A Bjerrum defect is a
crystallographic defect
A crystallographic defect is an interruption of the regular patterns of arrangement of atoms or molecules in Crystal, crystalline solids. The positions and orientations of particles, which are repeating at fixed distances determined by the Crysta ...
which is specific to
ice
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
, and which is partly responsible for the electrical properties of ice. It was first proposed by
Niels Bjerrum in 1952 in order to explain the electrical polarization of ice in an electric field. A
hydrogen bond
In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...
normally has one
proton
A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...
, but a hydrogen bond with a Bjerrum defect will have either two protons (D defect, from "doppel" in German, meaning "double"
) or no proton (L defect, from "leer" in German, meaning "empty"
). D-defects are more energetically favorable than L-defects.
The unfavorable
defect strain is resolved when a water molecule pivots about an oxygen atom to produce hydrogen bonds with single protons. Dislocations of
ice Ih along a slip plane create pairs of Bjerrum defects, one D defect and one L defect.
Nonpolar molecules such as methane can form
clathrate hydrate
Clathrate hydrates, or gas hydrates, clathrates, or hydrates, are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped ins ...
s with water, especially under high pressure. Although there is no
hydrogen bond
In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...
ing of water molecules when methane is the guest molecule of the clathrate, guest-host hydrogen bonding often forms with guest molecules in clathrates of many larger organic molecules, such as
pinacolone
Pinacolone (3,3-dimethyl-2-butanone) is an important ketone in organic chemistry. It is a colorless liquid with a slight peppermint or camphor odor. It is a precursor to triazolylpinacolone in the synthesis of the fungicide triadimefon and in sy ...
and
tetrahydrofuran
Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...
. In such cases, the guest-host hydrogen bonds result in the formation of L-type Bjerrum defect in the clathrate lattice. Oxygen atoms (in alcohol or carbonyl functional groups) and nitrogen atoms (in amine functional groups) in the guest molecules lead to transient hydrogen bonds and misoriented water molecules in the hydrate lattice.
See also
*
Ice rules
In chemistry, ice rules are basic principles that govern arrangement of atoms in water ice. They are also known as Bernal–Fowler rules, after British physicists John Desmond Bernal and Ralph H. Fowler who first described them in 1933.
The rule ...
References
Water ice
Crystallographic defects
Electrochemistry
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