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What is a schiff base?

post #1 of 21
2/23/12 at 6:43pm
Thread Starter 
Hello everyone!
I am wondering what does a schiff base do in a perfume. It is formed with methyl anthranilate I think with lilial or lyral or a few more but I have no idea what it practically does to a composition.
Also I have read somewhere that orange bloddom is created with a schiff base. Is it true? And anyone knows how to do it?
Thank you in advance!
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post #2 of 21
2/24/12 at 12:52am
How much chemistry do you have? A Schiff's Base is made by reacting an aldehyde (like Lilial or Lyral) with a compound containing an amino group (NH2). In Perfumery the most commonly used Schiff's Base is Aurantiol (made from reacting Methyl Anthranilate with Hydroxycitronellal). Schiff's Bases tend to be highly coloured, usually bright yellow to orange and have a fixative effect. They are definitely base notes. Rather difficult to make yourself as a by product of the reaction is water, which is very difficult to remove, although it is easy to see the reaction working. If you mix the two materials together in the right proportions and warm gently, you will see a change in colour and viscosity. However the product will be cloudy, due to the water. Aurantiol, and the Schiff's Bases using Lilial and Lyral, do indeed smell like Orange blossom, or Tuberose.
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post #3 of 21
2/24/12 at 1:36am
Davids answer already covers the essentials, but if you want to understand a bit more about the chemistry that is going on, you can read about it in The Chemistry of Fragrances: from perfumer to consumer by Charles Sell - its well enough written so that you should be able to cope with it even if your organic chemistry isnt that brilliant (as mine isnt).

Best of all, quite a lot of it is available on Google Books, including the section explaining Schiffs Bases in the context of perfumery and a little about the wider chemistry use of the term.

One thing worth knowing is that if you use methyl anthranilate in your blend together with an aldehyde then you are going to get this reaction taking place in the blend, albeit rather slowly: so its worth understanding whats going on. Especially as there are so many aldehydes in use in perfumery that can potentially undergo this reaction.
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post #4 of 21
2/26/12 at 1:04am
Thread Starter 
Thank you so much for your reply both!
One thing I have not understood. Should I avoid adding methyl anthranilate into my perfumes in case I know it will create a schiff base due to the fact it will create also water? Should I only use ready made schiff bases like Aurantiol and if so which are those?
Sorry about that but English is not my native language
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post #5 of 21
2/26/12 at 5:59am
I dont think you need to avoid using methyl anthranilate and in any case the reaction can occur between any chemical with the NH2 group and any aldehyde. The important thing is to understand that its going to happen.

If you allow the reaction to take place in the perfume, then the water produced need not be a problem as long as you are using sufficient ethanol that adding a little water wont result in cloudiness. For example you can do this with vanillin and methyl anthranilate, resulting in a sweet, floral accord that is very long lasting. Just be aware that when you add methyl anthranilate it is going to change the nature of the aldehydes youve used - in general making them longer lasting and more stable - which in most cases will be a good thing.

The other type of Shiffs Base that I use (pre-made) is Indolene - made with 50/50 indole and hydroxycitronellal. This results in a softer indolic note that, again, lasts well.
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post #6 of 21
2/27/12 at 1:02am
The main problem when using Methyl Anthranilate in the presence of aldehydes is not the production of water (although this does happen) but discolouration. Chris has mentioned mixing Vanillin with Methyl Anthranilate, well the corresponding Schiff's Base is almost black. Both Vanillin and Methyl Anthranilate are notorious for their discolouring properties even when used by themselves. However, please do not be put off, and if discolouration is not a problem (and indeed all fine fragrances tend to discolour over time) then go ahead and use Methyl Anthranilate in the presence of aldehydes. Just be aware, that the fragrance will change over time as the two molecules react with each other, and discolouration will occur.
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post #7 of 21
2/27/12 at 6:01am
Quote:
Originally Posted by David Ruskin View Post

The main problem when using Methyl Anthranilate in the presence of aldehydes is not the production of water (although this does happen) but discolouration. Chris has mentioned mixing Vanillin with Methyl Anthranilate, well the corresponding Schiff's Base is almost black. Both Vanillin and Methyl Anthranilate are notorious for their discolouring properties even when used by themselves. However, please do not be put off, and if discolouration is not a problem (and indeed all fine fragrances tend to discolour over time) then go ahead and use Methyl Anthranilate in the presence of aldehydes. Just be aware, that the fragrance will change over time as the two molecules react with each other, and discolouration will occur.

Thanks for pointing that out David - I should have mentioned it in my reply - it is of course a vital consideration in many applications.

If you want a vanilla note that does not cause such discolouration then isobutavan (vanillyl isobutyrate) is a good choice.
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post #8 of 21
2/27/12 at 8:09am
I should also have mentioned that one reason why you might want to continue to use methyl anthranilate is that it forms part of the natural scent of many flowers - look at recent headspace analysis in particular and youll often see it - so it can be very useful for helping to make flower scents more natural-seeming.

Its in a few absolutes but tends to be lost because of the heat involved in capturing essential oils.
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post #9 of 21
3/8/12 at 4:36am
Thread Starter 
Is there a standard analogy that works best between methyl anthranilate and aldehydes or is it pure experimentation? -difficult to do as the final reaction takes time to evaluate. When i say analogy I mean ratio..like 10 parts m.anthranilate 10% : 1 part Lilial 1% or something like that. Thank you!
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post #10 of 21
3/8/12 at 11:48am
No Im afraid it varies, depending on the two materials involved, however quite a few work in a 50:50 mix so if you are planning on making some you could try that to start with.

When Im blending direct into the ethanol perfume I dont think of it in those terms so much as about the combined effect Im looking for. Then I use them in appropriate proportions for that, let it work for a week or three and see if I like it, tweak as needed and so on. As the Schiffs base almost always smells very much like a combination of the things its made from only slower (less strong and longer lasting) this works quite well.

Experiment!
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post #11 of 21
3/9/12 at 12:43am
Are you asking what proportions of Methyl Anthranilate and aldehyde you need to make a Schiff's Base, or are you asking what proportions are needed to make a good accord between the two? If you want to know how much anthranilate and how much aldehyde is needed for the Schiff's base, the answer is the molecular weight of each. So if you wanted to make Aurantiol you would take 151 gms of Methyl Anthranilate (its molecular weight in grams) and 172 gms of Hydroxycitronelllal (It molecular weight in grams) and mix together. Depending in the aldehyde used so the abut used will vary. If you want to make a nice accord of the two, then you will have to experiment yourself.
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post #12 of 21
3/9/12 at 12:01pm
Thanks for adding that precision David - very useful - Ive never made my own Aurantiol (except as a side-effect of a complete blend) so I didnt know those numbers without looking it up.
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post #13 of 21
3/9/12 at 4:31pm
Best it is! Thanks a lot!
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post #14 of 21
3/9/12 at 11:26pm
As I said before, it is rather difficult to make your own Schiff's Bases because of the water that is a by product of the reaction. Removing that water is a problem, I think Vacuum distillation is used commercially, but I'm not sure.
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post #15 of 21
3/14/12 at 9:59am
Yes, could well be. There are some dehydration chemicals used in some of these things too I think, but Im at the limit of my knowledge of the matter now.

Except as an educational exercise I cant see why it would be worth making your own anyway as Aurantiol is easy to buy. With some of the more exotic combinations it might be though as you cant buy them ready-made.
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post #16 of 21
4/17/12 at 6:03am
Schiff base is colorless crystals, weakly basic, hydrolyzed by water and strong acids to form carbonyl compounds and amines. It is used as chemical intermediates and perfume bases, in dyes and rubber accelerators, and in liquid crystals for electronics.
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post #17 of 21
4/18/12 at 12:51am
Sorry David, you are wrong. Schiff's Bases are generally coloured. They are the condensation product of a carbonyl group and an amino group. In Chemistry a specific amino donor is used to determine the identity of a carbonyl containing compound as the corresponding Schiff's base has a specific melting point.

In Perfumery a Schiff's Base is generally understood to be the reaction between an amino donor (usually Methyl Anthranilate) and a carbonyl donor (usually an aldehyde). All Perfumery Schiff's Bases (there are about 5 or 6 commonly and commercially available) are brightly coloured; yellow to orange. They are all viscous liquids.
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post #18 of 21
4/18/12 at 8:13pm
Anthranilate with Hydroxycitronellal). Schiff's Bases tend to be highly coloured, usually bright yellow to orange and have a fixative effect. They are definitely base notes. Rather difficult to make yourself as a by product of the reaction
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post #19 of 21
4/19/12 at 12:39am
Anthranilate with Hydroxycitronellal).
That is called "Aurantiol". There are others commercially available. Yes, they are rather difficult to make yourself for the reasons I gave before.
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post #20 of 21
4/19/12 at 4:50pm
Quote:
Originally Posted by Chris Bartlett View Post

Davids answer already covers the essentials, but if you want to understand a bit more about the chemistry that is going on, you can read about it in The Chemistry of Fragrances: from perfumer to consumer by Charles Sell - its well enough written so that you should be able to cope with it even if your organic chemistry isnt that brilliant (as mine isnt).

Best of all, quite a lot of it is available on Google Books, including the section explaining Schiffs Bases in the context of perfumery and a little about the wider chemistry use of the term.

One thing worth knowing is that if you use methyl anthranilate in your blend together with an aldehyde then you are going to get this reaction taking place in the blend, albeit rather slowly: so its worth understanding whats going on. Especially as there are so many aldehydes in use in perfumery that can potentially undergo this reaction.

Just bumping the link here to support what David Ruskin has re-stated.

Also to recommend the book mentioned above which, quite apart from the excellent bits written by Charles Sell himself contains a number of chapters by others that give a variety of different perspectives on the subject.
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post #21 of 21
4/19/12 at 6:54pm
The Sell book is amazing.

Here's some more info: http://1000fragrances.blogspot.com/2...er-effect.html
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