Preparation of a Haloalkane

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Experiment 2

Preparation of a Haloalkane

Date: 11-9-2006


To produce 2-chloro-2-methylpropane from 2-methylpropan-2-ol.

To find the yield of 2-chloro-2-methylpropane.


        2-chloro-2-methylpropane is formed when 2-methylpropan-2-ol and concentrated hydrochloric acid are added together.

Because alcohols undergo substitution rapidly, the reaction takes place at room temperature. Afterwards, the haloalkane would be separated with a separating funnel, dried with anhydrous sodium sulphate and extracted by distillation.


  1.  About 9 ml of 2-methylpropan-2-ol was poured into a measuring cylinder and        the measuring cylinder was weighed.
  2. The 2-methylpropan-2-ol was poured into a 50ml separating funnel. The mass of the empty measuring cylinder was weighed again.
  3. About 20ml of concentrated hydrochloric acid was added into the separating funnel, 3ml at a time. This procedure was carried out by the window side.
  4. After each addition, the funnel was sealed and was shaken. The tap was opened at intervals to allow the gas produced to be released.
  5. The separating funnel was allowed to stand near the window for 20 minutes.
  6. A distillation apparatus was set up, as in the diagram below.
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7.  The small flask in the above set-up was weighed.

8.  The lower aqueous layer in the separating funnel was discarded into a beaker.

9.  Excess sodium hydrogencarbonate was added 2ml at a time into the separating funnel until no more gas was produced.

10.  The lower aqueous layer was once again separated.

11.  The organic layer was run into a dry conical flask.

12.  Anhydrous sodium sulphate was added into the conical flask until the powder added does not stick together anymore.

13.  The liquid in the conical flask was decanted into ...

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Giving some background to the experiment and why it is carried out in industry etc. would help to show relevant but additional knowledge that may not be on the syllabus, evidence of reading around the subject is particularly vital at A level. I feel that at the moment the candidate has listed too much and not evaluated their method enough, there needs to be a section dedicated to evaluating and more could be written on experimental error, possible causes etc. as this is what the top candidates are including to achieve the best marks. Similarly expanding the conclusion to include more than just the bare findings would help but the particular aims of this investigation make this difficult. The lack of health and safety analysis is also a problem as including this would both help show your knowledge of chemical properties and ensure safety when the experiment is repeated.

A well written, concise investigation of average quality. All the basics are present but further explanation of procedure and experimental calculations would make this piece more detailed and clear, important for showing mastery of the subject and understanding. Being scientific and concise is important but it’s always worth making sure your work is understandable even by a non-scientist to ensure the experiment could be easily replicated.