Nov 2, 2022
Hello everyone,

I am studying Schiff bases in consumer fragrance and their potential for coloration. I was wondering if there are any pH conditions required for the formation of Schiff bases (for example, hydroxycitronellal and methyl anthranilate to form aurantiol). Would this type of reaction only work under basic conditions or will it work in acidic conditions ? Would a Schiff's base reaction occur in a conditioner for example, where the pH is around 3.5-4.0?

Looking forward to your replies! Thank you! :)
 

pkiler

Basenotes Plus
Basenotes Plus
Dec 5, 2007
Acid is often used as a catalyst for encouraging reluctant schiff base reactions to occur. Many schiff bases would still likely form in slightly basic blends.
 
Nov 2, 2022
Thank you for your response. So for the formation of aurantiol, which is quite readily formed when both hydroxycitronellal and methyl anthranilate are present in the mixture, it would be safe to say the reaction would occur faster than usual in an acidic medium
 

pkiler

Basenotes Plus
Basenotes Plus
Dec 5, 2007
Ye
Thank you for your response. So for the formation of aurantiol, which is quite readily formed when both hydroxycitronellal and methyl anthranilate are present in the mixture, it would be safe to say the reaction would occur faster than usual in an acidic medium
Yes, Probably.
 

LaFou

Super Member
Sep 18, 2022
And what will be the medium of scent release here? is it skin or moisture
just to try to follow wigh you guys

im not sure if if it was meant that the acid will be the release medium
 

pkiler

Basenotes Plus
Basenotes Plus
Dec 5, 2007
And what will be the medium of scent release here? is it skin or moisture
just to try to follow wigh you guys

im not sure if if it was meant that the acid will be the release medium
When making only a schiff base, the acid catalyst is a very small amount, and just evaporates out when the water condenses after making the schiff base molecule.
 

LaFou

Super Member
Sep 18, 2022
When making only a schiff base, the acid catalyst is a very small amount, and just evaporates out when the water condenses after making the schiff base molecule.
Ah okay, so the scent molecule will be enveloped and then after the medium of release will be the skin or moister!
thank you Paul 🙏🙏
 

chyprefresh

Basenotes Dependent
Jan 15, 2018
I made two more Schiffs bases, one I call Bergamate (Bergamal + Methyl Anthranilate) it's a rosy lemon with a bergamot-y moiety, very lovely. And the other Triplal + MA (Vertosine) is a super grassy tenacious orange blossom, very unique and useful for getting a long lasting grass note which is seldom found.
 

LaFou

Super Member
Sep 18, 2022
I made two more Schiffs bases, one I call Bergamate (Bergamal + Methyl Anthranilate) it's a rosy lemon with a bergamot-y moiety, very lovely. And the other Triplal + MA (Vertosine) is a super grassy tenacious orange blossom, very unique and useful for getting a long lasting grass note which is seldom found.
Niiice! I can imagine the smell already, I will try to make it 👍
 

pkiler

Basenotes Plus
Basenotes Plus
Dec 5, 2007
Some Schiff bases are solids, many as liquids are quite thick or viscous, many are very strong.
Dilute as you see fit... or not.
 

LaFou

Super Member
Sep 18, 2022
Some Schiff bases are solids, many as liquids are quite thick or viscous, many are very strong.
Dilute as you see fit... or not.
Indeed, I wanted to be sure, was worried that the ethyl will affect the scent release of the encapsulates!
I’ll dilute for sure , much easier to work with always!
thank you Paul
 

chyprefresh

Basenotes Dependent
Jan 15, 2018
Indeed, I wanted to be sure, was worried that the ethyl will affect the scent release of the encapsulates!
I’ll dilute for sure , much easier to work with always!
thank you Paul
I'm probably just being extra cautious here but I actually don't recommend diluting Schiffs bases in ethanol as it is more prone to absorbing water which I believe can reverse some of the reactions, DPG IPM or BB is probably your best bet.
 

mnitabach

Basenotes Dependent
Nov 13, 2020
I'm probably just being extra cautious here but I actually don't recommend diluting Schiffs bases in ethanol as it is more prone to absorbing water which I believe can reverse some of the reactions, DPG IPM or BB is probably your best bet.
Totally agree! I've seen direct evidence of some schiff bases hydrolyzing in EtOH dilution over long periods of time. DEP works great as a schiff base diluent.
 

chyprefresh

Basenotes Dependent
Jan 15, 2018
Totally agree! I've seen direct evidence of some schiff bases hydrolyzing in EtOH dilution over long periods of time. DEP works great as a schiff base diluent.
Another issue with diluting in ethanol unless it is necessary is that it is prone to evaporation more than the other carriers, every time you open it to use it a little ethanol evaporates, over time you will have a stronger concentrate.
 

LaFou

Super Member
Sep 18, 2022
I'm probably just being extra cautious here but I actually don't recommend diluting Schiffs bases in ethanol as it is more prone to absorbing water which I believe can reverse some of the reactions, DPG IPM or BB is probably your best bet.
Oh thank you, I would have went the opposite way entirely! I have Dpg, IPM and BB! I’ll dilute small quantities Always for formula uses, better this way I think!
 

LaFou

Super Member
Sep 18, 2022
Another issue with diluting in ethanol unless it is necessary is that it is prone to evaporation more than the other carriers, every time you open it to use it a little ethanol evaporates, over time you will have a stronger concentrate.
But ethanol in general maintain a better dilution than others like DPG, i found that DPG in time alters the original scent of the materials! I had hands on experience with that! Especially when you introduce it in a concentrate mix! I might be wrong, that was my take.
I prefer always to dilute in Ethanol unless it requires not to, like what you shared on the shiff base 🙏🙏
 

mnitabach

Basenotes Dependent
Nov 13, 2020
Hi all, hope your staying well and healthy,
I know it’s a different topic, but I want to ask, are tincture worth doing!? I mean if your not in natrual perfumery and consistency is not your main concern, wouldnt tinctures be counter productive?
for Shiff bases, you can have an acurate result, but I feel tincture or better yet, home or non lab tinctures might not be the best option! i dont mean to say it’s bad to do it, but unless I have a supper rare ingredient, like ambergris, is not ideal to do so, right? Better buy reliable consistent materieals! Which are affordable in the large range of it!
The time for tincture and effort feels better spent somewhere else!
maybe I’m wrong, and there is a way to have consistent materials by doing it outside a lab, and thus I came here to ask, thanking you in advance 💚
It's worth considering whether it's a good idea to post completely different topics not even remotely relevant to an existing thread like this, as opposed to finding relevant existing threads to post in or starting a new thread.
 

LaFou

Super Member
Sep 18, 2022
It's worth considering whether it's a good idea to post completely different topics not even remotely relevant to an existing thread like this, as opposed to finding relevant existing threads to post in or starting a new thread.
Done, I’ll delete and create new thread! As long as you stay happy 😊

#TheThreadCrasher #NoMore
 

polysom

Basenotes Junkie
Apr 4, 2021
If you want to learn more about a specific chemical reaction, it is always helpful to sketch the reaction mechanism. I made a quick drawing about the schiff base reaction.
schiff-base.jpg

You can see that the amine and the aldehyde (or ketone) react to an intermediate and the proton of the acid (H+) helps to release water from the intermediate which then forms the schiff base. This would also work without the acid, if the (purple) H and the (black) OH of the second intermediate step do form water, but this is more unlikely to happen and therefore slower.
 

polysom

Basenotes Junkie
Apr 4, 2021
When making only a schiff base, the acid catalyst is a very small amount, and just evaporates out when the water condenses after making the schiff base molecule.
When you say an acid evaporates, it sounds like acids are volatile compounds. But an acid is ionic and therefore not volatile. But I assume you meant something else.
 

Alex F.

Basenotes Junkie
Nov 29, 2019
When making only a schiff base, the acid catalyst is a very small amount, and just evaporates out when the water condenses after making the schiff base molecule.
When you say an acid evaporates, it sounds like acids are volatile compounds. But an acid is ionic and therefore not volatile. But I assume you meant something else.
😵‍💫
 

pkiler

Basenotes Plus
Basenotes Plus
Dec 5, 2007
When you say an acid evaporates, it sounds like acids are volatile compounds. But an acid is ionic and therefore not volatile. But I assume you meant something else.
Some acids are certainly volatile.
I use acetic acid in selected perfumes.
 

Thioacetone

Super Member
Sep 7, 2022
When you say an acid evaporates, it sounds like acids are volatile compounds. But an acid is ionic and therefore not volatile. But I assume you meant something else.
o_O😮😮😮😮


Acids are indeed volatile, my friend. I suggest you do not try inhaling vapors from glacial acetic acid for instance, unless you enjoy a strong burning sensation in your nose.

Vapor pressure at 20-25 deg C:
Acetic acid 2.1 kPa
Butyric acid 0.43 kPa
Hydrochloric acid (30%) 1.41 kPa
 

Thioacetone

Super Member
Sep 7, 2022
I use acetic acid in selected perfumes.
Interesting.
What kind of concentration do you use it at, and what do you find it does?
I have experimented with using carboxylic acids in perfumes - acetic, propanoic, 2-methyl butyric, 2-methyl pentanoic, isobutyric acids. I find they tend to be very short lasting (i.e. top note). The longer/branched acids seem to last somewhat longer (but still < 30 min)

I wonder to what extent esterification (with ethanol) is occuring if carboxylic acids are added to perfume.
I don't think it seems to be happening to a great extent/rate. Probably because of the lack of catalyst

I want to get hold of some butyric acid to see if it could be used in a very small % to add something to a perfume.
I tried making my own by hydrolysing butter, which did make butyric acid but not high enough quantity or purity
 

Quay Limey

Basenotes Junkie
Nov 1, 2020
That sounds nasty 😝 I have no clue.
heh

Yeah it is a bit nasty, but so is the donor material.

The name I used was incorrect - I called it Ekchuajia, after the Mayan merchant deity Ek Chuaj. The AC was cocoa hexenal. The result is very a powerful version of that with the obvious orange blossom aspect. Quite unusable as it brings the smell of wet dog to the perfume - disgusting!

Some work, some don't.
 

Alex F.

Basenotes Junkie
Nov 29, 2019
On that topic, I wish to apologise to all for making comment on the forum when very drunk on Thursday evening/Friday morning. I need to stay away from the internet when in that state.

I was..uh... testing rum for perfumery purposes etc.
If I'd had to take a breathalyser each time I wrote a post here, there wouldn't be quite as many of them. Waiting for or going by the underground on the way home on a weekend night, ... And oh, what I would have written sometimes in answer to the usual nonsense from some of the folks on here, if my better nature hadn't taken over. 😅 (By the way, I'm waiting for the tube right now and it's still 7 mins out.)
 

polysom

Basenotes Junkie
Apr 4, 2021
o_O😮😮😮😮


Acids are indeed volatile, my friend. I suggest you do not try inhaling vapors from glacial acetic acid for instance, unless you enjoy a strong burning sensation in your nose.

Vapor pressure at 20-25 deg C:
Acetic acid 2.1 kPa
Butyric acid 0.43 kPa
Hydrochloric acid (30%) 1.41 kPa

Sorry that I have to be a bit offtopic and boring now, but I think you didn't quite understand what I meant.
To better understand this, you need to look at what was used to determine the vapor pressure you found there. The vapor pressure was determined with high purity CH3-COOH (in this form the term hydrogen acetate would fit better). Highly pure means without traces of water or other impurities. In this form, hydrogen acetate is an organic molecule like any other. Of course, one can determine a vapor pressure from it.
But I was talking about the acid in the reaction mixture. By definition, acids are characterized by the release of protons (H+), for example to water. This happens automatically with acetic acid, because acetic acid is hydrophilic and therefore always contains some water. These are then present in the Schiff base mixture when the acid is added. And in there, the vapor pressure then only plays a subordinate role, because the acid is in equilibrium with its dissociated form and the proton interacts with whatever is in the mixture. Of course, you can still smell the acetic acid, but that does not mean that the acid is volatile (the hydrogen acetate is). You can easily check this yourself: Take a pot and add some distilled water. Measure the pH value. It should be around 7. Now add a little acetic acid. Measure the pH value again, it should be 4-5. Now boil the whole thing, 10 minutes, 15 minutes, whatever, it doesn't matter. Let everything cool down (important!) and measure the pH again. You will see that it is still in the range of 4-5.
 

Thioacetone

Super Member
Sep 7, 2022
Sorry that I have to be a bit offtopic and boring now, but I think you didn't quite understand what I meant.
To better understand this, you need to look at what was used to determine the vapor pressure you found there. The vapor pressure was determined with high purity CH3-COOH (in this form the term hydrogen acetate would fit better). Highly pure means without traces of water or other impurities. In this form, hydrogen acetate is an organic molecule like any other. Of course, one can determine a vapor pressure from it.
But I was talking about the acid in the reaction mixture. By definition, acids are characterized by the release of protons (H+), for example to water. This happens automatically with acetic acid, because acetic acid is hydrophilic and therefore always contains some water. These are then present in the Schiff base mixture when the acid is added. And in there, the vapor pressure then only plays a subordinate role, because the acid is in equilibrium with its dissociated form and the proton interacts with whatever is in the mixture. Of course, you can still smell the acetic acid, but that does not mean that the acid is volatile (the hydrogen acetate is). You can easily check this yourself: Take a pot and add some distilled water. Measure the pH value. It should be around 7. Now add a little acetic acid. Measure the pH value again, it should be 4-5. Now boil the whole thing, 10 minutes, 15 minutes, whatever, it doesn't matter. Let everything cool down (important!) and measure the pH again. You will see that it is still in the range of 4-5.
Duuuude. This makes no sense.

What on earth does boiling of acetic acid and water have to do with anything? The pH doesn't change because their boiling points are similar so they will both boil off at around the same temp.
 

Citroasis

Super Member
Jul 24, 2021
Sorry to dig up and old thread...but I had a question on Scfiffs Bases.

I know most of you are making your own Schiffs base blends as a separate base (only combining the 2 materials at the right molecular proportions), but my question is more geared for unintentional schiffs bases forming on a full perfume formula if the said formula happens contains Methyl Anthrilate.

As an example....If a full perfume formula contains lets say 2ppt of Methyl anthrilate and 18ppt of Vanillin. Even thought these 2 proportions are not the exact required ratio to form an 'intentional Schiffs base', would it still likely change the perfume over time and a "slight" schiffs base occur?

Ive always been hesitant to use Methyl Anthrilate in any of my perfume blends at all, in fear of unintentional schiffs forming. But I thought id ask because I want to break that fear of using it.
 

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