• Place 30 cm³ of water, 35 g of powdered sodium bromide and 25 cm³ of butan-1-ol in a 250 cm³ round bottomed flask.

• Fit a tap funnel to the flask via a stillhead.

• Place 25 cm³ of concentrated sulphuric acid in the tap funnel, and then allow the acid to fall drop by drop into the flask, keeping the contents well shaken and cooled occasionally in an ice-water bath.

• Why is the sulphuric acid added slowly, and why is cooling and shaking needed?
• Sulphuric acid when diluted with water gives out a great deal of heat, enough sometimes to raise steam which would cause dangerous splashing. Also, hot 50% sulphuric acid (which is what is produced in the flask) will cause significant oxidation of the sodium bromide to bromine, which is useless in this experiment. The yield of 1-bromobutane could therefore be affected adversely.

• When the addition is complete, replace the tap funnel and stillhead with a reflux water condenser and gently boil the mixture over a sand-bath for about 45 minutes, shaking the flask gently from time to time.

• Why is a sand-bath used for heating?
• The sand spreads the heating uniformly over the base of the flask. This reduces the likelihood of cracking, and of unwanted side reactions occurring (e.g. excessive oxidation either of bromide ions to bromine or of the alcohol to carbon) owing to hot-spots.
• Why is the mixture heated for 45 minutes?
• Most organic reactions are slow because of the need to break strong covalent bonds.

• Remove the reflux condenser and rearrange the apparatus for distillation. Distil off the crude 1-bromobutane (about 30 cm³).

• Why is the mixture distilled at this stage?
• The liquid 1-bromobutane is removed from the involatile sodium salts (mostly sodium hydrogen sulphate at the end of the reaction) and the much less volatile sulphuric acid. The 1-bromobutane will be contaminated with water, unchanged butan-1-ol, and some sulphuric acid carried over as tiny droplets during the distillation.

• Shake the distillate with water in a separating funnel, and run off the lower layer of 1-bromobutane; reject the aqueous layer.

• What does shaking with water achieve?
• Water will remove sulphuric acid and some of the butan-1-ol.
• How do you decide which layer is to be kept?
• On the basis of density; 1-bromobutane has a density of 1.276 g cm^-3.

• Return the 1-bromobutane to the funnel, add about half its volume of concentrated hydrochloric acid, and shake. Run off and discard the lower layer of acid.

• Why is concentrated hydrochloric acid added?
• The acid protonates the butan-1-ol, giving an ionic species that is much more soluble in water than the alcohol itself:

CH₃CH₂CH₂CH₂OH  +  H⁺ →  CH₃CH₂CH₂CH₂OH₂⁺

• Shake the 1-bromobutane cautiously with dilute sodium carbonate solution, cautiously releasing the pressure at intervals.

• Why is the mixture shaken with sodium carbonate solution?
• This removes hydrochloric acid dissolved in the 1-bromobutane:

Na₂CO₃ +  2HCl → 2NaCl  +  CO₂  +  H₂O

• Why must the pressure be periodically released?

• To avoid the stopper being pushed out and product being lost and sprayed all over you. The pressure is due to liberated carbon dioxide.

• Run off the lower layer of 1-bromobutane and add some granular anhydrous calcium chloride. Swirl the mixture until the liquid is clear.

• What is the function of the calcium chloride?
• Calcium chloride is a drying agent.
• What if the mixture isn't clear?
• Then it is not dry; the cloudiness is caused by tiny droplets of water in the 1-bromobutane.

• Filter the 1-bromobutane into a clean dry flask, and distil it, collecting the fraction boiling between 99 - 102^oC.

• What is the significance of the temperatures quoted?
• 1-bromobutane has a boiling temperature of 101.5^oC, so the range is narrow enough to ensure that this is the distillate.