Haloalkanes and Haloarenes Flashcards

Vocabulary flashcards covering core definitions, classifications, mechanisms, physical properties, stereochemistry, and name reactions for Haloalkanes and Haloarenes.

Haloalkane (Alkyl Halide)

An aliphatic hydrocarbon derivative in which one or more hydrogen atoms are replaced by halogen atoms ($X = F, Cl, Br, I$).

Haloarene (Aryl Halide)

An aromatic hydrocarbon derivative in which one or more hydrogen atoms attached to an aromatic ring are replaced by halogen atoms.

Primary Alkyl Halide ($1^\circ$)

An alkyl halide in which the halogen atom is attached to a primary carbon atom ($R-CH_2-X$).

Secondary Alkyl Halide ($2^\circ$)

An alkyl halide in which the halogen atom is attached to a secondary carbon atom ($R_2CH-X$).

Tertiary Alkyl Halide ($3^\circ$)

An alkyl halide in which the halogen atom is attached to a tertiary carbon atom ($R_3C-X$).

Allylic Halide

A compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond ($C=C$).

Benzylic Halide

A compound in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom adjacent to a benzene ring.

Vinylic Halide

A compound in which the halogen atom is directly bonded to an $sp^2$ hybridized carbon atom of a carbon-carbon double bond ($C=C$).

Aryl Halide

A compound in which the halogen atom is directly bonded to an $sp^2$ hybridized carbon atom of an aromatic benzene ring.

Nature of $C-X$ Bond

A polar covalent bond resulting from the higher electronegativity of halogen compared to carbon, yielding partial charges $\mathbf{C}^{\delta+} - \mathbf{X}^{\delta-}$ where bond length follows $C-I > C-Br > C-Cl > C-F$.

Free Radical Halogenation

A substitution method for preparing haloalkanes from alkanes by reacting with halogens in the presence of heat or ultraviolet light ($h\nu$).

Sandmeyer's Reaction

A method to prepare aryl chlorides or bromides by treating a primary aromatic amine with $NaNO_2 + HCl$ to form a diazonium salt, followed by reaction with cuprous halide ($Cu_2Cl_2$ or $Cu_2Br_2$).

Markovnikov's Rule

An addition rule stating that when an unsymmetrical hydrogen halide ($HX$) adds to an unsymmetrical alkene, the halogen adds to the carbon atom containing fewer hydrogen atoms.

Anti-Markovnikov Addition (Peroxide Effect)

The addition of $HBr$ to an unsymmetrical alkene in the presence of peroxide where bromine attaches to the double-bonded carbon bearing more hydrogen atoms.

Finkelstein Reaction

A halogen exchange reaction in which alkyl chlorides or bromides react with sodium iodide ($NaI$) in dry acetone to yield alkyl iodides.

Swarts Reaction

A halogen exchange method for preparing alkyl fluorides by heating alkyl chlorides or bromides in the presence of metallic fluorides such as $AgF$, $Hg_2F_2$, or $SbF_3$.

Plane Polarized Light (PPL)

Light whose electric field vibrations are confined to a single plane perpendicular to the direction of propagation.

Optical Activity

The property of certain chiral chemical compounds to rotate the plane of plane-polarized light when passed through their solution.

Dextrorotatory Compound

An optically active isomer that rotates plane-polarized light to the right (clockwise), denoted by ($d$) or ($+$).

Laevorotatory Compound

An optically active isomer that rotates plane-polarized light to the left (counter-clockwise), denoted by ($l$) or ($-$).

Chiral Carbon (Asymmetric Carbon)

An $sp^3$ hybridized carbon atom bonded to four different substituents or groups.

Chirality

The property of an object or molecule being non-superimposable on its mirror image.

Enantiomers

Stereoisomers that are non-superimposable mirror images of each other and rotate plane-polarized light in equal magnitudes but opposite directions.

Diastereomers

Stereoisomers that are not mirror images of each other and differ in physical properties.

Racemic Mixture

An equimolar mixture containing two enantiomers in equal proportions, resulting in zero net optical rotation ($dl$ or $\pm$).

Racemisation

The chemical process of converting an optically active enantiomer into an optically inactive racemic mixture.

Retention of Configuration

A reaction outcome where the relative spatial arrangement of bonds at an asymmetric carbon atom remains identical before and after the reaction.

Inversion of Configuration

A reaction outcome where the spatial arrangement around an asymmetric carbon atom is reversed during substitution, as observed in $S_N2$ mechanisms.

Concerted $S_N2$ Mechanism

A single-step bimolecular nucleophilic substitution proceeding through a transition state where nucleophile attack and leaving group departure occur simultaneously.

Steric Effects in $S_N2$ Reaction

The decrease in the rate of $S_N2$ substitution as steric crowding increases around the carbon bearing the halogen, giving a relative rate order: $\text{Methyl (30) > Primary (1) > Secondary (0.02) > Tertiary (0)}$.

$S_N1$ Reaction

A unimolecular nucleophilic substitution proceeding in two steps via a carbocation intermediate, following first-order kinetics ($\text{Rate} = k[Alkyl\,halide]$) and leading to racemisation.

Elimination versus Substitution Competition

The competing reaction pathways of alkyl halides containing $\alpha$-hydrogens when treated with a nucleophile/base, governed by nucleophile strength/bulkiness, substrate structure, and temperature.

Grignard Reagent

An organometallic compound formed by reacting an alkyl halide with magnesium metal in dry ether, represented as $R-Mg-X$.

Wurtz-Fittig Reaction

A reaction involving a mixture of an alkyl halide and an aryl halide treated with sodium in dry ether to yield an alkylarene.

Fittig Reaction

A coupling reaction of two molecules of aryl halides with sodium metal in dry ether to form a biaryl compound.