Structural formulas from

The familiar problem of misleading stoichiometries, and the frequent impossibility of deducing the correct structural formula from the empirical composition is well illustrated by the... 

Keep in mind that carbon atoms are not shown in a line structure, so the first step in constructing a structural formula from a line structure is to place a C at every line intersection and at the end of eveiy line. Then add singly bonded hydrogen atoms (—H) until every carbon atom has four bonds. Example 3-3 illustrates this procedure. 

Even if it were possible to identify sufficient structural elements in a molecule to account for the molecular formula, it may not be possible to deduce the structural formula from a knowledge of the structural elements alone. For example, it could be demonstrated that a substance of molecular formula C3H5OCI contains the structural elements ... 

Figure 4. Structural formulas from Couper s second paper in 1858, and the modem versions of the same formulas. Note that Couper s structure for cyanuric acid is not correct, having the oxygen atoms bonded to nitrogen.

EXAMPLE C.l Drawing structural formulas from condensed structural formulas and stick formulas... 

Draw structural formulas from all of the 3D Models of the examples of the families of organic molecules in eChapter 23.8. Circle the functional group in each of the molecules. Which families do you expect to exhibit hydrogen bonding ... 

When used alone however, the methods also have several disadvantages. The amount of information is limited, because scarcely the physical properties alone will give sufficient information to elucidate the chemical constitution of a fossil particle. So it will be mostly impossible to write the structural formula from spectral... 

A number of people have compiled data on the range and average composition of glauconite (Hendricks and Ross, 1941 Smulikowski, 1954 Borchert and Braun,1963). For the present review 69 analyses and 82 structural formulas from the literature were selected. 

The absolute configuration, (25,45,55) as shown or (2R,4R,5R), cannot be deduced by NMR. For larger structures the insertion of the shift values and the coupling constants in the stereo projection of the structural formula, from which one can construct a Dreiding model, proves useful in providing an overview of the stereochemical relationships. 

I thank Dr. Frans riuijing for his n,j,ny helpful suggestions in all areas of this book. Dr. Bert Pressman provided a number of useful discussions. Charles Messing drew the Biochemistryiand map, the cover illustration, and the text figures. I am grateful to the Boehringer-Mannheim Biochemical Co. for their kind permission to reproduce, in the Structural Index, many of the structural formulae from their excellent map of the pathways in biochemical metabolism. 

DENDRAL uses a set of rule-based methods to deduce the molecular structure of organic chemical compounds from chemical analysis and mass-spectrometry data. This process includes detecting structural fragments, generating structural formula from these fragments, and verifying it by determining the correlation between... 

Dubois and colleagues studied the problem of overlapping fragments. They developed the program DARC-EPIOS, which can retrieve structural formulas from overlapping C-NMR data [29]. The COMBINE software uses similar techniques. 

DARC-EPIOS is an automated software for retrieving structural formulas from overlapping C-NMR data. 

Organic compounds have essential information about their reactivity encoded in their structural formulae from which their reactivity can be deduced. Furan, benzo[6]furan, isobenzofiiran, dibenzofuran and tetrahydrofuran are good examples of this. 

Writing structural formulae from names of alkanes... 

To write a structural formula from a systematic name, the naming process is reversed. For example, how would we write the structural formula for 4-methyl-2-pentene The name indicates (1) five carbons in the longest chain, (2) a double bond between C-2 and C-3, and (3) a methyl group on C-4. 

So far we have learned how to name a compound by examining its structural formula. We also must be able to do the reverse write the structural formula from the name. 

The above proposition can be used to determine both a molecular formula and a structural formula from a mass spectrum I. We will use Proposition 8.12 to calculate a match value (MV) for a given candidate molecular or structural formula K that measures the plausibility that K explains spectrum I. Ideally, such a compatibility match value should fulfill several requirements It should be between 0 and 1... 

Solution To get the structural formula from the lUPAC name, first write the longest chain or ring, number it, and then locate the multiple bond. In this case, note that the chain has five carbons and that the double bond is located between carbon-2 and carbon-3 ... 

SAMPLE PROBLEM 17.2 Drawing Structural Formulas from... 

To be unambiguous (one structural formula from one representation on the basis of a certain representation rule)... 

The following procedure is generally adopted for assigning a systematic name to a given compound or for deriving a constitutional/structural formula from a given name ... 

Table 3.4 Derivation of a structural formula from oodde weight percents. See the text for details of the cation assignment to the different structural units.

EXAMPLE 3-15 Writing Structural Formulas from the Names of Organic Compounds... 

In summary, to obtain a structural formula from the name, we split the name into its component pieces stem, prefix, and suffix. All three components provide information about the structure of the molecule. 

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