Objective

To prove that Boc-Glycine reacts with TFA to produce tert-butyl trifluoroacetate.

Procedure

Weighed 175mg (1mmol) Boc-Gly-OH and dissolved it in 900uL of CDCl3. A HNMR of the aminoacid was obtained. To it 100uL of Trifluoroacetic acid was added. The reaction was monitored for about the first 20mins by NMR spectroscopy.

Results

Boc-Gly-TFA Reaction
Boc-Gly (175mg/ 900uL CDCl3)
TFA (100uL / 900uL CDCl3)
Boc-Gly / TFA 03min (175mg / 100uL in 900uL CDCl3)
Boc-Gly / TFA 09min
Boc-Gly / TFA 16min
Boc-Gly / TFA 20min

Discussion

Over a period of time it is clear that the t-buyl group of the aminoacid is lost and another peak at 1.56ppm starts emerging. This is similar to what has been observed in Exp065 and Exp067. However, because there is 10 fold more boc compound for the same amount of TFA, the reaction is much slower.
Boiling point of tert-butyl trifluoroacetate in the literature has been found to be 83C.

Conclusion

t-butyl trifluoroacetate is formed by the addition of TFA to Boc-Glycine

Log


2007-03-11

19:15 : Made up a solution of Boc-Glycine in CDCl3 and obtained a HNMR
20:00 : Added 100uL TFA to the solution
20:03: Obtained HNMR
20:09 : Otained HNMR
20:16 : Obtained HNMR
20:20 : Obtained HNMR

References

1.Removal of t-butoxycarbonyl protecting groups with trifluoroacetic acid. (Lundt, Johansen, Volund, Markussen) Int J Pept Protein Res. 1978 Nov;12(5):258-68

Tags

Boc-Gly-OHInChI=1/C7H13NO4/c1-7(2,3)12-6(11)8-4-5(9)10/h4H2,1-3H3,(H,8,11)(H,9,10)
TFA InChI=1/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7)
t-butyl trfluoroacetate InChI=1/C2HF3O2/c3-2(4,5)1(6)7/h(H,6,7)