Organic I core practicals

Question 1

CP4 - hydrolysis of halogenoalkanes method part 1

Answer 1

• set up water bath at 50˚C
• fill 250ml beaker 3/4 full of water
• fill 3 test tubes with 5cm^3 ethanol
• add four drops of 1-iodobutane to the first tube, four drops of 1-bromobutane to the second tube and four drops of 1-chlorobutane to the third tube
• place bungs on the tubes and place in water bath
• pour 5cm^3 of silver nitrate solution into three clean test tubes and place in water bath
• when the halogenoalkane-ethanol solutions reach the temp. of the water bath, add silver nitrate solution to one of the tubes and replace the bung
• start a stopclock
• measure time taken for precipitate to appear and stop the clock
• repeat for other halogenoalkanes

Question 2

CP5 oxidation of ethanol method

Answer 2

• add 20cm^3 of acidified sodium dichromate solution to a 50ml pear-shaped flask
• cool the flask in an ice water bath
• set up the flask for reflux
• place anti-bumping granules into the pear-shaped flask
• measure out 1cm^3 of ethanol
• pipette ethanol down the reflux container a few drops at a time
• when all ethanol has been added, remove ice-water bath and allow to warm to room temp.
• position flask in hot water bath using water from a kettle
• use bunsen to maintain boiling water bath for 20 mins
• distil and collect 3-4cm^3 of clear, colourless liquid

Question 3

CP4 method part 2

Answer 3

repeat part 1 using 1-bromobutane, 2-bromobutane, and 2-bromo-2-methylpropane

Question 4

CP4 part 1 reactivity explanation

Answer 4

Rate of hydrolysis increases down group 7 because the bond enthalpy of the carbon-halogen bond decreases down the group meaning less energy is needed to break this bond

Question 5

CP4 part 2 reactivity explanation

Answer 5

2-bromo-2-methylpropane precipitates the fastest because it undergoes the SN1 reaction rapidly due to the formation of a highly stable tertiary carbocation