organic chemistry

Cards (47)

  • Organic
    Study of carbon compounds extracted from living organisms
  • Hydrocarbon
    Class of organic compounds containing carbon & hydrogen only - covalently bonded
  • Types of hydrocarbons
    • Alkanes -> saturated hydrocarbons
    • Alkenes -> unsaturated hydrocarbons
  • Alkanes
    • Saturated hydrocarbons
    • Family of organic compounds in which the carbon atoms are single bonded
  • Functional group of alkanes

    [C-C] single covalent bonds between carbon atoms
  • Homologous series
    Family of organic compounds with same functional group = same chemical properties, same general formula, difference between 2 successive members are constant
  • Chemistry of alkanes
    • Only undergo substitution reaction where Hydrogen replaced by monovalent atom in presence of light
  • Organic solvents
    • CHCl3 (chloroform)
    • CCl4 (carbon tetrachloride)
    • are volatile, have low boiling point and are flammable
  • Alkanes
    • Burn in excess oxygen to give CO2 & H2O
    • Used as fuels
    • main constituent of natural gas is methane
  • Alkenes
    Unsaturated hydrocarbons, organic compounds with a double covalent bond between carbon atoms
    general formula -> [ Cn H2n ]
    functional group -> c double bond c
  • Alkenes
    • Form homologous series
    • Undergo addition reactions
    • have same general formula
    • have same functional group so have same chemical properties
  • Addition reactions of alkenes
    2 monovalent atoms (radicals) are added to 2 adjacent carbon carrying the double bond which will break down to give a single bond, forming saturated compound
  • Addition reactions of alkenes
    • Hydrogenation - in presence of nickel catalyst and heat
    • alkene + hydrogen -> alkane
    • Halogenation
  • Hydration of alkenes
    Alkene + Steam -> Alkanol, in presence of phosphoric or tungestic acid + heat and pressure
  • Alkanes undergo substitution which give 2 products, alkenes undergo addition which gives only 1 product
  • Test for unsaturation (presence of double bond)
    • Using aqueous bromine/bromine dissolved in CCl4 (orange) - alkane no change, alkene decolourisation
    • Using acidified potassium manganate VII (purple) - alkane no change, alkene decolourisation
  • Alkenes burn in good supply of oxygen to give CO2 & H2O and a large amount of heat, so they can be used as fuels
  • Isomers
    Organic compounds with same molecular formula & different structural formula
  • Crude oil (petroleum)
    Complex mixture of saturated hydrocarbons (alkanes) of similar boiling points, can be separated by fractional distillation but each section is still a mixture of alkanes
  • Products of fractional distillation of crude oil
    • Refinery gas - heating and cooking
    • Petrol - fuel for cars
    • Naphtha - chemicals
    • Kerosene - jet fuel and used in stoves
    • Diesel oil - fuel for diesel engines
    • Fuel oil - fuel for ships and home heating systems
    • Lubricating oil - lubricants, waxes and polishes
    • Bitumen - roads and roofs
  • Cracking
    Breakdown of long chain alkanes to small chain alkanes to obtain more petrol
  • Cracking
    • Thermal cracking (high temp and pressure)
    • Catalytic cracking (in presence of catalyst)
  • Cracking of alkanes can produce alkenes & hydrogen making it an industrial process to prepare hydrogen like electrolysis
  • Alcohols (alkanols)

    Homologous series of compounds of alkanes in which a hydrogen atom is replaced by an OH group
  • General formula (alcohols)
    CnH2n+1OH or CnH2n+2O
  • Industrial preparation of ethanol
    1. Catalytic hydration of ethene gas
    2. Fermentation of sugar in presence of yeast
  • Fermentation
    • Max ethanol concentration 15%, if exceeded yeast will die
    • If 100% ethanol needed, fractional distillation is used
    • Optimum temp 35-40°C
    • Ethanol can oxidise to ethanoic acid if air enters apparatus
    • what is seen during fermentation? - bubbles of CO2
    • - froth is obtained
  • Fermentation is a process of biotechnology, using micro-organisms in production of compounds
  • Alcohols
    • undergo oxidation to give corresponding acid. slow when done in air and can be sped up by oxidising agents such as potassium manganate VII and potassium dichromate VI
    • alkanols are reducing agents
    • Alkanol + 2 oxygen -> Alkanoic acid (oxygen given by oxidising agent)
    • Burn to give clean flame in exothermic reaction
  • Uses of ethanol
    • Alcoholic drinks
    • Solvent
    • Fuel
  • Carboxylic acids (alkanoic acids)

    Compounds with a carboxyl functional group [-C(=O)OH]
  • General formula (carboxylic acids)
    CnH2nO2 or CnH2n+1COOH
  • Preparation of ethanoic acid
    Oxidation of ethanol by oxidising agent or bacterial oxidation
  • Carboxylic acids
    • Weak acids, partially ionise in water
    • Can react with bases & carbonates
  • Esterification reaction
    Organic acid + Alcohol -> Ester + Water, using sulfuric acid as catalyst
  • Esters
    Have a fruity smell, used for flavouring food & perfumes
  • Dehydration of ethanol
    Ethanol -> Ethene, using concentrated H2SO4 (sulfuric acid) or Al2O3 & high temp or pumice stone & high temp
  • Formation of alkyl
    Alkane - hydrogen -> alkyl
  • for alkanes to react with bromine it should be used as liquid Br2 without dissolving in solvent and reaction must be in presence of light
  • ethene is not used as fuel because it is used for manufacturing some industrial products like polyethene (plastic) and ethanol