Halogen Compounds & Derivatives

Comprehensive practice flashcards covering vocabulary and core concepts of Halogen Compounds and Derivatives, including reaction mechanisms and preparation methods.

Alkyl Halide

Also known as haloalkanes, these are halo-substituted alkanes with the general formula $RX$, where $R$ is an alkyl group and $X$ represents a halogen atom ($F$, $Cl$, or $Br$).

Primary ($1^{\circ}$) Alkyl Halide

An alkyl halide classified according to the halogen being attached to a carbon atom that is bonded to only one other carbon atom.

Secondary ($2^{\circ}$) Alkyl Halide

An alkyl halide where the halogen-bearing carbon atom is attached to two other carbon atoms; for example, isopropyl chloride.

Tertiary ($3^{\circ}$) Alkyl Halide

An alkyl halide where the carbon bearing the halogen is attached to three other carbon atoms; these are highly reactive in $S_N1$ and $E1$ reactions.

Markovnikov Rule

A rule stating that in the addition of $H-X$ to an alkene, the acid hydrogen ($H$) attaches to the carbon with the greatest number of hydrogens, while the halide ($X$) attaches to the carbon with the fewest hydrogens.

Initiation Step

The first step in radial halogenation of alkanes where a halogen molecule is cleaved by $UV$ light or high temperature to form two reactive radicals, e.g., $Cl-Cl \xrightarrow{hv} 2Cl\cdot$.

Propagation Step

A repeating cycle in radical halogenation involving two steps: first, a halogen radical reacts with an alkane to form a carbon radical and $HX$; second, the carbon radical reacts with a halogen molecule to form the alkyl halide and regenerate the halogen radical.

Termination Step

The final stage of radical halogenation where any two radicals collide and combine to form a stable molecule, effectively ending the chain reaction.

Leaving Group

The group replaced during a nucleophilic substitution reaction; its effectiveness increases with atomic radius ($I > Br > Cl > F$) as larger atoms have weaker nuclear attraction to the bonding electrons.

$S_N2$ Mechanism

A single-step bimolecular nucleophilic substitution ($rate = k[Substrate][Nucleophile]$) where the nucleophile performs a backside attack, resulting in an inversion of configuration.

$S_N1$ Mechanism

A multi-step unimolecular nucleophilic substitution ($rate = k[RX]$) that proceeds via a carbocation intermediate and is favored by tertiary substrates in polar protic solvents.

Polar Aprotic Solvent

A solvent that does not have a hydrogen atom attached to an electronegative atom and cannot form hydrogen bonds, such as $DMSO$ (dimethylsulfoxide) or $DMF$ (dimethylformamide); these favor $S_N2$ reactions.

Polar Protic Solvent

A solvent with a hydrogen atom attached to an electronegative atom that can form hydrogen bonds (e.g., $H_2O$, $CH_3OH$); these favor $S_N1$ and $E1$ reactions by stabilizing intermediates.

Williamson Synthesis

The preparation of an ether by the addition of a sodium alkoxide ($Na^{+}-O-R'$) to an alkyl halide ($R-X$).

$E2$ Reaction

A bimolecular elimination reaction ($rate = k[Substrate][Base]$) that occurs in a single step when an alkyl halide is treated with a strong base (like $OH^-$ or $RO^-$), leading to the formation of an alkene.

$E1$ Reaction

A unimolecular elimination reaction involving the spontaneous dissociation of an alkyl halide to form a carbocation intermediate, followed by the loss of a neighboring proton ($H^+$) to form a double bond.

Grignard Reagent

An organometallic compound prepared by reacting an alkyl or aryl halide with magnesium ($Mg$) in dry ether, represented by the formula $RMgX$ or $ArMgX$.

Nitrile Synthesis

The reaction of a primary alkyl halide with sodium cyanide ($NaCN$) to produce a nitrile ($R-C\equiv N$).

Nucleophile

A chemical species that is electron-rich and seeks out an electron-deficient site; strong examples include $OH^-$ and $OR^-$, while weak examples include $H_2O$ and $ROH$.

Electrophilic Bromination of Benzene

A substitution reaction where benzene reacts with $Br_2$ in the presence of a catalyst like $FeBr_3$ to produce bromobenzene and $HBr$.