In catalytic oxidation of alkene reaction, aromatic, cyclic and longer chain alkenes gave aldehyde as a sole product [Ru catalyst, NaIO4 (oxidant), ACN/EtOAc/H2O].
But in case of cis 2-heptene and allylcyclopentane gave their corresponding acid as s sole product using the above same condition. Please explain the reason for over-oxidation.
Could you give the reference to the procedure you used? There are several variants of this reaction. The grade of the oxidation in this process might be depending on the distribution of the aldehyde in the two-phase system. Perrhenate (the real oxidation agent) is in the water phase, if your aldehyde is small and, therefore, sufficiently water-soluble, it will be oxidized to the acid.
The coordination mode of th substrates to the catalyst might be different in the case of these compounds, due to steric reasons, or in case of allylic compound, due to delocalization. It means, the intermediate aldehyde does not release from the catalyst but is kept in the sphere of catalyst so further oxidation might take place. But in order to say sure, more informatioon would be needed about the coditions.
As pointed out by the other responses: the more detail you can provide, the better answers you can expect.
Given the reported solvent system is MeCN/EtOAc/H2O, I wonder whether this is a biphasic reaction. If so, presumably the oxidant (NaIO4) is almost entirely in the aqueous phase. If the short-chain aldehydes are somewhat soluble in water, the oxidation might take place in the aqueous phase without the action of the catalyst. If this is the case, the longer chain products will likely stay in the organic phase, and will not be oxidized in the same way (or at least the process will be orders of magnitude sower due to differences in partition coefficient)
According to chemeo.com, butanal and ethanal (putative initial products of 2-heptene oxidation) have logP values of 0.99 and 0.21 (respectively), while octanal has a logP value of 2.5, and decanal has a value of 3.3
Dear,
The conditions mentioned by you clearly indicates that you are bound to get carboxylic acid as a product.
I am a little amazed that you got aldehyde in some cases.
Anyway, the problem is due to moisture, you have H2O so clearly it is bound to give carboxylic acid product.
If your goal is to get the aldehyde product I suggest you use Tetrapropylammonium perruthenate, N-methylmorpholine N-oxide & molecular sieves.
Molecular sieves should be activated as they will absorb the moisture in it.
I have personally performed this oxidation, so I told you about my experience.
A link has been attached for you and it is called ley griffith oxidation
https://en.wikipedia.org/wiki/Tetrapropylammonium_perruthenate
Thanks for one and all for your suggestions/answers. Finally, It has been found that the over oxidation for these substrate are due to higher concentration of oxidant.
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