I want to dissolve glycine to DMF to conduct an Sn2 reaction. I have added ammonia and triethylamine to the deprotonate carboxyl group, however, the deprotonated glycine dissolved poorly in either case. How can I prove solubility of glycine in depronated form into DMF?
Glycine (2-aminoethanoic acid) H2N-CH2-COOH undergoes internal proton migration easily when the pH reaches the isoelectric point (ip) value. It becomes NH3+-CH2-COO- i.e. zwitterion having cation & anion in the same species. The solubility of glycine is far higher in water than in methanol or ethanol or other polar solvents such as DMF or DMSO for the reason of intermolecular attraction & zwitterions formation.
So, the carboxylic acid group is already deprotonated when the (pH) changes into (ip).
When a reaction is desired to proceed by SN2 mechanism, polar solvents are usually avoided because they facilitate the SN1 mechanism (i.e. the pathway in which carbocation is formed & stabilized by solvation due to the polar medium).
My advice is to switch from single solvent to mixed solvents & to select those with lower polarities or even without polarity.
Hi Peng,
You could try to titrate it with Tetrabutyl ammonium hydroxide. I used it with polisaccharides. please let me know if it works.
Where do you want to alkylate it, have you considered reductive amination as an alternative to the SN2 reaction on the nitrogen ?
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