The short version of my question is: how can I separate n-methylalanine from a solution that also contains monosodium phosphate?
And now for the detailed version -- after following Uncle Fester's procedure (in Secrets of Methamphetamine Manufacture) for synthesizing n-methylalanine, I am having trouble isolating the product. You can find the paper he uses as his source by googling "Reductive methylation of primary and secondary amines and amino acids by aqueous formaldehyde and zinc."
Basically, you mix up a monosodium phosphate buffer solution (200ml H2O + 9.5g NaOH + 16ml H3P04) to which is added 0.1mol alanine, 0.15mol formaldehyde, and 0.2mol powdered zinc and, after stirring for 45min, the zinc is filtered and the pH adjusted to 7 with NaHCO3. Afterwards, the n-methylalanine is supposed to precipitate out as about 10g of white needle-like crystals. Simple enough, right?
Now, here's the problem -- instead of 10g of crystals, I keep getting ~18g of flakey white and transparent crystals that will begin to melt at around 40c! By my calculations, the maximum possible yield should be around 11g n-methylalanine and so clearly something else is also precipitating. After weeks of repeated trials and going back to the original paper, I think I finally figured out what is happening -- although Uncle Fester says to use NaHCO3 to adjust pH to 7, I think that adding baking soda is converting some monosodium phosphate to disodium phosphate which is MUCH less soluble. Additionally, disodium phosphate forms several hydrates all of which melt between 36c and 50c, which would explain both the low melting point (N-MeAla should melt ~200c) and the extra weight of the product.
If that's the case, then the problem is how to adjust the pH of the final solution without forming the not-so-soluble disodium phosphate. After carefully examining the original paper, I noticed that they "added ammonia to the solution" afterward and so I decided to try using ammonia to adjust the pH but nothing precipitated and it is possible they only added ammonia to destroy any residual formaldehyde.
So does anyone have any ideas on how to either (A) separate a powdered mixture of disodium phosphate and n-methylalanine or (B) adjust the pH of a monosodium phosphate buffer to 7 without converting any of it to the disodium phosphate? Any help would be greatly appreciated
And now for the detailed version -- after following Uncle Fester's procedure (in Secrets of Methamphetamine Manufacture) for synthesizing n-methylalanine, I am having trouble isolating the product. You can find the paper he uses as his source by googling "Reductive methylation of primary and secondary amines and amino acids by aqueous formaldehyde and zinc."
Basically, you mix up a monosodium phosphate buffer solution (200ml H2O + 9.5g NaOH + 16ml H3P04) to which is added 0.1mol alanine, 0.15mol formaldehyde, and 0.2mol powdered zinc and, after stirring for 45min, the zinc is filtered and the pH adjusted to 7 with NaHCO3. Afterwards, the n-methylalanine is supposed to precipitate out as about 10g of white needle-like crystals. Simple enough, right?
Now, here's the problem -- instead of 10g of crystals, I keep getting ~18g of flakey white and transparent crystals that will begin to melt at around 40c! By my calculations, the maximum possible yield should be around 11g n-methylalanine and so clearly something else is also precipitating. After weeks of repeated trials and going back to the original paper, I think I finally figured out what is happening -- although Uncle Fester says to use NaHCO3 to adjust pH to 7, I think that adding baking soda is converting some monosodium phosphate to disodium phosphate which is MUCH less soluble. Additionally, disodium phosphate forms several hydrates all of which melt between 36c and 50c, which would explain both the low melting point (N-MeAla should melt ~200c) and the extra weight of the product.
If that's the case, then the problem is how to adjust the pH of the final solution without forming the not-so-soluble disodium phosphate. After carefully examining the original paper, I noticed that they "added ammonia to the solution" afterward and so I decided to try using ammonia to adjust the pH but nothing precipitated and it is possible they only added ammonia to destroy any residual formaldehyde.
So does anyone have any ideas on how to either (A) separate a powdered mixture of disodium phosphate and n-methylalanine or (B) adjust the pH of a monosodium phosphate buffer to 7 without converting any of it to the disodium phosphate? Any help would be greatly appreciated
