Organic Chemistry

In a homologous series.

•  same general formula
•  molecular formulae differ by CH₂
•  a gradual variation in physical properties
•  similar chemical properties.

• 4 different homologous series

  • the alkanes
  • the alkenes
  • the alcohols
  • the carboxylic acids

They are Saturated Hydrocarbons (Hydrocarbons are compounds which contain only hydrogen and carbon)

Are Saturated as there are no C=C bonds (only single bonds)

General Formula: C_nH_2n+2. ( learn table on pg4)

Physical properties

• CH4 --->C4H10  Gas at RTP            

     C5H12--->C15H32  Liquid at RTP

     C16H34 and above   Solid

Immiscible, less dense than water

Chemical properties

• Generally unreactive (no functional group-contain single covalent bonds which are difficult to break)
• Burns in oxygen with orange flame to produce CO2 annd water
• If O2 supple is limited- carbon monoxide is produced 

The alkenes are unsaturated hydrocarbons.

Hydrocarbons – because they contain hydrogen and carbon only Unsaturated – because they contain at least one C=C

general formula: C_nH_2n

learn table on pg 6

Addition Reactions

Ethene(C2H4) + Bromine( Br2)---> C2H4Br2

observation: colour change orange --> colourless (this is the test for c=c or unsaturation)

--------

Alkene + hydrogen --->alkane eg. propene + hydrogen ---> propane

Alkene + steam ---> alcohol   eg. ethene + steam ---> ethanol

Functional group: -OH

General formula: C_nH_2n+1OH

*Learn table on pg 11

Fermentaiton

sugar---> ethanol + carbon dioxide

Combustion 

alcohol + oxygen → carbon dioxide + water *Observation: clean blue flame, heat released

incomplete combustion of alcohol produces carbon monoxide and water

Uses of ethanol: fuel, alcoholic drinks, solvent

When alcohols are exposed to air/acidified potassium dichromate, oxygen is added and hydrogen is removed, making a carboxylic acid eg ethanol --> ethanoic acid

general formula: C_nH_2nO₂

Functional group: COOH

*learn pg 13 table

Properties

Carboxylic acids are weak acids because they only partially ionise in solution

C. Acid + Metal ---> Salt and hydrogen eg. Mg + ethanoic acid--> Magnesium ethanoate +hydroge

C.Acid + Alkali -> Salt and water (eg) Sodium Hyrdroide + Ethanoic acid ->sodium ethanoate+wate

C.Acid +Metal carbonate--> Salt +water+carbon dioxide (eg)Sodium carbonate +ethanoic acid->Sodium ethanoate  + Carbon Dioxide + water 

Uses of ethanoic Acid : flavouring