Alkyl Halides Lecture Notes

A collection of vocabulary flashcards covering the definitions, classifications, reactions, and mechanisms of alkyl halides based on Prof. R. Jagessar's lecture notes.

Alkyl halides

A class of organic compounds with the general formula $RX$, where $R$ is an alkyl or aryl group and $X$ is a halogen.

Aryl halide

An aromatic alkyl halide where a halogen group is bonded to the $sp^2$ hybridized carbon of the aromatic ring.

Vinyl halide

A halide where a halogen is bonded to one of the $sp^2$ hybridized carbons of an alkene.

Vicinal dihalide

A compound containing two halogens bonded to adjacent $sp^3$ hybridized carbons.

Geminal halide

A halide where two halogens are bonded to one carbon of the $sp^3$ hybridized carbons.

$sp^3$ hybridized carbon

A tetrahedral carbon atom.

$sp$ hybridized carbon

A triple bonded carbon atom.

$sp^2$ hybridized carbon

A double bonded carbon atom.

Primary ($1^\bullet$) alkyl halide

An alkyl halide that has one $R$ group bonded to the carbon bearing the halogen.

Secondary ($2^\bullet$) alkyl halide

An alkyl halide that has two $R$ groups bonded to the carbon bearing the halogen.

Tertiary ($3^\bullet$) alkyl halide

An alkyl halide that has three $R$ groups bonded to the carbon bearing the halogen.

Markovnikov’s rule

A rule stating that in the addition of hydrogen halides to an unsaturated centre, the hydrogen attaches itself to the carbon bearing the greater number of hydrogen atoms.

Anti-Markovnikov addition

A reaction occurring in the presence of peroxides where the hydrogen halide addition to an alkene does not follow Markovnikov's rule.

Bromonium ion

A cyclic intermediate formed during the reaction of an alkene with a halogen ($X_2$).

NBS (N-bromosuccinimide)

A reagent used for the selective bromination of an allylic carbon by providing a low constant concentration of bromine.

Allylic halide

A compound where a halogen is attached to a carbon adjacent to a carbon-carbon double bond.

$S_N2$ reaction

Substitution nucleophilic bimolecular; a second-order reaction where two molecules are involved in the rate-determining step, typically resulting in inversion of stereochemistry.

$S_N1$ reaction

Substitution nucleophilic unimolecular; a first-order reaction where only one molecule is involved in the rate-determining step, typically involving a carbocation intermediate.

Solvolysis

A reaction in which the solvent acts as the nucleophile, characteristic of $S_N1$ reactions.

Carbonium ion (or Carbocation)

A carbon atom bearing a positive charge and six electrons, having an incomplete octet.

Aprotic solvent

A polar solvent that has a net dipole moment but will not release or donate a proton (e.g., DMSO, DMF).

Protic solvent

A solvent that can donate a proton (e.g., $CH_3CH_2OH$).

Elimination reaction

A reaction involving the loss of two atoms or groups on adjacent carbons, resulting in the formation of a $\pi$ bond.

$E2$ elimination

Elimination bimolecular; a second-order reaction ($Rate = K[RX][Base]$) where two molecules are involved in the rate-determining step.

$E1$ elimination

Elimination unimolecular; a first-order reaction ($Rate = K[Alkyl halide]$) preferred by tertiary alkyl halides.

Nucleophile

A species that can attack an electron-deficient carbon, bearing either an overall negative charge or lone pairs of electrons.

Leaving group

A group that is electron-withdrawing to polarize the carbon-halogen bond and is stable (usually a weak base) once it has departed.