alkenes and alkynes

Identify!

3-sec-butyl-1,1-dimethylcyclopentane

Identify!

4-ethyl-2-isopropylbicyclo[4.1.0]heptane

Identify!

2,6,6-trimethylbicyclo[3.1.1]heptane

Alkenes and Alkynes

Aliphatic

Saturated

Alkanes

Unsaturated

Alkenes Alkynes

Classification of Organic Compounds

Alkenes• compounds that contain carbon and

hydrogen and have at least one C C ‑double bond.• low melting and boiling point,

insoluble in water, relatively reactive• Molecular formula is CnH2n

Important Alkenes

Ethylene (ethene)

α-Pinene

cis-tricos-9-ene, ‘‘muscalure’’

Alkene NomenclatureSimple alkenes are named much like

alkanes, using the root name of the longest chain containing the

double bond.

Ethylene (ethene)

Alkene Nomenclature• When the chain contains more

than three carbon atoms, a number is used to give the location of the double bond.

• The chain is numbered starting from the C closest to the double bond, and the double bond is given the lower number of its two double-bonded carbon atoms.

1-butenebut-1-ene

Alkene Nomenclature

Cycloalkenes are assumed to have the double bond in the number 1 position.cyclohexene

Alkene Nomenclature• A compound with two

double bonds is a diene. A triene has three double bonds, and a tetraene has four.

• Numbers are used to specify the locations of the double bonds.

1,3-butadienebuta-1,3-diene

Alkene Nomenclature Step 1

• Find the longest chain that contains both carbon atoms of the double bond.

Pentene


• Number the carbon chain from the end(carbon) that gives the multiple bond the lower number.

1-pentene1

2

3

4

5


• Number and name the substituents, and write the name.

2,3-dimethyl-1-pentene2,3-dimethylpent-1-ene2-methyl

3-methyl

Alkene Nomenclature•Draw 2-methyl-3-heptene. What is its other IUPAC name?

2-methyl-hept-3-ene

Alkene Nomenclature•Identify the structure. Give its two IUPAC names.

1,3,5-heptatrienehepta-1,3,5-triene

Alkene Nomenclature•Draw 1,3,5,7-cyclooctatetraene.•What is its other IUPAC name?

cycloocta-1,3,5,7-tetraene

Alkene Nomenclature•Identify the structure. Give its two IUPAC names.

3-ethyl-1-heptene3-ethylhept-1-ene

Alkene Nomenclature•Draw 7-bromo-1,3,5-cycloheptatriene.•What is its other IUPAC name?

7-bromocyclohepta-1,3,5-triene

Alkene Nomenclature• Alkenes named as

substituents are called alkenyl groups.• They can be named

systematically (ethenyl, propenyl, etc.), or by common names.

CH2=methylene / methylidene

Alkene Nomenclature

• Vinyl (ethenyl)

• Allyl (1-propenyl)

• Crotyl (2-butenyl)

CH2=CH--

CH3CH=CH--

CH3CH=CHCH2--

Alkene Nomenclature•Identify the structure.

3-methylenecyclohexene

1


3-vinyl-1,5-hexadiene3-vinylhexa-1,5-diene

1


allyl chloride3-chloropropene

1

CH2=CH--CH2--Cl


2,6-dimethyl-3-heptene2,6-dimethylhept-3-ene

1


3,6-dimethyl-5-propyl-3-octene3,6-dimethyl-5-propyloct-3-ene

1


4-isopropyl-1-cyclohexene4-isopropylcyclohex-1-ene


6-chloro-4-ethyl-6-methyl-1,4-heptadiene6-chloro-4-ethyl-6-methylhepta-1,4-diene

1

Alkene Nomenclature•Draw 5-sec-butyl-nona-3,6-diene.•What is its other IUPAC name?

5-sec-butyl-3,6-nonadiene

Alkene Nomenclature•Draw 5-allylnona-2,6-diene.•What is its other IUPAC name?

5-allyl-2,6-nonadiene

Alkene Nomenclature•Draw 1,3,5-cyclohexatriene.•What is its most popular name?

Benzene, cyclohexa-1,3,5-triene

Alkynes• compounds that contain carbon and

hydrogen and have at least one C C ‑triple bond.• Relatively not common in nature

compared to alkenes• Molecular formula is CnH2n-2

Alkynes• Non-polar, nearly insoluble in water.• Many have mildly offensive odors.• Used by some plants for protection

against fungal diseases.

Important Alkynes

Ethyne (acetylene)

methylacetylene

Alkyne NomenclatureThe IUPAC

nomenclature for alkynes is similar to that for alkenes. We

change the -ane ending of the parent

alkane to –yne.

Propyne

Alkyne Nomenclature Step 1

• Find the longest chain that contains both carbon atoms of the triple bond.

Pentyne

2-pentyne


• Number the carbon chain from the end(carbon) that gives the multiple bond the lower number.

12

3 4

5


• Number and name the substituents, and write the name.

4-methyl-2-pentyne4-methylpent-2-yne

4-methyl

Alkyne NomenclatureIf a double bond and triple bond are on the same parent chain, naming priority will be given to the triple bond. The struture will be named as an alkyne.

1-penten-4-ynepent-1-en-4-yne

Alkyne NomenclatureIf the double bond and the triple bond are equidistant

from the ends of the chain, number the chain so that the double bond receives a lower number than the triple

bond (because “ene” comes before “yne” in the alphabet).

1-penten-4-ynepent-1-en-4-yne

1

4

Alkyne NomenclatureIf the double bond and the triple bond are equidistant

from the ends of the chain, number the chain so that the double bond receives a lower number than the triple

bond (because “ene” comes before “yne” in the alphabet).

2-methyl-1-penten-3-yne2-methylpent-1-en-3-yne

Alkyne Nomenclature•Identify the structure. Give its two IUPAC names.

4-ethyl-2-hexyne4-ethylhex-2-yne

Alkyne Nomenclature•Draw 6-bromo-2-methyl-3-heptyne.•What is its other IUPAC name?

6-bromo-2methylhept-3-yne

Alkyne Nomenclature•Draw 5,5-dimethyl-3-heptyne.•What is its other IUPAC name?

5,5-dimethylhept-3-yne

Alkyne Common Names• The common names of

alkynes describe them as derivatives of acetylene.•Most alkynes can be

named as a molecule of acetylene with one or two alkyl substituents.

Acetylene(Ethyne)

Alkyne Common Names

alkylacetylene dialkylacetylene

ethylmethylacetylene2-pentynepent-2-yne

Alkynyl Substituents• Alkynes named as

substituents are called alkynyl groups.• They can be named

systematically (ethynyl, propynyl, etc.), or by common names.

ethynylCH C

Alkynyl Substituents

1-propynyl

CH3C Cpropargyl

2-propynyl

CH C CH2

Alkyne Nomenclature•Identify the structure.

2,2,9,9-tetramethyl-3,5,7-dectriyne 2,2,9,9-tetramethyldec-3,5,7-triyne


3-propyl-1-heptyne3-propylhept-1-yne


2,2-dimethyl-3-hexyne2,2-dimethylhex-3-yne


7-chloro-4-isopropyl-2-hepten-5-yne7-chloro-4-isopropyl-hept-2-en-5-yne

Alkyne Nomenclature

6-methyl-7-methylene-2-nonyne

Numbering Priority•Multiple Bond• First Point of Branching•Greater No. of Branches•Alphabetical Ordering of

Branches

Naming Priority• Multiple Bond–(-enes, then –ynes.)

• Branches in Alphabetical Order–(includes iso- and cyclo-)

Organic Compounds

Hydrocarbons

Aliphatic Aromatic

Hydrocarbon Derivatives

Halogen Containing

Oxygen Containing

Alcohols and Phenols Ethers Aldehydes

and KetonesCarboxylic

AcidsAcid

Derivatives

Acid Chlorides Anhydrides Esters Amides

Nitrogen Containing

Amines

What is a functional group?

• a group of atoms that reacts as a single unit and determines the properties and structure of a class of compounds.

Priority of Functional Groups in Naming Organic Compounds

1. Acids2. Esters3. Aldehydes4. Ketones5. Alcohols6. Amines7. Alkynes, Alkenes8. Alkanes9. Ethers10. Halides

alkenes and alkynes

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