Organic Chemistry Notes

Alkanes, Alkenes, and Functional Groups

• Alkanes:
  • Family group name.
  • Differ by length.
  • Example: Ethane (CH3CH3).
• Alkenes:
  • Similar to alkanes but contain a carbon-carbon double bond.
  • Name changes from "ane" to "ene".
  • Example: Ethene (CH2=CH2).
• Alcohols:
  • Contain an -OH (hydroxyl) group.

Isomers and Structural Formulas

• Hexane Example (C6H{14}):
  • An alkane with six carbon atoms, described by the general formula CnH{2n+2}.
  • Multiple ways to arrange six carbons and fourteen hydrogens.
  • Straight chain or branched structures are possible.
• Isomers:
  • Molecules with the same chemical formula but different structural arrangements.
  • Example: Hexane can have multiple isomers, like 2-methylpentane.

Naming Conventions

• IUPAC Nomenclature:
  • Number the longest continuous carbon chain.
  • Identify and name substituent groups (e.g., methyl).
  • Indicate the position of the substituent group with a number.
  • Example: 2-methylpentane (methyl group attached to the second carbon of a five-carbon chain).

Isomer Properties

• Physical Properties:
  • Isomers have different physical properties, such as boiling points.
  • Branched isomers generally have lower boiling points compared to straight-chain isomers.
• Example:
  • Isomers of Hexane and their boiling points:
    • Hexane: Highest boiling point
    • 2-methylpentane, 2,3-dimethylbutane, 3,3-dimethylbutane: Lower boiling points as branching increases.

Skeletal Formulas

• Line-angle Drawings:
  • Simplified way to represent organic molecules.
  • Each vertex represents a carbon atom.
  • Hydrogen atoms are implied but not explicitly drawn.
  • Example: Two methylpentane.
• Interpretation:
  • Understanding that each carbon has enough hydrogen atoms to satisfy its four bonds is key.

Alkenes: Carbon-Carbon Double Bonds

• Nomenclature:
  • For alkenes, the position of the double bond is indicated by a number.
  • But-1-ene: Double bond between the first and second carbon.
  • But-2-ene: Double bond between the second and third carbon.
• Isomerism:
  • The position of the double bond can create different isomers.

Alcohols: -OH Group

• Nomenclature:
  • Alcohols are named with the suffix "-ol".
  • Propanol: Three-carbon alcohol.
  • Propan-1-ol: Hydroxyl group on the first carbon.
  • Propan-2-ol: Hydroxyl group on the second carbon.

Combustion and Balancing Equations

• Combustion:
  • A chemical process involving rapid reaction between a substance with an oxidant, usually oxygen, to produce heat and light.
• Balancing Chemical Equations:
  • A balanced equation has the same number of atoms of each element on both sides of the equation.
  • Leave oxygen to the end when balancing.

Weak Acids

• Weak acids:
  • Do not fully dissociate into ions in water.
• Equilibrium:
  • Exist in equilibrium between the undissociated acid and its ions.
• Example:
  • Vinegar contains weak acids and is safe to consume, unlike strong acids like hydrochloric acid (HCl).

Functional Groups

• Building Blocks:
  • Functional groups are structural motifs within molecules that define their properties and reactivity.
• Examples:
  • Alcohols (-OH group).
  • Carboxylic acids (-COOH group).
• Complex Molecules:
  • Complex substances like caffeine contain multiple functional groups.