The prismanes are a class of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

compounds consisting of

prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentary ...

-like polyhedra of various numbers of sides on the

polygon In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two toge ...

al base. Chemically, it is a series of fused

cyclobutane Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commercial ...

rings (a

ladderane In chemistry, a ladderane is an organic molecule containing two or more fused cyclobutane rings. The name arises from the resemblance of a series of fused cyclobutane rings to a ladder. Numerous synthetic approaches have been developed for the synt ...

, with all-

cis Cis or cis- may refer to: Places * Cis, Trentino, in Italy * In Poland: ** Cis, Świętokrzyskie Voivodeship, south-central ** Cis, Warmian-Masurian Voivodeship, north Math, science and biology * cis (mathematics) (cis(''θ'')), a trigonome ...

/all- syn geometry) that wraps around to join its ends and form a band, with

cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...

edges. Their chemical formula is (C₂H₂)_n, where ''n'' is the number of cyclobutane sides (the size of the cycloalkane base), and that number also forms the basis for a system of nomenclature within this class. The first few chemicals in this class are: Triprismane, tetraprismane, and pentaprismane have been synthesized and studied experimentally, and many higher members of the series have been studied using

computer models Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be deter ...

. The first several members do indeed have the geometry of a regular prism, with flat ''n''-gon bases. As ''n'' becomes increasingly large, however, modeling experiments find that highly symmetric geometry is no longer stable, and the molecule distorts into less-symmetric forms. One series of modelling experiments found that starting with 1rismane, the regular-prism form is not a stable geometry. For example, the structure of 2rismane would have the cyclobutane chain twisted, with the

dodecagon In geometry, a dodecagon or 12-gon is any twelve-sided polygon. Regular dodecagon A regular dodecagon is a figure with sides of the same length and internal angles of the same size. It has twelve lines of reflective symmetry and rotational sym ...

al bases non-planar and non-parallel.

Nonconvex prismanes

For large base-sizes, some of the cyclobutanes can be fused anti to each other, giving a non-convex polygon base. These are

geometric isomer Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ...

s of the prismanes. Two isomers of 2rismane that have been studied computationally are named helvetane and israelane, based on the star-like shapes of the rings that form their bases. This was explored computationally after originally being proposed as an April fools joke. Their names refer to the shapes found on the flags of

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

and

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

, respectively.

Polyprismanes

The polyprismanes consist of multiple prismanes stacked base-to-base. The carbons at each intermediate level—the ''n''-gon bases where the prismanes fuse to each other—have no hydrogen atoms attached to them.

Related structures

The asteranes contain a

methylene group In organic chemistry, a methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by two single bonds. The group may be represented as , where the '< ...

bridge on each edge between the two ''n''-gon bases. Each side is thus a cyclohexane rather than a cyclobutane.

References

{{reflist, 2

External links

Triprismane

Cubane

Pentaprismane

Hexaprismane
Molecular geometry Polycyclic nonaromatic hydrocarbons