how are organic compounds analysed and used?

testing for C=C bonds

• bromine water test

• iodine number

bromine water test

• unsaturated compound + Br₂ → brominated product (addition reaction)

  • orange/brown → colourless

• saturated compound + Br₂ → no reaction

  • orange/brown colour persists

iodine number

m (I₂) reacts with 100g cheical substance

• 1 mol of I₂ = 1 mol of C=C

testing for hydroxyl groups

• sodium metal test

• oxidation test

• esterification test

sodium metal test

• if sample is alcohol, mixing it with Na _(s) will create H_{2 (g)}

• pop test to confirm

oxidation test

• primary alcohol → _{oxidising agent (}Cr₂O₇^2-/H⁺_{) (low temp)} aldehyde → _{oxiding agent (}Cr₂O₇^2-/H⁺_{) (high temp)} carboxylic acid

  • orange → green

• secondary alcohol → _{oxidising agent (}Cr₂O₇^2-/H⁺₎ ketone

  • orange → green

• tertiary alcohol → no reaction

  • orange persists

esterification test

• if fruity smell detected, ester is produced

testing for carboxyl group

• pH test

• hydrogen carbonate test

• esterification test

pH test

• acid-base indicators

• carboxylic acids are weak and only partially ionise

• ↑ [H⁺]/[H₃O⁺], ↑ acidity, ↓ pH

hydrogen carbonate test

• if sample is a carboxylic acid, mixing it with HCO₃^- will produce CO_{2 (g)}

• can confirm it is CO_{2 (g)} if it turns limewater cloudy

melting point determination

• allows for identification of compound by comparing with literature value

• purity of compounds can be determined

simple distillation

1. mixture heated to target temp to vaporise component to be seperated

2. vapour passes through condenser

3. distillate obtained

• cannot seperate compounds with similar BP

fractional distillation

1. mixture heated to target temp to vaporise component to be seperated

2. vapour moves up the fractionating column, some condenses & flows down until hot enough to vaporise again

3. after each boil-condense cycle, the more volatile substance will be at the top

4. vapour passes through condenser

5. distillate obtained

features of the fractionating column

• colder at the top

• glass beads to increase surface area

standard solution

solution with accurately known concentration by dissolving water & a primary standard

primary standard

substance with high purity & stability

what is the volumetric glass rinsed with?

distilled water

what is the conical flask rinsed with?

distilled water

what is the volumetric pipette rinsed with?

substance it will deliver

what is the burette rinsed with?

substance it will deliver

what is the volumetric flask used for?

prepare standard solution

what is the conical flask used for?

hold the aliquot of solution that will be titrated

what is the volumetric pipette used for?

deliver an aliquot of a solution

what is the burette used for?

deliver the solution

equivalence point

two reactants have reached correct mole proportions

• estimated by the end point

end point

permanent colour change