Multiple exchange factor

Rudakov and coworkers have proposed another mechanism for multiple exchange [14], The authors found that the multiple exchange factor M for H-D exchange of cyclohexane increases from 1 to 1.8 with an increase of acidity. Proceeding from the assumption that the dissociation rate... 

M= multiple exchange factor denoting the average number of hydrogen atoms exchanged within one contact. 

The differences in the factor of multiple exchange for aromatic molecules could be explained to a considerable extent by steric factors. The large value of the factor M for benzene testifies for a high probability of the 1,2-shift (possibly via the intermediate formation of dehydrobenzene) ... 

The contributions to the integral Z that we discarded in Z are simply those where solvent molecules in S and in Sm exchanged position. Since all solvent molecules are identical, the discarded contributions to the integral Z are equivalent to the ones in Z (Eq. 2.4), and the two expressions differ only by a multiplicative constant factor C Z = Z/C. 

An economic exchanger design cannot normally be achieved if the correction factor Ft falls below about 0.75. In these circumstances an alternative type of exchanger should be considered which gives a closer approach to true counter-current flow. The use of two or more shells in series, or multiple shell-side passes, will give a closer approach to true counter-current flow, and should be considered where a temperature cross is likely to occur. 

---