Author Topic: PP's General Chem Question Thread  (Read 15985 times)

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PrimoPyro

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PP's General Chem Question Thread
« on: October 30, 2001, 08:00:00 AM »
Hi. I am starting this thread to ask several general chemistry questions relevant to the topic at hand here. I don't want to start a myriad of threads however for such shallow discussions, consisting of Q --> A, and thats it. I don't think the Hive would appreciate a bunch of 3 post threads starting with questions. So I will consolidate them here. If you know the answers, by all means, please answer. If you have a similar question spawned off one currently operating, go ahead and ask. If you do not have anything at all to contribute, please dont shit on my simple thread here. However, if a search query would happen to yield the necessary info, by all means cite utfse. I will use tfse b4 ever asking here, keep that in mind ppl. So just because the answer may seem simple to those in the know of advanced organic chem, keep in mind that some simply havent run across that information yet, and are trying to do so now.

Thank you for even reading this thread and considering my curiosity, I highly appreciate it.


The first question that comes to mind is:

Are there any known reactions that dyhydroxylate an aromatic ring in a single reaction? In either one step, or in a one-pot multiple step reaction. The ideal desired reaction is one that dihydroxylates the ring with the position of the OH's ortho respective to one another, but para/meta to another group already substituted on the ring. For example to illustrate my point: benzaldehyde --> pyrocatechualdehyde would be the most relevant reaction I can think of at the moment.

However, it need not be perfectly this case. At the moment I am interested in all reactions similar to this, but have no clue if there are any, and if so, what they are called, and thus have nothing to search for further than dihydroxylation and derivatives of the word.

Thank you for any info that comes to light in this thread, I really appreciate everyone's interest and/or tolerance.  ;)

                                                  PrimoPyro

How does one win a race when the finish line runs faster than you?  :(

foxy2

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Re: PP's General Chem Question Thread
« Reply #1 on: October 30, 2001, 11:32:00 AM »
I don't think an easy selective one step is possible.  The only easy additions I can think of are halogens and nitro groups

Do Your Part To Win The War

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #2 on: November 07, 2001, 11:47:00 PM »
Thanx foxy.

I have another series of interesting questions. (well I find them interesting  :P )

PrimoPyro is now interested in the hypothetical synthesis of ephedrine-like compounds. Specifically 1-phenyl-1-hydroxy-2-amino-propanes. This should be no big issue, until:

Im trying to find a synthesis route from the propenyl-benzene. On top of that, the product has to be the correct chirality for an oxazoline cyclization. Now to be honest, PP never put too much interest in learning chirality. I get the concept, but some of the terms evade me. I know what the difference between different isomers of ephedrine are, but I cant name which is which, the names escape me. So, that said, bear with my alternative language for them in this post. Thank you.

Now, I assume that the needed configuration is between the hydroxy and the amine for cyclization. I assume they need to be near each other, to be in proximity. this would denote a sort of cis isomer right? I dont think you name optical isomers this way, but I am here anyway. So, assuming what I have said thus far is ok, I would like to propose this:

The propenylbenzene is epoxidated, then reacted with hydrobromic acid to open up the epoxide to the alpha-hydroxy-beta-bromo-propane. This is then aminated with ammonia to form the 1-OH-2-NH2-propane.

I would think that the epoxidation would occur, having the correct bonding, as stated as having been needed above. (cis) as trans bonding would have a longer stretch on the oxygen bond and be less stable, or it would simply cause torsion in the C-C bond to revert to the stated "cis". Forgive me its hard to explain myself without a lot of pictures. Let me know if this is totally not understandable and I will draw some up.

Since this epoxide should be the correct configuration, so would be the products upon opening it up.

But, I wonder, could the 1-bromo-2-hydroxy-propane be a byproduct? I remember reading old ADC posts awhile ago stating that HBr only adds to the beta carbon in safrole, but I wonder if this is only applicable to alkenes.

If this step worked as well, when you aminated with ammonia, the hydroxy and amine groups would be in the assumed correct positions for cyclization.

I'd like to hear any questions on this, as well as many bees comments on anything posted herein. Thank you.

P.S. buying the correct isomer is not an option. This topic is about the synthesis of such a compound, so while all pointers on where to buy or extract this from are a nice thought, they arent the desired information.

Also, I have only presented here what I thought of in my head, id like to know if it will work etc., but I also want to know of any known syntheses of such compounds, or any known similar reactions that come to mind. It doesnt HAVE to be regarding this synthesis. Thanx again.

                                                   PrimoPyro

Vivent Longtemps la Ruche! STRIKE For President!

Osmium

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Re: PP's General Chem Question Thread
« Reply #3 on: November 08, 2001, 01:58:00 AM »
Ring opening of an epoxide by H(+) will not produce the cis diol. As far as I remeber it always produces the trans.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #4 on: November 20, 2001, 03:29:00 AM »
Ok, bummer, but thank you. Now I know not to proceed further assuming that part to be correct, and waste more time.

Next, we have to move to good old electrochemistry, very simple electrochemistry, I hope.

Has anyone ever thought about the two very useful species locked up in Epsoms before? The o so nice element Magnesium, and the better half of the Sulfuric Acid structure. Wouldn't it be nifty to seperate em into two good clandestine tools?

Im wondering about doing this. Solvate Anhydrous magnesium sulfate (if the solvent is anhydrous. If its aqueous, who gives a shit) and electrolyze it to seperate the ions.

I assume magnesium could be absorbed into a mercury cathode to form an amalgam, like the method used for sodium production? As for the sulfate ion {SO4-2} It would be changed to SO4: What the hell would you do to procure sulfuric acid out of this? Would it decompose to sulfur trioxide? If so, this could be led into water to produce the H2SO4. But thats a random guess.

Is this even a possibility? Id think it should be. I just dont know how to do it. I did utfse btw, learned a decent bit, too, browsing the not-what-I-was-looking-for results.

So people, tell me what you think and/or know.

                                                 PrimoPyro

Vivent Longtemps la Ruche! STRIKE For President!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #5 on: November 20, 2001, 03:57:00 AM »
It is theoreticaly possible, but not practical at all. Magnesium is abundant OTC (see

https://www.thevespiary.org/rhodium/Rhodium/chemistry/hydrogen.html

) and there are much better sources for sulfuric acid - even if you cannot get the concentrated acid, you can always resort to concentration of 30-40% battery acid, using a lot less money and equipment than if you were to do an electrolysis (in which I don't know if sulfuric acid would be formed at all).

The only instance where electrolysis of a salt is warranted at all would be in the preparation of sodium metal, and even that is a big hassle (just look in the search engine).

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #6 on: November 20, 2001, 04:19:00 AM »
Thanx Rhodium. I read that page, but Im reminded of the thought that Mg forms a metal oxide coating in air. Would this be suitable for grignard reactions? I know the surface is oxidized or an alloy of some sort, because you can add water to these parts "sources" and Mg(OH)2 is never formed.

Vivent Longtemps la Ruche! STRIKE For President!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #7 on: November 20, 2001, 04:31:00 AM »
Magnesium alloys are not suitable, it must be pure magnesium. In preparing magnesium (preferably in the form of turnings or shavings, but a coarse powder may work satisfactorily) for use in a grignard reaction, it is first washed with dilute (about 1M) hydrochloric acid to remove any oxide coating (which always forms on the Mg surface upon exposure to air), followed by washing away the acid/water with alcohol, and finally washing away the alcohol with anhydrous ether. The clean magnesium is then directly transferred to the reaction flask and covered with anhydrous ether, and the reaction is begun as usual.

There is a way around the trouble of dirty magnesium, and that is the use of an ultrasonic bath to "shake" away the oxide coating, and this procedure also allows the chemist to use normal ether, and it does not have to be rigorously dried (usually over sodium wire), ether dried over MgSO4 is sufficiently dry.

Ultrasonicated grignard reactions:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignard.wet.html






Osmium

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Re: PP's General Chem Question Thread
« Reply #8 on: November 20, 2001, 04:42:00 AM »
Never cleaned Mg for grignards at all. The oxide coating of Mg isn't that hard to overcome, stirring alone will expose some of the metal and allow the reaction to start. Whenever it didn't start a crystal of iodine took care of it.

But if you have access to an ultrasonic bath then of course use it.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #9 on: December 10, 2001, 03:12:00 PM »
Is there a reaction that changes from an ester to a ketone by eliminating the terminal acid-alcohol oxygen, leaving the acid carbonyl, and thus creating a ketone?

I searched for esters, ketones, and rearrangements here and abroad, and didn't find what I was looking for  :(

I did find the reverse: the rearrangement of a ketone to an ester. Sigh, this is the opposite of what I want to do.

Anyone know?

                                                PrimoPyro

Vivent Longtemps la Ruche! STRIKE For President!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #10 on: December 10, 2001, 06:41:00 PM »
You can hydrolyze the ester, and react the carboxylic acid with 2 equivalents of methyllithium, see the two last steps in:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/p2p.azlactone.html


PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #11 on: December 10, 2001, 07:01:00 PM »
Thank you, Rhodium. It is more knowledge, but sadly, doesn't apply to what I desire to do.

The example I wanted it for was to take either ethyl benzoate and make acetophenone, or even more desireable, to take benzyl acetate and make phenylacetone.

For the process you mentioned, I'd need phenylacetic acid, or a phenylacetic ester. I was hoping to find a method to do away with these reagents.

Benzyl alcohol + acetic acid + sulfuric acid --> benzyl acetate

Very OTC. If I could find a way to eliminate that oxygen to produce phenylacetone, or the acetophenone from ethyl benzoate, I'd be very very pleased.

Thanks for your reply.

                                                PrimoPyro

Vivent Longtemps la Ruche! STRIKE For President!

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #12 on: December 16, 2001, 07:56:00 PM »
Is it possible to perform ANY type of condensation between any of these:

an ether, and either ammonia, or a primary amine?

The ether plus ammonia would make a secondary amine by replacing the oxygen in the ether, with the nitrogen, forming the secondary amine and water.

If it were a primary amine, a tertiary amine would form, plus water.

Is this possible at all? I have never sen this talked about ever, so I wonder if it can even be done? If so, I have some new ideas to write out. Thanks for any help.

                                                 PrimoPyro

Vivent Longtemps la Ruche!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #13 on: December 16, 2001, 09:12:00 PM »
Not with ordinary reaction conditions. It might happen something at 450°C and 300 atm pressure over some zeolite catalyst, but under such conditions it is usually possible to turn donald duck into dihydro-mickey mouse, so I guess that doesn't count.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #14 on: December 16, 2001, 09:17:00 PM »
LOL!

Thanx Rhodium. I didnt put too much hope in it, but I was really curious about that possible conversion and had to ask. Thanx again.

                                                   PrimoPyro

Vivent Longtemps la Ruche!

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #15 on: December 23, 2001, 07:34:00 PM »
Back to a previous topic outlayed above: The formation of ephedrine derivatives from propenyl benzene. This time I wonder about PPA instead of the methylated ephedrine version.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/ppa.synthesis.html



This shows how NBS and H2O can be used to change propenyl benzene into the amino-alcohol. It also says that it will work for substituted benzenes as well. Good.

My question is: Will this procedure produce the correct chiral aminoalcohol for clyclization to 4-MAR with HNCO, as outlayed in the thread "4-MAR w/o CNBr" ?

I would think it would depend on the chirality of the propenyl benzene right? Like I said before, I don't really know nomentclature for chirality, but speaking from a picture point of view, in the standard picture scheme for alkylbenzenes, with the phenyl on the left, and the alkyl coming out to the right from the 1 o clock position (god I sound so stupid, all because of a lack of vocabulary...)

Well, if the propenyl alkene part curves down like shown in that url, then the halogen is on the same side as the hydroxy, but if the alkene curves to the right, the hydroxy will be "up" and the amino "down" and I would think this isomer to be the incorrect one for cyclization.

Am I on the right track here, or am I speaking utter nonsense? I am taking a wild stab in the dark here trying to figure it out.

So specifically: Will this alkene-opening reaction produce the chirally correct compound for cyclyzing to 4-MAR with HNCO?

Don't forget to explain your answer.  ;)

Thank you everyone. You are most helpful, and it is very appreciated.

                                                   PrimoPyro

Vivent Longtemps la Ruche!

terbium

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Re: PP's General Chem Question Thread
« Reply #16 on: December 23, 2001, 08:51:00 PM »
then the halogen is on the same side as the hydroxy, but if the alkene curves to the right, the hydroxy will be "up" and the amino "down"
This seems to be cis/trans isomers that you are refering to in the above, not optical isomers. It is only when you are speaking of optical isomers that you use the term chirality.

Rhodium

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Re: PP's General Chem Question Thread
« Reply #17 on: December 25, 2001, 03:33:00 PM »
Primopyro: Halohydrin formation is trans-regiospecific (regardless if the starting alkene is cis or trans, as the intermediate is a flat bromonium ion), and produces the incorrect isomer (the same as pseudoephedrine) for use with the cyanate route to 4-MAR.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #18 on: January 04, 2002, 03:33:00 AM »
Powers that bee, and bees buzy a buzzin' right now:

Here's a simple yes/no question  :)

If para-Dichlorobenzene is exposed to NaCN or KCN in solution, or w/o solution (two different scenarios) will a reaction commence to swap the chlorines on benzene with the nitriles of the alkalais?

Essentially:

PhCl2 + 2KCN ___> Ph(CN)2 + 2KCl

That is what I am curious about. I know that such reactions readily take place on alkyl halides, and on arylalkyl halides, but does this apply to aryl halides as well? Please say yes.  ::)

I think you know why I am curious about this.  ;)

                                                        8) PrimoPyro 8)

Vivent Longtemps la Ruche!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #19 on: January 04, 2002, 04:55:00 AM »
It generally does not apply to aryl halides unless extreme rxn conditions are used. See any org chem textbook for the conversion of chlorobenzene to phenol (350°C and a lot of pressure).