Born-Haber cycle Charge

The initiation of the cationic polymerisation of alkenes is examined in detail by means of simple thermodynamic concepts. From a consideration of the kinetic requirements it is shown that the ideal initiator will yield a stable, singly charged anion and a cation with a high reactivity towards the monomer by simple, well defined reactions. It must also be adequately soluble in the solvent of choice and for the experimental method to be used. The calculations are applied to carbocation salts as initiators and a method of predicting their relative solubilities is described. From established and predicted data for a variety of carbocation salts the position of their ion molecule equilibria and their reactivity towards alkenes are examined by means of Born-Haber cycles. This treatment established the relative stabilities of a number of anions and the reason for dityl, but not trityl salts initiating the polymerisation of isobutene. 

It is quite remarkable that electrostatic calculations based on a simple model of integral point charges at the nuclear positions of ionic crystals have produced good agreement with values of the cohesive energy as determined experimentally with use of the Born-Haber cycle. The point-charge model is a purely electrostatic model, which expresses the energy of a crystal relative to the assembly of isolated ions in terms of the Coulombic interactions between the ions. 

In this experiment ionisation potentials ,(n) and dissociation energies for positively charged clusters EM) have been measured. Fig. 10 shows the Born-Haber cycle relating these quantities with the electron affinities [ e.(n)] and dissociation energies for neutral clusters [ d(n)]. Energy conservation... 

The availability of laser photodetachment techniques has permitted more accurate experimental determinations of electron affinities. Even so, tables of electron affinities list some calculated values, in particular for the formation of multiply charged ions. One method of estimation uses the Born-Haber cycle, with a value for the lattice energy derived using an electrostatic model. Compounds for which this is valid are limited (see Section 5.15). 

Construct a Born-Haber cycle for the formation of the hypothetical compound NaCl2, where the sodium ion has a 24-charge (the second ionization energy for sodium is given in Table 7.2). (a) How large would the lattice energy need to be... 

Calculation of Lattice Energies The Born-Haber Cycle 304 Oxidation Numbers, Formal Charges, and Actual Partial Charges 319... 

The ionic bond results from the Coulomb attraction of oppositely charged ions. Its strength is characterised by the electrostatic energy in MX ionic crystals it is the crystal lattice energy C/(MX), which can be determined experimentally from the Born-Haber cycle or calculated theoretically from the known net charges of ions (Z, not to be confused with nuclear charges ) and inter-ionic distances d), as... 

Learn a mental check list to help you construct Born-Haber cycles have I included the enthalpy of formation have i included both enthalpies of atomisation have i converted all atoms into ions of the correct charge have i considered how many moles of each ion are in 1 mole of the compound ... 

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