In-situ infra-red spectroscopy of reduced forms of vitamin K1.

• Main Author: Chng, Elaine Lay Khim.
• Other Authors: Richard David Webster
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Science::Chemistry::Analytical chemistry
• Online Access: http://hdl.handle.net/10356/39814
• Institution: Nanyang Technological University

Infra-red spectra of the redox products of Vitamin K1 (VK1) were obtained in order to acquire information on the positions of their characteristic bands. We have investigated the reduction processes of VK1 in acetonitrile containing 0.2 M Bu4NPF6 as the supporting electrolyte with an amalgamation of electrochemistry techniques and in-situ infra-red spectroscopy. A spectroelectrochemical cell with a glass frit fitted at the bottom was used as the cathodic compartment to produce redox products and to allow monitoring of the electrolysis process simultaneously in the infra-red spectral range. In acetonitrile, two chemically reversible one-electron transfer reactions were detected via cyclic voltammetry and the E0 values obtained from it were used to determine the potentials for generating the reduced products during constant potential electrolysis. The reduction processes were also conducted at very low water concentrations and it was found that the second reduction step could not proceed due to the reduced forms undergoing adsorptive process with the electrode surface. The effect of water on the shifting of infra-red bands for both reduction processes was investigated and it was revealed that only bands belonging to the second reduced product were affected. The sequential addition low volumes of water (0 μL - 100 μL) to the VK1 in dry acetonitrile without Bu4NPF6 was discovered to cause a dramatic increase of approximately twenty-fold in the intensities of the absorbance bands belonging to VK1. Hydrogen bonding effect and solubility effect are the two plausible reasons deduced to explain the effects observed. The hydrogen bonding effect was investigated by using dimethyl terephthalate and VK1 model compound; and the solubility effect examined by using Vitamin E to find out which is responsible for the effect we observe on the intensities of the bands so as to have a better understanding of how VK1 is able to interact with water.