JKZzz (Stranger)
05-12-03 03:56
No 432736
      best crystalization method?  Bookmark   

This is a simple question but I haven't been able to find any direct answers to this question so here goes:
Which is the better method of crystalization: boiling off excess slovent or pouring the mix into cold/chilled solvent? Which would result in the most pure product?

I've seen both used for cryst' 2,5-dimethoxynitrostyrene from IPA, but nothing about why one or the other or which is better.

thanks in advance to any replies!smile
(Hive Addict)
05-12-03 06:11
No 432758
      In principle  Bookmark   

you can do single or multisolvent recrystallization.
In the single sovent recryst. you dissolve in hot solvent to achieve a supersaturated solution then chill to crystallize.
This belongs in the newbee forum.
05-12-03 09:40
No 432782
      theres probably a post on this somewhere...  Bookmark   

theres probably a post on this somewhere... but... imho the best method for recrystalization is to take up your product in a minimum amount of boiling solvent... whatever solvent that may be... use stiring or whatever to ensure that everything is disolved.. then just sit your flask on a bench somewhere and leave it for a while... overnight if you can be bothered... this works on the principle that solvents can disolve more when they're hot... so a good choice of solvent wouldnt disolve much at rt.... if you get bored..stick it in an ice bath... that will speed things up... but the slower you let the crystals for the bigger they'll be .. i like large crystals... just think they look cooler :D .... you can evaporate the filtrate off and recrystalize the stuff left over.. but it wont be as pure :(
05-12-03 22:58
No 432846
      decomposition  Bookmark   

In SWIP's experience, nitrostyrenes decompose quite quickly at elevated temperatures, and rextallisation from a boiling solvent seems to give an impure product.
05-14-03 02:52
No 433046
      Thanks for the input  Bookmark   

Sorry bout putting this in the wrong forum, guess it is pretty basic. 
Based on what psygn (thanks to uwink) it seems like boiling off solvent isn't such a good idea. I'll recryst using the chilln.
any other suggestions? any pointers on 2C-B synth or things I should be careful about?
thanks and peace
(Hive Addict)
05-14-03 07:26
No 433078
      Boiling away your solvent isn't really a great  Bookmark   

Boiling away your solvent isn't really a great method for recrystallization, especially when it is possible to risk decomposition, boiling over, etc. Zubrick's Organic Survial Manual is mandatory reading as is the MaDMAx sticky in the newbee forum which should help you on your quest for suitable answer.

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