9.10-9.16 - Hydrocarbons

Methane Ethane Propane Butane (Monkeys Eat Peanut Butter)

CnH2n+2 e.g. methane is CH₄

A C covalently bonded to another C, each covalently bonded to Hs e.g. for Ethane = H | H — C — H | H — C — H | H

Because they are hydrocarbons (compounds made of hydrogen and carbon only) with only single bonds between the carbon atoms

Ethene Propene Butene

CnH2n e.g. ethene is C₂H₄

A C double bonded to 1 other C (any other Cs are connected to the next by a single bond). A C on one end is bonded to 2 Hs. Except for in ethene, one C atom has only 1 H bond e.g. for But-1-ene = H — C — H || H — C | H — C — H | H — C — H | H

Their molecules contain the functional group C=C. An unsaturated molecule contains one or more double covalent bonds, as alkenes do.

But-1-ene and But-2-ene have the same molecular formula. However, their structure is different as But-1-ene has the double bond between the first 2 Carbon atoms and in But-2-ene the double bond is between the 2nd and 3rd carbon atom. But-1-ene = H — C — H || H — C | H — C — H | H — C — H | H But-2-ene = H | H — C — H | H — C || H — C | H — C — H | H

Ethene + Bromine -> 1,2-dibromoethane CH2=CH2 + Br2 → CH2BrCH2Br H H | | H — C — C — H | | Br Br This is an addition reaction because one molecule combines with another molecule forming one larger molecule and no other products. This reaction works the same for any alkene or halogen.

Alkenes react with bromine water, turning it from orange to colourless. Alkanes don’t react with bromine water.

The combustion of hydrocarbons releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised to produce carbon dioxide and water. alkane/alkene + oxygen –> carbon dioxide + water