monotropy

chemistry

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June 30, 2026

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Monotropy describes a relationship where one form of a substance is stable under all conditions, and any change from an unstable form to the stable one is irreversible. This is in contrast to enantiotropy, where different forms are stable under different conditions and can convert back and forth.12

An example of monotropy is seen with phosphorus, where red phosphorus is more stable than white phosphorus. Similarly, graphite is more stable than diamond, and diatomic oxygen (O₂) is more stable than ozone (O₃) under normal conditions. This concept is a part of allotropy, which refers to a chemical element existing in different forms.2

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allotropy
Allotropes may be monotropic, in which case one of the forms is the most stable under all conditions, or enantiotropic, in which case different forms are stable under different conditions and undergo reversible transitions from one to another at characteristic temperatures and pressures.
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Allotropes may be monotropic, in which case one of the forms is the most stable under all conditions, or enantiotropic, in which case different forms are stable under different conditions and undergo reversible transitions from one to another at characteristic temperatures and pressures.
Read More