Organics

• Prefixes for alkanes


  • 1 meth-
  • 2 eth-
  • 3 prop-
  • 4 but-
  • 5 pent-
  • 6 hex-
  • 7 hept-
  • 8 oct-

  
• Functional groups


  • Alkyne
  • Haloalkane (chloro)
  • Alcohol
  • Alkene
  • Methyl group
  • Amine
  • Carboxylic acid

  
• Numbering of the chain

  Starts from the end that carries the main functional group, and has smallest number
• Haloalkane


  • X e.g. chloroethane

  
• Alcohol


  • ol e.g. ethanol, propan-1-ol. (-OH is hydroxy as a side chain on a carboxylic acid)

  
• Alkene


  • ene e.g. ethene, but-2-ene

  
• Alkyne


  • yne e.g. propyne, but-2-yne

  
• Alkyl group


  • CH3 methyl, -C2H5 ethyl etc

  
• Amine


  • NH2 e.g. methanamine, propan-1-amine (-NH2 is amino as a side chain on a c.acid or alcohol)

  
• Carboxylic acid


  • COOH e.g. butanoic acid (is always C atom #1 to count from when naming)
• Saturated hydrocarbons


  • Have C-C bonds; each C atom is bonded to 4 other atoms

  
• Unsaturated hydrocarbons


  • Have C=C or C≡C bonds; not every C atom is bonded to 4 other atoms

  
• Testing for saturation


  1. Orange (red-brown) bromine water Br2 is slowly decolourised; needs UV light and/or heat - SUBSTITUTION

  2. Orange bromine water is rapidly decolourised (no need for UV and/or heat) – ADDITION

  3. Alkene + purple H+/MnO4- solution reacts to form a diol and the solution becomes colourless - OXIDATION
• Structural (constitutional) isomers


  Have the same molecular formula (same number of each type of atoms), but a different arrangement of atoms

  
• Geometrical isomers (cis and trans)

  • Have a C=C double bond (which cannot rotate)
  • Atoms / groups on each of the carbons of the double bond that are different
  • If one C of the C=C has 2 atoms/ groups the same e.g. 2 H's or 2 CH3's then if these were swapped it would still be the same molecule so that molecule can't have cis or trans isomers

  
• Substitution


  1. An atom or group of atoms is replaced with another atom or group of atoms. There are 2 products.

  2. Alkane → haloalkane: Br2 water and UV light and/or heat

  3. Alcohol → chloroalkane: SOCl2 or PCl5 or PCl3 or HCl (bromoalkane write Br instead of Cl)

  4. Haloalkane → alcohol: KOH(aq), heat

  5. Haloalkane → amine: conc NH3(alc), heat

  
• Addition


  1. The double bond is broken and two atoms/groups are added to each C atom of the double bond. There is one saturated product.

  2. Alkene → alkane: H2(g), Pt (or Ni) catalyst

  3. Alkene → alcohol: H+/H2O, heat

  4. Alkene → haloalkane: Add HX(g) or X2(g) (would make dichloro, dibromo etc)

  
• Addition reactions making 2 products

  1. There are two products if an asymmetric reagent e.g. H-OH (or H-Br or H-Cl) adds onto an asymmetric alkene (CH3CH=CH2). There are two carbons that the H or OH of water can bond with so there are two possible combinations.

  2. Predict the major product by using Markovnikov's rule, which states that the carbon with the most hydrogens gains more hydrogens (rich get richer). The other product will be the minor product.

  
• Addition polymerisation


  Addition polymerisation occurs when the C=C in monomers breaks and the carbon atoms in this double bond join to each other from adjacent molecules to form long chains
• Monomer and polymer


  • Monomer = ethene, polymer = polyethene

  
• Elimination


  1. Two atoms / groups are removed from adjacent carbon atoms and a double bond is created to form an alkene.

  2. Alcohol → alkene: conc. H2SO4, sulfuric acid (H and OH removed, C=C made)

  3. Haloalkane → alkene: KOH(alc), heat (H and X removed, C=C made)

  
• Elimination reactions making 2 products

  1. There are two products if the alcohol can lose an OH and a H from the C on either side.

  2. There are two products if the haloalkane can lose an X and a H from the C on either side.

  3. Predict the major product - the carbon with the least hydrogens loses the hydrogen (poor get poorer). The other product will be the minor product. (Saytzeff's rule).
• Oxidation


  1. Reaction with either MnO4- OR Cr2O72-, both "oxidising agents" – usually used "acidified", i.e. with H+

  2. 1o alcohol → carboxylic acid: MnO4-/H, heat (observe purple MnO4- to colourless Mn2+) OR Cr2O72-/H+, heat (observe orange Cr2O72- to green Cr3+0. (2o and 3o alcohols are NOT converted to carboxylic acid)

  3. Alkene → diol: MnO4-/H+ (purple to colourless) or MnO4- (purple to brown)
• Miscible


  Able to mix and form a homogeneous solution
• Acid-base


  1. Reaction of carboxylic acid with base NaOH (no visible reaction) or carbonate NaHCO3 or Na2CO3 (both release CO2 gas). The acid donates a proton. Will make ionic salts, e.g. CH3COO- Na+ . CH3COO- is the ethanoate ion.

  2. Reaction of amine with HCl or H2SO4 (no visible reaction). The base accepts a proton from the acid. Will make (ionic) salts e.g. CH3NH2 + HCl → CH3NH3+ Cl- (methyl ammonium chloride)
• Immiscible


  Unable to mix and form a homogeneous solution
• Water


  A polar molecule. Any (aq) solution also contains mostly water!
• Organic compounds insoluble in water

  • Alkanes
  • Alkenes
  • Alkynes
  • Haloalkanes
  • Bigger alcohols, carboxylic acids and amines (C4 and above approx.)

  
• Slow reaction needing UV light and/or heat


  Orange bromine water slowly decolourised
• Solubility of organic molecules in water

  • Non-polar (alkane, alkene, alkyne) are insoluble, two layers form / immiscible
  • As #C↑ solubility ↓ (as non-polar hydrocarbon bit gets bigger)
  • Small alcohols, small carboxylic acids and small amines (C1-4/5) are soluble as the -OH and -COOH and -NH2 groups are polar and are attracted to polar water molecules, one layer only / miscible
• Organic compounds that give this reaction

  • Alkane
  • Haloalkane

  
• Litmus and UI paper

  • Must be MOIST/DAMP
  • Blue litmus turns red, red litmus stays red
  • Green UI turns orange (weak acid)
  • Red litmus turns blue, blue litmus stays blue
  • Green UI turns blue (weak base)
  • Alcohols – neutral (no change to litmus or UI)
  • All other organic chemicals + LITMUS or IU at L2 – say "no change"
• Reaction with H+/MnO4-


  Purple permanganate is rapidly decolourised by an alkene (makes a diol)
• Classification of alcohols and haloalkanes

  • Primary: the -OH (or -Cl) is attached to a C atom that has ONE other C atom attached to it
  • Secondary: the -OH (or -Cl) is attached to a C atom that has TWO other C atoms attached to it
  • Tertiary: the -OH (or -Cl) is attached to a C atom that has THREE other C atoms attached to it

  
• Organic compounds soluble in water (C1-3 approx.)

  • Alcohols
  • Carboxylic acids
  • Amines
• Fast reaction: Orange bromine water rapidly decolourised
• Organic compounds that give this reaction

  • Alkene
  • Alkyne
• Amine


  Turns red litmus paper blue; blue litmus stays blue. Amines turn green UI solution blue.
• Carboxylic acid


  Turns blue litmus paper red; red litmus stays red. Carboxylic acids turn green UI solution orange.
• Amines stink! Many smell like dead fish or something decomposing.