In
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, trigonal planar is a
molecular geometry model with one atom at the center and three atoms at the corners of an
equilateral triangle, called peripheral atoms, all in one plane.
In an ideal trigonal planar species, all three ligands are identical and all bond angles are 120°. Such species belong to the
point group
In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ...
D3h. Molecules where the three ligands are not identical, such as
H2CO, deviate from this idealized geometry. Examples of
molecules with trigonal planar geometry include
boron trifluoride
Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.
Structure and bondin ...
(BF
3),
formaldehyde (H
2CO),
phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
(COCl
2), and
sulfur trioxide
Sulfur trioxide (alternative spelling sulphur trioxide, also known as ''nisso sulfan'') is the chemical compound with the formula SO3. It has been described as "unquestionably the most important economically" sulfur oxide. It is prepared on an ind ...
(SO
3). Some ions with trigonal planar geometry include
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
(),
carbonate (), and
guanidinium (). In organic chemistry, planar, three-connected carbon centers that are trigonal planar are often described as having
sp2 hybridization.
is the distortion of pyramidal
amines through a transition state that is trigonal planar.
Pyramidalization is a distortion of this molecular shape towards a
tetrahedral molecular geometry. One way to observe this distortion is in
pyramidal alkenes.
See also
*
AXE method
*
Molecular geometry
*
VSEPR theory
References
External links
3D Chem Chemistry, Structures, and 3D MoleculesIndiana University Molecular Structure Center
{{MolecularGeometry
Stereochemistry
Molecular geometry