Iso Failure Question

[ClearLight]

Finally got around to doing an isomerization attempt on some oil that had been laying around. Had recrystallized 2x still some minor faint secondary spots on tlc but fairly clean. The oil had been contaminated w/ H20 so I ran it up to 170 deg C and held it there for 30 min. Dropped to 120 deg C and added unopened reagent KOH.  Let stand for 15 min to remove any h20. 

   Then I hooked up the condensor and started the run... about 15 min into it, I would get these sizzle splashes into the oil. I am surmising that this was H20 that DIDN'T come off at the elevated temp. ( UTSFE, I found Labtop's suggestion to use Vac + temp to strip H20 too late, it wasn't included in rhodiums workup)

  The temp went to 234C and then after about 55 min went to 247 - 255. 

   The flask is full of thick gunk/tar with hideous encrustations on my thermometer bulb.

    So the question is:
     1)  Is this what a water contaminated Iso attempt looks like?

     2)  Any use in doing a distillation to recover iso-safrole / safrole?

     3)  What is better Hot Acetone, or NaOH solution to clean it out?


< I did utsfe on iso failure etc. and found no description of the remains of that other than black gunk >

[hCiLdOdUeDn]

Hmm...never heard of iso "ensrusting" while isomerizing. You should distill and see what temperature it comes over at. Water contaminated iso should not do that. You need to distill and see what comes over.

Read

Post 306186

(abacus: "Easy iso", Methods Discourse)

Its pretty much idiot proof if you follow the directions.

Also, your temp is too hot. For iso-safrole you add 1.5% by weight dry KOH to safrole, and heat to 160C, hold it there for 12hours under good stirring, then distill to get back ~95% as isosafrole. Easy as that.

Also to clean out tars from a flask, acetone ALWAYS works excellently.

[Bandil]

I've tried cleaning out those "gunk" flask, and its kinda hard, even with massive amounts of acetone. When theres ~20% left in the flask you'r distilling from, try adding some kind og high boiling inert oil and then continue distilling the rest. Makes it easier to get that last bit of goodies with you AND prevents the black tar from forming!!

Regards
Bandil

[raffike]

Raf has never had any problems cleaning distillation flask afterwards,he,however,uses pure 3 times frozen safrole not sassafras oil.Raf usually uses only tap water for cleaning iso flask,even soap isn't needed to get flask totally clean

[ClearLight]

Frozen oil... but the H20 is what I "think" may have gummed up the works litterally...

 As an interesting aside, the reaction mix had a beautiful deep midnite blue florescence under shortwave U.V.  No activity under long wave.

[hCiLdOdUeDn]

Thats probably not sassafras oil. I have never heard of oil doing that....

[raffike]

There couldn't be any water cuz you heated it over 200C,no water will stay in rx mix at that temperature.

[ClearLight]

Well that was my thinking as well.. the temp was held at 150-160 deg for 30 min.. i thought that would take care of it.. the h20 if it was buried in the mix, would have refluxed w/ the rest of the oil.. and continuously done it's damage...

  Well, i'll do another batch and then distill the gunk and see what i get when i compare the two..

[raffike]

150-160 C and 30 minutes surely doesn't get enough water out.Vacuum reflux or 230C at atmospheric is only way to make sure that water gets out.