Organic Halides

A structural unit in a molecule responsible for its characteristic behavior under a particular set of reaction conditions Functional Group

AlcoholROH Alkyl halideRX (X = F, Cl, Br, I) Amineprimary amine: RNH 2 secondary amine: R 2 NH secondary amine: R 2 NH tertiary amine: R 3 N tertiary amine: R 3 N Families of organic compounds and their functional groups

IUPAC Nomenclature of Alkyl Halides

The two that are most widely used are: functional class nomenclature substitutive nomenclature Both types can be applied to alcohols and alkyl halides. IUPAC Nomenclature There are several kinds of IUPAC nomenclature.

Name the alkyl group and the halogen as separate words (alkyl + halide) Functional Class Nomenclature of Alkyl Halides CH 3 F CH 3 CH 2 CH 2 CH 2 CH 2 Cl CH 3 CH 2 CHCH 2 CH 2 CH 3 Br H I

Name the alkyl group and the halogen as separate words (alkyl + halide) Functional Class Nomenclature of Alkyl Halides CH 3 F CH 3 CH 2 CH 2 CH 2 CH 2 Cl CH 3 CH 2 CHCH 2 CH 2 CH 3 Br Methyl fluoride Pentyl chloride 1-Ethylbutyl bromide Cyclohexyl iodide H I

Name as halo-substituted alkanes. Number the longest chain containing the halogen in the direction that gives the lowest number to the substituted carbon. Substitutive Nomenclature of Alkyl Halides CH 3 CH 2 CH 2 CH 2 CH 2 F CH 3 CHCH 2 CH 2 CH 3 Br CH 3 CH 2 CHCH 2 CH 3 I

Name as halo-substituted alkanes. Number the longest chain containing the halogen in the direction that gives the lowest number to the substituted carbon. Substitutive Nomenclature of Alkyl Halides CH 3 CH 2 CH 2 CH 2 CH 2 F CH 3 CHCH 2 CH 2 CH 3 Br 1-Fluoropentane 3-Iodopentane 2-Bromopentane CH 3 CH 2 CHCH 2 CH 3 I

Substitutive Nomenclature of Alkyl Halides Halogen and alkyl groups are of equal rank when it comes to numbering the chain. Number the chain in the direction that gives the lowest number to the group (halogen or alkyl) that appears first. CH 3 Cl Cl

Substitutive Nomenclature of Alkyl Halides 5-Chloro-2-methylheptane 2-Chloro-5-methylheptane CH 3 Cl Cl

Nomenclature of Alkyl Halides In the IUPAC system, alkyl halides are named as substituted alkanes

CH 3 CH 2 CH 2 CH 2 CH 2 F CH 3 CHCH 2 CH 2 CH 3 Br primary alkyl halide secondary alkyl halide ClassificationClassification CH 3 CCH 2 CH 2 CH 3 OH CH 3 tertiary alcohol H OH secondary alcohol

Different Kinds of Alkyl Halides

Aryl Halides Aryl halides are halides in which the halogen is attached directly to an aromatic ring. Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen bonds in alkyl halides.

Aryl Halides Aryl halides are halides in which the halogen is attached directly to an aromatic ring. Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen bonds in alkyl halides. Because the carbon-halogen bond is stronger, aryl halides react more slowly than alkyl halides when carbon-halogen bond breaking is rate determining.

Boiling point increases with increasing number of halogens CH 3 Cl -24°C CH 2 Cl 2 40°C CHCl 3 61°C CCl 4 77°C CompoundBoiling Point Even though CCl 4 is the only compound in this list without a dipole moment, it has the highest boiling point. Induced dipole-induced dipole forces are greatest in CCl 4 because it has the greatest number of Cl atoms. Cl is more polarizable than H.

Physical Properties of Aryl Halides resemble alkyl halides all are essentially insoluble in water less polar than alkyl halides Cl  1.7 D Cl  2.2 D

ROH + HX  RX + HOH Hydrogen halide reactivity HFHClHBrHI Reaction of Alcohols with Hydrogen Halides least reactive most reactive

An S N 2 reaction proceeds in the direction that allows the strongest base to displace the weaker base

ExampleExample ClOH 1.NaOH, H 2 O 370°C 2. H + (97%)

nitro-substituted aryl halides do undergo nucleophilic aromatic substitution readily But...But...Cl NO 2 + NaOCH 3 CH 3 OH 85°C OCH 3 NO 2 + NaCl (92%)

ReactionReactionF NO 2 + NaOCH 3 CH 3 OH 85°C OCH 3 NO 2 + NaF (93%)

Aryl Halides Undergo Substitution When Treated With Very Strong Bases Cl NH 2 KNH 2, NH 3 –33°C (52%)

Hydrolysis of Chlorobenzene Cl * NaOH, H 2 O 395°C OHOHOHOH * + OHOHOHOH* (54%)(43%) 14 C labeling indicates that the high- temperature reaction of chlorobenzene with NaOH goes via benzyne.