We are going to be preparing 5-iodo vanilla and there are a few ways to do this reaction

First we start by weighing out 10 grams of potassium, iodide and 5 grams of sodium bicarbonate into a beaker

We then weigh out 7.5 grams of pure vanillin powder. Pure vanillin is available under the RoVanil branded professional bakery suppliers

Next we weigh out and put it into a beaker

Prepare 12.6 grams of solid iodine

First we place a magnetic stir bar in the beaker containing the potassium, iodide and bicarbonate and add 200 ml of water

Then stir to dissolve

Now add the vanillin to the well stirred solution. This won't dissolve but it will form a suspension in the liquid

Now add the iodine to the beaker

Now add the iodine to the suspension one portion at a time

You should immediately see a yellow color as some of the iodine dissolves in the potassium iodide solution to form the I3-ion which is the reactive species

Keep adding the iodine and the color will change to orange and the vanillin in suspension will appear yellow in color

Not all the iodine will dissolve immediately

Be left stirring for 2 hours after which you'll see the solid iodine at the bottom of the beaker slowly dissolve and react

After 2 hours we're left with a yellow solid and a dark red solution

There's still some free iodine in here and also some unreacted vanillin so we need to clean our product up

Vacuum filter and dry the yellow solid then wash with

50 ml of a very dilute sodium thiosulfate solution followed by 50 ml of cold water

Dry the solid as much as you can on the filter but be warned this stuff doesn't like to dry

We then dry the damp tin colored solid by putting it in a sealed container containing calcium chloride granules after a few days it had dried fairly well and was ready for recrystallization

We recrystallized using a boiling mixture of 20% ethanol and 80% isopropyl alcohol

The solid took around 200 ml of boiling solvent but dissolved completely without any resin

Uncooling for 2 hours a massive needle like pale colored crystals was produced in the solution

Filter these and dry as much as you can again on the pump

Once again you'll find that the crystals just don't want to get dry and have a flaky consistency which makes it difficult to tell if they are actually dry

Remove the crystals, place in a beaker and use a vacuum desiccator to get a completely dry product if you need it

Our crystal is ready!

Our finished product was a pale tan almost gold colored solid with an almost quantitative yield from the starting vanillin

The product only has a very faint vanillin aroma

This is a useful intermediate compound which can be used to make 5-hydroxy vanillin and also syringaldehyde

Stay tuned!