Organic Chemistry Flashcards
What is a hydrocarbon?
Alkenes and alkanes are made of only Hydrogen and Carbon atoms
They are used for fuels
What happens if you increase the chain of a hydrocarbon?
- More viscous (sticky)
- Less volatile (higher boiling point)
- Less flammable
Equation for the combustion of hydrocarbons?
Hydrogen + Oxygen —-> Carbon dioxide + Water
What is crude oil?
Crude oil is a fossil fuel buried deep under ground
It is made of plankton and dead animals.
It is also non-renewable
Fractional Distillation of crude oil:
- The oil is heated until it is a gas
- The column temperature gradient (bottom hottest, top coolest)
- As the travel up they condense and separate
Uses of cracking alkanes?
1) Transport
2) Making new compounds (polymers e.g)
Shorter chain alkanes are more useful so we crack longer chain alkanes to form shorter ones
How do we crack alkanes?
A thermal decomposition reaction
Cracking long chain alkanes makes a short chain alkane and an alkene
Method of cracking:
- Heat long chain hydrocarbons to vaporise them
- Vapour is passed along a hot catalyst (catalytic cracking)
or - Pass vapour and mix with steam and then heat to very high temperatures (steam cracking)
What is an alkene?
Alkenes have a double C=C bond
This allows alkenes to open up and bond with other compounds
Alkenes are much more reactive than alkanes
CnH2n+2
Alkenes combust completely. What is this equation?
Alkene + oxygen —-> Carbon + Carbon Monoxide + Carbon dioxide + Water
How do we form an Alcohol?
Alkene + Steam —-> Alcohol
(water)
What is hydrogenation of alkenes?
R H H H
\ / | |
C = C + H2 —-> R - C - C - H
/ \ | |
H H H H
What happens to a halogen + alkenes?
H H H Br
\ / | |
C = C + Br2 —-> H - C - C - H
/ \ | |
H H H H
What is the test for alkenes?
Mix an alkene with Bromine water and the solution should turn orange to colourless
What are addition polymers?
Long chains of joined monomers
Polymerisation usually happens under high pressure and a catalyst
What do the monomers need to make polymers?
The monomers used need to have C=C bonds
How to show the reaction for polymerisation?
H H H H
| | | |
n ( C=C ) —->. -(-C=C-)-n
| | | |
H H H H
Many single ethenes | Poly-ethene
What happens to the molecules in polymerisation?
No molecules are lost the amount stays the same before and after
What is an alcohol?
An alkene reacted with steam
Has an -OH functional group
CnH2nOH
What are the properties of alcohols?
- Alcohols are flammable
- The first 4 are soluble in water and are neutral pH
- They react with sodium
- Form carboxylic acids
What are the uses of alcohols?
They dissolve most things so handsanatizer
the first 4 are used as fuels
How is ethanol made?
Fermentation:
YEAST Sugar ----------> Ethanol + carbon dioxide
Fermentation uses an enzyme in yeast to convert sugar into alcohol.
37C, no oxygen, slightly acidic
What are carboxylic acids?
Have a functional -COOH group
O
//
H - C
\
OH
Reactions of carboxylic acids?
Ethanoic acid + sodium carbonate —> Sodium ethanoate + water + carbon dioxide
