1. Agenda Today Lesson on Naming and Structure of: – Alkenes – Alkynes – Cis-Trans Isomers Practice Problems

2. 1.2 Alkenes and Alkynes Unsaturated hydrocarbon: a hydrocarbon that contains fewer than the maximum number of hydrogen atoms due to double or triple bonds Alkene: hydrocarbon that contains at least one carbon-carbon double bond Alkyne: hydrocarbon that contains at least one carbon-carbon triple bond Aliphatic hydrocarbon: a compound that has a structure based on straight or branched chains or rings of carbon atoms (i.e. alkanes, cycloalkanes, alkenes and alkynes) Comparing ethane, ethane and ethyne: Ethane C 2 H 6 Ethene C 2 H 4 Ethyne C 2 H 2 C n H 2n+2 C n H 2n C n H 2n-2 General Form:

3. Naming and Drawing Alkenes and Alkynes 1.Identify the parent chain or ring that contains the multiple bond. The parent chain is always the longest chain that contains the maximum number of double and triple bonds. If there are two or more chains competing for selection as the parent chain (chain with the most multiple bonds), the choice goes to (1) the chain with the greatest number of carbon atoms, (2) the # of carbon atoms being equal, the chain containing the maximum number of double bonds 2.Identify whether the chain or ring contains a double bond (alkene) or a triple bond (alkyne). If there are multiple bonds, add a suffix to show the number (i.e. –diene or –triene) 3.When both double and triple bonds are present, numbers as low as possible are given to double and triple bonds even though this may at times give "-yne" a lower number than "-ene". When there is a choice in numbering, the double bonds are given the lowest numbers (alphabetical order) 4.Number the parent chain or ring so that the first carbon atom involved in a multiple bond has the lowest possible number. Write this number before the suffix. (This is only necessary if there are more than 3 carbon atoms). 5.Number and name any substituents using the same rules as were used for alkanes. If the double or triple bond is in the middle of a chain, start the numbering from the end nearer the substituent group.

4. 1 2 3 4 CH 2 =CHCH 2 CH 3 1-butene CH 3 CH=CHCH 3 2-butene CH 3 C  CCH 3 2-butyne Note: Numbering for multiple bonds is only necessary for chains with 4 carbons or more. Numbering chains with less than 4 carbons is redundant.

5. Alkenes & Alkynes Examples: etheneethynepropene propynebut-1-enepent-2-yne

6. Practice: Naming Alkenes and Alkynes 1. Name the following compounds:

8. e) f)

9. What if it contains both a double and triple bond? 2. Name the following compounds: a) b) CH≡C-CH=CH-CH=CH 2

10. Practice: Drawing Alkenes and Alkynes 1.Draw the following compounds: a)7-methyl-3-octane b) 2-methyl-4-(propan-2-yl)-1-nonene

11. Cis-Trans Isomerism Stereoisomers: have the same chemical formula and atoms ordered in the same way but have different arrangements in space -Cannot be changed from one to another by rotation, bonds must be broken and formed -(See demo with molecular models) Cis-Trans Isomerism Tutorial

12. Cis Isomer  A stereoisomer where the two groups are attached to the same side of the double bond Trans Isomer  A stereoisomer where two groups are attached to the opposite sides of the double bond

13. Practice: Drawing Stereoisomers 1.Draw the following compounds: a)Cis-1,2-dichloroethane b) trans-1,2-dichloroethane

14. Practice Questions Page 21 #1, 2 Page 23 #1-3 Page 27 #2-8