Thermo Scientific
| Reagents, Solvents and Accessories
17
Perfluoroacylimidazoles (TFAI and HFBI)
Offer effective acylation of hydroxyl groups and primary and
secondary amines.
C R
O
N
N
R
Name
M.W.
b.p.
d
20
4
CF
3
TFAI
164.08
38-40˚C/14 mm 1.490
C
3
F
7
HFBI
264.10
57-58˚C/10 mm 1.562
In many cases, the use of
N
-acylimidazoles offers
considerable advantages over acid chlorides and
anhydrides. Advantages include:
Highlights:
• The reaction is smooth and positive, releasing no acids
into the system to hydrolyze samples
• The byproduct, imidazole, is relatively inert
• Ideal for FID and ECD techniques
• Derivatives are volatile, despite size of group
• Closely bound fluorines contribute stability
Fluorinated acylimidazoles acylate hydroxyl groups and
primary and secondary amines. They react smoothly with
indole alkylamines to quantitatively derivatize the indole
nitrogen, as well as other functional groups present.
Fluorinated imidazoles also are used for bifunctional
derivatizations and in exchange reactions from the TMS
derivative to the HFB derivative. In addition, a study by
lkekawa and colleagues found that
O-
TMS groups could
be exchanged to
O-
HFB groups by adding HFBI and a small
amount of HFB acid directly to the reaction mixture.
PROTOCOL 1
Preparing fluoro acyl derivatives for FID.
1. Place 0.1-2.0 mg sample in a 1.0 ml Thermo Scientific Reacti-Vial Small
Reaction Vial.
2. Add 0.2 ml desired
N
-acylimidazole.
3. Cap vial and heat at 60°C for 15-30 minutes, or until reaction is complete.
(Moderately and hindered steroids may require 2-6 hours heating.)
4. Analyze by GC using FID.
PROTOCOL 2
Preparing HFB derivatives of indolealkyl amines using HFBI for FID and
ECD techniques.
Milligram-scale Derivatization:
1. Combine 2 mg sample and 0.2 ml HFBI in a 3 ml Thermo Scientific
Reacti-ViaI Small Reaction Vial.
2. Cap vial and heat at 85°C for 1 hour.
3. Add 1 ml water and 2 ml toluene.
4. Cap vial and shake 2 minutes.
5. Analyze toluene layer by gas chromatography.
NOTE:
A small amount of HFB acid remains in the toluene phase. If it
interferes with analysis, wash toluene phase with 2-3 more 0.5 ml water
washes.
Microgram-Scale Derivatization:
1. Combine 2 µg to pg quantities residue and 20 µl HFBI in a 3.0 ml
Thermo Scientific Reacti-Vial Small Reaction Vial.
2. Cap vial and heat at 85°C for 1 hour.
3. Add 2 ml pure toluene and 0.5 ml distilled water.
4. Cap vial and shake 2 minutes.
5. Remove aqueous layer.
6. Wash toluene layer 3 times with 0.5 ml water.
7. Centrifuge toluene layer 2 minutes.
8. Analyze toluene layer by GC using ECD.
Ordering Information
Product # Description
Pkg. Size
TS-48882
TFAI
10 x 1 ml ampules
(Trifluoroacetylimidazole)
❉
TS-44211
HFBI
5 g bottle
(Heptafluorobutyrylimidazole)
❉
Additional dry ice and/or freight charges.
