Question

Crystal field theory predicts that octahedral complexes with six d electrons will be paramagnetic if this energy is large compared to the d orbital splitting energy. For 10 points each:
[10m] Name this energetic penalty imposed on molecules like singlet oxygen that do not follow Hund’s rule.
ANSWER: electron spin pairing energy
[10e] The energy required to pair the spins in oxygen is supplied as light from this region of the electromagnetic spectrum. This radiation produces radicals from diatomic halogens.
ANSWER: ultraviolet light [or UV; accept UV-A or UV-B]
[10h] Since pairing is spin-forbidden, this synthetic thia·zine dye is added as a sensitizer to improve yields of singlet oxygen. Microbiologists combine eosin with this dye to inhibit Gram-positive bacteria, and it is also the redox reporter bonded to gold in most electrochemical sensors.
ANSWER: methylene blue [or MB; or methylthioninium chloride; reject “methylene” or “methyl blue”]
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Summary

2023 ACF Nationals04/22/2023Y120.00100%100%0%

Data

Georgia Tech AChicago A1010020