C7 - Organic Chemistry

• Crude oil is a mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
• Crude oil is a finite resource and cannot be replaced as it is used up
• A hydrocarbon is a compound made up exclusively of hydrogen and carbon atoms
• Alkanes are saturated hydrocarbons with a general formula CnH2n+2
• A homologous series is a series of compounds with the same general formula, same functional groups, and similar chemical properties
• Combustion of hydrocarbons is an exothermic reaction that produces carbon dioxide and water in complete combustion, and carbon or carbon monoxide and water in incomplete combustion
• Physical properties of alkanes:

  • The first few in the series are gases, then change to liquids, then to solids
  • Boiling points and viscosity increase as molecules get bigger
  • Volatility and flammability decrease as molecules get bigger
  • Alkanes have poor reactivity
• Fractional distillation of crude oil:

  • Crude oil is heated and vaporized
  • Vapor rises up the fractionating column (tower)
  • The column is hotter at the bottom and cooler at the top
  • Hydrocarbons cool as they go up the column and condense at different heights based on their boiling points
  • Large molecules with high boiling points are collected at the bottom, while small molecules with low boiling points are collected at the top
  • This process gives fractions that can be used in various ways
• Cracking is when large hydrocarbons are thermally broken down into smaller and useful molecules
• Cracking is a type of thermal decomposition reaction
• Conditions for cracking:

  • Reactant is heated to vapor and passed over a hot catalyst (catalytic cracking) or mixed with steam and heated to high temperatures (steam cracking)
• Products of cracking, alkanes, and alkenes are used as polymers and starting materials for synthesis
• An alkene is an unsaturated hydrocarbon containing a C=C bond with a general formula CnH2n
• The test for alkenes is to add bromine water, resulting in a color change from orange to colorless
• Alkenes burn with smoky flames due to incomplete combustion
• Addition reactions of alkenes involve adding atoms across the carbon-carbon double bond to form a single bond:

  • With hydrogen (hydrogenation) requires a higher temperature and a nickel catalyst
  • With steam (hydration) requires high temperature, pressure, and concentrated phosphoric acid (H3PO4) as a catalyst
  • With halogens (Br2/Cl2/I2) results in the addition of halogens
• An alcohol is an organic compound that contains an -OH functional group
• Characteristics of methanol, ethanol, propanol, and butanol:

  • Dissolve in water to form a neutral solution
  • React with sodium to form hydrogen
  • Burn in oxygen
  • React with carboxylic acids in the presence of an acid catalyst to form esters
• Oxidation of alcohols leads to carboxylic acids
• Some uses of alcohols are as fuels, solvents, and drinks
• Conditions required for fermentation of glucose:

  • Temperature: 30 degrees Celsius
  • Medium: Aqueous solution of glucose
  • Environment: Absence of air
  • Catalyst: Yeast
  • Reaction: C6H12O6 → 2 CH3CH2OH + 2 CO2
• Carboxylic acids are organic compounds that contain a COOH functional group
• Characteristics of carboxylic acids:

  • Dissolve in water to form an acidic solution (contains H+ ions)
  • React with metal carbonates to form carbon dioxide
  • React with alcohols with an acid catalyst to produce esters
  • React with metals to give off hydrogen gas
• Carboxylic acids are weak acids because they are partially dissociated in water, resulting in a higher pH compared to a solution of a strong acid of the same concentration
• An ester is an organic compound containing a -COO- functional group, formed from a carboxylic acid and alcohol in the presence of a sulfuric acid catalyst. They have a fruity smell
• Polymer is a long chain molecule made by smaller molecules joining together. Molecules containing C=C bonds form polymers through addition polymerization reactions
• Examples of addition polymers and their uses:

  • Polyethene: Plastic bags
  • (Poly)tetrafluoroethene (PTFE): Teflon surfaces for non-stick kitchenware
  • (Poly)chloroethene (PVC): Water pipes
• Repeating unit of a polymer is the smallest structure that, upon numerous translations, yields the structure of the polymer. In addition polymers, it involves changing C=C to C-C and showing additional single bonds extending away from these carbons
• DNA (deoxyribonucleic acid) makes up chromosomes, storing genetic information. It consists of two polymer chains held together in a double helix, each made from 4 different monomers - nucleotides