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Everything posted by Knumbnuts

  1. Gentle hydrogenation over Pd/C removes halogen. Using a Rh cat e.g. Nishimura's cat hydrogenates the aromatic ring.
  2. Apparatus with ground glass joints is certainly a bit more expensive that individual pieces held in place with rubber bungs. But the expense is worth it. Have a look on e-bay you may well find apparatus quite cheaply there. If you look after it, like everything else, it will last forever, unlike rubber, which perishes over time. Anything that distills over in your "rubber apparatus" will be pure, unless it is an azeotrope, but even that will be pure! The whole point of distillation is purification so having stuff remain in the pot is ok. The trick is to know where to terminate the distillation.
  3. Labs do not use rubber stoppers these days, it's all ground glass joints. In the early days leeching of additives form the rubber by solvents etc was a problem. How do you know that nothing distilled with the isopropanol? Any additive will dissolve in the refluxing solvent and will not distill, as they are usually not volatile compounds. So if this is the problem they will concentrate in the distillation residue.
  4. If I see it correctly you have rubber stoppers connecting the bits of glassware? It may be that the isopropanol at reflux temperature has dissolved something out of the rubber, perhaps a radical inhibitor. You don't need much substance to get some colour.
  5. I think you should perhaps re-think the very first reaction, there is something else that could happen. It would help if you supplied some reaction conditions for the first step.
  6. It's probably a mixture of solids, salt, sodium chlorate, sodium hypochlorite (bleach). Most likely due to evaporation and decomposition. You can read more here: http://en.wikipedia.org/wiki/Sodium_hypochlorite
  7. Well you are correct. You generate the phenoxide anion which is more nucleophillic than the phenol. Thus is should react much much faster with the tosylate.
  8. Well you will not get a γ-butyrolactone if that's what you are looking for. Reduction of the carboxylic acid will give the alcohol if you use the correct reducing agent. Oxidation won't do much either, except give the amine-N-oxide, again it depends on the oxidation reagent.
  9. The longest chain is 5 carbon atoms long, pentatonic acid. The substituents are then included in alphabetical order. The numbers, the sum of which must be as low as possible.
  10. What about an F in the para position, does that vanish as well?
  11. OK, I sorted it out. It taught me to scan down the page! Here is what I am talking about in the above. epox.tiff
  12. The conversion from the disodium to the tetrasodium salt is done, as you say with sodium hydroxide. What you need to do is write a balanced reaction equation for this. From there you can calculate the number of moles and hence grams you require.
  13. You have gone from a 6 membered ring to a 5 membered ring upon reaction with benzylmagnesium bromide! Is this an error? I ask because the Grignard reagent will open the epoxide ring. On a side note how does one attach an image to a post?. If it was obvious then I would have posted the reaction I am talking about. Thanks for any clues to this.
  14. Strange this. Try the distillation again. As for the film, I would not expect 100% ethyl acetate to leave a film, so there must be some non-volatile stuff in there. Put a small fractionating column on your distillation apparatus and see if that makes any difference.
  15. Is this after distillation that it is yellow and leaves a film?
  16. Temperature will make it worse. As a base I was thinking of diisoproplyethylamine 1.1 equivalents.
  17. I notice you are not using a base to remove the HI. So first pick a base. I think you may see a lot of di-alkylation here, perhaps some cyclisation as well. Add the hydrazine to the di-iodide. This may help avoid di-alkylation. You can also use ethanol as the solvent or DMP or THF, etc.
  18. Well you need to link the biotin to your specific compound via a spacer. Then react it with your enzyme or protein or whatever. Then you put the bound substrate down a streptavidine coated column. This binds the biotin end of the substrate/enzyme/receptor complex. Once you have identified the column fractions containing the material of interest you displace the complex by treatment with excess biotin. This takes a lot of work, getting the spear length correct, making sure this bitionylated compound binds properly, properly functioning assays for your target of interest and so on. But when it works it is not a bad method.
  19. Ether may give a better separation of some of the impurities. Dichloromethane may well dissolve them where ether won't. You could use diisopropyl ether instead of diethyl ether. But I am still curious as to your procedure for pyridine removal. Are you filtering and washing the solid, as was suggested?
  20. He said "dissolve in ether/HCl and then evaporate the ether", so I assumed that there was no wash involved.
  21. What happens to the pyridine? You have not removed that by this procedure so how do you obtain 99% purity?
  22. They made a solution of the diazonium salt. They made a solution of copper sulphate in ammonia with hydroxyl amine, which they then added to the diazonium salt solution. They then added ether and let the reaction proceed.
  23. Usually one uses sodium nitrite to form the diazonium salt, you don't sen to have that in your mixture. From your mixture I won't expect any reaction except perhaps the hydroxylamine coordinating to the copper.
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