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