Oxidation of molecules question

[PerfumePoem]

Hello Everyone

My question is about the chemical formula of x molecule, does it change if it get oxidised ?
For example the limonene C10H16 what it would be after oxidation ?
And if yes .. is it possible to reformulate it back ?

Thank you

 

[David Ruskin]

In Chemistry "oxidation" is defined as the addition of oxygen to a molecule, or the removal of hydrogen from a molecule (there are other definitions, but this will do). It is a chemical process and so the molecule will be changed. So Ethyl Alcohol will be oxidised to Acetaldehyde, which will in turn be oxidised to Acetic Acid. Phenyl Ethyl Alcohol will be oxidised to Phenylacetaldehyde, which will in turn be oxidised to Phenylacetic Acid. It is possible to reverse this process, but it is unlikely to occur unless you radically alter the conditions.

By the way Limonene will oxidise to Carvone and Limonene oxide (mainly).

 

[wiserd]

I've been thinking about this recently, and wondering if a dilute solution of Sodium borohydride might reduce the process with some of the natural musks that have a ketone group on the 3 carbon, among other things. I'm not sure how a person without a lab can get their hands on the stuff and it would probably need to be neutralized before use.
I specifically want to reduce civetone to civetol, which is also an important component of natural civet musk, though not a component of synthetic civet musk. It's been suggested that the double bond in civetone might remain intact from such a reduction, though I don't know enough about O chem to know if this is true.

 

[parker25mv]

Normally fragrance molecules can't be reduced back after they've been oxidized. Even if you were to try to use a strong reducing agent, it would likely reduce other parts of the large complex molecule too, so it really depends on the molecule in question. Not every fragrance chemical is vulnerable to oxidation from exposure to air.

Chemically, the oxidation of unsaturated compounds requires both air and light, so you would be well advised to store your fragrances in a tightly closed container that is filled close to the top (so there is not too much air in the bottle) and keep it stored in a dark place. The chemistry is quite interesting; once a molecule of oxygen is exposed to light it can transform itself into a more excited state that can then oxidize double bonds between carbon atoms. The oil itself does not even necessarily have to be exposed to the light either, since singlet oxygen has an unusually long half-life of 72 minutes (in the gas phase) before it falls back to the ordinary ground state.

 

[luigi_g]

I've been thinking about this recently, and wondering if a dilute solution of Sodium borohydride might reduce the process with some of the natural musks that have a ketone group on the 3 carbon, among other things. I'm not sure how a person without a lab can get their hands on the stuff and it would probably need to be neutralized before use.
I specifically want to reduce civetone to civetol, which is also an important component of natural civet musk, though not a component of synthetic civet musk. It's been suggested that the double bond in civetone might remain intact from such a reduction, though I don't know enough about O chem to know if this is true.

The corresponding alcohols of the macro cyclic ketones are really very low in odor profile if any and have never been useful in perfumery.

 

[wiserd]

The corresponding alcohols of the macro cyclic ketones are really very low in odor profile if any and have never been useful in perfumery.

I've found some analogous alcohol-musks to have a good effect (not the cyclic keytone musks specifically), and better tolerated as musks by a much wider variety of people. I agree that the smell is a lot weaker, but the animal produced them as part of its scent for a good reason. ;-)

 

[luigi_g]

I've found some analogous alcohol-musks to have a good effect (not the cyclic keytone musks specifically), and better tolerated as musks by a much wider variety of people. I agree that the smell is a lot weaker, but the animal produced them as part of its scent for a good reason. ;-)

alcohol-musks? what is an alcohol musk?

"animal produced them as part of its scent for a good reason"
the reason they are found is they are the precursor to the ketones, which are the parts of the scent.

 

[Scentbox]

In Chemistry "oxidation" is defined as the addition of oxygen to a molecule, or the removal of hydrogen from a molecule (there are other definitions, but this will do). It is a chemical process and so the molecule will be changed. So Ethyl Alcohol will be oxidised to Acetaldehyde, which will in turn be oxidised to Acetic Acid. Phenyl Ethyl Alcohol will be oxidised to Phenylacetaldehyde, which will in turn be oxidised to Phenylacetic Acid. It is possible to reverse this process, but it is unlikely to occur unless you radically alter the conditions.

By the way Limonene will oxidise to Carvone and Limonene oxide (mainly).

Hello David; I am aware this is al old post but do Rose Ketones form Acetals when diluted in Perfumers alcohol ? thank you

 

[David Ruskin]

I have no idea if rose ketones react with ethanol. In theory ketones do.

 

[parker25mv]

For example the limonene C10H16 what it would be after oxidation ?

In the case of limonene, oxidation can go two different ways.
First, in the presence of air and light over time, it forms very small amounts of hydroperoxides, which end up making the limonene strongly sensitising to skin, causing redness, irritation, or a burning sensation. This is a problem in perfumes.
A greater amount of the limonene gets oxidized to p-cymene. This smells somewhere in-between D-limonene and L-limonene but is more sour and "flat"-smelling. I personally do not find its smell to be very pleasant. Normal oxidation can result in the smell of limonene changing over time, usually not considered for the better.

Explaining exactly why limonene gets oxidized to p-cymene is a little complicated and involves a discussion of advanced biochemistry.

The formula for p-cymene is C10 H14
The formula for the hydroperoxide of limonene is C10 H16 O2
In both cases, there is a rearrangement of the carbon-carbon double bonds, so it's not simply just a matter of removing hydrogen atoms or adding oxygen atoms.

 

[parker25mv]

I have no idea if rose ketones react with ethanol. In theory ketones do.

Ketones dissolve in alcohol and can transiently form hemiacetals. This means one molecule of alcohol can sometimes bond onto a ketone molecule. But the reaction can go both ways, and under normal conditions only a small fraction of the ketone molecules in the alcohol solution exist in the form of hemiacetal. This is known as an "equilibrium".
It is possible for ketones to go even further with alcohol, forming an acetal (bonded to two alcohol molecules), but this requires the presence of an acid for the reaction to go either way. It is possible for a ketone to get stuck as an acetal, and in fact there are several ACs which are acetals. This will not normally happen in perfumery (except perhaps with very long term storage, which is another discussion).

 

[parker25mv]

I also want to emphasise that you do NOT need to know all this chemistry stuff to be an advanced expert perfumer. The chemistry can really be quite complicated. (Probably even most biochemistry professors would not easily be able to answer these sort of questions, so there is no reason for you to feel bad)
I simply answered the question for any of you who were curious enough to want to take the trouble to understand exactly what happens.