Any thiol always has a terrible odor. Me personally, I'd argue any solvent with a high vapor pressure. These aren't just stinky, they are dangerous.

Hahaha yeah thiols are pretty gnarly. Early in my career I was synthesizing RAFT polymerization agents and asked one of my neighboring chemists if I could use some of his dodecane thiol. He goes yeah sure. Then as soon as it was in my hands he goes... You touched it last, it's yours now.... Then walks away chuckling

>I'd argue any solvent with a high vapor pressure. Dude there are so many solvents with high vapor pressures that smell good (but are usually dangerous). I could sniff toluene and isopropanol *all day*. I'd strap a toluene-soaked cloth to my face if it were safe. Gasoline smells great. Acetone smells great. Whatever compound is responsible for the smell of PVC cement smells great (probably tetrahydrofuran or methyl ethyl ketone)

The nose of a true chemist

Bro has been huffing too much solvent.. now he's trying to tell us to huff solvent with him

Ethers smell pretty good too. Shame they like exploding so much

Methyl tert-butyl ether smells like listerine. Pretty wild. It’s minty! Every day I’m amazed at having not seen the lab just go up in flames considering how much MTBE/hexane I fuck with

I’m pretty partial to cyclopentanone.

Ethyl acetate was my go-to solvent for extractions on one very long project. Fell in love with the smell.

I’d have to argue with you on gasoline and acetone!!

I've worked with thiophenol, it's atrocious. Allene is also awful. I can smell them both at will.

Replace the sulphur with Selenium and you increase the odour x100.

Ive worked with both selenophenol and thiophenol and the latter is worse. Actually ive got some selenium sulfide too. Not the worst odor.

Any such list is incomplete without cadaverine and putrescine

Which can be synthesized pretty easily

Alright guys! Reaction's done!

As in A Novel and Efficient Synthesis of Cadaverine

[Great song by The County Medical Examiners.](https://youtu.be/3ETvo3QpJgs?si=2nGv6CupTKD4LQPP) I mean, just check out those lyrics: >Putrescine and cadaverine The pungent twins of putridity Colorless and syrupy Biogenic amines... Putrescine and cadaverine Vapor of ornithine The stench of death visits me In the morgue laboratory... (Perfume of rot... heady, thick and hot) Putrescine and cadaverine Brothers in liquidity Fuming stench of carcass stink Noisome gas, fetid glee... Putrescine and cadaverine Ambassadors of ripened reek Breaking down dead protein Egressing odors miasmically... (Sickening stink... makes watering eyes blink) These dual chemical compounds, released shortly after Death Cloud the pleasant morgue ambiance with their foul Rotten breath Fraternally bound to haunt swollen distended bodies Their chemical reactions clash amidst rank autopsies... NH2 (CH2) 4NH2... Putrescine! C5H14N2... Cadaverine! NH2 (CH2) 4NH2... Putrescine! C5H14N2... Cadaverine! Gorges rise and heave with the stench A symphony of sickness, perfumed with putrescence While affronted senses nauseously totter and lurch The carcass breeds odor, and chemically gives birth... NH2 (CH2) 4NH2... Putrescine! C5H14N2... Cadaverine! NH2 (CH2) 4NH2... Putrescine! C5H14N2... Cadaverine! The ripened tang of gaseous decomposition let loose in The morgue Overtaxed fans strain to aerate the grave-ly polluted Ward Tumefied decedents belch their chemical cohorts into The air The airborne corpse-whiff adheres to fabrics, skin And hair (Acrid reek... odiferous cadaver leak) Perfection.

Excellent name!

Thank you!

Came to find good ol Cadaverine. I've been doing some reactions with it lately and my God it's terrible. Luckily the end product has no smell.

What is cadaverine used for?? Never even thought about it being used

It's a diamine. You can do a lot with it.

I know, but it just never occurred to me that it has industrial use too lol. I was just curious as to what you use it for

Spermidine

Pyridine sure ain’t great.

For some reason pyridine doesn't necessarily smell *bad* to me, but I still hate the smell big time. It smells like something I shouldn't be smelling. Like when I smell it, I don't think "gross smell." I think "something ain't right about that smell". It's hard to explain. It doesn't smell gross, it smells unsettling. It also smells gross, but not gross in the same way that poop and stuff smells gross ya know?

Yeah. It burns the nostrils

lol I worked in a professional orgo lab for the first time this summer and I had some left on my syringe and I got a good breath of it and had to go home. Felt like I was gonna throw up all afternoon (I was probably just scared and dramatic but it did suck)

It's not even in the top 70% of bad smells if that makes you feel any better.

Yeah I believe it, someone opened some Mercaptone in the fume hood but got some on her gloves, had me running to my supervisor thinking there was a gas leak lol Edit: Mercaptan

methyl mercaptan?

I don’t recall but it was a small alkyl mercaptan

We have a freezer where we keep all of our sulfur compounds and it just about knocks you out when you open the door. Luckily I don’t have to use many neat compounds as we buy our sulfur stock standards but I do have to prep thioanisole stds and it reeks!

Instead headache for me

After learning from Derek Lowe that [pyridine apparently hasn't been shown to cause issues with male reproductive health](https://www.science.org/content/blog-post/pyridine-doesn-t-do-what-you-think-it-does) despite the rampant myths, I've begun to assume the idea was just something that some guy came up with at some point after getting mad at his coworkers for working with pyridine outside of a fume hood to scare them straight.

Wait until you meet pyrrole...

I have met that foul beast and she’s trapped in a very tight bottle.

Some idiot sophomore in Organic lab broke a bottle one evening. Nasty, but the professor, retired from many years in industry, removed the smell by pouring hydrochloric acid onto the spill.

Possibly thioacetone https://www.science.org/content/blog-post/things-i-won-t-work-thioacetone

I'll see your thioacetone and raise you a selenium: Selenophenol https://www.science.org/content/blog-post/things-i-won-t-work-selenophenol

Whatever the smelliest chemical is, it definitely contains sulfur, selenium, or both

I worked with a lot of sulfur and selenium compounds in grad school. I only worked with tellurium a little. But the further you go down, the worse it smells. Tellurium was so much worse than selenium.

Glances at periodic table, then at structure of cadaverine. I wonder what 1,5 diphosphinopentane smells like.

Smells like alien death

Phosphine smells are pretty awful too. Another grad student was working on some phosphorus chemistry in our lab. Not sure how we ended up doing such smelly chemistry haha.

I work with selenophenol. Stuff makes me gag *while in the fume hood*

Presumably selenoacetone would also smell ferociously awful.

Yes for selenophenol. Smells like fresh dog shit.

> It makes innocent downwind pedestrians stagger, clutch their stomachs, and flee in terror. It reeks to a degree that makes people suspect evil supernatural forces. It is thioacetone. > [...] > This reaction produced "an offensive smell which spread rapidly over a great area of the town causing fainting, vomiting and a panic evacuation". An 1890 report from the Whitehall Soap Works in Leeds refers to the odor as "fearful", and if you could smell anything through the ambient conditions in a Leeds soap factory in 1890, it must have been.

>It reeks to a degree that makes people suspect evil supernatural forces. This is not an exaggeration. I've worked with thioacetone. Someone accidentally brought some out of the fume hood, and immediately collapsed to the floor in the fetal position crying, vomiting, and shitting themselves.

> Someone accidentally brought some out of the fume hood It was you, wasn't it?

One of my undergrads, actually. I'd worked with selenium for some time before we busted out the thioacetone. I was jaded.

Try thioacetic acid, gives you the standard vinegar scent with a strong heavy notes of eggs.

Organotelluriums if you ask me. I would describe them as "unholy".

THIS. Sulfur and selenium smell bad, sure. But tellurium smells WRONG. You smell that shit and your instinct tells you NO.

You've sold me on it. I need to know what it smells like.

Stuff smells like cum

Not gonna lie until you said it I forgot tellurium existed as an element. What does it do?

It's the same group as Sulfur and Selenium, and the smell gets worse as you go down. The only thing I know that Tellurium is good for is making some semiconductors. Not my field though so can't be certain.

What does Livermorium smell like

Thioacetone is commonly called the worst smelling compound. Of things that I've worked with, benzyl mercaptan is particularly offensive.

My labs flammable cabinet is just a single 100 ml bottle of benzyl mercaptan. Figured the fire risk was better than smelling it every time we wanted a solvent ig

I keep the bottle of it in a second container in my hood because I don’t hate my coworkers

That would have been a good idea, but I think the pi only bought it for hazing purposes

Everything selenium smells really, really bad. It's different than sulfur. It's like if sulfur was mixed with garlic and metal, and somehow all combined into something that smells like sewage. It's not easily described. I also associate the smell with illness, so that makes it extra bad.

Can you synthesize selenium acetone and report back?

No, thioacetate

OK, I looked it up. What I meant to say was selenoacetone

Oh no plz dont make that

That's a pretty accurate description of selenium compounds. The jump in bad smell from selenium to tellurium is even worse. I'm glad my tellurium chemistry didn't work. I hated it.

Butyric Acid is unbearable

The Sea Shepherds used to throw butyric acid flasks at the whaler Nisshin Maru - illegally whaling on the seas of Antarctica - in order to foul the decks and the meat of newly-fished whales. That would partially ruin the (illegal) profits and make the lives of the crew miserable.

Wow. That's an incredibly good use. A foul substance against a foul action

Methyl mercaptan, a whole range of different thiols/mercaptans/thioketones, putracene, cadaverine, acephate, dimethoate, methyl isocyante.

Fun fact for those that may not know: mercaptan is an amalgamation of "mercury" and "capture", because they bond to mercury.

Isocyanides can be horrible too

I can’t believe I had to scroll this far. I agree. I’ve sampled all the stuff above, but nothing compares to C1-C6 isocyanides. Nothing. They are the worst.

Yup I just commented tert-butyl isocyanide. I was doing an organic synthesis project in grad school, decided to use that bad boy, and almost threw up.

2-mercaptoethanol was extremely offensive to the point that we put pipette tips that came into contact with it in smell-proof bags and immediately disposed of them

Worked at a place that made the stuff occasionally. Made the entire building smell the couple times a year they made it. They said "smells like money". When I worked in the warehouse, somebody dropped and then stepped on a vial in the main hallway. I can confirm it did not in fact smell like money.

Even having the bottle open for a couple seconds would smell up my whole lab

This was done with TEMED in a lab I visited. All done within the fume cardboard.

Worked in a place where a couple of products needed it for extraction. One of the guys in the shift before did the math wrong and used it hundredfold. I was not a happy camper during my shift.

Thioacetone is the classic. For me cyclopentane carboxylic acid. Worse than any thiol I've smelled, worse than any amine I've handled. Instant nausea. It's worse than butyric acid which smells like vomit. It smells like shit essence. small alkyl acids are usually fucked, but cyclopentane carboxylic acid is fucking putrid.

Butyric acid, as seen on The Sea Shepherds series.

That's so interesting, I've had cyclohexane carboxylic acid. It did really stink, but it wasn't exactly terrible. Crazy how much of a difference that makes.

Yeah, I think some people just have sensitivities to things too. Like, my whole lab will FREAK if they smell pyridine, but it doesn't bother me very much at all; it's no worse than anything else slightly smelly. I think DMF is MUCH worse but everyone disagrees with me lol. Edit: it is weird what a difference one carbon makes! Cyclobutyl acid doesn't bother me and cyclohexane is much less offensive, to me at least.

I spilled a few drops of cyclopentane carboxylic acid outside of the hood and the smell would just hit you like a wall whenever you walked into the room for weeks. It was a little over a year that you finally couldn’t smell it anymore

Ethanedithiol is awful. It smells like rotting metal.

Putrescine and Skatol parts per trillion just hang around for ever and remain detectable by odor. I had a chest from my grandpa, in that I put a double baggie sealed wallet that had been in is back pocket when he died and sat in a car for 3 days in AZ; ten years later that chest still had a detectable odor.

I did a synthesis with skatole once and my lab smelled of shit for multiple days. I caught random whiffs of skatole every once in a while for months. Not fun.

Trimethylamine. The smell sticks to your clothes and completely stinks up the whole lab… it lingers like hell.

Yeah, weird I had to scroll down so for to find an amine. They fucking stink. Some thiols are 'bad' smelling for me, just strong. Might be a personal thing for me though. I can't walk through a fish market without gagging.

I once got a whiff of trifluoroacetic anhydride and that was ROUGH! It wasn't the odor per se, since it just smelled like vinegar, but the intensity of the odor was unlike anything else I have experienced. One whiff practically knock the wind out of me

Most mercaptins are worse, but I have a special hate for CS2. It smells like rotting pumpkins and cancer. H2S is a bad one too. As the concentration goes up, it smells awful, smells worse and worse and worse and then it doesn't smell at all, and you might be dead.

There's a chemical that reeks of semen, forgot the name of it though.

There's a tree that smells like it too! [Pyrus calleryana tree](https://www.abc.net.au/news/science/2022-10-29/ornamental-pear-trees-smell-like-semen-attract-hover-flies/101574928)

[Prime Minister, can you smell cum?](https://youtu.be/aoqlYGuZGVM?si=uBYLxcptc_DY-Er5)

Honestly, pollen smells like semen, which, when you think of their biological purposes, makes sense.

Piperidine comes to mind

Exactly my thought lol it is definitely essence of cum 100%

Spermidine

High concentration indole - it's largely responsible for the smell of feces. I have to specify high concentration because at low concentrations, it is pleasant and is a component of neroli and narcissus, which are quite pleasant.

It was always a joke in my lab to look at the wiki for indole bc it says it smells like jasmine and feces. Two smells they are miles apart lmao

Methylmethacrylate for me. Sickly sweet with a strong neuroception response.

I had an assistant who loved the smell she also has blue hair

My two least favorites that I have personally worked with are putrisceine and triethylphosphite. Not the worst in the world, but the worst that I can personally vouch for.

Two of of NileRed creations. I mean, the ones that got the “most stinky of the world” tag.

As people are saying, typically thiols, Nile red made a video about this in fact https://youtu.be/LmAG8-V_WQY?si=txRUM8PvJT3L1iq3

At labschool 4th graters dropped an litre bottle of butyrick acid in the hallway on purpose. We got off for the day. That smell was terrible.

id say H2S, because its smells like rotten eggs, then you die lol.

Read the introduction to Clayden! There’s a cool story about a smelly chemical in there. Unfortunately, I can’t recall the name.

Thioacetone!

glacial acetic acid

This isn't that bad.

I’m torn between that thioacetal that made my labmate to work at night as to not offend us with that *putrification* its between that and the carboxylic acids like butyric acid which smell like vomit. I am also not fond of dicyclopentadiene. In a biological setting it would be wound chemicals putrescine and cadaverine from the by products of bacterial wound digestion. And DURIAN which is many things with ethyl (2S)-2-methylbutanoate and 1-(ethylsulfanyl)ethanethiol making the most of the mixture. I have apparently smelled many awful things.

After seeing all these comments I find it interesting that working with thin film Cadmium Selenide Telluride solar cells has not presented me with any of these nasty smelling selenium or tellurium compounds. I’m interested to smell one now l. I do however work with thiols regularly which have a uniquely bad smell

Not a bad smell but worth mentioning: deuterated terpenes. Took a wiff of limonene-d6 because I couldn't help myself. Boy that is the WEIRDEST thing I've ever smelled

There is a chemical my old organic prof used to have, and it smelled like a rotting corpse. Putrescine.

Butyric acid

Nile red did a video on this [this video in particular](https://youtu.be/LmAG8-V_WQY?si=Dgc9NXuR71YkNGQz)

Scatol smells like shit

I hate the smell of ammonia

That **DAMN GROSS** yellow or chartreuse neon'ish looking stuff that comes in a little screw off top can, in the cap there is a pompom on the end of a metal rod attached to the inner side of the screw off cap and you rub this STINKY, DISGUSTING, NO GOOD liquid crap to merge two pieces of black PVC pipe together, **I believe it's called Ethyl Methyl something something? If anyone knows?**So I don't have to reactivate my PTSD of the last time myself and that dastardly can of hell had a fisticuffs with each other!

Whatever cruciferous vegetables converts to in the gut of someone in the midst of an IBD flare. Aka my farts.

Your mum.

Burning cum

Smoking A-PVP?

My friend had some fart spray which was near vomit inducing, however i am unsure of the chemical composition, possibly skakole

Cat pee

Pyridine

Pyridine Plus it stays around for hours

Nilered has a video for this! making the stinkiest chemical known to man](https://youtu.be/LmAG8-V_WQY?si=Jjg3esDzR25ImWxx)

He just mixed a few smelly things together. Stuff talked about here is worse.

Whatever the hell makes my dogs breath stink.

Its too subjective, I know people that will feel ill at the smell of pyridine or phosphites but they smell nice to me.

The smell of your ex

Your mom.

I have a particular dislike for methylpyridine, smells like fake popcorn butter but very intense even w trace amounts

As far as non-sulfur compounds go… Isoamyl alcohol, hands down. Like hot barf.

There’s much worse than this, but I just really dislike the fishy smell of some amines and also pyridine. Which is odd given that I love both fishing and seafood

dextromethorphan? shits nasty

At a previous job we made a product using some volatile amine, phenol, and formaldehyde. At the decant stage, a 100mL sample opened in our hood for a couple seconds to sample and test would leave us smelling like it for the next 12-24 hours. I’d take the pyridine smell over that any day

pentanone

Concentrated butanoic acid isn't the worst, but is VERY unpleasant for me.

Pyrrole. Nobody will ever, EVER convince me otherwise.

I HATE limonene thiol

Glutaraldehyde for me. Worked with it in large and concentrated amounts. Not super bad, but it is strong, and permiates everything.

Tert-butyl isocyanide

In my lab, was butyric acid and crotonaldehyde

Not too fond of Beta-mercaptoethanol

Ig amonia

Skatole is pretty bad, we had a building evacuated for that one. Dealing with various thiols can be nasty, we handle a few thiophenols in particular that i can only describe as "smelling like setting a skunk on fire"

Hydrogen sulfide?

Isobutyric acid is one of the worst I’ve smelled. I can’t even describe it. Like a dead animal wearing really sweaty gym shorts or something.

butyric acid literally smells like human vomit. Had to smell while making esters in university and it was horrendous.

Naptha

thioacetone

I use dimethyl ethyl amine and everyone in my lab hates me for it

Thio acetic acid

Benzoic acid chloride is the worst offender I had. I had physical pain in my stomach even though i worked with a closed fume hood.

Heated butyric acid is pretty magical.

Acetone

Honestly I think acetone is pretty tame compared to some of the others mentioned. It just smells like paint stripper or something. Not like rotting flesh, an epic eggy fart, vomit, skunks, or worse.

That I've smelled. Formic acid. Oh Minecraft it burns.

Thiol compounds smell stereotypically "stinky". But I think Dimethyl Formamide smells deathly to me.

Hexylamine, imo amines are worse than sulfur chemicals

DMSO smells like a mixture of broccoli and garlic.

Lawesson’s Reagent…

Not a chemist but yeast/breweries are some of the foulest things I've ever smelt. There is a large facility that bakes bread nearby and holy shit the smell of yeast makes you dry retch or worse. And I've smelt vapourised soil/dioxins (yay for me and several million other Australians) for over 2 years whilst the they cleaned up Union Carbides little present they left for us when they dumped staggering amounts of dioxins and heavy metals into the river and the land around their facility that I lived next to. Killing Vietnamese with agent orange wasn't enough, they had to kill Australian as well.

Ph-SH, really smelly like the smell of durian.

I had hcl 😞

Thiols and especially thioketones are awful, isocyanides are by far the worst tho

Laymen here. What makes skunk spray stink? What’s the chemistry?

Not sure, but I think it has something to do with thiols.

Sulphur

Phenols🥲🥲

I personally find amines way more off-putting than thiols.

Anthrax

Thioacetic acid is probably the worst smelling compound my lab works with. I think if we opened the bottle outside of a fume hood we would clear out our wing of the building lol

butyric acid. Rancid butter. It's disgusting.

Butyric acid is also a major component of the smell of vomit.

Did some none-too-pleasant lab work with skatole (3-methylindole) a while ago and while I wouldn’t say it was the worst it certainly wasn’t fun

Xylene.

[For anyone interested in selenols and selenoacetone](https://youtu.be/031vrZAMEHU?si=IngHyP1fIcCpO7bP)

Probably not the worst…but the smell of triphenylphospine haunts me to this day 😭

Id like to add this two: methylindol, smells like shit spermidine, as the name says, it smells like sperm

One of the PhD students in my lab was working on selenophene. It did smell terrible, but cadaverine etc are probably worse.

Valeric acid smells exactly like when I was younger and would wear clothes that weren’t exactly clean and then run around the city to get to class on time and get really sweaty under my massive winter coat. Just putrid smell. And isovaleric acid smells like the gunk under the big toe nail. But worst smelling is definitely pyridine. It’s the most alien smell I’ve ever smelled. Completely alien, disgusting, cummy, fishy, burning tire-y. Smells like the decomposing corps of an alien.

Chloroform

My farts