Preparation of butanone by oxidation

  1. I've done an experiment on preparing butanone by oxidation of butan-2-ol. Here are the simplified procedures.

    1. Sodium dichromate-2-water were acidified by few cm^3 concentrated sulphuric acid, then the acidified dichromate and butan-2-ol were mixed.

    2. Few pieces of anti-bumping granules were added and then simple distillation was carried out. Colourless distillate was obtained.

    3. Add anhydrous calcium chloride to the distillate until the solid was in excess and the liquid was clear. Excess calcium chloride was then filtered. <purification of butanone>

    4. Tests such as 2,4-dinitrophenylhydrazine solution test and Fehling's test were carried out.

    In my lab report, I need to suggest a reason why sodium dichromate was used in the experiment in place of potassium dichromate. I can't think of a reason why since both potassium dichromate and sodium dichromate are strong oxidizing agents and both can react with butan-2-ol to form butanone.

    Any help would be appreciated.
  2. jcsd
  3. Ugh. First off, I'd mention that all chromate oxidations suck and are antiquated. They're highly toxic and bad for the environment. You should be running TPAP, NMO, Swern oxidations, or even Dess-Martin Periodinane oxidations.

    As for reasons why you used what you used, just say that was what was available. Often times chemists will use weird reagents because that's just what they happened to have on their shelves.
  4. I seems that you have a strong hatred towards chromate oxidation. There's no hazard warning in my lab manual telling us it is highly toxic and we weren't provided with gloves.

    I'm in high school and have to follow the lab manual. Also, I haven't learnt the other oxidations that you mentioned.

    In fact lots of accidents happened during this experiment, like in one group (4 persons in a group) after mixing butan-2-ol, sodium dichormate solution and concentrated suphuric acid, because the reaction is highly exothermic, the mixture started to boil and spilled out on a classmate's hands and lab garment. Also when doing simple distillation, a group's pear-shaped flask cracked and fireball was formed since a Bunsen burner was right under the pear-shaped flask.
  5. Chromium (VI) can be pretty nasty. Have you seen the movie Erin Brokovich? I'd be really careful in this lab, doesn't sound very safe. Make sure you've got all the proper MSDS available. It's required by law if you live in the US. Chromium oxidations have pretty much gone the way of the dodo in modern organic chemistry. Be safe.
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