Organic Chemistry

1. Organic Chemistry Nathan Watson Lincoln High School Portland, OR

2. Orgins • Originally defined as the chemistry of living materials or originating from living sources • Wohler synthesized urea from non organic sources • Now generally defined as the chemistry of carbon and its compounds

3. Carbon Characteristics • Electron configuration 1s2 2s2 2p2 • Four valence electrons • Hybridization • Forms four bonds with other atoms including other carbon atoms • Able to catenate – form chains and rings • Able to form multiple bonds

4. Carbon is Unique • More than 90% of all known compounds are carbon compounds and therefore organic • Living systems are all carbon based • Carbon has unique characteristics that make multiple compounds possible

5. Bonding in Ethane • Sp3 hybridized orbitals

6. Bonding in ethene

7. Hydrocarbons • Hydrocarbons are organic compounds that are made up of only carbon and hydrogen. • There are several different categories of hydrocarbons including: • Alkanes • Alkenes • Alkynes • Cyclic Hydrocarbons • Aromatic hydrocarbons

8. Homologous Series • Compounds that have the same general formula but differing lengths of carbon chains form a homologous series

9. Homologous Series: Ex 1 • Each compound in this series differs from the previous compound by a –CH2 – • The general formula for these compounds could be written as CnH2n+2 A homologous series of alkanes

10. Homologous Series: Ex 2 • Each compound in this series differs from the previous compound by a –CH2 – • The general formula for these compounds could be written as CnH2n A homologous series of alkenes

11. Homologous Series: Ex 3 • Each compound in this series differs from the previous compound by a –CH2 – • The general formula for these compounds could be written as CnH2n+1OH A homologous series of alcohols

12. Classifying Organic Compounds • Many configurations of carbon atoms are possible in a molecule • Empirical and molecular formulas are the same for many different compounds • The relative locations of various combinations of atoms in a formula is very important • Structural formulas show the location and bonding pattern for each atom in a formula

13. Structural Formulas • The two molecules below both have the same empirical and molecular formulas but they have very different characteristics. They are considered different compounds.

14. Functional Groups

15. Functional Groups

16. Functional Groups

17. Functional Groups • Many larger molecules have more than one functional group.

18. Functional Groups • The physical and chemical properties of organic compounds are related to their functional groups. • Compounds may have different numbers of carbon atoms but the same functional group(s) will often have similar properties.

19. Physical Properties of Organic Compounds Boiling points of organic compounds reflects the strength of the intermolecular attractive forces that hold the molecules of a substance together in a condensed phase Organic compounds typically melt and boil at much lower temperatures than most inorganic compounds. The melting and boiling points correlate with the polarity of the molecules and their molecular mass 19

20. Physical Properties of Organic Compounds Boiling Point Trends The melting points and boiling points of most organic compounds increase with increasing molecular mass 20

21. Physical Properties of Organic Compounds The boiling points of most organic compounds increase with increasing molecular polarity. The above compounds have similar molar masses, but their boiling points vary considerably. 21

22. Solubility of Organic Compounds The solubility of organic compounds in water depends on the polarity of any attached functional groups. Nonpolar organic compounds are hydrophobic, so, they are less soluble in water than in organic solvents. Organic compounds that contain polar groups such as low molecular weight alcohols and others dissolve in water. They are sufficiently polar for hydrogen bonding to occur. 22

23. Organic Solvents Organic compounds tend to dissolve in a variety of organic solvents. These solvents can be either pure substances like acetone or ethyl alcohol, or mixtures such as petroleum ether. The solubility of organic compounds in these different solvents depends upon the type of solvent and in particular the functional groups if present. As the molar mass of organic compounds increases the compound becomes more hydrophobic. 23

24. Alkanes • Alkanes are hydrocarbons that have only C-C single bonds. • Examples • Methane CH4 • Ethane CH3-CH3 • Propane CH3-CH2-CH3 • Butane CH3-CH2-CH2-CH3 • Pentane CH3-CH2-CH2-CH2-CH3