When trying to determine if a molecule is generally unstable or not, what do you look for? Also, is it possible to determine exactly how it will degrade?
For example, if I have an aqueous solution of alpha-ketoglutarate, what do you look for to decide what temperature it's best to store it at, or if it is even stable? Is this even possible without experiments?
What can you gain from looking at different (or combinations of) functional groups? (aldehydes, acids, amines, etc)
One example I am interested is 4-amino-2-oxobutanoic acid,hydrochloride (CAS # - 92614-52-3). It has several functional groups and I've been told it is unstable. Why is this evident? Further, is it possible to predict the most likely degradation product?
Please pardon me when I answer a single question because the other questions require details & I do not have time to do that at the moment. So my answer will be for your question (What do you look for in a molecule to determine if it's stable?)
I shall look for, e.g.
- Structure of the molecule; if it has filled octets for the second row elements( C & elements that bond to it such as N,O, and F) then stability is expected.
- Structures which display resonance (e.g. benzene) are stable; the more there are resonance forms, the higher is the stability.
-Molecules, in which there is minimum number of formal charges & maximum number of bonds, are relatively stable. Remember: Bonding ===> Stability.
-Molecules, which have negative charge or positive charge or free radical somewhere in the structure, are unstable. The charges & the radical are activity sites.
-Close to the previous point is that highly reactive molecules are relatively unstable. For example, a carboxylic acid RCOOH may have a derivative such as R-CO-Cl (which is highly reactive; hence less stable) or it may have a derivative such as R-CO-NH2 (which is less reactive; hence more stable).
(CAS # - 92614-52-3) Regarding this compound specifically, alpha keto carboxyl functionalities tend to be quite electrophilic at the alpha carbonyl center. I expect when this compound is not in the hydrochloride salt form, it is susceptible to polymerization by the following mechanism (see attached).
I would also expect some esterification of the butanoic acid group (an impurity), particularly if it is diluted in Metanol.
- Badges
- Science topic
- Similar topics
- Chemistry
- Biochemistry