Kinetic analysis and subambient temperature on-line on-column derivatization of an active aldehyde.
The chromatographic analysis of aldehydes under typical reversed-phase conditions may be a challenging task due to an equilibrium process leading to the formation of a gem diol species regardless of acidic or basic conditions. Initially, a reversed-phase HPLC gradient elution was developed to determine the amount of a n acetylenic aldehyde in a reaction mixture. Significant fronting was observed under acidic and basic conditions even at -5 degrees C. In order to circumvent this problem, a reversed-phase HPLC gradient method on a C18 column at subambient temperature was developed using diethylamine as a mobile phase additive for on-line on-column derivatization of the aldehyde moiety. The on-line on-column reaction rate for the derivatization of the aldehyde with diethylamine was determined as a function of column temperature. An Arrhenius plot was constructed and the activation energy was calculated. The chromatographic behavior of the derivatized acetylenic aldehyde and products formed in-situ in the chromatographic system were studied at various temperatures ranging from -10 to 60 degrees C. It was found that the reaction products could be controlled by adjusting the column temperature. Different reaction pathways were identified as a function of temperature. The products and the reaction pathways were characterized by NMR, LC-MS and UV spectra.
LoBrutto
R
R
Merck Research Laboratories, RY818-C220, PO Box 2000, Rahway, NJ 07065-0914, USA. rosario_lobrutto@merck.com
Bereznitski
Y
Y
Novak
T J
TJ
DiMichele
L
L
Pan
L
L
Journet
M
M
Kowal
J
J
Grinberg
N
N
D000447:Aldehydes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013696:Temperature
D000447:Aldehydes