Chemical substance consisting of a lattice that traps or contains molecules
A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin clathratus (clatratus), meaning 'with bars, latticed'.[1] Most clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest complexes and inclusion compounds.[2] According to IUPAC, clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules."[3] The term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites.
Clathrates can be divided into two categories: clathrate hydrates and inorganic clathrates. Each clathrate is made up of a framework and guests that reside the framework. Most common clathrate crystal structures can be composed of cavities such as dodecahedral, tetrakaidecahedral, and hexakaidecahedral cavities.
The molar fraction of water of most clathrate hydrates is 85%. Clathrate hydrates are derived from organic hydrogen-bonded frameworks. These frameworks are prepared from molecules that "self-associate" by multiple hydrogen-bonding interactions. Small molecules or gases (i.e. methane, carbon dioxide, hydrogen) can be encaged as a guest in hydrates. The ideal guest/host ratio for clathrate hydrates range from 0.8 to 0.9. The guest interaction with the host is limited to van der Waals forces. Certain exceptions exist in semiclathrates where guests incorporate into the host structure via hydrogen bonding with the host structure. Hydrates form often with partial guest filling and collapse in the absence of guests occupying the water cages. Like ice, clathrate hydrates are stable at low temperatures and high pressure and possess similar properties like electrical resistivity. Clathrate hydrates are naturally occurring and can be found in the permafrost and oceanic sediments. Hydrates can also be synthesized through seed crystallization or using amorphous precursors for nucleation.[4]
Unlike hydrates, inorganic clathrates have a covalently bonded framework of inorganic atoms with guests typically consisting of alkali or alkaline earth metals. Due to the stronger covalent bonding, the cages are often smaller than hydrates. Guest atoms interact with the host by ionic or covalent bonds. Therefore, partial substitution of guest atoms follow Zintl rules so that the charge of the overall compound is conserved. Most inorganic clathrates have full occupancy of its framework cages by a guest atom to be in stable phase. Inorganic clathrates can be synthesized by direct reaction using ball milling at high temperatures or high pressures. Crystallization from melt in another common synthesis route. Due to the wide variety of composition of host and guest species, inorganic clathrates are much more chemically diverse and possess a wide range of properties. Most notably, inorganic clathrates can be found to be both an insulator and a superconductor (Ba8Si46). A common property of inorganic clathrates that has attracted researchers is low thermal conductivity. Low thermal conductivity is attributed to the ability of the guest atom to "rattle" within the host framework. The freedom of movement of the guest atoms scatters phonons that transport heat.[4]
^Latin dictionary Archived 2012-04-14 at the Wayback Machine
^Atwood, J. L. (2012) "Inclusion Compounds" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a14_119
^IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "clathrates". doi:10.1351/goldbook.C01097
^ abcdKrishna, Lakshmi; Koh, Carolyn A. (February 2015). "Inorganic and methane clathrates: Versatility of guest–host compounds for energy harvesting". MRS Energy & Sustainability. 2 (1): 8. doi:10.1557/mre.2015.9. ISSN 2329-2229.
and 27 Related for: Clathrate compound information
bars, latticed'. Most clathratecompounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest...
natural gas hydrate, or gas hydrate, is a solid clathratecompound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped...
hydrogen bonded, frozen water molecules. In other words, clathrate hydrates are clathratecompounds in which the host molecule is water and the guest molecule...
crystalline compound with sodium under pressure. Suitable pressures to force helium into solid combinations could be found inside planets. Clathrates are also...
only isolated compounds of noble gases were clathrates (including clathrate hydrates); other compounds such as coordination compounds were observed only...
L-type Bjerrum defects in the clathrate lattice. The stability of hydrates is generally determined by the nature of the compounds, their temperature, and the...
nature. Neon has been shown to crystallize with other substances and form clathrates or Van der Waals solids. Neon has a high first ionization potential of...
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes...
another compound. One example is xenon hydrate (Xe·5+3⁄4H2O), where xenon atoms occupy vacancies in a lattice of water molecules. This clathrate has a melting...
Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form clathrates with water when atoms of argon are trapped...
guest is enclosed on all sides so that it is 'trapped', the compound is known as a clathrate, not an inclusion complex. In molecular encapsulation, a guest...
a wide range of nonpolar and polar chemical compounds. THF is water-miscible and can form solid clathrate hydrate structures with water at low temperatures...
clathrate or nitrogen hydrate is a clathrate consisting of ice with regular crystalline cavities that contain nitrogen molecules. Nitrogen clathrate is...
With ice, argon forms a clathrate hydrate. Up to 0.6 GPa, the clathrate has a cubic structure. Between 0.7 and 1.1 GPa the clathrate has a tetragonal structure...
allowing it to feed and gain nutrition through organic compounds that are found in the methane clathrate deposits. "Sirsoe methanicola". Global Biodiversity...
addition to the compounds where a noble gas atom is involved in a covalent bond, noble gases also form non-covalent compounds. The clathrates, first described...
dark-green solutions that very slowly decompose in the dark. Crystalline clathrate hydrates ClO2·nH2O (n ≈ 6–10) separate out at low temperatures. However...
molecular receptors with important application to biology and medicine. Clathratecompound Host–guest chemistry A. Petitjean; R. G. Khoury; N. Kyritsakas; J...
partnerships. Captisol, a Ligand indication, is a chemically modified clathratecompound of the cyclodextrin class designed to improve solubility, stability...
occurs when Portland cement hardens. Water ice can form clathratecompounds, known as clathrate hydrates, with a variety of small molecules that can be...
another compound. One example is xenon hydrate (Xe·5+3⁄4H2O), where xenon atoms occupy vacancies in a lattice of water molecules. This clathrate has a melting...
An yttrium compound is a chemical compound containing yttrium (element symbol: Y). Among these compounds, yttrium generally has a +3 valence. The solubility...
reverses the equilibrium, producing sulfur dioxide and water vapor. A clathrate with the formula 4SO2·23H2O has been crystallised. It decomposes above...
Binary compounds of silicon are binary chemical compounds containing silicon and one other chemical element. Technically the term silicide is reserved...
(1895) Clathrus P. Micheli ex L. (1753) Fruiting bodies are latticed (clathrate), and made of hollow tubular arms that originate from the basal tissue...
with dry water, combine with the water, which then traps them in a solid clathrate hydrate cage. This presents the possibility that explosive gases could...
the Earth suffers from a giant hurricane spawned by the release of clathratecompounds, as the result of a nuclear explosion. While the hurricane spawns...