Some typical bond lengths

If tbe molecular geometry is optimized by the program, only a rough estimate of the parameters is necessary, hi term of internal coordinates, this is fairly easy. Some typical bond lengths (A) and angles are given below. 

Since the size of halogen atom Increases as we go down the group in the periodic table, fluorine atom is the smallest and iodine atom, the largest. Consequently the carbon-halogen bond length also Increases from C—to C— I. Some typical bond lengths, bond enthalpies and dipole moments are given in Table 10.2. 

Only a few X-ray crystal structure determinations on 1,3-dithioles have been carried out. Some typical bond lengths and bond angles of the tetrathiafulvalene (5), l,3-dithiole-2-thione derivative (6) and 1,3-dithiolanes (7) and (8) are given in Tables 2 and 3, respectively. Also bond lengths and bond angles of the radical cation of tetrathiafulvalene in the tetrathiafulvalene-7,7,8,8-tetracyanoquinodimethane complex have been determined <74AX(B)763>. 

If the molecular geometry is optimized by the program, only a rough estimate of the parameters is necessary. In term of internal coordinates, this is fairly easy. Some typical bond lengths (A) and angles are given below.------------------------------------------... 

Table 3.1. Some typical bond lengths and angles...

Some typical bond lengths are listed in Table 15.5, where Xn denotes an atom X bonded to n neighbors and Car is an aromatic carbon. 

TABLE 15.5 Some Typical Bond Lengths in Angstroms ... 

Table 5.2 Typical bond lengths and dissociation energies for some selected primary bonds...

TABLE 2.1. Bond Lengths of Some Typical Bonds (A)... 

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. 

As a result of many observations on the energetics of the formation and dissociation of molecules it has been found possible to give typical bond energies and bond lengths to a number of bonds. Some of these are given in Table 5.2. 

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