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Author: Subject: Chloralose synthesis help
Rhodanide
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[*] posted on 14-5-2019 at 09:06
Chloralose synthesis help


Hi everyone,
Yesterday I attempted the synthesis of the Chloraloses, and ran into some issues. I was following the PrepChem synthesis, which called for equal amounts of Chloral Hydrate and anhydrous Glucose to be mixed together and heated at 100C for 2 hours. Pretty simple. I was using 10g of AR grade Chloral Hydrate as well as 10g of AR grade anh. Glucose, nothing else. The synthesis says that after the heating period, the Chloral Hydrate is to be steam distilled off, but I wasn't in the mood to set up the apparatus (nor do I know if I have the appropriate equipment) so I just skipped that. Unfortunately, after the heating period and after cooling, there were no crystals, but rather a sticky, extremely thick, clear, resin-like mass in the bottom of the RBF. The heck?
Do you guys think that the steam distillation is really necessary? If so, any tips for a good steam distillation would be appreciated as I've never done one before. Many thanks, you're helping out an Inorganic chemist with O-chem stuff so any help is a lifesaver!
Appreciate it, fellas.
-R

Link to synthesis: http://www.prepchem.com/synthesis-of-chloralose/




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Pumukli
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[*] posted on 14-5-2019 at 09:25


You need equal quantities of the reagents. It doesn't necessarily means equal weights! Correction by the molecular masses should be done.

If the recipe calls for steam distillation, then do it!
Simplest approach: after the reaction is over let the mixture cool a bit and add some water to the reaction flask, then start to heat it again and distill off the water. (Do it in a real distilling flask, not in a beaker or something like that, because you want to collect the distillate!) With the distilling water vapor the unreacted chloral would distill too. You could observe "oily" water droplets and/or phase separation, maybe just a milky appearance of the distillate. Do this until you get a clear distillate, it means that you freed the chloralose from chloral.

Then comes the "fun" part, the separation of the two isomers by crystallisation.

Keep in mind that parachloralose is toxic, so the separation step may be really important (or not), depending on the aim of the synthesis!

[Edited on 14-5-2019 by Pumukli]
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Rhodanide
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[*] posted on 14-5-2019 at 16:31


Couldn't have asked for a better answer. Thanks fella!



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