Isoeugenol is a sought after chemical as both an intermediate in MDMA/MDA manufacture, as well as the intermediate to synthetic vanillin. It can be made a number of ways, but only one of those ways is cost effective and easy. It can be isomerized by forming the intermediate potassium eugenolate with potassium hydroxide then hydrolyzing.
C1012O2 + KOH ----> C10H11O2K + H2O
C10H11O2K + H2SO4 ----> C10H12O2 + KHSO4
The formula is exactly the same as you can see, because the only thing that changes is a double bond gets flopped (basically). Below you can see the difference between the two - note the methyl group at the end of isoeugenol as opposed to the methylene group at the end of eugenol.
|Eugenol||1000ml RBF w/ 24/40 joints|
|Potassium hydroxide||Reflux column w/ 24/40 joints|
|>93% Sulfuric acid||Separatory funnel|
|Diethyl Ether (Prep / OTC)||Vacuum distillation equipment (24/40)|
|Fabric softener (NOTE C)||Blue litmus paper|
Into the 1000ml RBF, place 50g (47.17ml) of eugenol and 20g of potassium hydroxide (NOTE A), followed by 5-10ml of your favorite fabric softener (as a PTC) - I used snuggle. Set up the reflux column and begin running cold water through it while simultaneously heating the mixture. It will gradually darken as it heats. Continue heating to reflux, which is at about 150C at atmospheric pressure. The potassium hydroxide will eventually all dissolve and you will be left with a very brown mixture. Reflux for about 1 hour, or until a strong, almost fishlike odor is encountered from sampling the air in the condenser. Upon cooling, it will solidify into solid potassium eugenolate. While waiting for it to cool, make a mixture of 15ml sulfuric acid and 145ml of water, and chill this in a refridgerator.
Once the potassium eugenolate mixture (which may or may not be solid) has reached anywhere below 80C, add your solution of sulfuric acid and swirl. All of the brown solid/liquid will dissolve in this. You should be left with no solid on the bottom of the flask. You will notice a very brown layer floating above your sulfuric acid - this is your isoeugenol. Cool it in an ice bath to below 30C once everthing has full dissolved. Once below 30C, add 50ml of diethyl ether (NOTE B), and swirl it well. Drain off lower aqueous layer, keeping organic/solvent layer. Extract the aqueous solution once again and combine both either extracts. The aqueous layer can be dumped down the drain now.
Clean the equipment and set up for vacuum distillation. Empty the solvent/isoeugenol mixture into the distillation flask and add some magnesium sulfate or calcium chloride. Distill most of your solvent off without vacuum, and empty the receiver. Connect the vacuum and adjust your thermometer (but keep the bulb below the vapor path) so you can see the range +/- 10C of the BP of your eugenol (you do remember it, don't you?). Pull the same amount of vacuum you did when you distilled the eugenol and watch the temp. Discared everything up to eugenol's boiling point, and collect any eugenol. After this you should notice the temp rise anywhere from 8-12C and then hold that. This is now your isoeugenol coming over. It's never wise to distill to dryness, especially if using ether, but don't leave too much product in the distillation flask. Weigh your yeild. Theoretical is of course 50g, but after spilling much, I obtained 35g (70% yeild) of pure isoeugenol - a pale yellow liquid with a smell very similar to eugenol. Some notice a sweeter smell however so keep that in mind.
NOTE A: Sodium hydroxide will not work for isomerization
NOTE B: Diethyl ether can be traded with any non-polar solvent that doesn't react with dilute acid (no ethyl acetate). It is wise to use one with a lower boiling point than water as it's easier, also try to use a solvent with a lower density than water so it is the top layer during separation.
NOTE C: The fabric softener participates a phase-transfer catalyst. I developed this procedure to use fabric softener straight from the bottle, so there is absolutely no reason you should withdraw this or attempt the synthesis without it. I've never tried it without it. The 1 hour reflux time can be shortened or lengthened as needed. It all depends on the fabric softener you use. Longer wont hurt unless it's excessive, and shorter will just give you some eugenol back unchanged.