2.5 - Basic organic chemistry Flashcards
What are fractions?
Molecules that have similar boiling points
What is a hydrocarbon?
A molecule that only contains hydrogen and carbon
What is an alkane?
A hydrocarbon that only has a single bond between the carbon atoms
Why are alkanes known as being saturated?
Because they can’t have any more hydrogen atoms added to the carbon atoms
What are short chain alkanes used for?
For fuels and combustion
Why do long chain alkanes have to be cracked?
To break the alkanes into shorter chains and into alkenes
How is crude oil separated into fractions?
Oil is heated and pumped into the bottom of a fractionating column where it vaporizes. As the vapourized oil rises it cools and condenses. The heavy fractions have high boiling points and condense near the bottom of the column
How to remember how many carbon atoms there are in each alkane
- M - methane
- E - ethane
- P - protane
- B - butane
- P - pentane
- H - hexane
What are alkenes
Hydrocarbons that contain at least one double covalent bond between the carbon atoms
Why are alkenes unsaturated hydrocarbons?
Because they contain at least one double covalent bond between carbon atoms
How to distinguish between saturated and unsaturated compounds?
- add red bromine water
- red colour disappears in the presence of unsaturated compounds (alkenes)
What is cracking?
The process of breaking down large hydrocarbons into smaller ones
How do we crack alkanes?
By heating a large chain alkane and putting it over a hot catalyst
Why do we crack alkanes?
Because large chain alkanes are less useful and are not in demand
C2H4 + BR2 = (addition reaction)
C2H4BR2
Equation for complete combustion
Fuel + O2 = CO2 + H20
Equation for incomplete combustion
Fuel + O2 = CO + H20
What happens when you crack an alkene?
Polymerisation - polymers
Why are alkenes very reactive?
Because they have a double bond
What is addition polymerisation?
The process by which alkenes are joined together
What does addition polymerisation involve?
The reaction of many unsaturated monomers to form a saturated polymer
What is a condensation polymer?
Made from two or more different monomers
What are thermoplastics?
Plastics that soften when heated e.g plastic bags, home containers
Why can thermoplastics be reshaped?
The forces are so weak so the chains can slide past each-other
They have no cross links
E.g polythene, PVC
