Alkenes and alkynes

1. Alkenes and alkynes • Saturated organic compounds: bonds between carbons are single bonds (share 1 pair of electron; alkanes) • Unsaturated organic compounds: there is at least one bond between carbons that is a double (alkene) or a triple (alkyne)

2. alkenes • Contain one or more double bond. • Ethene is simplest alkene, also called ethylene • To name an alkene: 1. find the longest chain that contains the double bond, this is the parent alkene. 2. ending of parent alkenes is –ene 3. the chain is numbered so that carbons of the double bond have the lowest possible numbers. 4. Substituents are named and numbered the same way as in alkanes.

3. Ex. Name the following alkene CH2=C-CH2-CH3 CH3 • Draw the structure for 1,4-hexadiene

4. Learning check • Write the structure for 2,3-diethyl-1-cyclohexene • Name the following alkene: CH3 CH3C=CCH3 CH3

5. alkynes • Contain one or more triple bond. • Ethyne is simplest alkyne, also called acetylene (used in welding torches) • To name an alkyne: 1. find the longest chain that contains the triple bond, this is the parent alkyne. 2. ending of parent alkynes is –yne 3. the chain is numbered so that carbons of the triple bond have the lowest possible numbers. 4. Substituents are named and numbered the same way as in alkanes.

6. Properties of alkenes and alkynes • Alkenes • Are nonpolar • Low melting and boiling points • More reactive than alkanes • Alkynes • Similar to alkenes • More reactive than alkenes

7. Classwork • P761 #17-18, p764 #19-22