Introduction Organic chemistry is the study of molecules that contain carbon Carbon is special because: - can form 4 strong covalent bonds - can bond with other carbons to form chains and rings - can bond with a variety of other elements Learning organic chemistry will help you understand the nature of the world around you: - pharmaceuticals, household products, plastics, etc. - essential for understanding biology and biochemistry

Organic Compounds Organic compounds are covalent They most commonly consist of carbon bonded to H, N, O, S, F, Cl, Br, I and/or other C’s Chemical properties are based on functional groups Recall that the number of covalent bonds an atom will form can be predicted from its group # Molecular shape can be predicted using VSEPR theory Example: CH4 is tetrahedral (4 electron groups) We can extend this to larger molecules Example: C2H6 is tetrahedral around both C’s

Molecular Polarity Recall that a covalent bond can either be polar (if electronegativity difference ≥ 0.5) or nonpolar Examples: C-H is nonpolar, C-O is polar However, molecular polarity is primarily based on shape: - Symmetrical molecules are nonpolar - Nonsymmetrical molecules are polar if: - there is at least one lone pair on central atom - or, there is at least one polar bond Examples: CCl4 is nonpolar, CHCl3 is polar

Organic vs. Inorganic Compounds In chem 101, you mostly studied inorganic compounds such as salts and inorganic acids and bases Many inorganic compounds(NaCl, H2SO4, NH3 etc.): - are soluble in water - ionize in water (electrolytes) - have high boiling points - are not flammable Many organic compounds (CH4, C6H6, CH3OCH3 etc.) - are insoluble in water (soluble in organic solvents) - do not ionize in water (nonelectrolytes if soluble) - have low boiling points - are flammable

Functional Groups A functional group is a part of a molecule with characteristic chemical reactivity Organic compounds are classified by functional group - alkanes, alkenes, alkynes and haloalkanes - aromatic hydrocarbons - alcohols, thiols and ethers - aldehydes and ketones - carboxylic acids and esters - amines and amides You will study each functional group in detail in the remaining chapters, for now just become familiar with the structures

Constitutional Isomers Isomers are compounds with the same molecular formula, but a different arrangement of atoms There are many types of isomers One type, constitutional isomers, have the same formula, but atoms are connected in a different order Examples: C4H10 has two constitutional isomers: CH3-CH2-CH2-CH3 and CH3-CH(CH3)-CH3 C2H6O also has two constitutional isomers: CH3-CH2-OH and CH3-O-CH3