Organic Chemistry Flashcards
What is the formula of alkanes?
CnH2n+2
What are the first 4 alkanes?
Methane
Ethane
Propane
Butane
What are the properties of a shorter chain?
Less viscous
More flammable
more volatile
What is the equation for combustion?
Hydrocarbon + oxygen —–> carbon dioxide + water
What happens to carbon and hydrogen in combustion?
They are oxidised
How does fractional distillation work?
Oil is heated and turned to gas
Hottest at the bottom
Long chains at the bottom as they have higher boiling points
Shorter chains at the top as they have a lower boiling point
Why are short chains good?
They are flammable so they make good fuels
What is cracking?
Thermal decomposition
How does cracking work?
Heat to vaporise long chain
Vapor passed over hot powdered aluminium oxide catalyst
Long chain split apart on catalyst surface
What is another way of cracking?
Vaporise them
Mix them with steam
Then heat to a very high temperature
What is the general formula for alkenes?
CnH2n
What are the first four alkenes?
Ethene
Propene
Butene
Pentene
What happens if you burn alkenes in the air?
They undergo incomplete combustion
What is the word equation for incomplete combustion of alkenes?
Alkene + oxygen —–> carbon + carbon dioxide + water
What does incomplete combustion result in?
Smokier flame
Less energy being released
What happens in addition reactions of alkenes?
The double carbon bond opens up to leave a single bond and a new atom is added to each carbon
What can be added to alkenes?
Halogens
Hydrogen
Steam
What is the addition of hydrogen known as?
Hydrogenation
What happens in hydrogenation?
Alkene is reacted with hydrogen in the presence of a nickel catalyst
What would be the product of ethene + bromine?
Dibromoethane