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Comparatively Speaking: Alkoxylation vs. Ethenification

Contact Author Anthony J. O'Lenick, Jr., Siltech LLC
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Alkoxylation, as seen in Figure 1is a process that reacts lower molecular weight epoxides (oxiranes) such as ethylene oxide, propylene oxide and butylene oxide. These epoxides are capable of reacting with hydroxyl generally under base catalysis, causing a ring opening and the addition of an oxyalkylene group. The resulting compound contains a hydroxyl group, so a varied number of moles of oxide can be added.

Therefore, the reaction of ethylene oxide is ethoxylation, the reaction of propylene oxide is propoxylation and mixtures of oxides is alkoxylation.

Ethenification, as seen in Figure 2, is related to alkoxylation, but the reactant is an ester, not an alcohol. Lower molecular weight epoxides (oxiranes) such as ethylene oxide and propylene oxide are capable of reacting with esters (generally triglycerides under base catalysis), causing a ring opening and insertion of oxyalkylene group. Reaction with ethylene oxide insets polyoxyethylene groups, and reaction with propylene oxide inserts polyoxypropylene groups. These groups and resulting mixtures bring new solubility properties to the compounds to which they are added. Similar to alkoxylation, these reactions also make use of lower molecular weight oxiranes that are very reactive.

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Ethoxylation of castor oil is a good example of a reaction in which a mixed product (i.e. alkoxylation/ethenification) occurs.1

1. http://www.zenitech.com/documents/Castor_Ethox_Article.pdf

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Figure 1. Alkoxylation

Alkoxylation results in a hydroxyl group present on the terminal end of the molecule.

Figure 2. Ethenification

Ethenification results in insertion into the molecule.

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