Dear All,
I want suggestions/comments/ideas behind what are real factors affecting epimerization or broadly isomerization for any chiral molecule.
Are physical factors such as Atmospheric Pressure, Room Temperature, Light, etc. can be responsible for isomerization?
I am facing this issue with one of my compound. Even after caring about everything I could (Moisture, temperature, Light, etc.), I observe that my molecule epimerizes. Its a short chain linear molecule with two chiral centers.
Its becoming hard for me to know the real cause of that process.
Any references from your side will be of great help.
Thanks
Hi Sachin,
In addition to temperature, light (I am not aware of atmospheric pressure), please keep in mind that pH plays a significant role in isomerisation.
Even in the case of enzyme catalysed isomerzation, the general mechanism involves the proton abstraction by the base component of the enzyme near a carbonyl centre. Additionally, Oxidation of target compounds, followed by base catalysis is also a possibility.
Thus, please verify any changes in pH that could be affecting your result.
Definitely the primary factor is pH. Lok at the structure of the molecule and make your own assessment.
The problem is that some structures are naturally prone to isomerisation (or racemisation). Carbonyl and some nitro compounds tend to undergo reversible alpha-elimination in basic conditions, which interferes strongly with optical purity in some compounds. Double bonds can be reversibly broken with light (via radicals), causing mixture of isomers to rise in time. Maybe you should have a thorough look at your structure and see if there are some parts that are prone to isomerization in some conditions
this link is useful
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4188265/
regards
Thanks everyone for your comments. Indeed I acquire some information from the responses.
I would like to put up an additional point.
When a volatile natural compound for e.g. pheromones are released in atmosphere by insects and we know only a certain isomer of that compound is active pheromone actually, so even being under drastic environmental conditions that particular active isomer doesn't undergo any kind of isomerization. What if the same compound when synthesized in laboratory conditions undergoes isomerization?
In pure form it has higher "concentration", so if isomerisation is induced by some concentration-dependent factor, it may be enhanced by purity of compound. See if storing it as a dilute solution works.
Also, in some cases (probably not this one, if its volatile) there can be a stabilizing compound present, like antioxidant.
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