Structural formula A representation

Structural formula A representation that shows how atoms are connected in a compound. 

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. 

The following structure is a representation of histidine, an amino acid constituent of proteins. Only the connections between atoms are shown multiple bonds are not indicated. Give the molecular formula of histidine, and complete the structure by showing where the multiple bonds and lone pairs are (red = O, gray = C, blue = N, ivory = H). 

The only information that structural formulas provide is how a given atom is bonded (if at all) to others, or, in the words of Butlerov, how the chemical interaction is distributed . Moreover, when chemists began using the graph theory, they simplified the representation of a molecule as compared to the classical one. In distinction to a structural formula a topological graph, as a rule, has no... 

Strong electrolyte a material that, when dissolved in water, gives a solution that conducts an electric current very efficiently. (4.2) Structural formula the representation of a molecule in which the relative positions of the atoms are shown and the bonds are indicated by lines. (2.7)... 

Structural formula the representation of a molecule in which the relative positions of the atoms are shown and the bonds are indicated by lines. 

Structural formula (A) contains both an amino group (a base) and a carboxyl group (an acid). Proton transfer from the stronger acid (— COOH) to the stronger base (— NH2) gives an internal salt therefore, (B) is the better representation for alanine. Within the field of amino acid chemistry, the internal salt represented by (B) is called a zwitterion (Chapter 18). 

The middle formula above is a structural formula, a formula that shows not only the number and type of each atom in a molecule, but the structure as well. Structural formulas are not three-dimensional representations of the molecule— as space-filling models are— but rather two-dimensional representations that show which atoms are bonded together. A structural formula is like a Lewis structure, but it typically depicts bonding electron pairs as dashes and omits lone pairs. 

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... 

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... 

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. 

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 ... 

A single unstable compound of known composition is placed in the main first volume and is located on the basis of its empirical molecular formula expressed in the Hill system used by Chemical Abstracts (C and H if present, then all other element symbols alphabetically). The use of this indexing basis permits a compound to be located if its structure can be drawn, irrespective of whether a valid name is known for it. A representation of the structure of each compound is given on the third bold title line while the name of the compound appears as the first bold title line. References to the information source are given, followed by a statement of the observed hazard, with any relevant explanation. Cross-reference to similar compounds, often in a group entry, completes the entry. See Trifluoroacetyl nitrite p. 244. 

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. 

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. 

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