Chapter 7 - Families of Organic Compounds

What Useful Compounds Does Crude Oil Contain?

Introduction to Hydrocarbons

• Organic Chemistry: Deals with most compounds containing carbon.

• Hydrocarbons: Compounds consisting of carbon and hydrogen only.

• Examples of Organic Compounds:

  • Alkanes: e.g., ethane (CH3CH3)

  • Alkenes: e.g., ethene (CH2CH2)

  • Haloalkanes: e.g., chloroethane (CH3CH2Cl)

  • Alcohols: e.g., ethanol (CH3CH2OH)

  • Carboxylic Acids: e.g., ethanoic acid (CH_3COOH)

• Misconceptions:

  • Carbon dioxide and carbonates are not considered hydrocarbons or organic compounds.

  • The term 'organic' in chemistry can refer to both natural and synthetic compounds.

Hydrocarbons

• Hydrocarbon Definition: Compound consisting of carbon and hydrogen only.

• Alkane Definition: Hydrocarbon containing only single carbon-to-carbon bonds.

  • General formula: CnH{2n+2}

• Alkene Definition: Hydrocarbon containing at least one double carbon-to-carbon bond (C=C).

  • General formula: CnH{2n}

Homologous Series

• Homologous Series Definition: Series of hydrocarbons with similar chemical structure and properties.

• Alkanes Homologous Series: Differ by CH_2.

  • Methane (CH_4)

  • Ethane (C2H6)

  • Propane (C3H8)

  • Butane (C4H{10}

  • Pentane (C5H{12}

  • Hexane (C6H{14}

  • Heptane (C7H{16}

  • Octane (C8H{18}
    *Note: Spelling of chemical names is important.

Homologous Series - Alkenes

• Alkenes homologous series: contains at least one C = C double bond.

  • Ethene (C2H4)

  • Propene (C3H6)

  • Butene (C4H8)

  • Pentene (C5H{10}

  • Hexene (C6H{12}

  • Heptene (C7H{14}

  • Octene (C8H{16}

Hydrocarbon Bonding

• Intramolecular Bonding: Covalent within hydrocarbon molecules.

• Carbon Chain: Linear set of carbon atoms.

• Intermolecular Forces (IMF): Dispersion forces are the strongest IMF in alkenes and alkanes due to their non-polar nature.

Saturated vs Unsaturated Hydrocarbons

• Saturated Hydrocarbons (Alkanes): Contain only single bonds between carbon atoms.

• Unsaturated Hydrocarbons (Alkenes): Contain at least one carbon-to-carbon double bond.

Boiling Point of Alkanes

• Physical Properties: Boiling point, melting point, and viscosity are influenced by intermolecular forces (IMF).

• Boiling Point Trend: Increases with the number of carbons due to increased dispersion forces.

  Number of Carbons	Boiling Point (°C)	State at 25°C
  1	-164	gas
  2	-89	gas
  3	-42	gas
  4	-1	gas
  5	36	liquid
  6	69	liquid
  7	98	liquid
  8	125	liquid

Chemical Reactivity of Alkanes and Alkenes

• Alkenes: More reactive than alkanes due to the presence of a C=C double bond (electron-rich).

  • Type of reactions: Addition, incomplete combustion

  • Enables other atoms to be added to C.

• Alkanes:

  • Type of reactions: Substitution (in presence of UV light), combustion.

  • Less reactive.

  • Application: Fuels, starting material for synthesis of other chemicals.

• Substitution Reaction: One atom or group of atoms replaces part of another molecule.

• Addition Reaction: One molecule combines with another to form a larger molecule.

Summary

• Hydrocarbons: Contain carbon and hydrogen.

• Alkanes: Saturated hydrocarbons with single bonds between carbons.

  • General formula: CnH{2n+2}

• Alkenes: Unsaturated hydrocarbons with at least one C=C double bond.

  • General formula: CnH{2n}

• Homologous Series: Family of compounds that differ by CH_2.

• Intermolecular Forces: Dispersion forces between adjacent molecules.

• Boiling Point: Increases with carbon chain length due to stronger dispersion forces.

• Chemical Properties:

  • Alkanes are less reactive than alkenes.

    • Undergo combustion and substitution reactions.

  • Alkenes undergo incomplete combustion and addition reactions.

Nomenclature (Part 1)

• Nomenclature: System developed by the International Union of Pure and Applied Chemistry (IUPAC) to name organic compounds.

• Systematic Name: Standardized name used to identify organic compounds.

• Examples:

  • CH2O2: formic acid (common name), methanoic acid (systematic name)

  • C2H4O_2: acetic acid (common name), ethanoic acid (systematic name)

  • C4H8O_2: butyric acid (common name), butanoic acid (systematic name)

  • C3H6O: acetone (common name), propanone (systematic name)