Organic Chemistry 😤

• Organic chemistry is the study of compounds containing carbon
• Hydrocarbons are compound formed from hydrogen and carbon atoms only.
• Alkanes are a homologous series. A homologous series is a group of organic compounds with similar properties therefore they react in a similar way
• The first four alkanes are

  1. Methane (CH4)
  2. Ethane (C2H6)
  3. Propane (C3H8)
  4. Butane (C4H10)
• alkanes are saturated hydrocarbons with the general formula CnH2n+2
• as the length of an alkane chain increases...

  • boiling point increases -smaller chain- gas at room temp
  • they become less volatile
  • more viscous (more sticky/thick)
  • less flammable
• The main uses of alkanes are fuels as when they react, they release lots of energy
• COMPLETE COMBUSTION

  Hydrocarbon + oxygen-----> carbon dioxide + water
• crude oil is a fossil fuel formed from the remains of plants and animals over millions of years when high temperatures and pressure turns them into oil
• crude oil is a finite resource
• crude oil is a mixture of lots of different hydrocarbons
• cracking is breaking down larger hydrocarbon chains into shorter, more useful ones
• cracking is a thermal decomposition reaction
• The 2 types of cracking are steam cracking and catalytic cracking
• long chain alkanes are broken down into shorter chains that can be used as fuels
• Alkenes are another homologous series that are Unsaturated as they contain a double bond
• alkenes are more reactive than alkanes
• Because alkenes are more reactive, they can react with bromine water so the test for alkenes is to add bromine water and it turns from orange to colourless
• Alkenes can open up their c=c bond to make a single bond, making them more reactive
• first four alkenes :

  1. ethene (2 carbons)
  2. propene (3 carbons)
  3. butene (4 carbons)
  4. pentene (5 carbon)
• The general formula for alkenes is - CnH2n
• with large amounts of oxygen, alkenes combust completely to produce carbon dioxide and water. However, when not enough oxygen is present, alkenes undergo incomplete combustion. This produces carbon monoxide and carbon.
• incomplete combustion in alkenes produces a smoky yellow flame and less energy is released
• Alkenes can undergo addition reactions. Their c=c functional group breaks and each carbon will form another bond
• functional group- a group of atoms that determine how a molecule reacts
• hydrogenation - hydrogen reacts with c=c to break it apart and form an alkane in the presence of a catalyst
• steam + alkene ---> alcohol

  water is added across the double bond to form an alcohol in the presence of a catalyst
• halogens + alkenes

  e.g bromine + ethene -----> dibromoethane
• polymers - lots of the same molecule joined together
• polymerisation requires high pressure and a catalyst
• polymers are usually carbon-based
• alkenes can form polymers because they have a double carbon bond
• alkanes cannot form polymers because they are saturated
• Alcohols have an OH functional group
• alcohols all end in 'ol'
• general formula of alcohols - CnH2n+1OH
• alcohols are flammable and undergo complete combustion in air
• alcohols are soluble
• alcohols can be oxidised into carboxylic acids
• alcohols are used as fuels as they release lots of energy, solvents in industry as they can dissolve things water cannot