Organic HalidesOrganic Halides

AA structural unit in a molecule responsible for its structural unit in a molecule responsible for its

characteristic behavior under a particular set ofcharacteristic behavior under a particular set of

reaction conditionsreaction conditions

Functional GroupFunctional Group

AlcoholAlcohol ROHROH

Alkyl halideAlkyl halide RRXX ( (XX = F, Cl, Br, I) = F, Cl, Br, I)

AmineAmine primary amine: Rprimary amine: RNHNH22

secondary amine: Rsecondary amine: R22NHNH

tertiary amine: Rtertiary amine: R33NN

Families of organic compoundsFamilies of organic compoundsand their functional groupsand their functional groups

IUPAC NomenclatureIUPAC Nomenclature

of Alkyl Halidesof Alkyl Halides

The two that are most widely used are:The two that are most widely used are:functional class nomenclaturefunctional class nomenclaturesubstitutive nomenclaturesubstitutive nomenclature

Both types can be applied to alcohols andBoth types can be applied to alcohols andalkyl halides.alkyl halides.

IUPAC NomenclatureIUPAC Nomenclature

There are several kinds of IUPAC nomenclature.There are several kinds of IUPAC nomenclature.

Name the alkyl group and the halogen asName the alkyl group and the halogen asseparate words (separate words (alkylalkyl + + halidehalide))

Functional Class Nomenclature of Alkyl HalidesFunctional Class Nomenclature of Alkyl Halides

CHCH33FF CHCH33CHCH22CHCH22CHCH22CHCH22ClCl

CHCH33CHCH22CHCHCHCH22CHCH22CHCH33

BrBr

HH

II

Name the alkyl group and the halogen asName the alkyl group and the halogen asseparate words (separate words (alkylalkyl + + halidehalide))

Functional Class Nomenclature of Alkyl HalidesFunctional Class Nomenclature of Alkyl Halides

CHCH33FF CHCH33CHCH22CHCH22CHCH22CHCH22ClCl

CHCH33CHCH22CHCHCHCH22CHCH22CHCH33

BrBr

Methyl fluorideMethyl fluoride Pentyl chloridePentyl chloride

1-Ethylbutyl bromide1-Ethylbutyl bromide Cyclohexyl iodideCyclohexyl iodide

HH

II

Name as halo-substituted alkanes.Name as halo-substituted alkanes.

Number the longest chain containing theNumber the longest chain containing thehalogen in the direction that gives the lowesthalogen in the direction that gives the lowestnumber to the substituted carbon.number to the substituted carbon.

Substitutive Nomenclature of Alkyl HalidesSubstitutive Nomenclature of Alkyl Halides

CHCH33CHCH22CHCH22CHCH22CHCH22FF CHCH33CHCHCHCH22CHCH22CHCH33

BrBr

CHCH33CHCH22CHCHCHCH22CHCH33

II

Name as halo-substituted alkanes.Name as halo-substituted alkanes.

Number the longest chain containing theNumber the longest chain containing thehalogen in the direction that gives the lowesthalogen in the direction that gives the lowestnumber to the substituted carbon.number to the substituted carbon.

Substitutive Nomenclature of Alkyl HalidesSubstitutive Nomenclature of Alkyl Halides

CHCH33CHCH22CHCH22CHCH22CHCH22FF CHCH33CHCHCHCH22CHCH22CHCH33

BrBr1-Fluoropentane1-Fluoropentane

3-Iodopentane3-Iodopentane

2-Bromopentane2-BromopentaneCHCH33CHCH22CHCHCHCH22CHCH33

II

Substitutive Nomenclature of Alkyl HalidesSubstitutive Nomenclature of Alkyl Halides

Halogen and alkyl groupsHalogen and alkyl groupsare of equal rank when are of equal rank when it comes to numberingit comes to numberingthe chain.the chain.

Number the chain in theNumber the chain in thedirection that gives the direction that gives the lowest number to thelowest number to thegroup (halogen or alkyl)group (halogen or alkyl)that appears first.that appears first.

CHCH33

ClCl ClCl

CHCH33

Substitutive Nomenclature of Alkyl HalidesSubstitutive Nomenclature of Alkyl Halides

5-Chloro-2-methylheptane5-Chloro-2-methylheptane

2-Chloro-5-methylheptane2-Chloro-5-methylheptane

CHCH33

ClCl ClCl

CHCH33

Nomenclature of Alkyl Halides

CH3Cl CH3CH2FCH3CHI

CH3

CH3CH2CHBr

CH3chloromethane fluoroethane2-iodopropane 2-bromobutane

In the IUPAC system, alkyl halides are named as substituted alkanes

CH3CH2CHCH2CH2CH2CH3

CH3

Br

2-bromo-5-methylheptane

CH3CH2CHCH2CH2CH2Cl

CH3

CH31-chloro-5,5-dimethylhexane

CH2CH3

I

1-ethyl-2-iodocyclopentane

Br

Cl

CH3

4-bromo-2-chloro-1-methylcyclohexane

CHCH33CHCH22CHCH22CHCH22CHCH22FF

CHCH33CHCHCHCH22CHCH22CHCH33

BrBr

primary alkyl halideprimary alkyl halide

secondary alkyl halidesecondary alkyl halide

ClassificationClassification

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

tertiary alcoholtertiary alcohol

HH

OHOH

secondary alcoholsecondary alcohol

Different Kinds of Alkyl Halides

Aryl HalidesAryl Halides

Aryl halides are halides in which the halogen is Aryl halides are halides in which the halogen is attached directly to an aromatic ring.attached directly to an aromatic ring.

Carbon-halogen bonds in aryl halides are Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen shorter and stronger than carbon-halogen bonds in alkyl halides.bonds in alkyl halides.

Aryl HalidesAryl Halides

Aryl halides are halides in which the halogen is Aryl halides are halides in which the halogen is attached directly to an aromatic ring.attached directly to an aromatic ring.

Carbon-halogen bonds in aryl halides are Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen shorter and stronger than carbon-halogen bonds in alkyl halides.bonds in alkyl halides.

Because the carbon-halogen bond is stronger, Because the carbon-halogen bond is stronger, aryl halides react more slowly than alkyl halides aryl halides react more slowly than alkyl halides when carbon-halogen bond breaking is rate when carbon-halogen bond breaking is rate determining.determining.

Boiling point increases with increasingBoiling point increases with increasingnumber of halogensnumber of halogens

CHCH33ClCl -24°C-24°C

CHCH22ClCl22 40°C40°C

CHCHClCl33 61°C61°C

CCClCl44 77°C77°C

CompoundCompound Boiling PointBoiling Point

Even though CClEven though CCl4 4 is the only compound in this list without a is the only compound in this list without a

dipole moment, it has the highest boiling point.dipole moment, it has the highest boiling point.

Induced dipole-induced dipole forces are greatest in Induced dipole-induced dipole forces are greatest in CClCCl44 because it has the greatest number of Cl atoms. because it has the greatest number of Cl atoms.

Cl is more polarizable than H. Cl is more polarizable than H.

Physical Properties of Aryl HalidesPhysical Properties of Aryl Halides

resemble alkyl halidesresemble alkyl halides

all are essentially insoluble in waterall are essentially insoluble in water

less polar than alkyl halidesless polar than alkyl halides ClCl

1.7 D1.7 D

ClCl

2.2 D2.2 D

RROOHH + + HHXX R RXX + + HHOOHH

Hydrogen halide reactivityHydrogen halide reactivity

HHFF HHClCl HHBrBr HHII

Reaction of Alcohols with Hydrogen HalidesReaction of Alcohols with Hydrogen Halides

least reactiveleast reactive most reactivemost reactive

An SN2 reaction proceeds in the direction that allowsthe strongest base to displace the weaker base

ExampleExample ClCl

OHOH

1.1. NaOH, HNaOH, H22OO

370°C370°C

2. H2. H++

(97%)(97%)

nitro-substituted aryl halides nitro-substituted aryl halides dodo undergo undergonucleophilic aromatic substitution readilynucleophilic aromatic substitution readily

But...But... ClCl

NONO22

++ NaNaOOCHCH33

CHCH33OHOH

85°C85°C

OOCHCH33

NONO22

++ NaNaClCl

(92%)(92%)

ReactionReaction FFNONO22

++ NaNaOOCHCH33

CHCH33OHOH

85°C85°C

OOCHCH33

NONO22

++ NaNaFF

(93%)(93%)

Aryl Halides Undergo Substitution WhenAryl Halides Undergo Substitution WhenTreated With Very Strong BasesTreated With Very Strong Bases ClCl

NHNH22

KNHKNH22, NH, NH33

––33°C33°C

(52%)(52%)

Hydrolysis of ChlorobenzeneHydrolysis of Chlorobenzene ClCl**

NaOH, HNaOH, H22OO 395°C395°C OOHH**++

OOHH

**

(54%)(54%)(43%)(43%)

1414C labeling C labeling indicates that indicates that the high-the high-temperature temperature reaction of reaction of chlorobenzene chlorobenzene with NaOH with NaOH goes via goes via benzyne.benzyne.