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newappeal t1_iu909ym wrote

Reply to comment by SmorgasConfigurator in Is an ionic bond really stronger than a covalent bond??? by jeez-gyoza

>But, thankfully for us, inside our bodies, near hemoglobin especially, that bond can be broken at very reasonable energies.

I'm not quite sure if this is what you're implying, but hemoglobin does not break the double bond in molecular oxygen. In mammals, oxygen (as an intact diatomic molecule) binds hemoglobin in the blood, then binds myoglobin in target tissues, and then is released into solution, where it is reduced to water in the mitochondria. And while I don't want to get bogged down in the definition of "reasonable" energy levels, I will point out that that redox reaction involves free electrons. Nonetheless, you are certainly correct that the bonds in molecular oxygen can be considered weak in many everyday contexts - that fact is synonymous with the fact that oxygen is highly reactive in many common chemical environments on Earth.

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SmorgasConfigurator t1_iu93ho0 wrote

In hindsight I should have used a better example to illustrate the point that the apparent durability of a covalent bond also depends on a relative free energy, where that delta can be highly dependent on environment, which in turn means that any ranking of bond strengths implicitly assumes some environment. I could have used, as you note, a host of other examples rather than a biological process with multiple intermediates etc. Since I stand by my bigger point in that comment, and it would be a substantial edit to correct the details, I’ll hope you’re helpful corrective will suffice if a fellow redditor wishes to dig into the details. Thanks.

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newappeal t1_iu98ju7 wrote

Yes I certainly don't think your fundamental point is wrong. I don't think it actually fully clarifies the commenter's particular misunderstanding, but it is relevant and a good contribution.

To summarize where I think OP's confusion arises from: ionic "bond strength" figures are actually molar lattice energies and therefore reflect the strength of multiple bonds. Molar energies for covalent bonds reflect the strength of individual bonds. I've added a top-level comment explaining that point, which is how it was clarified to me in undergrad chemistry.

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