Liu and Fan (2002) found that in the absence of hydrogen donor
viscosity of upgraded oil regresses with time, due to the reaction of high molecular weight active chains to terminate the free radicals.
In this work, the use of limonene as a solvent hydrogen donor
was investigated for the hydrogenation of the sunflower oil.
The result is the generation of ketyl radical, the radical centered on the hydrogen donor
. The ketyl radical does not initiate polymerization; it is a terminating radical.
The antioxidant activity of polyphenols is mainly due to their redox properties, which allow them to act as reducing agents, hydrogen donors
, singlet oxygen quenchers (Prior et al., 2005).
The molecules which are having the hydrogen donors
[less than or equal to] 5, hydrogen bond acceptor [less than or equal to] 10, molecular mass [less than or equal to] 500 daltons, and logP [less than or equal to] 5 are likely to obey Lipinski's rule, and Cramer's rule classifies the chemical compounds into three classes based on the 33 metabolic activities.
The additional polyether groups in the ethoxylated versions act as hydrogen donors
and therefore increase the reactivity.
Comparison of butyric acid, ethanol, lactic acid, and propionic acid as hydrogen donors
for the reductive dechlorination of tetrachloroethene.
The latters comprise 19 polar hydrogen donors
(ten phenolic and nine alcoholic hydroxyl groups) and 25 oxygen atoms in ether, ester and carbonyl functions.