Organic Chemistry Flashcards
What are hydrocarbons?
Compounds containing hydrogen and carbon atoms only. Bonded covalently. Each carbon atom shares four electrons and each hydrogen shares one.
What are alkanes?
Simplest type of hydrocarbon. They ar saturated - they have formed maximum bonds with other atoms + are unreactive
What are the first four alkanes?
Methane, Ethane, Propane, Butane
What is the general formula for alkanes?
What are alkenes?
Different type of hydrocarbon - unsaturated = more reactive. Contain double carbon bond, where two electrons are shared rather than one.
What are the first four alkanes?
Methene, Ethene, Propene, Butene
What is the test for alkanes/enes
Bromine water added to alkane - water remains orange
Bromine water added to alkene - water turns colourless
Are alkanes or alkenes more reactive?
Alekenes - double carbon bond.
Why do the properties of hydrocarbons change?
Depending on how long the chain is.
Give properties of hydrocarbons
Shorter molecules - more runny/less viscous
Shorter molecules - lower boiling point
Shorter molecules - more flammable hydrocarbon
What happens when you burn hydrocarbons?
Carbon and hydrogen react with oxygen to form carbon dioxide and water.
What is crude oil?
Crude oil is a mixture of hydrocarbons, all alkanes at different length molecules. Formed from remains of dead plants - finite resource/ fossile fuels.
How can crude oil be split into different groups of hydrocarbons?
Fractional distillation involves heating crude oil until it evaporates. The gas then rises through a fractional column, cools, and condenses at various temperatures, allowing different components to be collected at different levels of the column.
Which hydrocarbons condense near the top and bottom?
Hydrocarbons with many carbon have high boiling points, so condense near the bottom. Hydrocarbons with small carbon atoms have low boiling points so condense near the top.
What is cracking?
The process of breaking down loonger hydrocarbons produced from fractional distillation into smaller ones which are more usefull for fuels as they are more flammable.
Explain the process of cracking
A thermal decomposition reaction occurs when molecules are broken down by heat. In this process, a long hydrocarbon chain is heated until it evaporates, and then it is passed over a hot catalyst, which speeds up the reaction and causes the molecules to split apart.
What is polymerisation?
Alkenes turning into polymers. When small alkenes (monomers) open up double bonds and join together to form large molecules called polymers. Requires high pressure and catalyst.
