2. - Introduction - Alkanes

3. Organic Chemistry Organic Chemistry involves the study of Carbon based compounds –Almost all compounds utilized by living organisms involve carbon hence the name “Organic” chemistry What are some examples of Organic Based compounds? –Petrochemicals- Biochemicals –Dyes- Polymers –Pharmaceuticals- Life

4. Why so many C compounds? Carbon atoms can bond with other carbon atoms in chains, rings, and networks. covalentThese Bonds are covalent. Carbon has 4 unpaired electrons & can form 4 covalent bonds. C H can only form 1 bond Halogens only form 1 bond O, S can only form 2 N, P can only form 3

5. Carbons ability to form 4 covalent bonds, one or more Of which can even be to another carbon atom leads to carbons ability to form millions of different compounds.

6. Properties of Covalent Substances Covalent compounds are also called Molecular Compounds Why “Molecular” and What kind of properties do they have? Low melting & boiling points Poor conductors of heat & electricity (non- electrolytes) May be soft or brittle Generally nonpolar Tend to dissolve in nonpolar solvents (vs. polar) React more slowly than ionic compounds

7. Structural Formulas Show kind & number of atoms. Also show bonding patterns and approximate shapes of molecules. They are 2-D drawings of 3-D objects so structural formulas aren’t totally realistic. H H–C–H H

8. Structural Formulas “–” A single line represents one pair of electrons (a single bond). “=“ A double line represents two pairs of electrons (a double bond). “  ” A triple line represents three pairs of electrons (a triple bond).

9. Condensed Structural Formulas These formulas show kind & number of atoms as well as some information regarding what atoms are bonded to what atoms. They do not depict bonds Examples: CH 3 CH 2 CH 2 CH 3

10. Molecular Formulas These formulas show kind & number of atoms but not necessarily any other information Examples: CH 3 CH 2 CH 2 CH 3 becomes C 4 H 10

11. Terms: SaturatedSaturated: organic compounds containing only single bonds (carbon bonded to 4 atoms) UnsaturatedUnsaturated: organic compounds containing one or more double or triple bonds.

12. Vocabulary HydrocarbonsHydrocarbons: organic compounds containing only Carbon and Hydrogen. –Straight chain: All C bonded to only 2 other C’s Ex: c-c-c-c-c-c-c –Branched: One or more C bonded to 3 or 4 other C’s Ex: Homologous SeriesHomologous Series: a group of compounds with related structures and properties. Each member of the series differs from the one before it by the same additional unit. (Ex. The Alkanes) c-c-c-c-c-c-c-c c | | | c c c-c-c | c

13. Primary Categories of Hydrocarbons There are Five Hydrocarbon Categories –Straight Chain or Branched Alkanes (Single Bonds) [hydrogen = 2n +2] –CH 3 CH 2 CH 2 CH 3 Alkenes (Double Bond) [H = 2n] –CH 3 CH 2 CH=CH 2 Alkynes (Triple Bond) [H = 2n – 2] –CH 3 CH 2 C CH

14. Primary Categories of Hydrocarbons –Cyclic Aromatics (Benzene related compounds) Non-aromatic Cyclopropane Cyclobutane Cyclopentane Cyclohexane C 3 H 6 C 4 H 8 C 5 H 10 C 6 H 12 C6H6C6H6 The simplest aromatic Hydrocarbon (alternating Double bonds) Cyclopropane is the Simples cyclic hydrocarbon

15. Naming straight-chain Alkanes ane names aneAll alkane names have the suffix –ane. The prefix depends on the number of C’s. Ex: Methane1 Carbon Ethane2 Carbon What’s the chemical formula of each?

16. Alkanes A Homologous series of saturated hydrocarbons. Compounds with a related structure differing by the same repeating unit (-CH2-) FormulaName CH 4 Methane C2H6C2H6 Ethane C3H8C3H8 Propane C 4 H 10 Butane C 5 H 12 Pentane C 6 H 14 Hexane C 7 H 16 Heptane

17. Prefix# of C atoms Meth ane1 Eth2 Prop3 But4 Pent5 Hex6 Hept7 Oct8 Non9 Dec10

18. Alkanes: base unit CH 4 CH 3 CH 3 or C 2 H 6 CH 3 CH 2 CH 3 or C 3 H 8 CH 3 CH 2 CH 2 CH 3 or C 4 H 10 CH 3 CH 2 CH 2 CH 2 CH 3 or C 5 H 12 -D-Difference between each is one -CH2- -G-G-G-General formula is CnH2n+2 (n= no. of carbon atoms) Problem: What’s the formula for the alkane with 22 carbon

19. Problem: What is the structural formula for pentane? Problem: What is the name of the following Hydrocarbon? CH 3 -CH 2 -CH 2 -CH 3

20. Properties of Alkanes Physical Properties Change systematically with the number of C’s As the number of C’s increases, the b.p. and m.p. increases. Mol. Formula M.P.B.P. CH 4 -182-162 C2H6C2H6 -183-89 C3H8C3H8 -188-42 C 4 H 10 -138-0.5 C 5 H 12 -13036 C 6 H 14 -9569 C 7 H 16 -9198 C 8 H 18 -57126 C 9 H 20 -54151

21. SIMPLE HYDROCARBONS Draw the structural formula and condensed structural formula (chemical formula) of the following: –octane –hexane Which should have the highest B.P.?

22. Homework/Problems: Read Ch 9 For visual example of complete, condensed and line diagrams refer to page 325, right margin. Pg 332 # 1-4 Pg 336 # 5-7 Pg 338-339 # 8-11 Study table 9.4 on page 339 Added: Combustion pg 343 #12-16