Sciencemadness Discussion Board

Synthesis of Natural Smells

ScienceBum - 8-12-2015 at 12:21

Hey all, I was having a discussion with a chemist friend of mine about how some natural smells can be produced in the lab. I'm told that it's an incredibly difficult not-worth-it venture requiring knowledge of complex organic chemistry, but I was wondering if anyone here was familiar with any smell syntheses you could do in a home lab?

In particular I am interested in isolating the smell of various fruits such as strawberries(my personal favorite), apples and oranges. I do know that for strawberries there is a compound that emulates some of the many compounds responsible for their smell, called furaneol but I have been unable to find very much information on it's synthesis.

So if you guys know of any information regarding this subject, like if it is completely beyond the capabilities of a home lab or if you need special equipment or anything, please let me know! and thanks!

Detonationology - 8-12-2015 at 12:29

"Oil of Wintergreen" (methyl salicylate) is a very popular ester for high school chem labs. It can easily be made by esterify-ing salicylic acid with methanol in an acidic solution. There are thousands of different smells that can be synthesized in the lab. Start with this table, pick a smell, then research the synthesis.

imgres-1.jpg - 14kB

Volanschemia - 8-12-2015 at 13:20

Here's a link to that photo (it seems a bit small) and another similar table

ScienceBum - 8-12-2015 at 13:38

Ah thanks guys, I appreciate that :) Just out of curiosity though, wikipedia says that there's over 80-something compounds responsible for various fruit smells and flavors and that table only lists one ester per fruit from what I can see. Is this basically the equivalent of comparing food flavoring additive to the actual food, or are these compounds the "main" ones responsible for the smell?

aga - 8-12-2015 at 14:07

Quote: Originally posted by Detonationology  
"Oil of Wintergreen" (methyl salicylate)

Methyl salicylate is an excellent Fischer Esterification to do.

The starting reagents smell completely different to the end product (smells like listerine mouth wash) so you have an easy indication if it worked or not.

I did this version (there are several) :-
https://www.youtube.com/watch?v=lJLP2bcXDqY

Obviously, never stick anything you made in your lab in your mouth.

Ingesting 7g of this will kill you (same as sailicylic acid).

Smelling the mintiness is fine, just not all day long.

[Edited on 8-12-2015 by aga]

aga - 8-12-2015 at 14:18

Quote: Originally posted by ScienceBum  
Ah thanks guys, I appreciate that :) Just out of curiosity though, wikipedia says that there's over 80-something compounds responsible for various fruit smells and flavors and that table only lists one ester per fruit from what I can see. Is this basically the equivalent of comparing food flavoring additive to the actual food, or are these compounds the "main" ones responsible for the smell?

If you think about it, human taste buds and olfatory receptors cannot be sensitive to every single chemical (e.g. Nitrogen) and so there is a Limited range of chemicals they can detect.

The human 'Taste' and 'Smell' range is still enormous, as our detection apparatus combine the levels of the detected chemicals into a mixed signal, based on the amount of each compound detected.

[Edited on 8-12-2015 by aga]

diddi - 8-12-2015 at 14:25

make skatole :)

aga - 8-12-2015 at 14:57

Not.

Cadverene.
Butyric acid et al ...

You're being capricious diddi.

Amos - 8-12-2015 at 18:43

I just made benzaldehyde recently, and its smell is EXACTLY like almond extract, really lovely stuff.

diddi - 8-12-2015 at 21:38

I though with a name like "ScienceBum", that skatole was appropriate. if I seem capricious, then I had best increase my bipolar meds. I don't want to be all up and down over Christmas :)

UC235 - 8-12-2015 at 23:06

Quote: Originally posted by Amos  
I just made benzaldehyde recently, and its smell is EXACTLY like almond extract, really lovely stuff.


There's a reason for that. Essential oil of bitter almond (once treated to remove residual HCN) and it's synthetic equivalent used as almond extract are pure benzaldehyde.

Acidum - 10-12-2015 at 12:37

Quote: Originally posted by ScienceBum  
Ah thanks guys, I appreciate that :) Just out of curiosity though, wikipedia says that there's over 80-something compounds responsible for various fruit smells and flavors and that table only lists one ester per fruit from what I can see. Is this basically the equivalent of comparing food flavoring additive to the actual food, or are these compounds the "main" ones responsible for the smell?


Mostly, as aga said, we mix several chemical levels (concentrations) into one specific "aroma". Stated esters are just like You said "the main ones", althought I can recall several compounds that smell like very specific fruits and flowers but that are not present in them.

If you wish, in about two weeks I will be able to dig up through my older scripts from Bioorganic chemistry, and to sniff some sniffable stuff... :D

Alzador - 10-12-2015 at 13:27

Quote: Originally posted by Amos  
I just made benzaldehyde recently, and its smell is EXACTLY like almond extract, really lovely stuff.


How did you manage to make benzaldehyde? What method did you use?

Amos - 11-12-2015 at 10:44

Quote: Originally posted by Alzador  
Quote: Originally posted by Amos  
I just made benzaldehyde recently, and its smell is EXACTLY like almond extract, really lovely stuff.


How did you manage to make benzaldehyde? What method did you use?


I used potassium chlorochromate, which only oxidizes alcohols to the aldehyde and not a carboxylic acid, to oxidize benzyl alcohol.

Conveniently, there's a YouTube video on the very same oxidation: https://www.youtube.com/watch?v=WaZm8vmPSr4

MrMario - 20-2-2016 at 09:00

Are molecular sieves (4A) suitable to drive the equilibrium even more to the ester side when making benzoate esters and do they react with H2SO4?