Organic Practicals (1)

Question 1

Rate of hydrolysis of haloalkanes

Answer 1

Place 5 drops R-Cl in 5cm3 ethanol in a test tube and do the same with R-Br and R-I in another two test tubes. In 3 different test tubes place 5cm3 AgNO3 (aq)
Place all 6 test tubes in a water bath at 50 degrees Celsius and allow all to reach the same temperature
Add one AgNO3 test tube to the R-Cl test tube and time how long it takes for a precipitate to form
Repeat for R-Br and R-I
Reducing error- using water as a weak nucleophile (increases time)
Rate= 1/time

Question 2

Oxidation of ethanol

Answer 2

add 50cm3 potassium dichromate to round bottomed flask with anti bumping granules. Place in ice bath and add 1cm3 ethanol drop by drop. Remove from ice bath and allow to reach room temperature then reflux for 20mins. Remove condenser and change set up to distillation. Heat around 75-80 to collect distillate

Question 3

Chlorination of 2-methylpropan-2-ol

Answer 3

Nucleophilic substitution
Add 10cm3 alcohol and 35cm3 conc. HCl (excess) to a conical flask and seal
Swirl at room temperature for 20mins, removing the bung periodically (releases pressure as H2O (g) produced in the reaction)
Two layers form, the upper layer is (CH3)3CCl and the lower layer is H2O and the alcohol
Add 5g CaCl2 to the flask and swirl (removes H2O from upper layer/lower layer to purify them)
Transfer mixture to separating funnel and remove the lower layer of alcohol
Add 20cm3 NaHCO3 to the remaining liquid and swirl and remove bung periodically to remove excel HCl, producing CO2 and H2O
New lower layer forms (H2O) so remove and repeat (adding the NaHCO3)
Transfer to a conical flask and add anhydrous Na2SO4. Swirl and leave to settle until it’s clear
Transfer to distillation set up and distil at 50 to collect the pure (CH3)3CCl over an ice bath

Question 4

Reflux

Answer 4

Reduces loss of reactant/ product via evaporation
Increases yield of product
Heat from heating mantle as this controls heat better and organic compounds are flammable (Bunsen)
Use anti bumping granules as these prevent large bubbles from forming
Round bottomed flask
Water in from bottom (efficiency)
Water out from top
Liebig condenser
Open at top to prevent pressure build up

Question 5

Distillation

Answer 5

Thermometer placed at opening of Liebig condenser to measure the temperature of the vapour being condensed
Round bottomed flask
Heat from heating mantle
Anti bumping granules
Water out at start
Beaker for distillate
Lots of ice water mixture to ensure condensation
Ensues collect as much product as possible