Organic Chemsitry Exam #4 Review

Vocabulary and reagent-based flashcards covering key organic chemistry concepts from chapters 9-12, including alkyne and alkene reactions, radical mechanisms, and synthesis

Na, NH3 (liquid)

A reagent system used to convert an internal alkyne into a trans-alkene (or (E)-alkene).

Hydroboration-oxidation (alkene)

A reaction characterized by anti-Markovnikov regioselectivity with syn-stereochemistry and no carbocation rearrangement.

Fishhook arrows

Mechanism arrows used to show the movement of individual electrons, typically during homolytic bond cleavage or radical reactions.

NBS (N-bromosuccinimide)

A reagent used for allylic bromination when combined with heat or light ($hv$).

OsO4 / NaHSO3, H2O

A set of reagents used to perform the syn-dihydroxylation of an alkene.

KMnO4, NaOH, cold

Reagents that convert an alkene, such as cyclohexene, into a cis-1,2-diol via syn-addition.

Polyhalogenation prevention

A strategy in free-radical halogenation that involves using an excess of the alkane relative to the halogen to minimize higher substitution.

Alkynide anion with tertiary alkyl halides

A reaction scenario where an E2 reaction is more likely to occur than an SN2 reaction because the alkynide anion acts as a strong base with a sterically hindered electrophile.

Hydrocarbon acidity order

The ranking from most acidic to least acidic: Alkyne ($sp$) > Alkene ($sp^2$) > Alkane ($sp^3$).

Homolytic bond cleavage

The process where a covalent bond breaks and each atom takes one electron, resulting in the formation of two radicals.

Lindlar's catalyst

A poisoned palladium catalyst used with $H_2$ to reduce an alkyne to a cis-alkene.

Internal alkyne synthesis from an internal alkene

A multi-step process involving: 1. Bromination ($Br_2$), 2. Treatment with an excess of a strong base ($xs NaNH_2$), and 3. Water ($H_2O$) to perform double dehydrohalogenation.

9-BBN / H2O2, NaOH

Reagents used for the hydroboration-oxidation of alkynes; terminal alkynes are converted to aldehydes through this process.

m-CPBA / H3O+

A two-step reagent sequence used to achieve anti-dihydroxylation of an alkene.

Propagation

The stage of a radical chain reaction where a radical reacts with a non-radical to produce a new radical, continuing the chain.

9-BBN

A reagent used in the hydroboration-oxidation of alkynes, followed by $H_2O_2$ and $NaOH$, to yield an aldehyde final product.

Lindlar's catalyst

A poisoned catalyst used with $H_2$ to reduce an alkyne specifically to a cis-alkene.

Vicinal dihalide

A dihalide in which the halogens are attached on adjacent carbons.

Geminal dihalide

A dihalide in which both halogen atoms are attached to the same carbon atom.

Homolytic cleavage

A bond-breaking process where movement of individual electrons, shown using fishhook arrows, produces two equal halves that each have an unpaired electron.

Propagation step

A step in a radical reaction, such as monochlorination, where a radical reacts with a stable molecule to generate a product and a new radical.

Disiamylborane

A hindered borane reagent used in the conversion of terminal alkynes to aldehydes through hydroboration-oxidation.

Alkynide ion

A reactive intermediate formed when a strong base such as sodium amide ($NaNH_2$) deprotonates a terminal alkyne.

NBS (N-Bromosuccinimide)

A reagent used to achieve allylic bromination under free radical conditions, often involving light ($hv$).

Thermal cracking

A process, such as the heat-induced breakdown of butane, that produces ethyl radicals via homolytic cleavage.

Sodium amide ($NaNH_2$)

A strong base typically dissolved in liquid ammonia ($NH_3$) to prepare terminal alkynes by deprotonating them to drive formation of the alkynide ion.

Acid-catalyzed hydration

A reaction that adds water across a triple bond; for internal symmetrical alkynes like 3-hexyne, it yields a single ketone product.

MCPBA

A peroxyacid reagent used in the synthesis of epoxides from alkenes.

Allylic position

The carbon atom adjacent to a carbon-carbon double bond, which contains the weakest $C-H$ bonds in certain structures.

Regioisomeric compounds

Different constitutional isomers formed when a reaction, such as allylic bromination of methylenecyclopentane, can occur at multiple distinct sites.