Question

European REACH regulation for registration of chemical substances has an own definition of a polymer according to this regulation.

I've noticed the following problem.

I want to discuss here only the chemical aspects.

Can glycerol in substituted natural fats be a monomer according to European REACH Regulation?

Let's assume a fat obtained from animals, plants or fishes as industrial raw material (means a mixture of different triglycerides) that is substituted with a functional group (e. g. acetylated, hydroxylated, oxidated, sulfated or sulfited fat), e.g. at the double bonds of the unsaturated triglycerides or at the hydroxyl groups of castor oil. (See e.g. Wikipedia for the structure formulas of such triglycerides.)

REACH Regulation (1907/2006/EU), May 8 2023, states:
For the purposes of this Regulation:

polymer: means a substance consisting of molecules characterised by the sequence of one or more types of monomer units. Such molecules must be distributed over a range of molecular weights wherein differences in the molecular weight are primarily attributable to differences in the number of monomer units. A polymer comprises the following:
(a) a simple weight majority of molecules containing at least three monomer units which are cova-lently bound to at least one other monomer unit or other reactant;

(b) less than a simple weight majority of molecules of the same molecular weight. In the context of this definition a ‘monomer unit’ means the reacted form of a monomer substance in a polymer;

monomer: means a substance which is capable of forming covalent bonds with a sequence of additional like or unlike molecules under the conditions of the relevant polymer-forming reaction used for the particular process
Let's assume paragraph 5 is fulfilled for the mixture of differently substituted different triglycerides of the considered natural fat.

My question is:
Can glycerol meet the definition of a monomer according to paragraph 6?

If we synthesize the triglycerides starting with the reaction between the fatty acids and the substituent, glycerol is a monomer according to paragraph 6: glycerol is capable of forming covalent bonds with the sequence that consists of the substituent and the fatty acid.

But if we synthesize the triglycerides starting with the reaction between glycerol and the fatty acids, glycerol isn't capable of forming covalent bonds with a sequence of further molecules in the polymer formation reaction.

That means, if the mixture is a polymer according to REACH or not depends on the order of the synthesis steps in this case.

Am I right?

I found that there are gaps in the REACH polymer definition. I want to see if I'm right or looking for counterarguments.

Answer 1

According to the European REACH Regulation, glycerol can meet the definition of a monomer depending on the order of synthesis steps in the triglyceride formation process.

Step-by-step explanation:

Glycerol can meet the definition of a monomer according to the European REACH Regulation if certain conditions are met. According to the definition provided in the regulation, a monomer is a substance capable of forming covalent bonds with a sequence of additional like or unlike molecules under the conditions of the relevant polymer-forming reaction. If glycerol is reacted with the fatty acids to synthesize the triglycerides, it can be considered a monomer. However, if the triglycerides are synthesized starting from the reaction between the fatty acids and the substituent, glycerol would not meet the definition of a monomer. The order of the synthesis steps determines whether glycerol qualifies as a monomer in this context.