Clathrate
Definition and meaning of Clathrate in chemistry.
A clathrate is a compound in which molecules of one substance (the guest) are physically trapped within cage-like cavities of a crystal lattice formed by another substance (the host), with no covalent or ionic bond between host and guest.
In more detail
The host framework is typically held together by hydrogen bonds or van der Waals forces and self-assembles around guest molecules of a suitable size and shape, enclosing them through physical entrapment rather than chemical bonding. Because the guest is not chemically bonded, it can often be released unchanged by melting or dissolving the host lattice. Clathrates form only under specific pressure and temperature conditions, and their stability depends on the geometric fit between guest and cavity. Water is the most common host, forming clathrate hydrates (gas hydrates), but organic hosts such as hydroquinone also form clathrates with small guest molecules like methanol or CO2.
Key facts
| Formula | Variable, host-guest dependent (e.g., CH4·5.75H2O for methane hydrate) |
|---|---|
| Bonding | No covalent/ionic bond between host and guest; physical enclosure only |
| Common host | Water (clathrate hydrates); also hydroquinone, urea |
| Field | Inorganic Chemistry |
Methane clathrate (methane hydrate), approximately CH4·5.75H2O, in which methane molecules are enclosed within cages of hydrogen-bonded water molecules; it occurs naturally in permafrost and deep ocean sediments.
Frequently asked questions
How is a clathrate different from a true chemical compound?
In a clathrate the guest molecule is held only by the geometry of the host lattice and weak intermolecular forces, not by covalent or ionic bonds, so the guest can be released unchanged; a true compound involves chemical bonding between its components.
Why do methane clathrates matter beyond chemistry?
Methane clathrates in permafrost and seafloor sediments represent a large natural reservoir of trapped methane, a potent greenhouse gas, and their potential destabilization from warming is a topic of climate research.