Trigonal planar carbon

Formaldehyde (H2CO) H C=0 H Carbon has two bonded pairs + one double bond which is counted as one bonded pair Trigonal planar Trigonal planar ... 

Figure 8.2. (a) Carbon symmetry—tetrahedral isp ) C —C bond length 15.4 nm. (ft) Carbon symmetry trigonal planar (spi) C C bond length- 14.2 nm interplanar... 

The most ordered surface waters are those around charged side chains or in surface crevices. Occasionally those crevices can be very deep, such as the active site pocket in carbonic anhydrase, which extends about 15 A in from the surface, with a network of water molecules (Lindskog f al., 1971). The well-ordered waters at the protein surface are usually part of an approximately tetrahedral (but sometimes planar trigonal) network of hydrogen bonds to the protein and to other waters. An example from rubredoxin is shown in Fig. 60. 

Alkenes, also known as olefins, have a carbon-carbon double bond functional group. The simplest alkene is ethene (aka ethylene in industrial chemistry), and some representations of ethene are given in Figure 11.8. Notice that the geometry around alkene carbons is trigonal planar. 

Alkenes have a planar trigonal framework of sp2 carbon atoms. Each uses one sp2 orbital to form a a bond to tire other carbon atom and two sp2 orbitals to form c bonds to the substituents (here the general R ). Two carbon p orbitals are used for aC-C Jtbond. There are no lone pairs of electrons on either carbon atom. 

Figure 8.24. Inhibition by Transition State Analogs. (A) The isomerization of 1-proline to d-proline by proline racemase, a bacterial enzyme, proceeds through a planar transition state in which the a carbon is trigonal rather than tetrahedral. (B) Pyrrole 2-carboxylate, a transition state analog because of its trigonal geometry, is a potent inhibitor of proline racemase.

Most alkyl carbanions undergo facile pyramidal inversion. Cyclopropyl anions are an exception, presumably because the transition state, with a planar trigonal carbon, is more strained than the ground state. The configurational stability of cyclopropyl anions is of value in the synthesis of deuterated cyclopropanes by the Haller-Bauer reaction (see Section II.B). An interesting dilemma arises when a cyclopropyl anion is stabilized by a n-electron acceptor substituent such as a nitrile or an ester. Will the anion then retain its pyramidal equilibrium geometry for the strain reasons alluded to above, or will it become planar in order to maximize overlap of the filled orbital on carbon with the n orbital of the substituent Walborsky and coworkers addressed this question in a series of experiments in which rates of H/D exchange and racemization were compared for an optically active cyclopropane exposed to a base in a deuterated hydroxylic solvent. The outcome can be illustrated with the particular example of 1,1-diphenylcyclopropane-2-... 

Figure 3 A Sketch of the molecular structure of Fe3 (CO) 12, which has D3jj point symmetry, showing the central O3 orbit of iron atoms, the planar Ogh orbits of carbon and oxygen atoms and the non-planar (trigonal prismatic) Ogy orbits of carbon and oxygen atoms.

Molecular shape Tetrahedral at methyl carbon atom, trigonal planar at aldehyde C atom... 

The geometry around each carbon is trigonal planar, as though only three bonds were present. 

Graphite is the next aUotrope of carbon. This consists of sheets of sp carbon atoms with a planar trigonal stereochemistry that form a flat, condensed... 

Make a molecular model of benzene if your model kit allows this to be done effectively. Note that the molecule is entirely planar, that all carbons are equivalent, that all hydrogens are equivalent, and that each carbon is trigonal with 120° bond angles. 

Angle bending has been divided into in-plane and out-of-plane bending modes for planar trigonal centers such as a carbonyl carbon. This division was... 

---