Trigonal planar molecular geometry

In chemistry, 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.[1] In an ideal trigonal planar species, all three ligands are identical and all bond angles are 120°. Such species belong to the point group 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 (BF3), formaldehyde (H2CO), phosgene (COCl2), and sulfur trioxide (SO3). Some ions with trigonal planar geometry include nitrate (NO
3
), carbonate (CO2−
3
), and guanidinium (C(NH
2
)+
3
). In organic chemistry, planar, three-connected carbon centers that are trigonal planar are often described as having sp2 hybridization.[2][3]

Nitrogen inversion 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.[1]

Trigonal planar molecular geometry
Trigonal-3D-balls
ExamplesSO3
Point groupD3h
Coordination number3
Bond angle(s)120°
μ (Polarity)0
Boron-trifluoride-3D-vdW
Structure of boron trifluoride, an example of a molecule with trigonal planar geometry.

See also

References

  1. ^ a b March, Jerry. Advanced Organic Chemistry (3rd ed.).
  2. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
  3. ^ Miessler, G. L.; Tarr, D. A. Inorganic Chemistry (3rd ed.). Pearson/Prentice Hall. ISBN 0-13-035471-6.

External links

Borate

Borates are the name for a large number of boron-oxygen compounds usually containing oxyanions. The term "borates" may also refer to tetrahedral boron anions, or more loosely to chemical compounds which contain borate anions of either description. Larger borates are composed of trigonal planar BO3 or tetrahedral BO4 structural units, joined together via shared oxygen atoms and may be cyclic or linear in structure. Boron most often occurs in nature as borates, such as borate minerals and borosilicates.

Boron triiodide

Boron triiodide is a chemical compound of boron and iodine with chemical formula BI3. It has a trigonal planar molecular geometry. It is a crystalline solid, which reacts vigorously with water to form hydroiodic acid and boric acid. Its dielectric constant is 5.38 and its heat of vaporization is 40.5 kJ/mol. At extremely high pressures, BI3 becomes metallic at ~23 GPa and is a superconductor above ~27 GPa.

Group 13 hydride

Group 13 hydrides are chemical compounds containing group 13-hydrogen bonds (elements of group 13: boron, aluminium, gallium, indium, thallium).

Orbital hybridisation

In chemistry, orbital hybridisation (or hybridization) is the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. Hybrid orbitals are very useful in the explanation of molecular geometry and atomic bonding properties and are symmetrically disposed in space. Although sometimes taught together with the valence shell electron-pair repulsion (VSEPR) theory, valence bond and hybridisation are in fact not related to the VSEPR model.

SN1 reaction

The SN1 reaction is a substitution reaction in organic chemistry. "SN" stands for "nucleophilic substitution", and the "1" says that the rate-determining step is unimolecular. Thus, the rate equation is often shown as having first-order dependence on electrophile and zero-order dependence on nucleophile. This relationship holds for situations where the amount of nucleophile is much greater than that of the intermediate. Instead, the rate equation may be more accurately described using steady-state kinetics. The reaction involves a carbocation intermediate and is commonly seen in reactions of secondary or tertiary alkyl halides under strongly basic conditions or, under strongly acidic conditions, with secondary or tertiary alcohols. With primary and secondary alkyl halides, the alternative SN2 reaction occurs. In inorganic chemistry, the SN1 reaction is often known as the dissociative mechanism. This dissociation pathway is well-described by the cis effect. A reaction mechanism was first proposed by Christopher Ingold et al. in 1940. This reaction does not depend much on the strength of the nucleophile unlike the SN2 mechanism. This type of mechanism involves two steps. The first step is the reversible ionization of Alkyl halide in the presence of aqueous acetone or an aqueous ethyl alcohol. This step provides a carbocation as an intermediate.

Tennessine

Tennessine is a synthetic chemical element with the symbol Ts and atomic number 117. It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table.

The discovery of tennessine was officially announced in Dubna, Russia, by a Russian–American collaboration in April 2010, which makes it the most recently discovered element as of 2019. One of its daughter isotopes was created directly in 2011, partially confirming the results of the experiment. The experiment itself was repeated successfully by the same collaboration in 2012 and by a joint German–American team in May 2014. In December 2015, the Joint Working Party of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics, which evaluates claims of discovery of new elements, recognized the element and assigned the priority to the Russian–American team. In June 2016, the IUPAC published a declaration stating that the discoverers had suggested the name tennessine after Tennessee, United States. In November 2016, they officially adopted the name "tennessine".

Tennessine may be located in the "island of stability", a concept that explains why some superheavy elements are more stable compared to an overall trend of decreasing stability for elements beyond bismuth on the periodic table. The synthesized tennessine atoms have lasted tens and hundreds of milliseconds. In the periodic table, tennessine is expected to be a member of group 17, all other members of which are halogens. Some of its properties may significantly differ from those of the halogens due to relativistic effects. As a result, tennessine is expected to be a volatile metal that neither forms anions nor achieves high oxidation states. A few key properties, such as its melting and boiling points and its first ionization energy, are nevertheless expected to follow the periodic trends of the halogens.

Unsaturated hydrocarbon

Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. The term "unsaturated" means more hydrogen atoms may be added to the hydrocarbon to make it saturated (i.e. consisting all single bonds). The configuration of an unsaturated carbons include straight chain, such as alkenes and alkynes, as well as branched chains and aromatic compounds.

Except for aromatic compounds, unsaturated hydrocarbons are mostly reactive and undergo multiple reactions to their multiple bonds.

Coordination number 2
Coordination number 3
Coordination number 4
Coordination number 5
Coordination number 6
Coordination number 7
Coordination number 8
Coordination number 9

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