1. UNIT 3 – ORGANIC CHEMISTRY

2. OBJECTIVES

3. What does Organic mean? Is “organic” always good? (or better?)

4. Organic chemistry is defined as the study of compounds in which carbon is the principle element. Organic compounds always contain a combination of carbon and hydrogen. They may also contain oxygen and nitrogen.

5. MOST… Carbon based compounds are organic… DNA, protein, carbohydrates, fats, hydrocarbons, alcohols, aromatics… EXCEPT: Carbonates (CO 3 2- ) Carbon Monoxide (CO) and Carbon Dioxide (CO 2 )

6. The Carbon Atom What is so special about carbon that makes it able to form so many different compounds Can form four covalent bonds Can bond to any element on the periodic table Forms strong single, double, and triple bonds with other carbon atoms Single = 1 shared pair of e - Double = 2 Triple = 3

7. Organic compounds are held together by covalent bonds. Every carbon atom will have FOUR lines around it but these lines will not always be single lines. This is because carbon atoms don’t always form single covalent bonds. Double or triple bonds can form between the carbon atoms.

8. Can also forms rings and chains of various shapes and sizes Double and triple bonds change the structure of the geometry around the ‘central carbon’ Structure dictates the molecule’s properties

9. Saturated vs. Unsaturated Carbons Saturated: molecules with only single bonds, generally stable and unreactive Unsaturated: molecules with double or triple bonds, more reactive and less stable

10. Complete vs. Condensed vs. Line Diagrams Complete: Condensed: Line:

11. Molecular Shape and Polarity Polar covalent bond: covalent bond between two atoms with different electronegativities Electronegativity: measure of how strongly an atom attracts electrons in a chemical bond Every polar bond has a bond dipole

12. HYDROCARBONS Hydrocarbons are a group of organic compounds that contain ONLY carbon and hydrogen.

13. Hydrocarbons are classified into three different groups according to whether the molecules contain only single bonds between the carbon atoms, or some double or triple bonds between the carbon atoms.

14. Types of Hydrocarbons Aliphatic: carbon atoms are bonded in chains or rings Aromatic: based on the compound benzene Classified into three categories: alkanes, alkenes, and alkynes Functional groups: reactive group of bonded atoms that are members of the same chemical family and similar chemical properties (i.e. double and triple bonds)

15. ALKANES Alkanes are hydrocarbons that contain only single bonds between the carbon atoms. The general formula for an alkane is C n H 2n + 2.

16. ALKENES Alkenes are hydrocarbons that contain at least one carbon to carbon double bond in the molecules. The general formula for an alkene with one double bond in the molecule is C n H 2n.

17. ALKYNES Alkynes are hydrocarbons that contain at least one carbon to carbon triple bond in the molecule. The general formula for an alkyne with one triple bond in the molecule is C n H 2n-2.

18. NAMING HYDROCARBONS … and you thought you were done with naming compounds

19. Naming hydrocarbons The systematic name of hydrocarbons will have two parts. The first part of the name indicates the number of carbon atoms in the chain. The ending of each name indicates the type of hydrocarbon. - ane – alkane – all single bonds - ene – alkene – at least one double bond - yne – alkyne – at least one triple bond

20. These prefixes must be memorized.

21. Prefixes for side chains If there are branches present on the chain, then the branches are called alkyl groups The suffix to these is “-yl” but the root is still the same Example: methyl = CH 3 (root = 1 carbon) Give the prefix the lowest number for double and triple bonds

22. Naming Hydrocarbons 1. Find the root 2. Find the suffix 3. Give the position numbers 4. Find the prefix 5. Put it all together

23. Example 1: 1. Propane is a fuel that is commonly used in gas barbecues. Draw a structural formula for propane, and write its formula.

24. 2. Butane, commonly used in lighters, contains a four-carbon chain joined by single bonds.

25. 3. Octane, found in gasoline, contains an eight-carbon chain joined by single bonds.

26. 4. Methane, the natural gas that is used in homes and school science labs, is a single carbon atom with four hydrogen atoms.

27. Drawing Structural Formulas for Alkenes and Alkynes Draw a structural formula and write the molecular formula for 1-hexene. Step 1: Write Carbon Backbone of Appropriate Length Start with the name “hexene.” The hex- tells you that there are six C atoms in a chain.

28. Draw a structural formula and write the molecular formula for 1-hexene Step 2: Establish Location of Double Bond The -ene tells you that there is a double bond linking two of the C atoms The number at the beginning of the name tells you which C atom starts the double bond. Since the alkene is 1-hexene, the double bond starts at the first C atom and ends at the second C atom.

29. Draw a structural formula and write the molecular formula for 1-hexene Step 3: Fill Remaining Bonds with Hydrogen Atoms There are 6 C atoms and 12 H atoms in total, so the molecular formula is C 6 H 12

30. Write the IUPAC name and the molecular formula for each of the following alkenes:

32. Draw a structural formula and write the molecular formula for each of the following hydrocarbons: (a) ethene (b) ethyne (c) 2-hexene

34. Properties of Hydrocarbons Non-polar molecules Do not dissolve in water Low melting/boiling points, BUT increase as you add more carbons

35. Assignment Worksheet