Structural formula representation

A line structure is built by using information about how atoms are connected in the molecule. The stmctural formula is the basis for the line stmeture. Apply the guidelines to convert the structural formula representation into a line-structure representation. 

There is significant information encoded in structural formulas, however, the information is essentially qualitative. It is true that molecules described by different structures have different properties and that a ranking of expected properties may be predicted from the formulas of isomers however, the structural formula lacks a quantitative character. How numerically different are pentane, isopentane and neopentane The structural formula representation has usually been considered outside the realm of quantitative structure description, bounded by quantum mechanics and a count of atoms. 

Now write structural formulas for the remaining three isomers Be sure that each one IS a unique compound and not simply a different representation of one writ ten previously... 

Structure. The representation of the benzene molecule has evolved from the Kekule ring formula (1) to the more electronically accurate (2), which iadicates all carbon—carbon bonds are identical. 

The molecule NH2 has residual, unused bonding capacity and is extremely reactive. The molecule N2H4 (hydrazine) is much more stable. Draw an electron dot representation of the bonding of hydrazine. Draw its structural formula (show which atoms are bonded to each other). 

Notice that the structural formulas (52a) and (52b) use another representation of the bonding. It is quite familiar, of course, since it corresponds... 

If all the oxygen containing groups are reduced, n-hexane results. This test helps establish that the glucose molecule has a chain structure. One representation of the structural formula of glucose, C6Hi206, is... 

Chemists use both chemical names and molecular pictures to describe molecules. Molecular pictures take several forms, including structural formulas, ball-and-stick models, space-filling models, and line structures. These molecular representations can help you improve your ability to think molecules. ... 

Substituted ethylenes in which substituents occur on both carbon atoms (with the exception of the fluoroethylenes) usually are not prone to polymerize, although some of them, such as the maleates and fumar-ates, copolymerize readily with other monomers. The further fact that, with rare exceptions, the monomers unite through the addition of the substituted carbon atom of one unit to the unsubstituted carbon atom of the next permits representation of nearly all vinyl addition polymers by the general structural formula... 

Most of the models and descriptors discussed so far are based on the two-dimensional representation of the compounds, i.e. on their structural formula. 

FIGURE 60 Formulas of organic substances. The molecular formula of an organic substance conveys information about the nature of the component elements (expressed by symbols) and the number of atoms of each element that make up a molecule of the substance if greater than one, the number of atoms of each element is indicated by a subscript. The structural formula provides a two-dimensional representation of the arrangement of the atoms in the molecule, showing how they are attached to one another and the type of bonds involved. 

Electron dot formulas are useful for deducing the structures of organic molecules, but it is more convenient to use simpler representations—structural or graphic formulas—in which a line is used to denote a shared pair of electrons. Because each pair of electrons shared between two atoms is equivalent to a total bond order of 1, each shared pair can be represented by a line between the symbols of the elements. Unshared electrons on the atoms are usually not shown in this kind of representation. The resulting representations of molecules are called graphic formulas or structural formulas. The structural formulas for the compounds (a) to (e) described in Example 21.1 may be written as follows ... 

For the depiction of structural formulas of hexofuranoses, a combination of a three-dimensional, Haworth-perspective tetrahydrofuran ring with a Fischer projection of the C-5-C-6 side-chain is commonly used, as exemplified by formulas 3 and 6. With the formal closure of the second ring and formation of a 2,6-dioxabicyclo[3.3.0]octane system, however, the depiction of the C-6-C-3 ring, as in formula 7, also assumes three-dimensional geometry, and this does not correspond to the Fischer projection rule.11 Consequently, structural representations of such bicyclic molecules should be as close as possible to the actual steric situation, as shown by structures 4 and 8. 

In addition to monomeric compounds, Tabemaemontana plants contain many bisindole alkaloids that are classified on the basis of constituent monomeric units, as in the extensive review by Cordell and Saxton in Volume XX of this series (14). This classification is more rational and comprehensive than others (I, 13, 15) and will be used as a guide for the representation of structural formulas and for the discussion of the chemistry of single alkaloids. 

Perhaps critics of the chemists were understandably confused, since the formulas frequently were referred to as "constitutional" or "structural" formulas. (See fig. 5.) Frankland s use of the terms "graphic" and "glyptic" formulas is less misleading. This notation, he wrote, expresses the chemical function of atoms, and while some critics counsel the danger that students will regard them as representations of the actual physical position of atoms, Frankland reported that in practice he had not found "this evil to arise." 100... 

As a starting point in the description of the solid intermetallic phases it is useful to recall that their identification and classification requires information about their chemical composition and structure. To be consistent with other fields of descriptive chemistry, this information should be included in specific chemical and structural formulae built up according to well-defined rules. This task, however, in the specific domain of the intermetallic phases, or more generally in the area of solid-state chemistry, is much more complicated than for other chemical compounds. This complexity is related both to the chemical characteristics (formation of variable composition phases) and to the structural properties, since the intermetallic compounds are generally non-molecular in nature, while the conventional chemical symbolism has been mainly developed for the representation of molecular units. As a consequence there is no complete, or generally accepted, method of representing the formulae of intermetallic compounds. 

Beneath the synonyms is the structural formula, a graphic representation of atoms or group(s) of atoms relative to one other. This is given for every compound regardless of its complexity. The limitation of stmctural formulas is that they depict these relationships in two dimensions. 

Figure 15.2 Structural formula of tetrahydrofolate and representation of derivatives involved in single carbon transfer. The tetrahydrofolate is always part of a complex with several glutamate residues. The parent compound, pteroylglutamate (folate) lacks four hydrogen atoms, one each from carbon atoms 5, 6, 7 and 8. Tetrahydrofolate can exist in any one of three oxidation states, as shown they are interconvertible through oxidereduction reactions. Each plays a individual and different role is synthesis of key compounds (See below).

This representation is called a structural formula, in which lines depict two electron bonds between atoms. Look at the propane structure and observe that the 4 bonds to each carbon complete its valence orbitals with 8 electrons. 

The structural formula for propane shows 3 axial carbon atoms and 8 peripheral hydrogen atoms. The composition of propane can be more compactly expressed as C3 Hg. This representation is a molecular formula. Such a formula does not directly tell how the various atoms are interbonded. 

B. A. Arbuzov, I. S. Andreeva, and Z. G. Isaeva, Bull. Acad. Sci. U.S.S.R., 1976, 25, 1584 Chem. Abs., 1977, 85, 143 311 has the structures of these cyclic sulphites hopelessly in error, presumably because conformations and structural formulae have been confused from poor representations in the paper. 

Fig. 1. Schematic representation of basic silicate structures (a) modes of linkage of Si04 tetrahedra (b) the corresponding bonding patterns and (c) structural formulas (3). The Si atoms that appear to be joined to only three O atoms are joined to a fourth also, which is above the plane of the diagram.

Figure 13.9 Structure formula of rotaxane 9H3+ and representation of its operation as a pH controllable molecular shuttle.

Start 1D WIN-NMR, enter the Preview window and use the Frame option to open a frame for the 2D layout copied into the clipboard in the previous Check it. With the cursor positioned within the frame double click on the left mouse button to open the dialog box. Click on Paste and then OK to Import the 2D layout. Double click the left mouse button and in the Metafile Options dialog box adjust x-Factor and y-Factor to position the 2D layout correctly within the frame. Open additional frames to accommodate the entire 1D C spectrum D. NMRDATA GLUCOSE 1D C GC 001999.1 R) and the structural formula (Fig. 4.33). Arrange and resize these frames for the best representation. Use additional graphical elements (Lines, Rectangle) available within the Preview window of 1D WIN-NMR for assignment purposes. Set up your output device and plot the layout. 

Orbital is the highest occupied molecular orbital (HOMO) in the ground state. It corresponds to the structural formula of the molecule, with double bonds between and C2, and between C3 and C4. Orbital is likewise the lowest unoccupied molecular orbital (LUMO) in the ground state and corresponds to a biradical structure of the molecule with unpaired electrons on Gj and C4. Such a biradical structure can be a very simple but sometimes useful representation of the excited molecule (in states Si or T. ... 

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