Alexis St-Gelais, M. Sc., Chimiste – Popularization
Essential oils are worth quite a lot of money. It so happens that, in order to boost profits, unscrupulous people alter oils in various ways. This “Adulterants and you” series is there to introduce you to some of the adulterations we encounter. This is because not all of them are necessarily obvious, nor bear the same level of risk for the final consumer.
One of our recent public reports for an adulterated bergamot oil mentions the presence of 1-acetonaphthone. This compound has to be presented along with its close analog, 2-acetonaphthone.
What are they?
These two siblings are quite similar molecules (Figure 1) which bear unequivocal names: 1-acetonaphthone (1) is also called oranger liquid, while 2-acetonaphthone (2) is known as oranger crystals. They are reportedly prepared since the late 60s by means of a classical chemical reaction, called Friedels-Craft acylation, to add an acetyl group to naphthalene , which is a very cheap and accessible raw material.
|Figure 1. Structures of 1- and 2-acetonaphthones.|
Oranger liquid, as its name suggests, shows as a yellow-brown liquid, while oranger crystals is a nearly white solid, and both are readily soluble in apolar media, such as essential oils. They are on sale at accessible prices: purchasing 25 kg of these at Vigon will cost respectively 27$/kg and 30$/kg.
What do they do as adulterants?
Both compounds feature a delicious, orange-like scent, over a significant period of time [2,3]. This has made them ingredients of choice in perfumes, cosmetics, households products [2,3], and food  for decades. Sadly, it also seems that it is used to mimic or boost the poor quality of batches of neroli or bergamot essential oils, at levels below 3%. From our experience, this occurs along with some other adulteration, such as addition of synthetic linalool and linalyl acetate.
Are they dangerous?
A volunteer was reportedly irritated during a patch test implying oranger crystal . Otherwise, the oral toxic doses on animal models were extremely high, and unless anyone takes teaspoons of the pure compounds, there should be no major side effects. The compounds are even used as flavoring ingredients in food .
How do we detect them?
A basic GC-MS run will easily detect these ingredients, although we still have to purchase both isomers to be able to fully discriminate them. They exhibit pretty similar behaviors (mass spectrum and retention indexes), but would hardly be confounded with anything else.
Bottom of the line
Oranger liquid and oranger crystal are affordable orange-flavoring ingredients which are at times used to artifically boost neroli or bergamot oils. They sometimes can be mild irritants. Be cautious when one of those oils smell like orange-flavored candy!
 Opdyke, D. L. J. β-Methyl naphthyl ketone. In Monographs on Fragrance Raw Materials: A Collection of Monographs Originally Appearing in Food and Comestics Toxicology; Pergamon Press: Oxford (UK), 2013; p. 560
 The Good Scents Company. Alpha-naphthyl methyl ketone, [On line], page consulted on February 14, 2016, URL: http://www.thegoodscentscompany.com/data/rw1008371.html; and The Good Scents Company. Beta-naphthyl methyl ketone, [On line], page consulted on February 14, 2016, URL: http://www.thegoodscentscompany.com/data/rw1033571.html
 Givaudan. Oranger Crystals, [On Line], page consulted on February 14, 2016, URL: http://eindex.givaudan.com/eindex/displayMolecule.xhtml
 United States Pharmacopeia. Methyl β-Naphthyl Ketone. In Food Chemicals Codex; The United States Pharmacopoeial Convention: Rockville (MD), 2010; p. 657