary alcohols?

$\text{PCC}$ in $\text{CH}_2\text{Cl}_2$ oxidizes primary alcohols to aldehydes without over-oxidizing them to carboxylic acids.

Why must ethers be stored carefully to avoid prolonged exposure to air ($\text{O}_2$)?

Ethers undergo autoxidation with excess $\text{O}_2$ to form explosive peroxides and hydroperoxides.

In the hydrohalogenation of conjugated dienes with $\text{HBr}$, how does temperature control the product outcome?

Low temperature ($0^\circ\text{C}$) yields the $1,2$-addition kinetic product (more stable transition state), while higher temperature ($40^\circ\text{C}$) yields the $1,4$-addition thermodynamic product (more stable compound).

What limitations exist for Friedel-Crafts alkylation of benzene rings?

It suffers from carbocation rearrangements, polyalkylation, and fails in the presence of strong electron-withdrawing groups or amino groups.

What reagents are used in the Clemmensen reduction, and which functional groups must be avoided?

The reaction uses $\text{Zn(Hg)}$ and $\text{HCl}$; alkenes, alkynes, alcohols, and amines must be avoided.

What requirement must be met for Nucleophilic Aromatic Substitution ($\text{S}_\text{N}\text{Ar}$) to occur via an Addition-Elimination mechanism?

Strong electron-withdrawing groups ($\text{W}$) must be located ortho and/or para to the leaving group.

How does Birch reduction affect benzene rings with electron-withdrawing groups versus electron-donating groups?

Electron-withdrawing groups direct the reduced carbons to become $\text{sp}^3$ at the site of attachment, whereas electron-donating groups keep the carbon attached to the substituent as $\text{sp}^2$.

Which reducing agent selectively reduces carboxylic acids to primary alcohols faster than any other functional group?

Diborane ($\text{B}_2\text{H}_6$) in diglyme.

What transformation is accomplished by the Hunsdiecker reaction, and what reagents are required?

It converts carboxylic acids into alkyl halides with one less carbon using $1)\,\text{HgO}$, $\text{Ag}_2\text{O}$, or $\text{Pb(OAc)}_4$ and $2)\,\text{heat}/\text{Br}_2/\text{CCl}_4$.

What are the reagents and purpose of the Hell-Volhard-Zelinsky (HVZ) reaction?

It converts carboxylic acids into $\alpha$-bromo carboxylic acids using $1)\,\text{PBr}_3/\text{Br}_2$ and $2)\,\text{H}_2\text{O}$.

What products are formed in the Haloform reaction when a methyl ketone reacts with excess $\text{X}_2$ and excess $\text{NaOH}$?

A carboxylate anion ($\text{R-COO}^-$) and haloform ($\text{HCX}_3$).

Why is Lithium Diisopropylamide ($\text{LDA}$) utilized for enolate alkylation of carbonyls rather than standard alkoxide bases?

$\text{LDA}$ is a strong, hindered base that quantitatively ($100\%$) removes the alpha proton from the least hindered carbon to form the kinetic enolate.

How does the Hofmann elimination differ from standard $\text{E2}$ eliminations regarding alkene major product selectivity?

The Hofmann elimination yields the least substituted alkene as the major product.

What transformation occurs during a Hofmann rearrangement of a primary amide?

A primary amide reacts with $\text{X}_2/\text{H}_2\text{O}/\text{NaOH}$ to form a primary amine with the loss of the carbonyl carbon.

What three steps are involved in the Stork enamine synthesis for the $\alpha$-alkylation of carbonyl compounds?

$1)$ Formation of an enamine using a carbonyl and a secondary amine, $2)$ $\text{S}_\text{N}2$ alkylation of the enamine with an alkyl halide or acid halide, and $3)$ Acid hydrolysis ($\text{H}_3\text{O}^+$) to regenerate the carbonyl.

Why do intramolecular Aldol condensations favor the formation of 5- or 6-membered rings?

Smaller rings experience severe ring strain, while larger rings are disfavored because the reactive ends are too far apart to readily undergo intramolecular reaction.