Atomic bonding energy, 43 Table

For approximate estimation of enthalpy changes during reactions, use can be made of empirical bond energies (Table 6-7) which represent the approximate enthalpy changes (-AH°) for formation of compounds in a gaseous state from atoms in the gas phase. Other more comprehensive methods of approximation have been developed 49/50... 

Exercise 10-28 Bromotrichloromethane, BrCC 3, adds to 1-octene by a radical-chain mechanism on heating in the presence of a peroxide catalyst. Use the bond-energy tables to devise a feasible mechanism for this reaction and work out the most likely structure for the product. Show your reasoning. Show the most likely product of addition of BrCCI3 to 1-octyne. [Note Radical-chain reactions involve abstraction of atoms, not abstraction of groups.]... 

From bond energies (Table 4-6) we know that the weakest C—H bonds of propene are to the allylic hydrogens, H2C=CHCH2—H. Therefore, in the first step of radical-chain chlorination of propene, an allylic hydrogen is removed by a chlorine atom (Equation 14-1). The allylic C-H bonds are weaker than the alkenic C-H bonds because of the extra stabilization of the radical obtained on hydrogen abstraction (Equation 14-1). Two equivalent valence-bond structures (1a and 1b) can be written for the 2-propenyl radical the electron delocalization enhances the stability of the radical (see Section 6-5C) ... 

Note The bond energy is the energy required to dissociate the gas-phase diatomic molecule Into its constituent atoms. Bond energies for the second-period homonuclear diatomic molecules are given in Table 6.3. 

Use bond energies (Table 9.2) to determine (The S atoms in H2S2O7 are bonded through an O atom. Assume Lewis structures with zero formal charges BE of S=0 is 552 kJ/mol.)... 

Another recommended method for the estimation of the hazard potential related to a synthesis is the calculation of the enthalpy of reaction with the help of increments. The methods using increments rely on a thermodynamic basis. One of the most common method makes use of the tables of atomic bond energies available in the literature. Educts and products are split into units of known bond energies, the increments. These are subsequently balanced in the well known thermodynamic way ... 

Poly(vinyl chloride), - CH2CHCl- , is a major commercial plastic. Trichloroethylene and tetrachloroethylene cannot be polymerized since the tendency toward transfer reactions increases for monomers containing halogen atoms of increasing size, and this can be traced back to differences in bond energies (Table 25-5). Likewise, only low degrees of polymerization... 

Similar bonds between the same pairs of atoms usually have similar bond lengths and bond energies. Thus, we can develop tables of typical bond energies (Table 7-3) and bond lengths (Table 7-4) for each type of covalent bond. 

The reaction rate of molecular oxygen with alkyl radicals to form peroxy radicals (eq. 5) is much higher than the reaction rate of peroxy radicals with a hydrogen atom of the substrate (eq. 6). The rate of the latter depends on the dissociation energies (Table 1) and the steric accessibiUty of the various carbon—hydrogen bonds it is an important factor in determining oxidative stabiUty. 

These data also show that the bond energies decrease as the atomic number of the metal increases in the same Group of the Periodic Table. 

Typical values of the energy to form vacancies are for silver, lOSkJmol and for aluminium, 65.5kJmol These values should be compared with the values for the activation enthalpy for diffusion which are given in Table 6.2. It can also be seen from the Table 6.2 that die activation enthalpy for selfdiffusion which is related to the energy to break metal-metal bonds and form a vacant site is related semi-quantitatively to the energy of sublimation of the metal, in which process all of the metal atom bonds are broken. 

From the following bond energy data and the ionization energies given in Table 15-111, calculate the entries in the last two columns of Table 16-111 for the compounds LiF and LiBr. The ionization energy, (, for bromine atom is 273 kcal/mole. 

Bond Energies and the Relative Electronegativity of Atoms.—In Table II there are collected the energies of single bonds obtained in the preceding sections. One additional value, obtained by a method to be described later, is also included 1.44 v. e. for N N. Under each bond energy is given the value for a normal covalent bond, calculated from additivity, and below that the difference A. It is seen that A is positive in twenty of the twenty-one cases. The exception, C I, may be due to experimental error, and be not real. 

Table 2-1. Bond energies for atoms of biologic significance.

C06-0030. Prepare a table listing all the bond energies involving halogen atoms (F, Cl, Br, I), organized so it... 

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