Molecular elevator

The use of water as a solvent should be avoided whenever possible, as its Molecular Elevation Constant is so low that only a small elevation of the boiling-point is obtained. 

The molecular elevation constants given on p. 440 can be used, but it is advisable to check the constant of the solvent, using a pure sample of a known compound under precisely the same conditions as those of the first determination. 

Where M is the molecular weight of the solute, Dt is the elevation of boiling point in °C, c is the concentration of solute in grams for lOOOgm of solvent, and K is the Ebullioscopic Constant (molecular elevation of the boiling point) for the solvent. K is a fixed property (constant) for the particular solvent. This has been very useful for the determination of the molecular weights of organic substances in solution. 

Corollary.—The molecular elevation of boiling-point is independent of the nature of the solute. 

TABLE 11.9 Molecular Elevation of the Boiling Point (Continued)... 

Figure 13.11 Structure formula of 10H39+ and its operation as a molecular elevator controlled by acid-base inputs.

The constant, K, for the molecular elevation of the boiling-point of carbon disulphide is 23-7.1 The specific heat, C, of liquid carbon disulphide is given by2... 

Figure 11.42 Components and schematic of the molecular elevator (image courtesy of Prof. Sir J. F. Stoddart).68...

Changes in pH have also been used to power a molecular elevator developing a force of some 200 piconewtons per molecule.68 The triple thread 11.70, when protonated as shown, is readily... 

Fig. 8.4 A pH-driven molecular elevator, 2-H39+/26+. The red saw-tooth trace shows the increase in the absorption intensity on addi-...

The molecular elevation of the boiling-point is calculated in a similar manner, and has the value 5-2° C. 

Fig. 17 (a) Seif-assembly of the triply threaded supramolecular system 14 j13H36+ and the subsequent synthesis of the triply interlocked species 15H39+. (b, c) Operation of I5H39+ as an acid-base controlled molecular elevator [78-80]... 

NMR data on the dethreading/rethreading and deprotonation/reprotonation mechanisms of these species, have ultimately led to the design and construction of the acid/base-driven molecular elevator 158c <2004SCI1845, 2006JA1489>. 

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