Homologous series

Homologous series

1. Similar Compounds

   • Same general formula
   • Similar Molecular structures
   • Similar Chemical properties
   • The physical properties change gradually as the compounds increase in size
     • Boiling points increase gradually with the size of the molecules
       • Molecules with fewer carbon atoms have lower boiling points
   • Naming compounds in a homologous series
     • METH-
       • One carbon atom
     • ETH-
       • Two carbon atoms
     • PROP-
       • Three carbon atoms

2. Alkenes

   • General formula of CnH2n
   • Unsaturated
     • C=C double bonds

3. Alkanes

   • Saturated
     • NO C=C Double bond
   • General formula of CnH2n+2

4. Alcohols

   • CnH2n+1OH
     • Always show the functional OH group
   • Methanol
     • Ethanol
       • Propanol
       • Can be made by Fermentation
         • Using yeast to convert carbohydrates into alcohol
           • The fermentation of sugars
             • Collected from plants
           • Yeast contains an enzyme
         • C6H12O6 ------> 2C2H5+2CO2
         • How?
           • Yeast and Carbohydrate
             • sealed and warm container
               • 30 - 40°C
                 • Higher = Denatured enzymes
               • Anaerobic conditions
                 • Because the oxygen converts the ethanol into Ethanoic acid, which is Vinegar
             • Alcohol concentration reaches 10 - 20%
               • Fermentation stops
                 • Yeast killed by alcohol
                 • Yeast will fall to the bottom of the container
               • Alcohol collected from the top
                 • Can be distilled
                   • More concentrated alcohol
                   • Brandy distilled from wine
                   • Whisky is distilled from fermented grain
                   • Vodka distilled from fermented grain or potatoes
                   • How?
                     • Dilute solution from fermentation
                     • Separate mixtures by heating them
                       • Ethanol had a lower boiling point than water
                         • Ethanol evaporates first
                           • Then condenses in a Liebig condenser
         • Pros
           • Renewable resource used
         • Cons
           • Not great quality of Ethanol
           • Expensive for what you get
       • Can be made by reacting Ethene with Steam
         • Ethene made by cracking crude oil
           • Non Renewable resource!
         • Cheap
           • Not much is wasted
           • Ethene is pretty cheap
           • made continuously and quickly
           • High quality Ethanol is made
             • No need for further refining
         • ethene + water (steam) -----> ethanol
       • ALCOHOL
         • Bad thing for the body
           • Lowers inhibitions
             • More likely to have unprotected sex
               • STI
               • Pregnancy
           • Reduces the activity of the nervous system
             • Unconsciousness
             • Coma
             • Death
             • Reduced reaction times
           • Binge Drinking
             • Liver Disease
             • Lower brain cell count
           • Dehydration
             • Damage to brain cells
               • Memory loss
                 • Long term or short term
         • Bad thing for society
           • Lowers inhibitions
             • More likely to commit a crime
             • Drink Driving
               • Accidents
                 • More people in A&E
           • Violent Crime
             • Increase in policing
               • £££££££
           • Alcoholism
             • Family breakdown
               • Loose Job
               • Homeless
       • Ethanol can be dehydrated to Ethene
         • Ethanol steam passed over catalyst
           • Aluminium
           • Opposite reaction of ethene and steam
             • ethanol ---> ethene + water

5. Carboxylic Acids

   • CnH2n+1COOH
     • Always show the functional COOH group
   • Methanoic Acid
     • Ethanoic Acid
       • Propanoic Acid
       • Is in vinegar
       • If wine or beer is left open the ethanol is oxidised to make ethanoic acid
         • ethanol + oxygen ----> vinegar + water
           • CH3CH2OH + O2 -----> CH3COOH + H2O
   • Reactions
     • Carbonate
       • Ethanoic Acid + Sodium Carbonate ------> Sodium Ethanoate + Water
     • Metal
       • Ethanoic Acid + Magnesium -----> Magnesium Ethanoate + Hydrogen
     • Base
       • Ethanoic Acid + Sodium Hydroxide ------> Sodium Ethanoate + Water + Carbon Dioxide
   • Alcohol + Carboxylic Acid -------> Ester + Water
     • Esters
       • Functional group COO
       • Often used in perfumes and flavourings
       • Polyesters
         • Polymers that contain the ester functional group
         • Plastic Bottles
         • Polyester fibres into fabric
         • Can be recycled
       • Ester + Alkali
         • Soap
           • In water, anions are formed
             • Hydrophobic part
               • Hates Water
                 • Loves fat
               • Tail
             • Hydrophillic part
               • Likes water
               • Head
               • Small and ionic
             • Let water and oil mix
               • Surround the oli and form droplets
                 • Lift the oily stains out of the fabric
         • Fat or oil + Alkali
         • The oil or fat breaks down into glycerol and long chain carboxylic acids
           • Carboxylic acid reacts with the Alkali
             • Acid + Alkali ---> Salt + Water
     • Ethanoic Acid + Ethanol -----> Ethyl Ethanoate + Water

6. Unsaturated oils

   • At least one C=C bond
   • Less viscous than saturated oils
     • Can be changed to solid SATURATED oils by adding hydrogen
       • Hydrogenated
         • Need a Nickel catalyst
           • Can be filtered out and used again
         • fat
           • oil that is solid at room temperature
       • Margarine
         • some of the margarine is still unsaturated
         • Firm enough to spread
           • But lower in saturates than butter