2,4-DNP spot test for solid-supported aldehydes
SyntheticPage 119
DOI:
Submitted: August 22, 2001, published: August 22, 2001
Authors
Daniel Hamza (danielhamza@yahoo.co.uk)
A contribution from
Chemicals
2,4-dinitrophenylhydrazine solution in
solid-supported aldehyde
solid-supported aldehyde
Procedure
This test is used to look for the disappearance of an aldehyde after a solid phase reductive amination or reduction.
2,4-Dinitrophenylhydrazine reagent: Dissolve 3 g of 2,4-Dinitrophenylhydrazine in 15 mL of conc. sulfuric acid. This solution is then added with stirring to 20 mL of water and 70 mL of 95% ethanol. This solution is mixed thoroughly and filtered.
A few beads of resin are swollen in a drop of DMF and a single drop of 2,4-DNP solution is added. A positive result is orange-red.
Author Comments
It is best to wash the beads with DMF in an Alltech tube (or a Pasteur pipette with a cotton wool plug) to remove the coloured 2,4-DNP solution. Also, perform the colour test on a negative control resin containing no carbonyl functionality as well as on the starting aldehyde resin to gauge the colour change.
Despite the fact that the resin tends to also be a yellow colour, this test is actually pretty reliable providing you also perform the control experiments mentioned above.
Data
N/A
Lead Reference
1. Furniss, Hannaford, Smith and Tatchell: Vogel's Practical Organic Chemistry, 5th Edition, John Wiley & Sons, New York p1218 and 1257.
2. Anal. Biochem. 1972, (49), 436.
3. Anal. Chim. Acta., 1974, (69), 481.