Sciencemadness Discussion Board

some details needed

feynmann - 18-8-2008 at 09:03

I want to know the supposed condition for this reaction if u please??
Reacting ester 8 with 3 using sodium methoxide ........what is the solvent used ,,,IS it methanol and what is the supposed temperature to be used ???(I don't think he didn't use a solvent as sodium methoxide has auto ignition point of 88 degree C

The picture of scheme is below and the paper is posted in the next post or u can download here

http://rapidshare.com/files/134990933/sdarticle.pdf.html

Note.jpg - 95kB

ScienceSquirrel - 18-8-2008 at 09:09

If you have a look in the experimental you will see that the substrates were heated with the neat sodium methoxide (page 199).

feynmann - 18-8-2008 at 09:10

here is the article

Attachment: sdarticle.pdf (557kB)
This file has been downloaded 727 times

feynmann - 18-8-2008 at 09:12

I read it
For the synthesis of 3-aryl-7-nitro-2H-l,2-benzothiazine-l,l-dioxide (7a) a
mixture of 3 (1.76 g, 10 mmol), 8 (O-15 g, 10.1 mmol) and sodium methoxide
(1.5 g) was heated for 8 h. The brown reaction mass was run into ice-cold
water (15 ml) and then neutralised with dilute hydrochloric acid. The
product was crystallised from dimethylformamide. Reaction conditions,
yields, physical and spectroscopic data are given in Table 1.

It doesn't mention the temperature and that what I wanted to know

ScienceSquirrel - 18-8-2008 at 09:17

I would guess that the mixture was heated until it melted and the melt was then stirred.
The reaction temperature would then depend on the substrates being used to a certain extent.
It does mention running the reaction mixture into ice water so I would guess it is molten at the end of the reaction.
You could write to the authors.

[Edited on 18-8-2008 by ScienceSquirrel]

feynmann - 18-8-2008 at 09:23

Heating sodium methoxide without solvent is strange to me somehow as it can ignite so easily and it decomposes before melting too

ScienceSquirrel - 18-8-2008 at 09:30

I would heat it under nitrogen to avoid the catching fire / oxidation of the substrate bit etc.

Also the reaction eliminates water so I think you probably end up with an oily mixture when the reaction is done.
Anyway I would heat it in a small flask under a condenser and N2 atmosphere until it melted and leave it in the overnight room and head off for my pie and chips.
See how the stuff was looking in the morning :D

Arrhenius - 18-8-2008 at 09:30

It's quite likely in methanol.

feynmann - 18-8-2008 at 09:35

To science squirrel I point also that sodium methoxide may decompose on direct heating

Did u meet any procedure with fusion of sodium methoxide before??

ScienceSquirrel - 18-8-2008 at 09:42

I don't think that they are fusing the sodium methoxide, I think it is is dissolving in the molten reactants.
The fact that DMF was chosen as a recrystallisation solvent suggests that the product is not overly soluble in most solvents.
Most experienced chemists would avoid DMF like the plague as a recrystallisation solvent as it is a right pain to get rid of.

Nicodem - 18-8-2008 at 09:57

Quote:
Originally posted by feynmann
To science squirrel I point also that sodium methoxide may decompose on direct heating

Did u meet any procedure with fusion of sodium methoxide before??

Sodium methoxide does not decompose so easily. It can catch fire if heated in the presence of air, but nobody is saying you can not use inert atmosphere. If the experimental does not say at which temperature the reaction mixture was heated, then follow with TLC like you are supposed to anyway.

PS: Please do not use pictures with such large width. It will deform the frame set of many members who use the most common monitor resolutions. Also, this forum is supposed to be about amateur chemistry and science and posting only questions related to your job is not particularly welcome unless you are involved in other discussions as well. There already exist a number of forums for professional chemists where you can discuss job related questions like this.

ScienceSquirrel - 18-8-2008 at 11:05

I am just giving my opinion on the basis of my experience and the sparse details in the paper. I am a computer bod these days.
I cannot remember the exact conditions but I remember using sodium methoxide in hot DMF to convert bromoarenes to aryl methoxyethers so as Nicodem says it will certainly take some welly before breaking down.