Database/Hair Conditioning/Quaternium-91
Mostly natural · ISO 16128

Is Quaternium-91 natural?

Mostly. The two long behenic-derived fatty chains are oleochemical and the sulfate of the methosulfate comes from mineral sulfuric acid, so all three count as natural origin, exactly as they do in Quaternium-27 and Quaternium-83. The earlier figure used a molecular weight of 841 Da and treated the whole counter-ion as petrochemical.

INCI nameQuaternium-91
FormulaC51H103N3O5S · 870.4 Da
FunctionHair Conditioning
FeedstockBehenic acid, typically from rapeseed, is condensed with…

How we scored it

The supplied formula C51H103N3O5S weighs 870.46 Da. Natural origin is the docosanamido (behenoyl) group C22H43O (323.58 Da), the heneicosyl chain C21H43 (295.57 Da) and the sulfate part of the methosulfate counter-ion (SO4, 96.06 Da) = 715.21 Da. Petrochemical is the imidazolinium ring with its ethyl bridge and N-methyl (140.21 Da) plus the methyl carried by the counter-ion (15.04 Da). So 715.21/870.46 = 0.82.
What counts. ISO 16128-2 scores the atoms that remain in the final ingredient. Reagents, solvents, catalysts and protecting groups used during manufacture leave no mass behind and are not counted.

Where it comes from

Behenic acid, typically from rapeseed, is condensed with a synthetic diamine to form an imidazoline ring, then quaternised with dimethyl sulfate. The fatty chains are oleochemical and the sulfate is mineral; the ring and the methyl groups are petrochemical.

In plain English

A hair-conditioning ingredient with two long fatty chains attached to a synthetic ring structure. Most of its weight comes from natural fatty acid, but part of its core is lab-made.

CosIng definition: 1-(Docosanamidoethyl)-2-heneicosyl-1-methyl-4,5-dihydroimidazolium methyl sulfate

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Structure

2D structure of Quaternium-91

N-[2-(2-docosyl-1-methyl-4,5-dihydroimidazol-1-ium-1-yl)ethyl]docosanamide;methyl sulfate

PubChem CID 139032655 ↗

References

  1. 1ISO 16128-1:2016 and ISO 16128-2:2017 — Guidelines on technical definitions and criteria for natural and organic cosmetic ingredients and products. ISO, Geneva.
  2. 2Quaternium-91. PubChem CID 139032655. National Center for Biotechnology Information. pubchem.ncbi.nlm.nih.gov ↗
  3. 3QUATERNIUM-91. CosIng — European Commission cosmetic ingredient database. ec.europa.eu/cosing ↗
  4. 4QUATERNIUM-91. CosIng u2014 European Commission database for information on cosmetic substances and ingredients. https://ec.europa.eu/growth/tools-databases/cosing/search?search=QUATERNIUM-91