Alkanes and Industrial Processes

Vocabulary flashcards covering the characteristics, nomenclature, industrial processing, reactions, and environmental impacts of alkanes as discussed in the lecture notes.

Alkanes

Saturated hydrocarbons containing only carbon-carbon and carbon-hydrogen single bonds.

Saturated

Molecules that contain only single bonds between atoms.

General Formula (Chain Alkanes)

$$\text{C}_n\text{H}_{2n+2}$$

Straight Chains

Unbranched alkane chains where the $\text{C-C-C}$ angle is $109.5^\text{o}$, meaning the chains are not actually straight.

Ring Alkanes

Alkanes with the general molecular formula $\text{C}_n\text{H}_{2n}$ because the end hydrogen atoms are not required.

Isomerism

When molecules have the same molecular formula but different arrangements of atoms; the number of possible isomers increases with more carbon atoms.

Van der Waals Forces

Weak intermolecular forces between almost non-polar alkane molecules that increase in strength relative to molecule size.

Boiling Point Trend

The boiling points of alkanes increase as chain length increases due to increasing intermolecular forces.

Crude Oil

A fossil fuel and non-renewable resource that is a mixture mostly of branched and unbranched alkanes.

Fractional Distillation

An industrial physical process used to separate crude oil into mixtures of hydrocarbons (fractions) with similar chain lengths and boiling points.

Fractionating Tower

A tower used for distillation that is cooler at the top than the bottom, allowing vapors to condense on trays containing bubble caps.

Tar (Bitumen)

The thick residue that collects at the base of the fractionating tower used for road surfacing.

Fracking

Short for hydraulic fracturing; extracting natural gas trapped in shale rock by drilling and forcing pressurized water mixed with sand and chemicals into the rock.

Cracking

The process of breaking longer, less useful hydrocarbon chains into shorter, more valuable lengths such as petrol and reactive alkenes.

Thermal Cracking

A reaction at a high temperature ($700-1200\text{ K}$) and high pressure (up to $7000\text{ kPa}$) that produces a high proportion of alkenes.

Free Radicals

Highly reactive fragments ending in a carbon atom with an unpaired electron, formed when a covalent bond breaks homolytically.

Catalytic Cracking

A process occurring at about $720\text{ K}$ and lower pressure using a zeolite catalyst to produce branched alkanes, cycloalkanes, and aromatic compounds.

Zeolite Catalyst

A catalyst consisting of silicon dioxide and aluminium oxide ($\text{aluminosilicates}$) with a honeycomb structure and large surface area.

Aromatic Compounds

Compounds based on the benzene ring ($\text{C}_6\text{H}_6$) where electrons are spread around the ring for stability.

Fuel

Substances that release heat energy when they undergo combustion.

Incomplete Combustion

Burning of a fuel in a limited supply of oxygen to form poisonous carbon monoxide ($\text{CO}$) or carbon soot.

Nitrogen Oxides ($\text{NO}_x$)

Pollutants produced in petrol engines at high temperatures when nitrogen and oxygen combine; they contribute to acid rain and photochemical smog.

Flue Gas Desulfurisation

The process of removing sulfur dioxide ($\text{SO}_2$) from power station gases using a slurry of calcium oxide ($\text{lime}$) or calcium carbonate ($\text{limestone}$).

Gypsum

Calcium sulfate ($\text{CaSO}_4 \times 2\text{H}_2\text{O}$), a byproduct of flue gas desulfurisation used in builders' plaster and plasterboard.

Catalytic Converter

A ceramic honeycomb coated with platinum and rhodium catalysts in car exhaust systems to reduce carbon monoxide and nitrogen oxide emissions.

Greenhouse Effect

The trapping of infrared radiation by atmospheric gases like $\text{CO}_2$, methane, and water vapour, leading to global warming.

Carbon Neutral

Activities that produce no net carbon dioxide emissions overall.

Halogenoalkane

A compound formed when an alkane and a halogen react under ultraviolet ($\text{UV}$) radiation through a substitution reaction.

Initiation

The first stage of free-radical substitution where a halogen molecule absorbs UV light and breaks homolytically into free radicals.

Propagation

A two-stage chain reaction step where free radicals react with stable molecules to produce new radicals and stable products.

Termination

The final step where two free radicals react together to form a stable compound, ending the chain reaction.

Ozone ($\text{O}_3$)

A molecule in the stratosphere that protects Earth from harmful UV rays; it can be destroyed by chlorine free radicals acting as catalysts.