The Chemistry of Carbon
Organic chemistry is the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds. Carbon is unique because:
1.It can form four stable covalent bonds.
2.It can form long chains and rings, both single, double, and triple bonds.
This allows for an immense diversity of molecules.
Functional Groups
A functional group is a specific group of atoms or bonds within a molecule that is responsible for the characteristic chemical reactions of that molecule. The rest of the molecule is often referred to as 'R'.
Key Functional Groups:
Alcohol (-OH): Contains a hydroxyl group. (e.g., ethanol, R-OH).
Aldehyde (-CHO): Contains a carbonyl group (C=O) at the end of a carbon chain. (e.g., propanal, R-CHO).
Ketone (-CO-): Contains a carbonyl group (C=O) in the middle of a carbon chain. (e.g., acetone, R-CO-R').
Carboxylic Acid (-COOH): Contains a carboxyl group, which is a carbonyl and a hydroxyl on the same carbon. They are acidic. (e.g., acetic acid, R-COOH).
Ester (-COO-): Similar to a carboxylic acid, but the hydroxyl hydrogen is replaced by another carbon group. They often have fruity smells. (e.g., ethyl acetate, R-COO-R').
Amine (-NH₂): Contains a nitrogen atom bonded to carbon. They are basic. (R-NH₂).
Ether (-O-): An oxygen atom bonded to two carbon groups. (R-O-R').
Isomers: Same Formula, Different Structure
Isomers are molecules that have the same molecular formula but a different arrangement of atoms.
1. Structural (or Constitutional) Isomers:
Atoms are connected in a different order.
They have different physical and chemical properties.
Example: Butane and Isobutane both have the formula C₄H₁₀. Butane is a straight chain, while isobutane is branched.
2. Stereoisomers:
Atoms are connected in the same order, but have a different spatial arrangement.
Geometric Isomers (cis-trans): Occur due to restricted rotation, usually around a double bond.
cis isomer: The two higher-priority groups are on the same side of the double bond.
trans isomer: The two higher-priority groups are on opposite sides.
Enantiomers (Optical Isomers): Molecules that are non-superimposable mirror images of each other, like a left and right hand. They occur in molecules with a chiral center (a carbon atom bonded to four different groups).