ketel-one
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Can diethyl-ether substitute for ethanol?
Would Li + Et2O work when trying to reduce a 2-attached pyridine ring to a piperidine? Also, does anyone know any common ways to make thionyl
chloride?
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ammonium isocyanate
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I'm guessing the reduction your refferring to is the one from Organic Syntheses. If this is the case, it seems very unlikely that diethyl ether would
work in place of absolute ethanol, as it appears that the reduction requires alkoxide formation, which wouldn't occur with Et2O, as there is no
hydrogen that the sodium can displace. And why use Et2O? Additionally, what side chain are you referring to on the pyridine? It may be important,
depending on what it is (particularly if it is easily reducable).
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Also, does anyone know any common ways to make thionyl chloride?
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Please UTFSE! This information can be found easily on the board. Also, if you don't know anything about the synthesis of SOCl2, you probably
shouldn't be messing around with it. It's nasty stuff if mishandled.
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ketel-one
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Alright, ethanol it is and screw the thionyl chloride. It is 2-benzylpyridine I'm interested in exept with an -OH and -CH3 at the non-aromatic carbon.
Would the pyridine in that reduce to piperidine?
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entropy51
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This from the guy who tried to make ether over a burner. And who thinks ethyl acetate is insoluble in water (it isn't) because of osmotic pressure.
And who asked if CO2 could carboxylate soaps to carboxylic acids.
See poseur. http://en.wikipedia.org/wiki/Poseur
It just gets worse and worse.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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ammonium isocyanate
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No need to flame me, entropy.
I made Et2O once over a burner, yes, as I had seen the prep on rhodium and it seemed doable given that I don't have a hotplate (like many members
here, my budget isn't exactly large). A small scale prep. Outdoors. I also tested for leeks. Still, it was a bad idea, and I readily admit this.
I never said anything about ethyl acetate being insoluble in water. Where the hell did you pull that out of?
And about carboxylating soaps, thats impossible. Soaps are salts of carboxylic acids. Either you thought that's what I said, which it isn't, or you
don't have any idea what carboxylation is. I asked if carbon dioxide could acidify the soaps to form carboxylic acids and alkali bicarbonates, which
it can, but under greater pressure than I had hoped. And so I wasn't far off at all with my question.
Clearly you need to do some more research before you try to flame someone. Try doing your homework next time. If you want to add anything of worth
to the discussion, feel free. But stop flaming me.
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JohnWW
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Piperidine, an aliphatic secondary amine C5NH11, is the completely saturated form of pyridine, C5H5N, which is an aromatic tertiary amine. To convert
pyridine, or its derivatives, to piperidine, or its corresponding derivative, would, comparably to hydrogenation of benzene to cyclohexane, require
hydrogenation under quite rigorous conditions, involving H2 under high pressure and temperature with a Pd/C or Pt catalyst (or with Ni under even
higher pressure). Similar reactions are used in oil refining to reduce the content of aromatics, by conversion of them to cyclohexane and
bicyclodecane ("naphtha") derivatives. An easier small-scale way to piperidine and its derivatives may be from nicotine.
There is NO WAY that Li + ether could do that. However, you may be confusing hydrogenation with the nucleophilic substitution reaction of the ionic
aryllithiums or alkyllithiums, e.g. C6H5Li, with pyridine to form 2-substituted aryl or alkyl derivatives, at about 110ºC in toluene or xylene or
similar under argon, with LiH formed as byproduct.
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ketel-one
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You're right John, the synthesis I was originally looking at says to use "H2, Pt, CH3CH2OH"
But I thought that Lithium + ethanol reduces pyridine rings... I must have been sadly mistaken =(
And wouldn't Et2O be pretty easy to make from EtCl and LiOEt?
[Edited on 9-9-2009 by ketel-one]
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panziandi
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Ketel,
Ethanol reacts with Sodium as shown below:
2CH3-CH2-OH + 2Na => CH3-CH2-ONa + H2
The hydrogen released is able to reduce SOME compounds. I have a feeling that sodium dissolving is ethanol might reduce pyridine rings to piperidine
rings, but I can't be sure and I ain't looking! Know then lithium would also react similarly, however it is varsly more expensive than sodium. Diethyl
ether has the structure:
CH3-CH2-O-CH2-CH3 as you can see there is no "reactive" hydrogen to be released by sodium (or lithium). In fact sodium is frequently used to dry ether
by reacting with traces of ethanol and water that are present in it... Would I be wrong is suggesting you are getting ou lithium from batteries (like
you were going to get phosphorus from matchboxes)?
Also you're going to get much more help if your posts were better formulated. State the reaction you are wishing to perform, chemical names and / or
reaction scheme. That way people know exactly what you are referring to. The piperidine and benzyl groups is starting to sound a little bit like a PCP
system... Or am I just being very skeptical?
[Edited on 9-9-2009 by panziandi]
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DJF90
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You're being skeptical panziandi - He claimed matches were a good way of getting sulfur, not phosphorus, by digestion in HCl. And PCP has the
benzyl group on the nitrogen of the piperidyl group, whereas this chap describes 2-benzylpyridine (and the reduction product he's looking for,
2-benzylpiperidine). But who knows, he may be working with analogues. Considering he's asking about acetyl chloride in another thread, it vould be
possible he intends to acetylate the benzylic alcohol. But what do I know. As far as reduction of pyridine goes, I believe its possible via the birch
reduction, but am unsure and dont have time to check. Lithium (or sodium) and anhydrous liquid ammonia are pretty tough requirements for someone who
gets sulfur from matches... Maybe he can do it though 
One good thing you can do with 2-benzyl pyridine is nitrate it to make a photochromic compound. The reaction is simple and I have a procedure here
somewhere. The resulting compound (If I remember correctly the phenyl ring is dinitrated) is a yellow ochre (ish) colour in the dark, but a steel-blue
colour in the light.
[Edited on 9-9-2009 by DJF90]
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entropy51
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https://www.sciencemadness.org/whisper/viewthread.php?tid=12...
The osmotic pressure part was the joke.
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ketel-one
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Quote: Originally posted by DJF90  | | One good thing you can do with 2-benzyl pyridine is nitrate it to make a photochromic compound. The reaction is simple and I have a procedure here
somewhere. The resulting compound (If I remember correctly the phenyl ring is dinitrated) is a yellow ochre (ish) colour in the dark, but a steel-blue
colour in the light. |
If you have that at hand, I'll love to look at it, just out of interest. And yeah of course lithium is from batteries, where else would I get alkali
metals =(
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DJF90
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At risk of dragging the whole thread offtopic...
" Synthesis of a photochromic compound from 2-benzylpyridine
Prepare a salt-ice bath by adding enough salt to an ice bath to lower the temperature of the water to -10*C
Place concentrated sulfuric acid (10ml) into a 100ml round bottomed flask containing a stirring bar, clamp the flask securely in the ice bath and wait
until the temperature of the acid is below 5*C. Whilst stirring the cold acid, add the 2-benzylpyridine (1.6ml) dropwise, using a clean pipette,
sufficiently slowly that the internal temperature does not exceed 10*C
Once all the reagent has been added, add concentrated nitric acid (2ml) dropwise, again using a clean pipette and maintainig a reaction temperature
below 10*C. Whilst adding the acid, set up a steam bath for the next step.
The temperature will rise more quickly upon the addition of the nitric acid than it did with the addition of the pyridine derivative. Do
not rush this step If the core reaction temperature rises above 10*C, the reaction will fail
Upon completion of the acid addition attach a condenser to the flask, replace the ice bath with a steam bath then alloow the reaction to heat to
reflux for 20 minutes. Whilst waiting, add 20g sodium hydroxide pellets to a 250ml beaker and cool in an ice bath before adding water (100ml). Leave
in the ice bath until needed.
Pour the reaction mixture onto 50g of ice in a 250ml beaker and place into an ice bath. With stirring, add the cold sodium hydroxide solution dropwise
until the reaction has been completely basified (pH approximately 11). Towards the end of the addition of the base, the product will separate to give
a milky yellow suspension.
Add diethyl ether (70ml) and stir the reaction for a further 10-15 minutes to extract the product into the organic layer. Transfer the biphasic
mixture to a separatory funnel and collect the ethereal layer [Note: ether is less dense than water]. Wash the aqueous layer with more diethyl ether
(50ml) and combine the ethereal layer with the original organic layer. Dry the solution over anhydrous magnesium sulfate, filter and concentrate the
solution (to roughly 10ml) using a rotary evaporator. Crystallise the crude product by cooling the concentrate using an ice bath. Filter and
recrystallise the product from ethanol.
Split the product in half; place one half in a vial and store in the dark whilst the other half is stored in a vial on the bench. Observe the two
vials after 30 minutes."
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ketel-one
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Thanks man I might try that if I ever have 2-benzylpyridine (I can get the other reagents fairly easily).
As for the original reaction Li + EtOH would probably work, I found a similar reaction on wikipedia in the synthesis of coniine from
methyl-2-picolylalkine (scroll down http://en.wikipedia.org/wiki/Coniine) although Li + NH3 (birch reduction) would definitely probably work (although it seems to me that the benzene
ring would also get hydrogenated).
Another short question: does birch reduction also cleave ethers?
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UnintentionalChaos
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| Quote: Originally posted by DJF90 | At risk of dragging the whole thread offtopic...
" Synthesis of a photochromic compound from 2-benzylpyridine
Prepare a salt-ice bath by adding enough salt to an ice bath to lower the temperature of the water to -10*C
Place concentrated sulfuric acid (10ml) into a 100ml round bottomed flask containing a stirring bar, clamp the flask securely in the ice bath and wait
until the temperature of the acid is below 5*C. Whilst stirring the cold acid, add the 2-benzylpyridine (1.6ml) dropwise, using a clean pipette,
sufficiently slowly that the internal temperature does not exceed 10*C
Once all the reagent has been added, add concentrated nitric acid (2ml) dropwise, again using a clean pipette and maintainig a reaction temperature
below 10*C. Whilst adding the acid, set up a steam bath for the next step.
The temperature will rise more quickly upon the addition of the nitric acid than it did with the addition of the pyridine derivative. Do
not rush this step If the core reaction temperature rises above 10*C, the reaction will fail
Upon completion of the acid addition attach a condenser to the flask, replace the ice bath with a steam bath then alloow the reaction to heat to
reflux for 20 minutes. Whilst waiting, add 20g sodium hydroxide pellets to a 250ml beaker and cool in an ice bath before adding water (100ml). Leave
in the ice bath until needed.
Pour the reaction mixture onto 50g of ice in a 250ml beaker and place into an ice bath. With stirring, add the cold sodium hydroxide solution dropwise
until the reaction has been completely basified (pH approximately 11). Towards the end of the addition of the base, the product will separate to give
a milky yellow suspension.
Add diethyl ether (70ml) and stir the reaction for a further 10-15 minutes to extract the product into the organic layer. Transfer the biphasic
mixture to a separatory funnel and collect the ethereal layer [Note: ether is less dense than water]. Wash the aqueous layer with more diethyl ether
(50ml) and combine the ethereal layer with the original organic layer. Dry the solution over anhydrous magnesium sulfate, filter and concentrate the
solution (to roughly 10ml) using a rotary evaporator. Crystallise the crude product by cooling the concentrate using an ice bath. Filter and
recrystallise the product from ethanol.
Split the product in half; place one half in a vial and store in the dark whilst the other half is stored in a vial on the bench. Observe the two
vials after 30 minutes."
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Does the reaction reverse when the sample is placed back in the dark, or is it irreversible?
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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ketel-one
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Well wikipidea says that photochromism is supposed to be reversible. Then again it's not even clear what this prepared pyridine compound is so it may
depend, maybe DJF90 knows.
So does anyone know what birch Reduction does to ethers?
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