**Before trying to understand this, you may want to review Nomenclature: Hydrocarbons.

The combustion of hydrocarbons (alkanes, alkenes, and alkynes) all follow the same basic format:

Hydrocarbon + O₂ CO₂ + H₂O

ALKANES: Reactions with halogens to form "alkyl halides"

Alkanes - Hydrocarbons that contain only single bonds (saturated hydrocarbons) with the generic formula:

C_nH_2n+2

Halogens - Elements in Group 17 (or VIIA) on the periodic table.

• • e.g.  F, Cl, Br, I

Rule: One H atom from the alkane is substituted for one halogen atom.  The H atom that is removed combines with the other atom of the halogen.

• NOTE: Remember BrINClHOF - the atoms that are naturally found in their diatomic state.
  • e.g.  Br₂, I₂, N₂, etc.

Examples

• Methane gas is heated with an excess of chlorine gas.

• Propane reacts with excess bromine in the presence of light.

• Octane reacts with fluorine gas in the presence of light.

ALKENES/ALKYNES: Additions across the double or triple bond

Alkenes - Hydrocarbons that contain C=C double bonds (unsaturated hydrocarbons) with the generic formula:

C_nH_2n

Alkynes - Hydrocarbons that contain CC triple bonds (unsaturated hydrocarbons) with the generic formula:

C_nH_2n-2

Rule: The reactants are generally just added together.

• NOTE: If an ALKYNE (with triple bonds) reacts with an "EXCESS" of some other reactant, the product will contain as much of the other reactant atoms that can fit to replace the triple bond.

Examples

• Propene gas is mixed with bromine vapor.

• Pure 2-butene is treated with hydrogen bromide gas.

• Excess chlorine gas is added to pure ethyne.

BENZENE: Substitution Reactions

Benzene - C₆H₆

Rule: One H atom from benzene is substituted for one atom in the diatomic reactant.  The H atom that is removed combines with the other atom of the diatomic reactant.

Example

• Benzene is treated with bromine in the presence of a catalyst.

ALKENES: Other reactions with alkenes

1) Rule: An alkene combines with a water molecule to form an alcohol.

Example

• Propene reacts with water in the presence of a catalyst.

2) Rule: An alkene combines with hydrogen (H₂) to form the corresponding alkane.

Example

• Butene reacts with hydrogen in the presence of a catalyst.

ALCOHOLS: Reactions with carboxylic acids to form "carboxylic acid esters"

Alcohols - Organic compounds in which a hydrogen from an alkane is replaced with a hydroxide (-OH) group.

• The suffix -ane is changed to -anol

Carboxylic acid - A compound that contains the -COOH functional group.

Rule: The H atom from the alcohol is combined with the hydroxyl (OH) group of the carboxylic acid to form an H₂O molecule.  The remaining parts of the alcohol and the carboxylic acid are combined to form a carboxylic acid ester.

• When writing the carboxylic acid, a bond is generally formed between the O atoms of each reactant compound.

Examples

• Pure methyl alcohol and pure acetic acid are mixed.

• Ethanol is mixed with formic acid and warmed.

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