Oxidation of pentanol to pentanoic acid with potassium permanganate

I have adapted Nile red's video on the oxidation of butanol to butyric acid to instead make pentanoic acid(aka valeric acid) from pentanol via the following procedure:

Reagents:
7g Potassium permanganate
0.75g Sodium carbonate (anhydrous)
3g n-Pentanol
Dichloromethane
2M Sulfuric acid
45ml 3% Hydrogen Peroxide
Magnesium sulfate
pH paper

Apparatus:
Assorted beakers
Sintered funnel/Normal filter paper
Pressure equalized addition funnel(at least 125ml but 250 or more is ideal)
500ml Jointed flask
Hotplate stirrer
Magnetic stir bar
125ml sep funnel
Glass pipettes
Spatula
Balance accurate to 10mg

Lets begin
First, weigh out 7g of potassium permanganate



Then dissolve it in about 125ml of water, you may need to heat the solution like i did



Then set that aside and weigh out 0.75g of sodium carbonate then add to the 500ml jointed flask



Then weigh out 3g of pentanol



Now add to the 500ml jointed flask then measure out about 75ml of water in a beaker then wash the pentanol weighing vessel out into the flask with water from the beaker, when it is clean just add the leftover water to the 500ml flask and stir



Then attach the addition funnel and close the stopcock, then add the potassium permanganate to the addition funnel



Now start the permanganate adding dropwise the rate should be about 1 Mississippi 2 Mississippi drop 1 Mississippi 2 Mississippi drop and so on, after the addition is complete remove the addition funnel and cover the opening with cling film



The stirring in this step should be very strong, in fact it should be so strong as to splash liquid on the side of the flask so that liquid pours down the side of the flask constantly as shown above



Leave the flask stirring for 24 hours then add the hydrogen peroxide solution slowly, foam will be produced, try and get about half of the solution to run down the side of the flask to neutralize permanganate on the side of the flask



Now filter off the manganese dioxide, wash the flasks and the filter with water to get all of the products into the beaker



Then evaporate the solution, this can be accomplished by medium heat and stirring.



Evaporate down to about 15ml by using progressivly smaller beakers, washing the contents of the bigger beakers into the smaller beaker(sorry the next pics were taken at night)



Wash the contents of the small beaker into a seperatory funnel, then add 2.5ml of dichloromethane then proceed to add 2M Sulfuric acid until it stops fizzing when added, procced to cap shake and vent



Test the pH, it should be 1



At this point the funnel should look as pictured above, if there is a white powder in the funnel, add more water until it dissolves. If the DCM forms a suspension then add another 2.5ml of DCM



Repeat the DCM extraction with 2.5ml twice then combine the washings and dry with magnesium sulfate(do not use calcium chloride as I think it is soluble in carboxylic acids)



Filter off the magnesium sulfate then wash the beaker and funnel with DCM twice, then wash the solution into a vial



Now boil off the DCM, I heated the vial to 120c although the boiling point steadily increased to 120c at this point only a very small amount of bubbles were produced, does anyone know why the boiling point increased slowly and didn't just jump from 40c after all the DCM came off



And here is the end product, 2.55 grams of pentanoic acid, this constitutes a 73.3 percent yield based on starting pentanol



The brown MnO₂ stains were cleaned with a solution of sodium metabisulfite

Thanks for reading, hope you enjoyed if you have any questions or suggestions don't hesitate to post.

[Edited on 26-2-2017 by NitratedKittens]

Quote: Originally posted by JJay

Very nice job with the pentanoic acid. I wish my permanganate oxidations went so well.