Author Topic: Short Questions Thread (Read 10820 times)

shroomedalice · « **Reply #400 on:** February 19, 2010, 09:22:10 AM »

azeotropic distillation of caustic alcohol solutions does not make methoxide it makes ethoxide and isopropoxide
but you always have a small amount of caustic still in the solution due to equalibrium.

no probs for converting halobenzenes too methoxy benzenes but a problem for claisen condensations.

shroomedalice · « **Reply #401 on:** February 19, 2010, 12:34:25 PM »

evilblaze yes all amines will make the amino alcohol but it sounds like your after a special isomer if I am correct.

for this it is best to use trialkyl amines not polyamines.

Enkidu · « **Reply #402 on:** February 20, 2010, 03:26:01 AM »

Sulfur dioxide is produced as a byproduct of some rxns. As it is a gas, the whole area will get very stinky quite quickly. Can anyone direct me to a page/thread/post describing the neutralization of the offgas? I wondered if it could just be bubbled into a a few tubes full of a sodium hydroxide solution to form the sulfite, but I don't know how quickly or at what temperatures that rxn occurs.

Vesp · « **Reply #403 on:** February 20, 2010, 03:51:39 AM »

SO2 dissolves really well in NaOH in my experience, I've had it solidify so I think it might be wise to use a semi-dilute solution.

2bfrank · « **Reply #404 on:** February 22, 2010, 07:34:57 AM »

I think this question has been covered, but for the life of me I cannot find. Its codeine extraction of nurofen plus. Now the two main players are codiene and ibuprofen, which has a pKa of 4.4. My thinking is to add tabs to water, chill separate from any solids, and then bring the pH down to 3.3. so that the carboxylic group is protonated. I am thinking whether the addition of CO2, thus in aquarius environment would likely produce carbonic acid, but not so sure, so perhaps just using H3PO4, till the pH is down to at least 3.3. Any better ideas, would be appreciated.

Vesp · « **Reply #405 on:** February 23, 2010, 04:02:47 AM »

Why not an acid such as acetic acid? That is OTC, and a stronger acid then carbonic acid.

Locked · « **Reply #406 on:** February 23, 2010, 02:45:51 PM »

Why does the indole nitrogen not methylate when methylating tryptamine?

Enkidu · « **Reply #407 on:** February 23, 2010, 06:58:05 PM »

The lone pair on the nitrogen is delocalized because of the aromatic nature of the pyrrole moiety of the indole. Aromatics are very stable, so the nitrogen is not reactive. However, you can alkylate it if you first use a very strong base to deprotonate the the nitrogen. There are a few other methods too; if you look up the synthesis of the JWH compounds you'll find them.

2bfrank · « **Reply #408 on:** February 23, 2010, 10:44:49 PM »

Quote from: Vesp on February 23, 2010, 04:02:47 AM

Why not an acid such as acetic acid? That is OTC, and a stronger acid then carbonic acid.

Piping in CO2 till saturation was probably not thought out so well, It popped into my head, thinking, what is a way to reduce the pH value to crash out the ibuprofen, which has a pKa of 4.4. I also dont want to add anything else in the aquarious phase that I cannot remove easily - which fueled the CO2 idea. Once the unwanted is crashed out, I"d need to filter, and then get this baby back to neutral or close too, because low pH is not so good I have heard for this particular molecule
What about plain phosphoric acid, i.e. work out how much I need to bring the pH down to say 3.2 - the ibuprofen would crash out, I seperate via filtering. and then add CaOH to bring the pH back up to what it started as, and the calcium phosphate would also crash out.

??

Vesp, if I did use the correct amount of acetic acid, and got the pH to around 3, I need some way to remove it, and bump up the pH. Perhaps I need to find out if codiene can indeed cope with pH 3, and with gentle heating, around 40C, the acetic would slowly be removed. I think. Im not sure of course. for this theoretical situation.

ziggy

Naf1 · « **Reply #409 on:** February 23, 2010, 11:37:51 PM »

If I was given that job, first thing I would do is prepare a codeine resinate which would take all of 5 minutes. That could then be filtered and washed before treating it with a buffered solution liberating your codeine in well over 90% yields. Free from those nasty contaminates, but hey what do I know

@Enk, It is an acid/base reaction so is going to be pretty quick (instantaneous) also sulfur dioxide is soluble in water if it is chilled to 0*C you can hold 23grams of SO2 in 100ml of water which is a lot of gas, a second wash bottle could be employed with your NaOH with some soda lime. That will produce calcium sulfite pretty quickly, you see methods also using alcoholic solutions of NaOH to SO2 as SO2 gas is much more soluble in alcohol than water so you have a much larger buffer.

Aqueous solution containing sulphur dioxide and sodium in high percentages, its manufacture and use
patent 5041237
http://www.freepatentsonline.com/5041237.html

Absorption mechanism of sulfur dioxide into alcoholic sodium hydroxide solutions

Abstract
The chemical absorption of sulfur dioxide into alcoholic solution of sodium hydroxide was studied by simultaneous mass transfer and multiple instantaneous irreversible reaction. The experimental data showed the values of mass transfer enhancement factor to be much higher in the alcoholic sodium hydroxide solution. The results of present studies are compared with reversible and irreversible models over a wide range of sodium hydroxide solution concentrations, reported previously.

http://cat.inist.fr/?aModele=afficheN&cpsidt=18465535

Evilblaze · « **Reply #410 on:** February 24, 2010, 11:02:46 PM »

Has anyone got any reference for the reaction between phenols and methanol with a dehydrating acid e.g.: 80% H3PO4 or cc H2SO4?

Actually does this works? I'm afraid, that the cc H2SO4 would make the corresponding sulfonate from the phenols, but it is used just in catalytic amounts, so.... But I would prefer to use H3PO4 instead of the sulfuric acid, this is much friendly chemical for me.

The goal would be 1,4 dimethoxy benzene from hydroquinone.

Actually 1,4 dimethoxy benzene is sold nowhere (not even at Merck!), and because I don't want to use MeI or MeBr, this is why I need some reference from this reaction.

Thanks!

timecube · « **Reply #411 on:** February 24, 2010, 11:15:59 PM »

I searched for quite a while, but never found anything directly applicable to phenols.

The MeBr method actually doesn't look too particularly messy, as it can be generated and bubbled directly into a hydroquinone solution.
http://www.sciencemadness.org/talk/viewthread.php?tid=10507#pid126542

There's actually an attempt at an acid catalyzed methylation right above it, but the main product is methoxyphenol. The posted suggests a long reaction time might give complete methylation.

Evilblaze · « **Reply #412 on:** February 24, 2010, 11:57:59 PM »

The reaction with MeBr doesn't looks so messy, but to work in gas masks with special protection because of the MeBr... yuck.

If there is no other "normal" synthesis, than I will do this, but I can imagine lots of better things than MeBr. The reaction with phosphoric acid would be much better, because of the reagents and the safety, but if it has so bad yield as the H2SO4 catalyzed reaction, than I have to choose the MeBr method.

Vesp · « **Reply #413 on:** February 25, 2010, 12:00:40 AM »

There is a lot of dicussion about the methoxylation of hydroquinone here and on sciencemadness to produce 4-methoxyphenol. Search for it a bit - I believe douchermann has produced some and documented it here.. and perhaps len1 or klute produced a very nice write up about it on SM.
Let me know if you need help finding it -- but I think you should be able to find it relatively easily.

2bfrank · « **Reply #414 on:** February 25, 2010, 12:07:05 AM »

I searched and found this, straight up.

Dont know how useful this is, but it may shed some light on how we can go about this OTC/backyard setups etc. As advised, I dare say SM would have the goods on this.

timecube · « **Reply #415 on:** February 25, 2010, 02:00:39 AM »

Yeah, Klute has a great write-up on p-methoxyphenol:
http://www.sciencemadness.org/talk/viewthread.php?tid=9835#pid116136

The thing with going through methoxyphenol is that after you formylate it, you're still going to have to use MeBr or similar to methylate the other OH group.

If you control the rate of production of the MeBr carefully, I think you may be able to keep most of it absorbed in the hydroquinone solution. Of course I'd never advise against additional safety precautions.

timecube · « **Reply #416 on:** February 25, 2010, 10:03:00 PM »

I posted this a couple of pages back. I hate to repost, but it was the bottom post of the page and I'm not sure that many people saw it.

Quote

We studied the effect of the temperature, molar ratios of the components and the reaction time on the yield
of the alkenylaromatic hydrocarbons. It was observed that the alkenylation with allyl alcohol in the presence of
zinc chloride does not go at a temperature below 110 ~ for which reason the alkenytation of benzene was run in
undecane solution.

How does this allow the entire mixture to rise to 110 rather than the benzene and alcohol just distilling out?
Would this be better performed in a pressure bomb?

Locked · « **Reply #417 on:** March 06, 2010, 04:23:34 PM »

What is the best way to dehydrate magnesium chloride to anhydrous from the normal hydrate?

Wikipedia says heating to 300C will get to the dihydrate. EDIT-> The Merck says this is shit and produces HCl at 110C

Can azeotropic distillation with toluene dry a non-soluble salt like MgCl₂?

All the refs call for anhydrous MgCl₂ for catalyzing the Leuckart, but will the hydrate work? There is more than that amount of water in the reaction already, so I would assume it will be fine.

Vesp · « **Reply #418 on:** March 10, 2010, 06:00:53 AM »

http://www.freepatentsonline.com/3966888.html

That is this method:

Quote

Anhydrous magnesium chloride may be prepared from magnesium chloride hydrates by the following sequence of processing steps:

1. Dissolving the magnesium chloride hydrate in ethylene glycol to form a magnesium chloride hydrate solution.

2. Heating the thus-formed solution to remove all the water therefrom thereby forming a ethylene glycol anhydrous magnesium chloride solution.

3. Treating the water-free magnesium chloride-ethylene glycol solution with ammonia to form a magnesium chloride ammonia complex which precipitates from the ethylene glycol.

4. Removing the precipitate from the ethylene glycol and washing it with a low boiling solvent for ethylene glycol to remove any ethylene glycol entrained in the precipitate.

5. Heating the magnesium chloride ammonia complex to drive off the ammonia which leaves as a finished product completely anhydrous magnesium chloride.

I guess this is a big pain -- since you would need to use anhydrous ammonia, which might be a bit difficult to produce effectively unless you have access to anhydrous urea, which should produce anhydrous ammonia.

Might be able to precipitate MgCl2 crystals by cooling or heating the ethylene glycol solution? If that is the case, this would be really easy to do assuming you can get decently pure Ethylene gylcol.

Here is another: http://www.freepatentsonline.com/5514359.html

If it doesn't decompose into Mg(OH)2 (MgO?) and HCl to a significant extent, perhaps the reaction would not be affected by the impurities to much and you could use the impure anhydrous MgCl2 produced by heating.

Goldmember · « **Reply #419 on:** March 10, 2010, 06:26:00 AM »

@Ziggy, Could you possibly drip your aqueous extract into store bought soda water perhaps?

Author Topic: Short Questions Thread (Read 10820 times)

shroomedalice

Re: Short Questions Thread

shroomedalice

Re: Short Questions Thread

Enkidu

Re: Short Questions Thread

Vesp

Re: Short Questions Thread

2bfrank

Re: Short Questions Thread

Vesp

Re: Short Questions Thread

Locked

Re: Short Questions Thread

Enkidu

Re: Short Questions Thread

2bfrank

Re: Short Questions Thread

Naf1

Re: Short Questions Thread

Evilblaze

Re: Short Questions Thread

timecube

Re: Short Questions Thread

Evilblaze

Re: Short Questions Thread

Vesp

Re: Short Questions Thread

2bfrank

Re: Short Questions Thread

timecube

Re: Short Questions Thread

timecube

Re: Short Questions Thread

Locked

Re: Short Questions Thread

Vesp

Re: Short Questions Thread

Goldmember

Re: Short Questions Thread