1 11 Lewis Structures of Organic Molecules Dr. C. Yau Fall 2011

2 Organic Molecules Organic chemistry is a study of compounds containing carbon. In addition, they contain mostly H, O and some N, S and P, and other elements. Those containing metals are said to be “organometallic.” Hydrocarbons are compounds containing only H and C. They nonpolar because they contain only C-C and C-H bonds, which are nonpolar.

3 Hydrocarbons CH 4 C 2 H 6 C 3 H 8 Remember that C with 4 bonds is tetrahedral.

4 Various Representations of Organic Molecules Abbreviated Line Drawings

5 Isomers of Hydrocarbons Beyond C 3 H 8, there are isomers. For example C 5 H 12 has 3 isomers.

Classification of Organic Compounds Organic compounds are classified by the “functional group” that replaces one or more of the H atoms in a hydrocarbon. Substitution of a H with –OH transforms it into an alcohol. For example, replacing one H with –OH in methane makes it methyl alcohol (or methanol). 6

Alcohols 7

8 Alcohols Contain -OH....but don’t call them hydroxides!!! They contain O-H and C-O bonds, which are polar.

9 Carboxylic Acids These contain –COOH group or –CO 2 H Learn this structure: Formic acid HCOOH or HCO 2 H

10 MEMORIZE THIS! Acetic acid CH 3 COOH or CH 3 CO 2 H Is it polar?

11 Amines Contain N They typically have an unpleasant odor, some with a fishy smell.

12 Acetone (fingernail polish remover) Acetone belongs in class called ketones. Memorize the structure of acetone. It is a very common organic solvent. CH 3 COCH 3 or (CH 3 ) 2 CO

13 Benzene Benzene is another very common organic solvent. What is its molecular formula?