Purification from SOCl2, PCl3, PCl5 reaction coproducts

[conte_...@my-deja.com]

Let's take the example of an aromatic carboxylic acid to be transformed
in its chloride. Ok, the reaction is easy: SOCl2 or PCl3 or PCl5 heated
together the acid. But, at the end of reaction, what do you suggest to
obtain a pure chloride? Please, consider that, as you know, often
chlorides are low boiling compounds or may sublime. Thus, not always
the easy removal of coproducts by distillation is a suitable way. And
consider also that many solvents can dissolve both the chloride and
those products.
In these cases, what do you do?
Thank you
Il conte

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[Uncle Al]

conte_...@my-deja.com wrote:
>
> Let's take the example of an aromatic carboxylic acid to be transformed
> in its chloride. Ok, the reaction is easy: SOCl2 or PCl3 or PCl5 heated
> together the acid. But, at the end of reaction, what do you suggest to
> obtain a pure chloride? Please, consider that, as you know, often
> chlorides are low boiling compounds or may sublime. Thus, not always
> the easy removal of coproducts by distillation is a suitable way. And
> consider also that many solvents can dissolve both the chloride and
> those products.
> In these cases, what do you do?

With SOCl2 all you have left in the pot is excess SOCl2, any solvent,
and your product. Fracitionally distill (reduced pressure) or
otherwise appropriatley purify.

With phosphorus chlorides the byprdouct is a non-volatile insoluble
mess. Decant your product, then fracitionally distill.

Oh yeah... I happily remember an undergad doing independent research
at Stanford who couldn't get her thionyl chloride to react for
anything, not even after extended reflux or after she added a drop
then a squirt of DMF. The porous solid jsut sat there swirling around
the magnetic stirrer. Finally, a grad student walked over, took the
can of SOCl2, dug into the vermiculite, and pulled out the plastic bag
containing the bottle. Descriptive chemistry is a good thing.

--
Uncle Al
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

[Gabriel Tojo]

conte_...@my-deja.com wrote:

> Let's take the example of an aromatic carboxylic acid to be transformed
> in its chloride. Ok, the reaction is easy: SOCl2 or PCl3 or PCl5 heated
> together the acid. But, at the end of reaction, what do you suggest to
> obtain a pure chloride? Please, consider that, as you know, often
> chlorides are low boiling compounds or may sublime. Thus, not always
> the easy removal of coproducts by distillation is a suitable way. And
> consider also that many solvents can dissolve both the chloride and
> those products.
> In these cases, what do you do?

Now you know why oxalyl chloride is so popular for this purpose. It
produces volatile HCl, CO and CO2 as by-products.

Best regards.

--
Gabriel Tojo

Scientific Consultant in Organic Synthesis
www.galquimia.com

Profesor Titular de Química Orgánica
Faculty of Chemistry
University of Santiago de Compostela
SPAIN

[mp...@my-deja.com]

> Oh yeah... I happily remember an undergad doing independent research
> at Stanford who couldn't get her thionyl chloride to react for
> anything, not even after extended reflux or after she added a drop
> then a squirt of DMF. The porous solid jsut sat there swirling around
> the magnetic stirrer. Finally, a grad student walked over, took the
> can of SOCl2, dug into the vermiculite, and pulled out the plastic bag
> containing the bottle. Descriptive chemistry is a good thing.
>

I've heard this story now for the third time and it still sounds like an
urban legend to me. I can hardly believe that there is t h a t much
stupidity out there.

Micha.

[kres...@my-deja.com]

In article <95mqtr$7nf$1...@nnrp1.deja.com>,

It's probably been embellished from "she opened the can and started to
weigh out the vermiculite..." into "she spent 6 months doin' a freakin'
chlorination with no freakin' chlorine...". The story in the former
form circulated my old school when I was there - with a name attached.
He wasn't stupid (and it wasn't me ;-). A colleague claims to have
witnessed it too at his. It isn't particularly stupid to open a can and
expect what's inside to be what it says on the label. I suppose with
SOCl2 you can put it down to inexperience and ignorance, but with
inorganics...? I expect it happens all the time.

[Bill Walker]

Oh my god.

You mean there's a bottle inside the can?

It that what they mean by "bottle inside can" on the label?
It wasn't covering half the side of the can in brightly fluorescing
international warning orange in 9 languages with a diagram, so I missed it.

There ought to be a government program to prevent just that sorta thing.

:)

Bill

[Uncle Al]

Bill Walker wrote:
>
> Oh my god.
>
> You mean there's a bottle inside the can?
>
> It that what they mean by "bottle inside can" on the label?
> It wasn't covering half the side of the can in brightly fluorescing
> international warning orange in 9 languages with a diagram, so I missed it.

Inside the pine crate filled with pearlite and constructed with wicked
barbed nails there is an aluminized polyester pouch filled with more
pearlite that contains a steel can filled with vermiculite in which a
sealed plastic bag holds the bottle of SOCl2 with its screw cap
secured by sticky tape and dipped in wax.

(We usually take the thing out back, fire a 30-06 through the center,
tip, and collect the drainage.)

[sch...@gefen.cc.biu.ac.il]

In article <3A7F3A6B...@hate.spam.net>, Uncle Al <Uncl...@hate.spam.net> wrote:

: (We usually take the thing out back, fire a 30-06 through the center,

: tip, and collect the drainage.)

Hoping, no doubt, that your shipment was accidentally switched with someone
else's order for sodium azide.

-----
Richard Schultz sch...@mail.biu.ac.il
Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
Opinions expressed are mine alone, and not those of Bar-Ilan University
-----
"Logic is a wreath of pretty flowers that smell bad."

[John Osborne]

In article <95mqtr$7nf$1...@nnrp1.deja.com>, mp...@my-deja.com writes
>
>
[snip]

> Finally, a grad student walked over, took the
>> can of SOCl2, dug into the vermiculite, and pulled out the plastic bag
>> containing the bottle. Descriptive chemistry is a good thing.
>>
>
>I've heard this story now for the third time and it still sounds like an
>urban legend to me. I can hardly believe that there is t h a t much
>stupidity out there.
>
>Micha.
>
>

Believe it. It's not necessarily stupidity as such, it's more the mind
being part of another world than ours. If you use problem-solving
ability as a measure of intelligence, then I once saw one of the
brightest (?) people I have ever known standing fascinatedly under the
remains of a hanging curtain wall while a demolition worker was swinging
away 10 feet over his head. Masonry was falling all around him. He was
mentally calculating the minimum necessary adhesive attraction between
bricks and mortar ... then again, I hear rumours that certain trainee
nurses omitted to remove the wrapping before inserting suppositories;
there was no instruction to do so on the label.
--
John Osborne, from Castle Despair (home to Henry the hairy German
shepherd).
"The only thing more devastating than incoming hostile fire is
incoming friendly fire." - Hints for Military Service in the Field #19