4. Organic Chemistry - Chemistry

What is a hydrocarbon?

A compound made of only carbon and hydrogen.

How can organic molecules be represented?

Empirical formula, molecular formula, general formula, structural formula, displayed formula.

What is a homologous series?

A family of compounds with the same functional group and similar chemical properties.

What is a functional group?

The part of a molecule responsible for its chemical reactions.

What is isomerism?

Compounds with the same molecular formula but different structural formulas.

What are the main types of organic reactions?

Substitution, addition, combustion.

How do you name organic compounds (up to 6 carbons)?

Using IUPAC rules.

What is crude oil?

A mixture of hydrocarbons.

How is crude oil separated?

Fractional distillation.

Name the main fractions of crude oil.

Refinery gases, gasoline, kerosene, diesel, fuel oil, bitumen.

What is the trend in physical properties of fractions?

As chain length increases: colour darkens, boiling point rises, viscosity increases.

What is a fuel?

A substance that releases heat when burned.

What are the products of complete combustion of hydrocarbons?

CO₂ and H₂O.

What are the products of incomplete combustion?

CO, C, and H₂O.

Why is CO poisonous?

Reduces blood's ability to carry oxygen.

How are oxides of nitrogen formed in car engines?

High temperature allows N₂ + O₂ → NOₓ.

How is sulfur dioxide produced?

Combustion of sulfur impurities in fuel.

How do NOₓ and SO₂ contribute to acid rain?

Dissolve in water to form acids.

What is catalytic cracking?

Breaking long-chain alkanes into shorter alkanes and alkenes using heat and a catalyst.

Why is cracking necessary?

To match supply of fractions with demand (more petrol and alkenes).

What is the general formula for alkanes?

CₙH₂ₙ₊₂.

Why are alkanes saturated?

Only single C-C bonds.

What is the reaction of alkanes with halogens?

Substitution reaction under UV light (mono-substitution).

What is the functional group of alkenes?

C=C (double bond).

What is the general formula for alkenes?

CₙH₂ₙ.

Why are alkenes unsaturated?

Contain at least one double C=C bond.

What is the reaction of alkenes with bromine?

Addition → dibromoalkanes.

How to distinguish alkane vs alkene?

Bromine water: alkene decolorises, alkane does not.

What is the functional group of alcohols?

−OH.

Which alcohols should be known?

Methanol, ethanol, propan-1-ol, butan-1-ol.

How is ethanol oxidised?

1. Combustion → CO₂ + H₂O; 2. Microbial oxidation → ethanoic acid; 3. With K₂Cr₂O₇/H₂SO₄ → ethanoic acid.

How is ethanol manufactured?

1. Hydration of ethene with steam + H₃PO₄; 2. Fermentation of glucose (anaerobic, ~30°C, yeast enzymes).

Why is fermentation anaerobic and at ~30°C?

Anaerobic prevents oxidation; 30°C is optimum for yeast enzymes.