Single bonds Table

The predicted bond order for a given bond is listed at the intersection of the two atoms of interest in the bond orders table. The illustration at the left shows the predicted bond orders for this molecule (where 1.0 is a traditional single bond, 2.0 is a double bond, and so on). The C-H bonds all have predicted bond orders of about. 9, while the C-C bonds have predicted bond orders of about 1.4. The latter arc consistent with the known resonance structure for allyl cation. ... 

TABLE 7.3 Topical Energies for Some Covalent Single Bonds (see Table 1.7) and the Corresponding Approximate Wavelengths... 

Incidentally, 31 contributes more to the hybrid than 32, as shown by bond-distance measurements. In benzenediazonium chloride, the C—N distance is 1.42 A, and the N—N distance 1.08 A, which values lit more closely to a single and a triple bond than to two double bonds (see Table 1.5). Even aromatic diazonium salts are stable only at low temperatures, usually only below 5°C, though more stable ones, such as the diazonium salt obtained from sulfanilic acid, are stable up to 10 or 15°C. Diazonium salts are usually prepared in aqueous solution and used without isolation, though it is possible to prepare solid diazonium salts if desired (see 13-20). The stability of aryl diazonium salts can be increased by crown ether complexion. ... 

C06-0094. Use average bond energies (Table 6-2) to compare the stabilities of ethanol, C2 H5 OH, and dimethyl ether, (CH3)2 O, which have the same empirical formula, C2 Hg O (all the bonds are single bonds). 

Although X-ray data show that in several of the protonated diamines the proton is located almost centrally between the nitrogen atoms within experimental error, the values of A[5( H) — 5( H)] prove that in only one case, 1,6-diazabicyclo[4.4.4]tetradecane [49], is the potential function of the single minimum type. It appears that the conditions for formation of a hydrogen bond with a single minimum potential function are a low N N distance and a linear —H N bond. Thus, Table 13 contains examples... 

The apparent enhancement we are discussing here is more pronounced, in general, the greater the number of terms in the S5munetry function. We now consider the third sort of function from Table 15.1. These are the 12 short-bond singly ionic functions, and in this case the enhancement of the coefficient is a factor of 5.0685, i.e., the reciprocal of the normalization constant for the symmetry function that is the sum of the individually normalized HLSP functions. The resulting coefficient would then be 0.261 637, a number essentially the same as the coefficient of the Kekule symmetry function. 

Molecules with a single helical unit, such as in hydrogen peroxide, are rare. More commonly found are bundles of two to nine units with coincident central bonds (see Table 1). The combination of two, e.g., in cyclophanes, and four, e.g., in biaryls and allenes, helical units are particularly important. Such compounds have a stereogenic axis, as stereoisomers may be... 

The observed B—O bond lengths are 1.47 0.01 A for the BO tetrahedron and 1.37 0.01 A for the BOs triangle. The B—O single-bond length (Table 7-5) is 1.43 A. The experimental values suggest that the bonds in B04 have bond number a little smaller than 1, and in BO3 a little larger than 1 (about 20 percent of double-bond character, with use of the fourth boron orbital). 

For the complex /ac,/ac-(H20)2(NH3)3Cr(0H)Cr(NH3)3(H20)25+ the first acid dissociation constant clearly shows that the singly deprotonated species must be hydrogen bond stabilized (Table XIX). However, the fact that the difference between the first and the second acid dissociation constants for this system is relatively small is consistent with stabilization also of the doubly deprotonated species (by two intramolecular hydrogen bonds) as shown in Fig. 15. A similar effect is expected for the cations (H20)5Cr(0H)Cr(H20)55+ and (H20)5Ir(0H)Ir(H20)55+. 

In the following tables, the valence state of the central atom is described in terms of orbital occupancy. Thus, for example, h h I p1 denotes a valence state in which two hybrid orbitals (of specified type) are singly occupied (and are used in bond formation) while a third accommodates a lone pair. The singly-occupied pure np orbital forms a p -p bond. Empty hybrid orbitals (denoted h°) always function as acceptor orbitals in the formation of coordinate (or dative) bonds. Doubly-occupied hybrid orbitals (h2) may be lone pairs, or may function as donor orbitals in coordinate bonds, in which case the h is underlined. A doubly-occupied np orbital always forms a dative n bond, while a singly-occupied np orbital always forms an ordinary ji bond. Singly-occupied nd orbitals form d -pn bonds. For the reasons discussed in Section 6.1, you will find few stable species where np orbitals are left empty. 

For the purposes of an engineering design at an early stage, the reaction enthalpy may be needed to an accuracy of only, say, 8 kcal/mol. Without resorting to a single bond energy table, one can predict that this reaction will be close to thermoneutral because the bonds broken and formed are so similar ... 

Bond lengths between a given pair of atoms are approximately constant from compound to compound if the nature of the bond (single, double, or triple) is the same. If it is assumed that the length of a single covalent bond is the sum of the covalent radii of the two bonding atoms, then quick and fairly reliable estimates of bond lengths can be obtained from readily available information, such as in Table 9-2. 

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