Nucleophilic Substitution and Elimination Flashcards

Comprehensive vocabulary flashcards covering nucleophilic substitution (SN1, SN2) and elimination (E1, E2) mechanisms, kinetics, and stereochemistry.

Alkyl halides

Electrophiles whose chemistry primarily involves polar reactions with nucleophiles or bases due to the polar C-X bond.

Substitution Reaction

A reaction where a nucleophile replaces a leaving group (X group) on an organic substrate.

Elimination Reaction

A reaction involving the removal of a proton from a beta ($\beta$) position and a leaving group to yield an alkene.

Concerted Process

A reaction mechanism where multiple steps, such as nucleophilic attack and loss of a leaving group, occur simultaneously.

Stepwise Process

A reaction mechanism where steps occur sequentially, such as the loss of a leaving group occurring first to form an intermediate followed by nucleophilic attack.

Substrate

The electrophile in a substitution reaction that must contain a leaving group.

Leaving Group

A group capable of separating from the substrate that stabilizes the developed negative charge and withdraws electron density via induction.

SN2

Substitution Nucleophilic Bimolecular; a concerted reaction with a second-order rate equation described by $\text{Rate} = k [RX] [Nuc:]$.

SN1

Substitution Nucleophilic Unimolecular; a stepwise reaction with a first-order rate equation described by $\text{Rate} = k [RX]$.

Inversion of Configuration

The stereochemical outcome of an SN2 reaction where the nucleophile attacks from the side opposite the leaving group.

Stereospecific

A reaction where the configuration of the product is dependent on the configuration of the starting material.

Steric Effect

The reduction in reaction speed caused by a bulky substrate whose carbon atom is shielded from an incoming nucleophile.

Polarizability

The ability of an atom to distribute its electron density unevenly in response to external influences, typically increasing with atomic size.

Protic Solvent

A solvent containing at least one hydrogen atom connected directly to an electronegative atom, capable of stabilizing both cations and anions.

Polar Aprotic Solvent

A solvent that contains no hydrogen atoms connected directly to an electronegative atom and stabilizes cations but not anions.

Rate-Determining Step (RDS)

The slowest step in a reaction mechanism, characterized by having the highest transition state energy.

Racemic Mixture

An equal mixture of inversion and retention products, which is the expected outcome of SN1 reactions.

Ion Pairs

A configuration formed initially upon the loss of a leaving group in SN1 that hinders attack on one face, often leading to a slight preference for inversion products.

Hammond Postulate

The principle stating that any factor stabilizing a high-energy intermediate also stabilizes the transition state leading to that intermediate.

Dehydrohalogenation

An elimination reaction specifically where the leaving group is a halide.

E2

Bimolecular elimination; a concerted process with a second-order rate equation: $\text{Rate} = k [\text{substrate}] [\text{base}]$.

Regiochemistry

A characteristic of a reaction that can produce more than one possible constitutional isomer as a product.

Zaitsev Product

The more substituted alkene formed in an elimination reaction, which is generally the major product.

Hofmann Product

The less substituted alkene formed in an elimination reaction, which becomes the major product when sterically hindered bases are used.

Anti-periplanar

A conformation where the proton at the beta position and the leaving group are nearly coplanar with a dihedral angle of approximately $180^{\circ}$.

E1

Unimolecular elimination; a stepwise process following first-order kinetics where the rate is linearly dependent on the concentration of only the substrate.