Why are most molecules in the singlet state instead of the triplet state?

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    Molecules Singlet State
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Discussion Overview

The discussion revolves around the states of molecules, specifically why most molecules are found in the singlet state rather than the triplet state. It touches on concepts from thermodynamics, molecular stability, and reactivity, with a focus on the ground state configurations of different molecules.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant suggests that since the singlet state is of higher energy than the triplet state, molecules should favor the triplet state according to thermodynamic principles.
  • Another participant counters that most molecules have a singlet ground state, where all electrons are paired, and that the triplet state is not a lower energy state for most molecules, with dioxygen being a notable exception.
  • A participant seeks clarification on why the ground state is singlet, indicating a lack of understanding of the underlying principles.
  • Concerns are raised about the reactivity of triplet state molecules, particularly regarding dioxygen, which is in a triplet state but is not perceived as highly reactive.
  • A later reply asserts that dioxygen is indeed reactive, citing combustion reactions as evidence of its reactivity despite its triplet ground state.

Areas of Agreement / Disagreement

Participants express differing views on the energy states of molecules and their implications for reactivity. There is no consensus on the reasons behind the predominance of the singlet state or the reactivity of triplet state molecules.

Contextual Notes

Some assumptions regarding energy states and molecular configurations are not fully explored, and the discussion does not resolve the complexities of molecular reactivity in relation to electronic states.

hariharan venkatasu
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Most molecules are in singlet ground state which is of higher energy than triplet lower energy state .According to thermodynamics molecule tend to remain in lower energy state.Therefore,I presume molecules should remain in triplet state .Could anyone clarify my point
 
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Most molecules do not have a "lower energy triplet state". For most molecules, the ground state is a singlet, in which all the electrons are paired. An exception is dioxygen, which has two degenerate antibonding orbitals and two electrons to go in them. In this case, the ground state is the triplet (one electron in each orbital, with parallel spins). Molecules with unpaired electrons tend to be reactive, which is why most stable molecules have all-paired electrons.
 
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Thank you very much for your reply .Let me know why the ground state is singlet?
 
Further to my last post , you have mentioned that molecules with unpaired electrons tend to to be reactive. That means triplet state molecules to be highly reactive .Then oxygen in triplet ground state should be reactive .This is not the case .Could you please clarify this point?
 
hariharan venkatasu said:
oxygen in triplet ground state should be reactive .This is not the case

Yes, it is. Oxygen is one of the most reactive molecules there is. We call such reactions "combustion" and they typically release a lot of energy.
 
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