Substitution and Elimination Reactions

These flashcards cover vocabulary and key concepts related to substitution and elimination reactions, focusing on SN1, SN2, E1, and E2 mechanisms.

SN1 Reaction

A type of nucleophilic substitution reaction where the rate-determining step involves the formation of a carbocation intermediate. This reaction typically occurs in two steps, leading to racemization at chiral centers.

SN2 Reaction

Substitution Nucleophilic Bimolecular; a one-step reaction where two reactant molecules come together to complete the substitution.

Nucleophile

An atom or molecule that donates an electron pair to form a chemical bond.

Leaving Group

An atom or group of atoms that can depart from the substrate, taking with it the electron pair that was shared with the substrate.

Activation Energy

The minimum energy required to initiate a chemical reaction.

Racemic Mixture

A mixture that contains equal amounts of enantiomers, resulting in no optical activity.

Enantiomers

Stereoisomers that are mirror images of each other and cannot be superimposed.

Trigonal Planar

A molecular geometry where a central atom is bonded to three other atoms, forming a flat shape.

Stereochemistry

The study of the three-dimensional arrangement of atoms in molecules and its impact on chemical reactions.

Carbocation

A positively charged carbon atom, typically formed as an intermediate in reactions involving the loss of a leaving group.

Antiperiplanar

A term describing the configuration where the leaving group and the hydrogen atom on the adjacent carbon are opposite to each other in a plane.

Alpha Carbon

The carbon atom that is directly bonded to a leaving group.

Beta Carbon

Any carbon atom that is bonded to the alpha carbon.

Zaitsev's Rule

In elimination reactions, the most substituted alkene will be the major product.

E1 Reaction

An elimination reaction that involves the formation of a carbocation intermediate and occurs in two stages.

E2 Reaction

A simultaneous (bimolecular) elimination reaction where the base removes a beta proton as the leaving group departs.

Substituent

An atom or group of atoms replacing a hydrogen atom in a hydrocarbon.

Nucleophilicity

The strength of a nucleophile, or how readily it can donate electron pairs.

Tertiary Substrate

A substrate with three carbon groups attached to the carbon bonded to the leaving group, favoring SN1 or E1 reactions.

Primary Substrate

A substrate with only one carbon group attached to the carbon bonded to the leaving group, favoring SN2 reactions.

Secondary Substrate

A substrate with two carbon groups attached to the carbon bonded to the leaving group, which can undergo either SN1 or SN2 reactions.

Steric Hinderance

The prevention of chemical reactions due to the physical size of groups within the molecule.

Strong Nucleophile

A nucleophile that has a high tendency to donate its electrons, often negatively charged.

Weak Nucleophile

A nucleophile with lower availability to donate electrons; often neutral or less highly charged.

Polar Protic Solvent

A solvent that has a hydrogen atom bonded to an electronegative atom, aiding in SN1 reactions.

Polar Aprotic Solvent

A solvent that does not contain any hydrogen atoms that can participate in hydrogen bonding, favoring SN2 reactions.

Diastereomers

Stereoisomers that are not mirror images of each other and have at least one but not all chiral centers the same.

Enantiomers Comparison

Enantiomers are compared based on their optical activity and the ability to rotate plane-polarized light in opposite directions.

Meso Compounds

Compounds that have multiple chiral centers but also possess a plane of symmetry, resulting in achirality.

Constitutional Isomers

Compounds that have the same molecular formula but different bonding arrangements.

Rate Determining Step

The slowest step in a reaction mechanism that determines the overall rate of the reaction.

Inverted Configuration

A configuration change where the arrangement around a chiral carbon is reversed during substitution reactions.

Five Bonds Stage

A transient stage in SN2 reactions where carbon appears to have five bonds during the nucleophilic attack.

Stereoisomer

Compounds that have the same molecular formula and bond connectivity but differ in the three-dimensional arrangement of atoms.

Concerted Process

A reaction mechanism where bond breaking and bond forming occur simultaneously in a single step.

Beta Hydrogen

Hydrogens that are attached to the beta carbon and are involved in elimination reactions.