Iso E Super is one of the most famous molecules in perfumery. It's one of the few perfume molecules known by name in popular culture. What is it and how is it used in perfumes? In this post I explain all you need to know about Iso E Super and I clear up some of the ambiguity in the different Iso E Super products on the market. By the end of this article you should know exactly what you're buying when making perfume with Iso E Super in its various forms and how to use it.
A Brief History
Research started in the 1960s when scientists were looking for Ionone analogues (i.e. similar molecules to the "Ionone" molecules, which smell like violets). Iso E Super was discovered by John B. Hall and James M. Sanders of IFF in 1973.
Iso E Super was originally used in small amounts and mostly in woody compositions. Everything changed in 1988 with "Fahrenheit" (Christian Dior) where it made up a quarter of the formula; this was the first instance of a trend of Iso E Super "overdosing". Not long after, its 18% "overdose" in Trésor (Lancôme) showed that it could be used in all types of compositions where it formed part of Sophia Grojsman's famous Grojsman accord, which was since often used as a base for floral (amongst other) perfumes. In 2006 it was used at 100% in the cult classic Molecule 01 (Escentric Molecules).
How does it smell? Iso E Super is often described as woody, cedar, amber, ambergris. It's not heavy nor difficult to work with and most people find it pleasant; it's popular and easy to use. Nowadays it's used in all perfume types and is produced on such a massive scale that it's very cheap, which only invites further use.
Structure & Isomers
In chemistry different arrangements of the same atoms often occur, producing similar molecules. These are called isomers. When chemicals are synthesised by scientists, different isomers often form together. This is not always an issue as often the isomers have similar properties, however, it's important to note that they're not exactly the same and can smell different.
Iso E Super is classed as an "Isocyclemone". The structure of the original Iso E Super molecule is as follows:
In 1990 it was discovered that the molecule "Iso E Super" was actually very weak smelling whereas another molecule (an isomer named Arborone) was responsible for most of the smell (100,000 times stronger) even though it was present at only 5% in the isomeric mixture (the original Iso E Super product sold by IFF was never 100% pure).
Despite much research and various improvements to the method, no one has yet come up with an industrially viable method of synthesis of high purity Arborone. Some methods are closer than others which is why you will see different trade names for variants (Iso E Super, Timbersilk & Sylvamber).
Arborone has the following structure:
Georgywood was invented in the 90s by Givaudan (another multinational fragrance company) as an Arborone alternative (not quite as good although still much better than the original); this is still a captive molecule though, meaning it's only available to Givaudan's perfumers:
Iso Gamma, another isomer, was also discovered:
A concern with Iso E Super is its high octanol-water partition coefficient of 5.7, meaning it much prefers to dissolve in lipids rather than water. The consequence of this is that it tends to bioaccumulate (in a similar way to polycyclic musks) since it likes to lodge itself into cells in living organisms (cell membranes have a lipid section for example). Iso gamma has less tendency to bioaccumulate since it's more polar, and hence is more likely to be washed out out things with water. The famous Molecule 01 (Escentric Molecules) fragrance reportedly uses an isomeric mixture high in Iso Gamma (a mixture said to be a captive of IFF).
Commercial variants
Since Iso E Super was the original name used since the 70s for what at the time was thought to be a single molecule, the name is now often used as an umbrella term for the isomers. This means that Iso E Super can refer to the original molecule, the original IFF product (including Arborone) or more generally some generic mixture of the isomers (although this may not be strictly correct terminology, it seems to be what's used out there in the wild).
You may also see some other trade names for Iso E Super variants:
- Timbersilk: Contains 0.07% AmberXtreme, 8.5% Arborone and 13.5% Iso Gamma
- Sylvamber Contains 14.9% Arborone, ~9.5% gamma isomer (sources conflict)
Closing remarks
Hopefully this post cleared up any questions you may have had regarding Iso E Super. If you're interested in how to use Iso E Super in your own perfumes, then check out the tips I give at the end of the video which accompanies this article:
References
Scent and Chemistry, The Molecular World of Odors: Wilhelm Pickenhagen, Günther Ohloff, Fanny Grau, Philip Kraft
https://basenotes.com/threads/some-interesting-info-on-ies-isomers.505669/
https://www.fragrantica.com/news/The-History-of-Iso-E-Super-in-Perfumery-7729.html