Author Topic: PP's General Chem Question Thread  (Read 15984 times)

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PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #20 on: January 05, 2002, 05:51:00 AM »
Could a pressure cooker supply enough pressure for a small scale reaction of this sort? I can heat it to 350C, but the only way I know of increasing pressure is in a pressure cooker, an autoclave, or a bomb.

Bomb is out of the question. NO WAY. I of all bees know what it's like when bombs go off unexpectedly. It's not fun.

I don't own an autoclave, nor do I have the funds to buy one for such a reaction.

So what about a pressure cooker?

                                                   PrimoPyro

Vivent Longtemps la Ruche!

Rhodium

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Re: PP's General Chem Question Thread
« Reply #21 on: January 05, 2002, 10:03:00 AM »
I would not reccommend heating cyanides to those temperatures under pressure, regardless of the quality of the container, there is a too large risk of poisoning yourself and others.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #22 on: January 05, 2002, 06:51:00 PM »
I was kinda worried about that, too. Acids liberate HCN from NaCN/KCN/Ca(CN)2 therefore you cannot have any acid present.

This case would be extra special. Bases such as NaHCO3 or Na2CO3 may not be strong enough to react with the weak HCN, so they would be worthless, but bases such as NaOH, KOH, etc will. Well that sounds fine, it would regenerate NaCN for the reaction, BUT: Under these conditions of pressure and heat, it would also react with the dichlorobenzene to produce sodium chloride and hydroquinone, a dihydroxybenzene. Well, as we all know, dihydroxybenzenes are not basic, they are acidic. It would possibly react with the NaCN present to form the hydroquinone salt and HCN.

So, in this situation, the pH must be neutral, or disasters could result either way. A thin line to tread to say the least.

                                                  PrimoPyro

Vivent Longtemps la Ruche!

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #23 on: March 02, 2002, 10:58:00 AM »
Can someone please help me out with a basic chemistry question, I just outright don't know the answer... ::)

If you were to halogenate 2-butanone, where would the halogen go? Would it go to the lone methyl on one side of the carbonyl, or to the ethyl on the other side?

Please say ethyl. If it is the ethyl, which carbon, the terminal carbon, or the one next to the carbonyl? Please say the one next to the carbonyl....

Thanks.  :)

                                                    PrimoPyro

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Rhodium

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Re: PP's General Chem Question Thread
« Reply #24 on: March 02, 2002, 11:23:00 AM »
It will end up on the most substituted carbon (the most stable enol form of the ketone involves that carbon, and the halogen only reacts with the enol form), and in this case that is in the 3-position, next to the carbonyl on the ethyl side chain.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #25 on: March 02, 2002, 11:28:00 AM »
Thanks Rhodium!  :)

Does this mean that since only the enol tautomer reacts, the halogenation with say bromine will be very slow?

                                                     PrimoPyro

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Rhodium

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Re: PP's General Chem Question Thread
« Reply #26 on: March 02, 2002, 12:06:00 PM »
It depends on the stability of the enol form. Acetone, for example, is in its enol form 1% of the time, while acetaldehyde is there 25% of the time. Say the bromination will then take 100 times longer than a regular halogenation of a double bond - it is still over in a few minutes.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #27 on: March 02, 2002, 01:09:00 PM »
Thanks again.  :)

Can you use alkyl chlorides and bromides for the Ullmann reaction with copper, or only iodides? Anyone who knows can answer these questions by the way.

And anyone who has other hypothetical questions can post them as well, as long as they involve chemistry, not a recipe.  :)

                                                    PrimoPyro

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Rhodium

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Re: PP's General Chem Question Thread
« Reply #28 on: March 02, 2002, 02:16:00 PM »
I may rain on your parade somewhat here, but I think only aryl iodides are suitable for the ullmann reaction, not aliphatic iodides. You may have to look into stille/suzuki coupling reactions instead, alternatively Cu(I)-catalyzed grignard couplings.

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #29 on: March 02, 2002, 02:20:00 PM »
Rain all you need to Rhodium. I already figured that was going to come out.  ;)

I was just seeing if anyone knew for certain that aryl iodides were the requirement. I figured if I asked, everyone would jump in and say "probabaly" but if they were absolutely sure, they'd catch me in my "error."

No grignards allowed Im afraid lol. But I will look into the other one. Thanks!  :)

                                                   PrimoPyro

Wir pumpen..... (Klatschen) Sie oben!

psychokitty

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Re: PP's General Chem Question Thread
« Reply #30 on: March 02, 2002, 04:23:00 PM »
First off, PrimoPyro, you have got to get yourself the 2001 edition of Advanced Organic Chemistry:  Reactions, Mechanisms, and Structure (Fifth Edition) by Jerry March.  This sucker is like Beilstein in one volume.  I am not kidding.  I only have the fourth edition (1992) but it too is fantastic!  Bees are always saying that I have a knack for finding obscure references (right under Foxy2) but I'll let you in on a little secret:  Practically all of my sources are actually from one source--namely the aforementioned textbook!

Anyway, to answer some of your questions (some from this thread and some from that other one of yours):

1.)  Benzyl iodide could be had from benzyl alcohol by way of NaI or KI and phosphoric acid or by AlI3 (formed in situ through reaction of Al and I2).  Al is otc; I2 can be had through reaction of NaI or KI and oxone).  But toluene and calcium hypochlorite are more OTC, I guess.

Regarding pool chemicals, what about that "brominating" shit that they carry.  I imagine that if it brominates, then it could possibly be used for brominating toluene or something.

2.)  The amino alcohol that you desire could be had by reacting any epoxide with hexamine and then hydrolyzing the intermediate complex.  Yields from styrene oxide and hexamine are, according to a reference that I've posted before, 100% of the desired amino alcohol (and by desired I mean that both the hydroxyl and amino groups are in the right place).  To get the halohydrin, one could react the epoxide with AlI3 made in situ.  Iodides are easier to swap with amines so this might be preferred over reacting the epoxide with HBr (which isn't all that OTC, BTW) and going from there.

3.) As for your question about whether or not aryl chlorides or bromides could switch for aryl iodides in the Ullman reaction, I refer you to "3-16 The Ullman Reaction (De-halogen-coupling)" on p 665 of the aforementioned fourth edition textbook:

". . . The best leaving group is iodo, and the reaction is most often done on aryl iodides, but bromides, chlorides, and even thiocyanates have been used."

Hope this has been helpful.  However, the best advice that I have given you is to buy that fucking book.  Enough said.


PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #31 on: March 02, 2002, 04:30:00 PM »
Thank you!  :)

I will purchase it the minute I locate a copy. I will begin searching for an online source right now. Thanks!  :)

I bought the last book recommended to me by foxy2, and it was worth the money. Operational Organic Chemistry, by John W. Lehman. It is full of procedures, especially for analysis, I love it.  :)  :)  :)

                                                     :) PrimoPyro :)

Wir pumpen..... (Klatschen) Sie oben!

PrimoPyro

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Re: PP's General Chem Question Thread
« Reply #32 on: March 02, 2002, 05:19:00 PM »
Guess what I just bought?  ;)

It's on it's way, hopefully my copy of the 5th edition will be here within a week. I look forward to its arrival. Found it really fast actually.

You can never have too many books, and you can never "read too much" no matter what anyone says. Money spent on information is money well spent. That's my story and I'm sticking to it.

Thanks again!  :)

                                                   PrimoPyro

Wir pumpen..... (Klatschen) Sie oben!

psychokitty

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Re: PP's General Chem Question Thread
« Reply #33 on: March 02, 2002, 05:25:00 PM »
Let me know when you get it.  I'll help you with the navigation.  I'm NOT saying you're a dumb-ass (in other words, that you can't figure it out for yourself), but actually I'm interested in a few things in there and helping you zero in on it quicker will help me as well.

cheeseboy

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Re: PP's General Chem Question Thread
« Reply #34 on: March 02, 2002, 07:40:00 PM »
So much great fun isn't it?So far cheese has invested in The Organic Chem Lab Survival Manual by Zubrick and Total Synthesis II by Strike.Thanks for the two other books, Pshychokitty and PrimoPyro  ...So toluene and calcium hypochlorite makes I2? Coolness.Is that synth on Rhodium's too?

Cheeseboy-a whiteboy with Soul Like a black guy without soul
May The Source Bee With You Always.

psychokitty

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Re: PP's General Chem Question Thread
« Reply #35 on: March 02, 2002, 08:29:00 PM »
No, toluene and calcium hypochlorite yields benzyl chloride; NaI or KI and oxone yields I2.

PrimoPyro

  • Guest
Re: PP's General Chem Question Thread
« Reply #36 on: March 03, 2002, 06:09:00 AM »
I am wondering, is Pd+2 the only oxygenation catalyst known, or are there others for catalytic oxygenation?

I know very little about catalysis for hydrogenation and oxygenation (still learning), but I seem to recall the reactions being an equilibrium that one influences by flooding the system with excess reactant to shift the equilibrium in the desired direction, such as adding shitloads of hydrogen to the catalyst to hydrogenate, and oxygen to oxygenate of course.

Would this imply that hydrogenation catalysts such as Nickels would also be applicable to catalytic oxegenation? If so, can you elaborate on any specific known hydrogenation catalysts that can double as oxygenation catalysts that are not palladium compounds?

If the answer to that is just a dead end, then I ask: Are there any other catalysts other than bipositive palladium, that can be used in Wacker-like oxygenation of olefinic bonds to ketones?

Thank you for your help. My interest is shifting from specialty reagents to catalysis lately. Very interesting topic. But palladium is expensive, and recycling it is a joke.

Thanks again.  :)

                                                    PrimoPyro

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PrimoPyro

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Acid-Base Reaction Variations
« Reply #37 on: March 26, 2002, 01:44:00 AM »
What would happen if one performed various acid base reactions, with using more powerful, non-hydroxide alkalai bases?

The instance Im thinking of, for example, is the splitting of acetamide with sodium hydroxide.

AcNH2 + NaOH --> AcONa + NH3

In these type reactions, the hydrogen and oxygen of the basic hydroxy are torn apart, something that is not "normallly seen" in reactions. The oxygen stays with the sodium in this case to form the acetate salt, while the hydrogen forms ammonia. This is a relative perspective, achieved by comparing reactants to products in various simple reactions. This one stands apart.

What if one were to use sodium methoxide? Would the sodium acetate still form, and the alkyl group attach to the amide, like the hydrogen did from the hydroxy? Using sodium methoxide would of course then procure methylamine, but this is but a small venture into this possibility.

If this would happen, I dont think it wise to prepare traditional alkylamines such as methylamine, nor to aminate alcoholates like P2Pol alcoholate; this is too unrealistic.

What I wonder about, is possibly using the Leuckart reaction with only formamide, not N-methyl formamide, to change P2P/MDP2P into the formyl-MDA, and react the formamide with sodium methoxide to form sodium formate and the N-methylated amine: MA/MDMA.

                                                    PrimoPyro

Vivent Longtemps La Ruche!

Rhodium

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Amide hydrolysis with methoxide
« Reply #38 on: March 26, 2002, 02:07:00 AM »
Nope, doesn't work that way - if you check the reaction mechanism of basic amide hydrolysis (reaction mechanisms is something you should look up every time you are unsure of reactants/products), you'd see that the basic anion (in my example methoxide) adds nucleophilically to the carbonyl, forming a tetrahedral intermediate, which then kicks out an amide anion, forming methyl acetate (if hydroxide was used, acetic acid would be the intermediate product). As the amide anion is so incredibly basic, it will not last for many microseconds, but will directly add to anything acidic, like the solvent protons (in my example methanol) re-forming sodium methoxide and free ammonia. If hydroxide was used as the base, the amide anion would abstract its hydrogen from there, forming ammonia and acetate).


PrimoPyro

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Aliphatic Diazo Compound Preparations
« Reply #39 on: May 07, 2002, 07:29:00 PM »
How to?

If someone would be so kind (Rhodium, you are setting a trend in my thread here, would you be so kind as to grace my thread once again? Osmium, you too?)

I'm wondering what the common methods (if any) are for the preparation of aliphatic diazo compounds (RN2) from whatever other compounds you know of. I don't think I mean diazonium salts, as the formula is only RN2. I really don't know a thing yet haha, and Im trying to look stuff up, when I figured it couldnt' hurt to ask here in this old thread.  :)

Thanks in advance for providing very informative answers to all my questions, including this one.  ;)  :P

Yes, Im Using FSEs right now.

                                                   PrimoPyro

Vivent Longtemps La Ruche!