Organic Chem Flashcards
Alkanes a group of saturated hydrocarbons. What does this mean?
They are compounds/ molecules that are made up of only carbon and hydrogen and they only contain single bonds.
What is the general formula of the Alkanes?
C n H 2n+2
What helps you remeber the first 4 Alkanes and Alkenes?
Monkeys- Meth ane/ ene (1 carbon)
Eat- Eth ane/ ene (2 carbons)
Peanut- Prop ane/ ene (3 carbons)
Butter- But ane/ ene (4 carbons)
Also- Pentane (5 carbons)
What does structural and displayed refer to?
Structural- the Molecular Formula
Displayed- the Displayed Formula
What reaction do hydrocarbons undergo when in the presence of air?
Combustion reactions
What is the difference between a complete combustion reaction and
an incomplete combustion reaction?
Complete Combustion:
Alkane + plenty of Oxygen —> Carbon Dioxide + Water
Incomplete Combustion:
Alkane + poor supply of Oxygen —> Carbon Monoxide + Water
How does the number of carbon atoms in a hydrocarbon affect the b.p / m.p?
+ explain
• More carbon atoms means that there are longer carbon chain lengths
• This creates more surface contact and therefore there is more intermolecular forces
• More energy is required to overcome these forces which results in a higher b.p / m.p
What is the general formula of the Alkenes?
C n H 2n
Alkenes are unsaturated. What does this mean?
They contain at least 1 double bond.
1) How many bonds can one Carbon atom have?
2) How many bonds does a double bond take up?
1) 4
2) 2 bonds
One way that you can test for Alkanes or Alkenes is by using bromine water (Br2)
How do you know which is which?
- Bromine water is orange.
- When it is mixed with an Alkane it stays orange.
- When it is mixed with an Alkene it starts off orange but it turns colourless.
Another way to test for Alkenes/ Alkanes is through combustion.
How can you tell which is which?
- Alkenes are more likely to undergo incomplete combustion.
- When you burn the substance, it will burn with a smoky flame which indicated that the substance is an Alkene.
- Alkanes however don’t burn with a smoky flame.
What is Cracking and why is it used?
- Cracking is used because there is a higher demand for smaller chain hydrocarbons because they can be used for fuels etc.
- Cracking is the process of breaking down long chain hydrocarbons into more useful, short chain hydrocarbons.
What does the process of Cracking entail?
- Using thermal decomposition of a long chain Alkane
- Aluminium oxide is used as a catalyst
- As a result you will get a shorter chain Alkane and an Alkene
