Conventions of Drawing Structures

The conventions for drawing organometallic and inorganic compounds differ in subtle ways from those used to draw ordinary organic compounds. The most important difference is the way in which bonds are drawn. In organic compounds, 

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Chemists and biochemists use simple conventions for drawing structures of carbon-containing compounds to avoid drawing every atom. Each vertex of a structure is understood to be a carbon atom, unless otherwise labeled. In the shorthand, we usually omit bonds from carbon to hydrogen. Carbon forms four chemical bonds. If you see carbon forming fewer than four bonds, the remaining bonds are assumed to go to hydrogen atoms that are not written. Here are some examples ... 

Inorganic phosphate chemists have normally treated their systems in much the same conventions in drawing structures and placing cations as organic chemists have done. In melts and glasses this is probably justified, but in a solid crystalline state it is well known that placement of cationic functions in structures is an oversimplification. Nevertheless, we shall follow the conventions for convenience, while recognizing that placement of anions and cations is often not a good representation. 

ChemSketch has some special-purpose building functions. The peptide builder creates a line structure from the protein sequence defined with the typical three-letter abbreviations. The carbohydrate builder creates a structure from a text string description of the molecule. The nucleic acid builder creates a structure from the typical one-letter abbreviations. There is a function to clean up the shape of the structure (i.e., make bond lengths equivalent). There is also a three-dimensional optimization routine, which uses a proprietary modification of the CHARMM force field. It is possible to set the molecule line drawing mode to obey the conventions of several different publishers. 

Testosterone, conformation of, 129 molecular model of, 129 structure and function of, 1082 Tetracaine, structure of, 967 Tetrahedral geometry, conventions for drawing. 8... 

Fig. 1 (a) Ball and stick structure of faujasite (FAU). (b) Conventional stick drawing of faujasite (FAU). 

Lavastre s approach is valid, but the use of (a) less reactive brominated arenes and (b) the obvious lack of solubilizing groups restricts the value of this approach. Perhaps all of the 96 polymers would have to be made in a conventional approach and compared to the polymers obtained by the high-through-put method to draw further conclusions. In addition, the fluorescence was measured in situ, in a THF/diisopropylamine mixture in the presence of the Pd-Cu catalyst. That approach may have an intrinsic problem too, because it is known that PAEs are solvatochromic, and as a consequence, the obtained fluorescence data might be biased. However, with some tweaking this is a powerful method to obtain a cornucopia of different structures quickly and without too much synthetic effort, if the monomers are easily available. 

How can we draw a hybrid, which has delocalized electron density First, we must determine what is different in the resonance structures. Two differences commonly seen are the position ol a multiple bond and the site of a charge. The anion (HCONH) illustrates two conventions foi drawing resonance hybrids. 

The stereogenic centers in sugars are often depicted following a different convention than is usually seen for other stereogenic centers. Instead of drawing a tetrahedron with two bonds in the plane, one in front of the plane, and one behind it, the tetrahedron is tipped so that horizontal bonds come forward (drawn on wedges) and vertical bonds go behind (on dashed lines). This structure is then abbreviated by a cross formula, also called a Fischer projection formula. In a Fischer projection formula ... 

The concepts and conventions behind Lewis structures were covered in your previous courses, and there is no need to recapitulate them here. One aspect of drawing Lewis structures that often creates errors, however, is the proper assignment of formal charges. A formal charge on any atom is calculated as follows ... 

A simpler way of drawing the structure of the benzene molecule and other compounds containing the benzene ring is to show only the skeleton and not the carbon and hydrogen atoms. By this convention the resonance structures are represented by... 

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