Chromatography Forum

Wondering if anyone has experience in using HFBI in acylation of OH, NH2 group. I find that this reagent forms white fume and then ppt readily once I break the ampoule. Needless to say, the HFB derivative could not form.

Hi Chhubert

Unsure if I used the exact same reagent a long time ago but I can share the following with regard to acylation:

I Used HFBA (Heptafluorobutyric anhydride).
There reagents are very moist sensitive, you need to make sure that what you working with is dry (use dried/very low moist content solvents).

Yes fumes can evolve with dervatization reagants forming HCL (g) or other stuff when reacting with moist in the air.

Acylation dervatives can generally be hard to prepare, try to work in an as moist free envoirement as possible, work quickly and perhaps use a flow of nitrogen over your working area.
You typically also need to remove reaction products (acid by products) before injection, when using HFBA you can use a stream of nitrogen after the dervatisation.

Typically used solvents that can accept the acid byproduct are: pyridine and THF.

If HFBI is a type of Perfluoroacylimidazole you will not have the acid by product problem but I still think you need to watch out for moist.

Hope it helped a bit

EDIT
Just want to confirm that HFBI reacts violently with water.

Have you considered another reagent such as MBTFA? Less Flour atoms so would lose sensitivity on an ECD.
Reacts slower especially on -OH and may need some heating to speed up reaction, but nicer/easier to handle.