Planar

(adjective)

Of or pertaining to a plane. Flat, two-dimensional.

Related Terms

  • Two-Dimensional
  • dimension

(adjective)

Of or pertaining to a plane, or a flat, two-dimensional surface.

Related Terms

  • Two-Dimensional
  • dimension

Examples of Planar in the following topics:

  • Tetrahedral and Square Planar Complexes

    • Both tetrahedral and square planar complexes have a central atom with four substituents.
    • In principle, square planar geometry can be achieved by flattening a tetrahedron.
    • As such, the interconversion of tetrahedral and square planar geometries provides a pathway for the isomerization of tetrahedral compounds.
    • Therefore, the crystal field splitting diagram for square planar geometry can be derived from the octahedral diagram.
    • Discuss the d-orbital degeneracy of square planar and tetrahedral metal complexes.
  • Reactive Intermediates

    • Carbocations have only three bonds to the charge bearing carbon, so it adopts a planar trigonal configuration.
    • Carbanions are pyramidal in shape (tetrahedral if the electron pair is viewed as a substituent), but these species invert rapidly at room temperature, passing through a higher energy planar form in which the electron pair occupies a p-orbital.
    • Radicals are intermediate in configuration, the energy difference between pyramidal and planar forms being very small.
    • Since three points determine a plane, the shape of carbenes must be planar; however, the valence electron distribution varies.
  • Two-Dimensional Space

    • Two-dimensional, or bi-dimensional, space is a geometric model of the planar projection of the physical universe in which we live.
    • Two dimensional, or bi-dimensional, space is a geometric model of the planar projection of the physical universe in which we live.
    • In physics, our bi-dimensional space is viewed as a planar representation of the space in which we move.
  • Antiaromaticity

    • As noted above, 1,3,5,7-cyclooctatetraene is non-planar and adopts a tub-shaped conformation.
    • Planar bridged annulenes having 4n π-electrons have proven to be relatively unstable.
  • Stereoselectivity in Addition Reactions to Double Bonds

    • As illustrated in the drawing below, the pi-bond fixes the carbon-carbon double bond in a planar configuration, and does not permit free rotation about the double bond itself.
  • Types of Synovial Joints

    • Synovial joints include planar, hinge, pivot, condyloid, saddle, and ball-and-socket joints, which allow varying types of movement.
    • These joints can be described as planar, hinge, pivot, condyloid, saddle, or ball-and-socket joints .
    • Planar joints have bones with articulating surfaces that are flat or slightly curved.
    • Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae .
    • (d) Planar (or plane) joints, such as those between the tarsal bones of the foot, allow for limited gliding movements between bones.
  • Other Aromatic Compounds

    • A planar (or near planar) cycle of sp2 hybridized atoms, the p-orbitals of which are oriented parallel to each other.
    • This molecule is not planar (a geometry that would have 135º bond angles).
    • It is planar, bond angles=120º, all carbon atoms in the ring are sp2 hybridized, and the pi-orbitals are occupied by 6 electrons.
    • As shown in the following diagram, 1,3,5,7,9-cyclodecapentaene fails to adopt a planar conformation, either in the all cis-configuration or in its 1,5-trans-isomeric form.
    • Naphthalene and azulene are [10]annulene analogs stabilized by a transannular bond.Although the CH2 bridged structure to the right of naphthalene in the diagram is not exactly planar, the conjugated 10 π-electron ring is sufficiently close to planarity to achieve aromatic stabilization.
  • Conformational Enantiomorphism

    • As shown in the following diagram, biphenyl itself is not planar, one benzene ring being slightly twisted or canted in relation to the other as a consequence of steric crowding.
    • Racemization requires passing through a planar configuration, and the increased angle and eclipsing strain in this structure contribute to a large activation energy.
    • The right hand compound is heavily ortho-substituted and most certainly resists assuming a planar configuration.
    • Biphenyl itself is not planar, so one benzene ring is slightly twisted or canted in relation to the other as a consequence of steric crowding.
  • Trihalides: Boron-Halogen Compounds

    • Trihalides adopt a planar trigonal structure and are Lewis acids.
    • The trihalides form planar trigonal structures and are Lewis acids because they readily form adducts with electron-pair donors, which are called Lewis bases.
    • This trend is commonly attributed to the degree of π-bonding in the planar boron trihalide that would be lost upon pyramidalization (the conversion of the trigonal planar geometry to a tetrahedral one) of the BX3 molecule, which follows this trend: BF3 > BCl3 > BBr3 (that is, BBr3 is the most easily pyramidalized).
  • The Configuration of Free Radicals

    • Since the difference in energy between a planar radical and a rapidly inverting pyramidal radical is small, radicals generated at chiral centers generally lead to racemic products.
    • However, unlike carbocation intermediates, which prefer to be planar, radicals tolerate being restricted to a pyramidal configuration.
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