trigone

(noun)

A triangle-shaped part of an organ, such as the bottom of the bladder.

Related Terms

Examples of trigone in the following topics:

  • Table of Geometries

    • The VSPER theory detremines molecular geometries (linear, trigonal, trigonal bipyramidal, tetrahedral, and octahedral).
    • Molecular geometries (linear, trigonal, tetrahedral, trigonal bipyramidal, and octahedral) are determined by the VSEPR theory.

  • Borates: Boron-Oxygen Compounds

    • The simplest borate anion, BO33-, has a trigonal planar structure and is analogous to the carbonate anion CO32-, with which it is isoelectronic.
    • Larger borates are composed of trigonal planar BO3 or tetrahedral BO4 structural units, joined together via shared oxygen atoms; these may be cyclic or linear in structure.
    • When a trigonal boron atom accepts a pair of electrons from a Lewis base, it adopts a tetrahedral configuration (sp3), and the octet rule is satisfied.
    • Both trigonal and tetrahedral units can co-exist in a complex borate, such as the anion in borax.

  • Molecular Geometries

    • The VSEPR theory describes five main shapes of simple molecules: linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.
    • Molecules with the trigonal planar shape are triangular and in one plane, or flat surface.
    • A trigonal bipyramidal shape forms when a central atom is surrounded by five atoms in a molecule.

  • Applying the VSEPR Model

    • This requires that all four atoms be in the same plane; the resulting shape is called trigonal planar, or simply trigonal.
    • Molecules with a coordination number of 5 are in the shape of a trigonal bipyramid; this consists of two triangular-based pyramids joined base-to-base.
    • Here are the shapes that we will talk about: tetrahedral, trigonal pyramidal, bent, trigonal planar, linear.

  • 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).

  • Urinary Bladder

    • The ureters enter the bladder diagonally from its dorsolateral floor in an area called the trigone, which is a triangle-shaped anatomical region.
    • The urethra exits at the lowest point of the triangle of the trigone.

  • The Shape of Molecules

    • The measured bond angles of these compounds (H2O 104.5º & NH3 107.3º) show that they are closer to being tetrahedral than trigonal or linear.
    • The compound boron trifluoride, BF3, does not have non-bonding valence electrons and the configuration of its atoms is trigonal.
    • However, in the trigonal-pyramidal configuration one hydrogen (the apex) is structurally different from the other three (the pyramid base).

  • Reactive Intermediates

    • Carbocations have only three bonds to the charge bearing carbon, so it adopts a planar trigonal configuration.

  • Development of the Urinary System

    • The lower ends of the metanephric ducts are incorporated into the wall of the urogenital sinus and form the trigone of the bladder.

  • Metal Cations that Act as Lewis Acids

    • Classically, the term "Lewis acid" was restricted to trigonal planar species with an empty p orbital, such as BR3 where R can be an organic substituent or a halide.