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Author Topic: Hofmann Rearrangement Yields  (Read 3632 times)

b6baddawg

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Re: Hofmann Rearrangement Yields
« Reply #140 on: October 02, 2011, 05:45:27 AM »
i didnt see much point (for myself) running the dilute hoffman. by dilute i mean enough h20 as solvent to completely dissolve amide. for personal its a winner.
thats how you got the high yield i think dingbow.
naocl is comparable to tcca i think yieldwise when run dilute, difference is reaction time.
(thats speculation not tried and tested 100% fact)

Enkidu

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Re: Hofmann Rearrangement Yields
« Reply #141 on: October 02, 2011, 05:56:48 AM »
DO NOT post in the PN thread on this topic.

The only reason that you get to play around with this is that people before you kept it quiet.

dingbow

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Re: Hofmann Rearrangement Yields
« Reply #142 on: October 12, 2011, 08:05:40 AM »
Yield of scaled up TCCA hofmann, an abysmal 18% molar. In hindsight I should have recycled/filtered the unconverted amide when I hit trouble, cleaned it and ran it again instead of attempting to re-arrange the whole mess.. oh well, live and learn, experimentation right?

b6baddawg, I believe the amide never dissolves in the water, it merely converts to the chloroamide, which is seemingly water soluble. This is a great indicator of how your hofmann is running, because if solids are visible you know your conversion to the intermediate is not complete.

Out of amide, what a bummer.

Letters, what happened to posting back your experience ? :)

letters

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Re: Hofmann Rearrangement Yields
« Reply #143 on: October 12, 2011, 11:31:33 AM »
sorry got caught up in other stuff. i got a very small yield, along the lines of what you got in your larger scale, however i used less dilute conditions. the only way for success at any reasonable scale with TCCA is with a cosolvent, just remember that THF will react with TCCA at and around r.t.

dingbow

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Re: Hofmann Rearrangement Yields
« Reply #144 on: October 12, 2011, 12:34:58 PM »
I think with careful temperature control, via external cooling and gradual addition of amide, this could be scaled to something reasonable.

Im curious enough to verify this with more experimentation, but thats probably some time away when more amide is available.

fries

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Re: Hofmann Rearrangement Yields
« Reply #145 on: October 22, 2011, 11:44:20 PM »
I've just run a cold(ish) coke bottle style Hoffman with bleach, similar to my writeup a few posts ago with a couple of small tweaks. I used my last 25.5g of amide which i recrystallised twice, but it still looked a little bit dirty and could probably have gone for one more.

So far i have salted and dried 11.6g of dirty looking amine, with what looks like another 1g or so still drying. So, so far that's 43% molar yield dry, with a few more % on the way!

DopeBee

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Re: Hofmann Rearrangement Yields
« Reply #146 on: October 23, 2011, 01:05:17 AM »
I use boiling water to recrystallize the amide, as it is slightly soluble in boiling water.

fries

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Re: Hofmann Rearrangement Yields
« Reply #147 on: October 23, 2011, 10:42:27 AM »
Total yield after drying was 12.5g, that's pretty close to 50%.

Edit: after recrystallisation i ended up with 12g of sparkling white amine, 45% molar yield.
« Last Edit: October 24, 2011, 12:20:04 AM by fries »

fries

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Re: Hofmann Rearrangement Yields
« Reply #148 on: October 24, 2011, 10:02:02 AM »
Here's what I did this time:

Into a coke bottle is placed:
1. 25.5g Amide, very clean, finely powdered.
2. 290ml of 4.7% NaOCl, pre-cooled to nearly 0c
3. 19.2g NaOH monohydrate in 260ml H2O, pre-cooled to nearly 0c

Mix all together in the coke bottle, shake really well for 5/10 minutes, place in fridge/freezer for a while, then shake again. Lots of shaking and keeping cold in the freezer/fridge for 24 hours. By now the amide had mostly turned into a very very fine white dust at the bottom of the coke bottle.

Allow the mixture to rise to room temperature. Make sure your room isn't too cold, above 23c should be ok - otherwise it takes ages. Try to shake it as often as possible, every hour for a few minutes should be good. As soon as the colour starts to change from yellow/white/green to red/brown, dump in another 10g NaOH monohydrate and shake till its dissolved (t+0). This should raise the temperature in the bottle a fair bit.

The next morning (t+9) I placed it on the warm radiator for 3/4 hours, then nearing the 24 hour point (t+18) i placed the bottle in a bath of hot water for a few hours, changing the water occasionally for more hot.

After 24 hours, i opened the bottle and noticed a smell of ammonia. The colour wasn't as dark as last time. I Extracted with 3x100ml toluene, titrated with about 20ml of 7% HCl and recieved my 45% yield.

thescientist3000

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Re: Hofmann Rearrangement Yields
« Reply #149 on: March 07, 2012, 06:06:03 PM »
Hello.

Ferret followed Fries advice, and similar ratios.  Here is ferret's update.
51gr amide
465ml of 6% NaOCl, pre-cooled in freezer for 30min
39gr NaOH, mixed in 520ml H2O.  pre-cooled in freezer for 1hour.

Mixed amide into bleach first, and shook around for 20 minutes.  The magnetic stirrer did not work for such a mix.  This by itself took on a brownish color, before any base was added.  Strange?

The NaOH solution was then added to the amide/bleach mix.  There was a thick foam that was created on top of the liquid, also brown, maybe a little purple in color.  This foam could be to a slushy consistency.  It wasnt violent foaming or anything, very calm actually. 

Color remains the same, and has been moved to the fridge instead of freezer after 30 mins.  Shaking every once in a while. 

Any recommendations for ferret on the color/foam?

How to proceed, long time cold method, or couple more hours cold, and move on to slow bumping of heat and ending at 60-65c max?

Bisulfite method?

Thanks.
TS3k

thescientist3000

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Re: Hofmann Rearrangement Yields
« Reply #150 on: March 08, 2012, 10:25:17 PM »
Cold temps kept it the dark color
50c- got lighter/white
60c- light yellow/orange, some dark oil droplets being thrown around
65c- darker yellow/orange, same or similar amount of oil, no more produced(possibly)
70c- darker orange
75c darker orange, temp shutoff

The ferret appeared to have a decent amount of this dark orange oil and thought success! NO, fail. Upon extraction, extraction is black.  A/B lead to a very very small white/yellow oil, which pretty much gave nothing.  Whered it all go?!?!?

Thoughts/impovements/questions:
1. One idea is to keep the temp under 60c or so.  Once the oil droplets formed, it appears that no more oil was being created as the temp rose higher to 65-70-75c.  The mix just appeared to get overall darker in color. Just an idea, shut off at 60c.
2. Aqueous layer was dripped on hot base, and extraction led to nearly nothing
3. Oil layer extraction, upon cooling had brownish particulate settle to bottom, this is supposedly unreacted amide and was filtered off.

All visual cues lead to success, somewhere along extraction, a/b perhaps something went wrong.   What if that black oil extraction was dried, and directly gassed instead?  Ferret knows, scary looking shit extraction, but direct gassing would bring black crystals idk hahahaha!

Ferret doesnt know if anyone will respond, but there is her note.  When will this hoffman be someones bitch!

DopeBee

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Re: Hofmann Rearrangement Yields
« Reply #151 on: March 09, 2012, 04:35:27 AM »
I posted this over at the silk road forums:
http://dkn255hz262ypmii.onion/index.php?topic=14484.0
Quote
Recrystallize the product with hot xylene [or boiling water]. Dry the recrystallized product and grind in into an extremely fine dust in a coffee grinder. It is very important that is a very fine dust with small particle size.
http://xfq5l5p4g3eyrct7.onion/upload/43ed083b3712d2bcf267a8e837c0ddee.jpg

Add 2000ml water and 1200ml bleach into a clean 4-liter plastic milk jug. Add 100g sodium hydroxide and shake it up well. Cool it in a fridge for several hours. Add 100g of the finely powdered product from the previous step to the milk jug. Shake this mixture up and place it in the fridge for 72 hours, shaking it every few hours [or as much as possible as often as possible]. Take it out of the fridge and let if sit at room temp for 24 hours, again shaking it up whenever you get the chance. Then place it in a hot water bath for 6-12 hours. It should be a milky orange color with tarry MDA base floating in it. Use a separatory funnel to extract the MDA base with xylene or toluene and discard the water layer. Next add diluted HCl acid until the pH of the water layer is 1 and discard the oil layer this time. Evaporate the acidified water layer in a pyrex baking tray. A kilo of the original substrate will yield about 250g of MDA.
http://xfq5l5p4g3eyrct7.onion/upload/41b65ce3728efeaaa9151285d87b1e22.jpg

jon

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Re: Hofmann Rearrangement Yields
« Reply #152 on: March 09, 2012, 05:34:38 AM »
i see what your doing with the cooler temperatures.
kinetic control allowing the chloramide to form at the lower temperatures first.
« Last Edit: March 09, 2012, 05:41:14 AM by jon »

thescientist3000

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Re: Hofmann Rearrangement Yields
« Reply #153 on: March 10, 2012, 01:34:48 AM »
Thanks.

S.R. forums, those look wild!! Little too wild for even a ferret.

What percent is the bleach used? 
Judging by the ratios at hand, looks like you use a bit more sodium hydroxide than usual, which is said to increase yields a bit.  Good move there ferret thinks.

H2o is also increased a bit more than anywhere else seen. 

Order of addition here looks like to add amide last.  Ferret seen elsewhere to add bleach/amide or base/amide and then the bleach or the base.  Seems to not matter.

Cheers!

thescientist3000

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Re: Hofmann Rearrangement Yields
« Reply #154 on: March 10, 2012, 01:47:46 AM »
Almost forgot.

Water bath temp is not stated.  Are you talking, like hot tap water, being replaced, or hotplate?

If you know temp, that would be very helpful. 

DopeBee

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Re: Hofmann Rearrangement Yields
« Reply #155 on: March 10, 2012, 03:15:18 AM »
Bleach was 6% namebrand stuff. I did this back in October and just put 8 milk jugs in an actual bathtub with hot tap water. As the water cools it is drained and refilled with new hot water. I think I may have left it in for even longer than 12 hours I can't remember exactly. Particle size is very important too, since the amide obviously doesn't dissolve much. I left one last milkjug in the fridge for a month to see what would happen. It eventually turned orange as well so it still reacts just much slower.

Carrion Fairy

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Re: Hofmann Rearrangement Yields
« Reply #156 on: April 12, 2012, 04:17:22 PM »
Interesting dopebee - How did you purify that gunk in the baking tray?

DopeBee

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Re: Hofmann Rearrangement Yields
« Reply #157 on: April 13, 2012, 06:21:55 AM »
Acetone and a putty knife.  :P

To re-x the brown sugar looking stuff heat up 1g H2O with 3g MDA.HCl on the stove (careful not to burn!). Once it liquifies take it off the heat and dump in cold acetone and let it cool at RT.

dingbow

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Re: Hofmann Rearrangement Yields
« Reply #158 on: April 18, 2012, 05:48:44 PM »
Quote from: dingbow on October 12, 2011, 12:34:58 PM
I think with careful temperature control, via external cooling and gradual addition of amide, this could be scaled to something reasonable.

Im curious enough to verify this with more experimentation, but thats probably some time away when more amide is available.
Been away for a while, but I did run another batch of amide and scaled up a TCCA hofmann (25g amide). Heres the procedude I used:
-used equimolar ammount of TCCA to amide
-1.5L h20 to 25g amide.
-Cool solution of NaOH down to 18c.
-Add TCCA, stir vigorously until FULLY dissolved, this is important. Some very slight foaming will occur. Do no proceed until it is all dissolved.
-Add amide in 5-10g portions, continue stirring vigorously, only add portions once the previous one is completely dissolved. Took something like 20-30min for each portion to dissolve. Also maintain 18c temperature, using ice bath if necessary.
-Once the solution is free of any solids and appears a somewhat opaque but still clear solution, raise temperature rapidly to 75c. Once this temperature is reached, hold for 30min.
-extract and work up as usual

I got something along the lines of 65% equimolar yield from memory, with the reaction being completed within 3hrs to reach extraction phase.

Sydenhams chorea

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Re: Hofmann Rearrangement Yields
« Reply #159 on: April 19, 2012, 04:42:12 PM »
from Rec. Trav. Chim. Pays-Bas Belg. vol 50 (1931) p 305:

Beta-2,4,5-trimethoxyphenethylamine from 2,4,5-trimethoxyphenylpropionamide (Hofmann reaction)

The amide, 7.5g, was suspended in 60ml water, a freshly prepared solution of 5g bromine in 50ml 25% KOH was added and the mixture heated to 60°C for 90 minutes. An oil gradually separated on the surface and, after cooling, a further 15g KOH were dissolved in the liquid, the latter extracted with ether and the extract dried over solid potash.

A small quantity of a colourless substance (unchanged starting material) separated out on the walls of the vessel from the initially clear solution. The clear filtrate was evaporated down and a pale yellow oil remained after the ether has been removed, which solidified to a white solid, mp 66-68°C [carbonate?]. This substance appeared to be beta-2,4,5-trimethoxyphenylethylamine, yield 4g.
It is perhaps the narcotic. Hyoscine affects certain people very oddly. One cannot be sure. Sometimes, these cases take strange forms. The victim becomes in a sense, 'mediumistic', a vehicle for all the intangible forces in operation around her.
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