Planar

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.