Conversation with Andy Brunning


Last month I had an email chat with Andy Brunning, owner of the site Compound Interest, a blog about “…creating graphics looking at the chemistry and chemical reactions we come across on a day-to-day basis.” Andy is also teacher* of chemistry in the UK.

I fell in love with his infographic The Chemistry of the Smell of Decomposition explaining the chemistry behind the odour of decaying things because I was thrilled to have scientific confirmation of something I’ve been coming across again and again in my perfumery education: that the molecule Indole, found in decaying matter, is also present in many alluring, sexy, provocative white flowers like “… jasmine, gardenia, tuberose and orange blossom to a lesser degree; but also in honeysuckle and lilac, technically not white flowers at all) doesn’t really smell of poop in isolation. On the contrary if I were to give it a common reference I’d compare it to the stale yet curiously “fresh” (as in sharp, penetrating, energizing instead of pacifying) scent of mothballs.” (Fragrantica)



And check out the Scents of Christmas graphic that to date has received close to 3,000 shares on FaceBook:


Being that I approach perfume formulating from a chemistry point of view — it just seemed to be the most natural, instinctive way that is evolving for me — I try to find harmonies between similar and juxtaposed chemical components in my compositions, Compound Interest has been a total trip for me and I had to find out more. I had to find out why a teacher would be interested in breaking down chemistry into understandable bits for some of the more chemically-challenged among us, which led to this conversation.

If you’re a perfumer who is at all interested in the molecular aspect of perfume making then you’ll probably enjoy this conversation with Andy:

Her Two Scents: I love your info graphics as a tool for simplifying chemistry! How did you come upon this idea, how did Compound Interest start?

Andy Brunning: The infographics actually came out of me just making a set of classroom posters on the different groups of elements. I’d wanted to make a selection of them to brighten up my classroom, and also to have something on the walls that wasn’t just there to take up the space, but was instead crammed with interesting information. Some of my friends who are also teachers then asked me to share them with them, and I figured that putting them online and making them available for free was the easiest way to do that, so the Compound Interest site was born!

Most of the graphics I make now are primarily intended for the website – I really enjoy taking a subject, then distilling it down into a page of information that gives a succinct but detailed overview on that particular aspect of chemistry. I still use them occasionally in the classroom too, and it’s gotten to the stage where my older pupils will quite often ask me in more detail about some of them, so I like to hope I’m making it easier for them to find out more about aspects of chemistry they maybe don’t study as part of their course.

H2S: There are two very passionate camps in perfumery, those that embrace composing strictly with naturals and those that see nothing wrong with aroma chemicals and include them in greater or lesser degrees in their creations. How would you put the use of synthetic compounds into perspective from an educational point of view?

Andy: Generally speaking, when it comes to natural vs. synthetic, there still seems to be a lot of misunderstanding out there. I’ve had discussions with followers of the site who’ve not realised that a synthetic version of a compound is identical chemically to the natural version. Of course, in perfumery, it’s maybe a little more complicated than that; synthetic imitations of a particular essential oil will probably focus on the main character-impact compounds that give a good imitation of that scent, whereas the essential oil will contain a more complex mix of compounds. A good example is that of jasmine; jasmone and methyl jasmonate are the primary character-impact molecules of the essential oil, and it’s these that a synthetic imitation will focus on. So, there is a difference between the essential oil and the synthetic version, but only in that the synthetic version is focusing on the key compounds that give the essential oil its aroma.

H2S: Regarding those aroma chemicals that can have a disruptive effect on the body, like some nitromusks, how should the perfumer approach the use or not of these materials?

Andy: I’ll admit to not knowing a great deal about the regulatory system in the perfumery industry, aside from recalling that it has its own regulatory body, so I don’t know what safeguards and recommendations are in place for families of chemicals like the nitromusks. However, I do know that they’ve been mostly superseded by other alternative compounds, such as the polycyclic musks. That shows the importance of the role of chemists in the process, being able to supply alternatives to chemicals used in personal care products and perfumery that can have undesirable effects. I suppose it’s then down to the perfumer to have a good knowledge of these alternatives.

H2S: Hydrocarbons, alcohols, esters and ketones! It can be quite confusing for the self taught perfumer with no previous experience in chemistry. Could you suggest a systematic approach to understanding these elements better to help with their compounding? What approach do you teach your students?

Andy: Our students have to know a number of different types of organic compounds for their course, so I’ve put together something of a ‘cheat sheet’ for them to help them memorise the different ones. Being able to recognise these groups in a molecule is a very important factor in organic chemistry, because it determines a multitude of different information, such as the name of the compound, as well as its properties.

When our students are first introduced to organic chemistry, we’ll start out drawing and naming the simplest of these, and gradually work towards more complex molecules as they progress. I always like to throw in contextual uses of the compounds they’re drawing as well to try and help them remember!

H2S: In your opinion as an educator, what is the benefit to a perfumer in understanding organic chemistry and therefore the chemistry of essential oils and aroma chemicals?

Andy: Whilst as a perfumer it might not be necessary to be able to interpret the chemical structure of a particular molecule, being able to recognise functional groups in a molecule can sometimes tell you a little about the type of aroma it possesses. Functional groups are basically specific arrangements of atoms within an organic molecule that give it its reactivity, and can also influence its aroma. For instance, molecules containing an solely an ester functional group can often have quite pleasant, fruity smells, whilst compounds with an aldehyde functional group can also be very fragrant. It’s not always that simple – there are some horrible smelling esters! – but I could certainly see how having that knowledge could be beneficial for a perfumer.

H2S: Why do you think so many people are afraid of chemistry?

Andy: I think it could partly be down to a lack of context when they’ve studied chemistry in the past? A lot of the content in textbooks is largely removed from context, or provided with a few limited contextual examples. Whilst it’s not necessary to understand the content, I think it does help in appreciation of the wider applicability and relevance of chemistry when you’re actually able to link it to your daily life. Pupils learn about methods for extracting metals and crude oil, which are obviously important parts of modern society, but aren’t really something they can directly relate to.

The plethora of ‘chemical free’ sloganeering in marketing doesn’t help the reputation of chemistry either. ‘Chemical’ has become something of a tarnished word, with sinister and unpleasant implications. Whilst I think the majority of people probably do have an appreciation that everything is made up of chemicals, for some the use of the word ‘chemical’ still instantly brings to mind those negative connotations. That’s something I hope that the Compound Interest site is making progress with, but it’s only a small corner of the internet, so I think there’s still a long way to go to escape the ‘chemicals = bad’ association!

H2S: Are you working on anything to help the self-taught perfumer better comprehend chemistry?

Andy: I’ve actually been working on a graphic looking at the key components in essential oils for a little while now – the trouble is trying to fit all the compounds on in a way that they’re still visible without a ridiculous amount of zooming in! At this stage I think I’m probably going to have to consider splitting it up into a series of graphics – but I’m hoping it’ll provide a bit of insight into the chemical structures behind a variety of fragrances.

H2S: Freaking finally!!! I can’t wait!

I would like to thank Andy for making chemistry something fun for me, for breaking down molecular concepts and turning them into a visual that I can use as a mental map during olfactory training, categorising and combining that form the heart of this never ending process of learning perfumery.

If you aren’t yet familiar with Andy’s really cool graphics and want to know where to start to get your feet wet, I would recommend checking out the infographics describing the Scent of the Sea, the Aroma of Chrismas Trees and the Aroma of Fresh Cut Grass.

Have a wonderful week!


* An earlier version of this post stated incorrectly that Andy is a professor.



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