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1 Name: Period: Date: UNIT 6: Organic Chemistry Lesson 2: Isomers and Side Chains By the end of today, you will have an answer to: What happens when two different molecules have the same formula? Do Now: Consider the hydrocarbon butane. 1. Determine the homologous series butane is: 2. What is the molecular formula butane? 3. Draw out the structural formula of butane in the box below. Now draw out the structural formula of pentene in the box below. CATALYST: With your modeling kits, build C 4H 10. Did everyone s models look the same? Explain. Can we call both of these models butane? Explain. Isomers: Compounds with the same molecular formula, but different structural formula: Butane 2-methyl propane Chemical formula: Chemical formula: Similarities: Differences:

2 Check Yourself! Isomer Questions: 1. The compounds CH 3CH 2OCH 2CH 3 and CH 3CH 2CH 2CH 2OH (1) Hydrocarbons (3) allotropes (2) isomers (4) carbohydrates 2. The compound C 4H 9OH is an isomer of (1) C 3H 7COCH 3 (3) C 2H 5OC 2H 5 (2) CH 3COOC 2H 5 (4) CH 3COOH Side Chains are one way to create isomers of hydrocarbons. Here is how you name these hydrocarbons follow the example: 1) Find the longest chain of carbons 1) If no branches, name is easy methane, ethane 2) If there is a branch, the longest chain determines second part of name: The longest chain has: carbons, so the second part is: 2) Assign each carbon in the parent chain a number, starting with the carbon closest to the branch. Write in numbers above each carbon in the longest chain. 3) How many carbons are in the branch? 1) Branches of alkanes are always missing one hydrogen. 2) The missing H is where a bond forms with a longer chain. 3) We name these branches by replacing the ane prefix with the prefix yl Name of side chain: 4) The side chain is numbered according to what carbon they come from in the chain. Number of carbon that attaches to side chain: 5) If there are more than 1 of a specific chain the prefixes di or tri etc are used. 6) If there are more than two different chains they are put in alphabetical order. Final name: Example 1 Example 2 Example 3 Name: 2,2-dimethyl-butane Name: 3-ethyl-2-methyl pentane Name: 3-methyl pentane

3 CW 6.2 Hydrocarbons 10 points 1) 2) Longest chain has: carbons; second part of name: Number carbons in longest chain (so that side chain is on the lowest number) Number of carbon in longest chain that the side chain is attached to: Name of side chain: Full name: 3) Name: 4) Draw the following structure: Name: 2-methylbutane 5) Draw the following structure: 3-ethyl,2-methylpentane 6)Draw the following structure: 2,2-dimethylpropane Review: 1. Which formula may represent an unsaturated hydrocarbon? (1) C 2H 6 (3) C 3H 6 (2) C 4H 10 (4) C 5H The compound CH 3CH 2CH 2CH 3 belongs to the series that has the general formula (1) C nh 2n-2 (3) C nh 2n+2 (2) C nh n-6 (4) C nh n+6

4 HW 6.2 Isomers and side chains 10 points 1. Compounds which have the same molecular formula but different molecular structures are called (1) isomers (3) allotropes (2) isotopes (4) homologs 2. Which compound is an isomer of CH 3CH 2OH? (1) CH 3CHO (3) CH 3OCH 3 (2) CH 3COCH 3 (4) CH 3CH 2COOH 3. Which compound is an isomer of CH 3COOCH 3? (1) CH 3OCH 3 (3) CH 3CH 2COOH (2) CH 3COCH 3 (4) CH 3CH 2CH 2OH 4. Which compound is an isomer of CH 3COOH? (1) HCOOCH 3 (3) CH 3CH 2OH (2) CH 3CH 2COOH (4) CH 3COOCH 3 5. If a compound has a molecular formula of CH 2O 2, then its structural formula must be (1) H O C O H (3) H C O H O H O / (2) C (4) O \ O H H C O H 6. Explain, in-terms of structural and molecular formulas why the following are isomers. H H H H H H H C==C C==C H and H C==C C C H 7. Which is a saturated hydrocarbon? (1) C 3H 8 (3) C 6H 6 (2) C 2H 5OH (4) C 2H 4O 2 H H Molecular formula: 8. Name the following: CH 3 CH 3 CH 3CHCH 2CHCH 3 b) CH 3 CH 2 CH 3CHCH 2CH 2CHCH 2CHCH 3 CH 3 CH 3 CH 3CHCH 2CHCH 2CH 3 9. Draw the following structural formulas: 2-methyl butane 3-ethyl,3-methylpentane 2,4dimethylhexane

5 Exit Ticket 6.2 Isomers and side chains 3 points 1. Table sugar, sucrose, is a combination of two simple sugars, glucose and fructose. The formulas below represent these simple sugars. Explain, in terms of atoms and molecular structure, why glucose and fructose are isomers of each other. [1] Exit Ticket 6.2 Isomers and side chains 3 points Consider the hydrocarbon hexane. 1. Draw the structural formula in the box to the right. 2. In the box to the right, draw an isomer of hexane. 3. Name the isomer that you drew in the box:

Organic Chemistry. A brief introduction

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