Radial Hexagon Analysis

FIGURE 6.8 Radial pentagon for acid chloride synthesis [6]. Thionyl chloride is counted as a reagent not a reaction solvent however, E-aux is not zero since benzene, toluene, and dichloromethane were used as solvents in the work-up procedure. 

A parameter that can describe the overall degree of greenness, or relative greenness, of a synthesis plan, with respect to the ideal green synthesis, may be defined as the vector magnitude ratio (VMR) given by Equation 6.5. 

FIGURE 6.10 Radial pentagon for classical resolution of l-phenylethylamine [8]. Note that the yield of the diastereomeric salt in the first step is less than 50%. 

The underlying assumption is that all six parameters are mutually independent. The root 6 factor applies to the magnitude of the vector when all six parameters have a value of 1. Another possible parameter that could have been chosen is the relative area of the actual and green limit hexagons. However, this is problematic because the area of the actual hexagon will depend on the order of the parameters chosen. The vector magnitude does not depend on the order of the coordinates. In the preceding two examples, the VMR values are 0.830 and 0.139, respectively. 

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Figure 12.3 shows the trend between % overall yield and VMR obtained from the radial hexagon analysis based on 587 plans for compounds with multiple plans as noted in Chapter 13. Most plans gravitate to the lower left-hand comer of the plot. The four plans in the top right comer are as follows with the % overall yields given in parentheses (a) Roesler plan [20] for vanillin (70.0) ... 

FIGURE 12.2 Correlation between AE and VMR from radial hexagon analysis. 

Other ionic systems were also studied for example, solutions of soap micelles such as potassium oleate were found to give sharp small-angle X-ray diffraction bands [4]. Brady carried out a Fourier analysis of the X-ray diffraction of solutions of sodium dodecyl sulfate to calculate the radial distribution function g(r) and the number of nearest neighbors (N ) [5]. At about 30%, the N was about 12, indicating that the spherical micelles tended to assume a close-jmcked hexagonal arrangement. 

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