Homologous series Flashcards
what’s a homologous series?
a family of compounds with the same general formula and similar chemical properties.
when hydrocarbons burn in oxygen what do they produce?
carbon dioxide and water
which type of hydrocarbon is saturated and why?
Alkanes because they have single carbon bonds
What’s cracking?
breaking molecules into smaller molecules
Alkane general formula
CnH2n+2
what are alkenes?
a family of hydrocarbons with a double carbon to carbon bond
which type of hydrocarbons are unsaturated and why?
alkenes are unsaturated due to double carbon bonds
alkene general formula
CnH2n
How do you saturate alkenes?
with additional reactions which break the double carbon to carbon bond
if you add alkenes to bromine water what happens?
the water turns colourless
What are the products of combustion from a hydrocarbon
hydrocarbon + oxygen = water + carbon dioxide
what’s the test for carbon dioxide?
turns limewater cloudy
products of incomplete combustion?
hydrocarbons + not enough oxygen = carbon monoxide + water
What happens in an addition reaction?
In an addition reaction, the double bond of the alkene partially breaks when the reactant molecule attacks and adds on across it.
What are isomers?
compounds with the same molecular formula but different structural formulae.
What does the number in but-1-ene mean?
Tells us where the double bond is positioned.
The smallest hydrocarbon rings contain __ carbons
3
General formula for cycloalkanes?
CnH2n
Cobalt chloride paper turns from blue to pink when…
water is present
When alkanes and cycloalkanes are added to bromine water what happens?
nothing, water remains orange-brown
What’s the addition of hydrogen to an alkene called?
Hydrogenation
What’s the addition of water to an alkene called?
Hydration
What’s produced if water is added to an alkene?
an alkanol (alcohol)
Why are shorter chain alkanes in high demand?
because they are more useful molecules and are used for fuels like petrol.
When setting up the cracking experiment take 3 precautions:
- loosely clam the boiling tube as it will expand when heated
- remove the delivery tube from water before heating it stopped to avoid “suckback”
- heat until gas is clearly produced
2 signs that a smaller molecule has been made in cracking reaction?
- A gas is produced from the liquid paraffin
- An unsaturated product is produced from the saturated paraffin
General formula of alkanols (alcohols)?
CnH2n+1 OH
Which 2 ways is ethanol commonly produced?
- Fermentation of glucose obtained from carbohydrate rich foods
- Hydration of ethene
What does the 2 in Butan-2-ol signify?
The location of the OH molecule
What’s an exothermic reaction?
A reaction which gives out heat energy.
What’s an endothermic reaction?
A reaction which takes in heat energy.
3 Rules of naming hydrocarbons
- longest chain (that includes the double carbon bond if alkene) is the main chain
- main chain numbered from end nearest double bond (no matter branches)
- branches named in alphabetical order at the start of the name
5 steps of naming a compound
- go from end to start
- single or double carbon to carbon bonds
(ane or ene) - name longest chain
- name branches
- state branch location
carboxylic acids contain which functional group?
carboxyl
alcohols contain which functional group?
hydroxyl
general formula of carboxylic acids
CnH2n+1 COOH
where is the carboxyl group positioned?
always at the end of the carbon chain
what are the 2 main types of addition reactions
- hydrogenation
- hydration
