© Prentice Hall 2001Chapter 21 Nomenclature of Alkyl Substituents If a Hydrogen is replaced by a halogen, the compound is an alkyl halide

© Prentice Hall 2001 Chapter 2 1

Nomenclature of Alkyl Substituents

If a Hydrogen is replaced by a halogen, the compound is an alkyl halide


Nomenclature of Alkyl Halides

Common name - Name the alkyl group first, followed by the name of the halogen expressed as an -ide name


Nomenclature of Alkyl Halides

IUPAC name - The halogen is treated as a substituent


Nomenclature of Ethers Common name -

Name(s) of alkyl group(s) listed first followed by the word “ether”


Nomenclature of Ethers IUPAC name - The smaller alkyl group

is converted to an “alkoxy” name and used as a substituent



If a hydrogen of an alkane is replaced by an OH group, the compound is an alcohol


Nomenclature of Alcohols

Alcohols are classified as primary, secondary or tertiary



Common name - Name of the Alkyl group followed by the word “alcohol”



IUPAC name - The OH group is a site of reactivity (a functional group)

Functional group is denoted by the suffix, “ol”

CH3OH CH3CH2OH

methanol ethanol


IUPAC Nomenclature of Alcohols

1. Parent Hydrocarbon is the longest continuous chain that contains the OH

2. Number the chain in direction that gives functional group the lowest number

3. If both a substituent and a functional group are present, the functional group gets the lower number



4. If the functional group gets the same number when counted from both directions, use direction which gives the substituent the lower number

5. If there is more than one substituent, cite substituents in alphabetical order



System is summarized as [Substituent] [Parent Hydrocarbon] [Functional Group]



If a hydrogen is replaced by an NH2, the compound is an amine


Nomenclature of Amines

Common name - Name of the Alkyl group(s) (in alphabetical order) followed by the syllable “amine”

The whole name is a single word

CH3NH2 CH3NCH2CH2CH3

methylamine methylpropylamine


Nomenclature of Amines IUPAC name - The NH2 group is a site of

reactivity (a functional group) Functional group is denoted by the suffix,

“amine” Final “e” of longest alkane group replaced by

suffix “amine”

1-butanamine

butan-1-amine

CH3CH2CH2CH2NH2


Nomenclature of Amines Amines are classified as primary, secondary or

tertiary depending on number of alkyl groups bonded to the nitrogen


Nomenclature of Amines In some compounds there are four alkyl groups

bonded to a nitrogen Such compounds must be salts because it is

impossible to have four bonds to nitrogen without having developed a positive charge

These are quaternary ammonium salts

CH3

N

CH3

CH3CH3 Cl


Structures of Alkyl Halides, Alcohols, Ethers, & Amines


Structures of Alkyl Halides, Alcohols, Ethers, & Amines


Properties of Alkyl Halides, Alcohols, Ethers, & Amines

Three physical properties are compared for these classes of compounds, 1.) boiling point, 2.) melting point, and 3.) solubility

Boiling point increases as the number of carbons in a hydrocarbon increases

As branching increases boiling point decreases


Properties of Alkyl Halides, Alcohols, Ethers, & Amines

Boiling point principally is a function of intermolecular attractions of which there are basically two kinds: 1.) dipole-dipole, and 2.) induced dipole-induce dipole

Dipole-dipole interactions stronger A particularly strong dipole-dipole

interaction is the hydrogen bond (requires a hydrogen atom bonded to a nitrogen, oxygen or fluorine atom)


Properties of Alkyl Halides, Alcohols, Ethers, & Amines For alkanes, there are only induced

dipole-induced dipole interactions (also known as van der Waals forces or London forces)

van der Waals forces are a function of surface area


Induced Dipole-Induced Dipole Interactions


Hydrogen Bonding: Strong Dipole-Dipole Interactions


Dipole-dipole Interactions

Particularly important for alcohols and amines Ethers and alkyl halides have dipole moments,

but their intermolecular attractions are not as strong as hydrogen bonds


Comparative Boiling Points


Melting Points

Melting point are a function of: intermolecular attractions packing in the crystalline state


Solubility The more carbons that are present, the

less soluble an organic compound is in water

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© Prentice Hall 2001Chapter 21 Nomenclature of Alkyl Substituents If a Hydrogen is replaced by a halogen, the compound is an alkyl halide