Electron-acceptation volume

The frontier orbital theory was developed for electrophilic aromatic substitution (Chapter Elements of a Chemical Orbital Theory by Inagaki in this volume). Application is successful to the ortho-para orientation (Scheme 23a) for the benzenes substituted with electron donating groups. The ortho and para positions have larger HOMO amplitudes. The meta orientation (Scheme 23b) for the electron accepting groups is under control of both HOMO and the next HOMO [25]. 

Ferrocene can be used to detect carbon monoxide (CO) by coordination, which increases the electron acceptability by the formation of a stable Fe-CO bond. Kim et al.222 have synthesized and investigated a ferrocenyl-based dendrimer as a CO gas sensor. The metalloden-drimer sensor showed a linear increase by 10 times up to 40% volume concentration, above which it was saturated. The transient responses exhibited a delay time of 50 seconds, a rising time of 150 seconds, and a falling time of 420 seconds, which were fair for a gas sensor when the diffusion time of gas into the chamber and the continued reaction with the remaining gas in the chamber after the introduction of the gas has been terminated are considered. 

The major drawback of CO2, insofar as solvent behavior is concerned, is that it is a poor solvent for many polar and nonpolar compounds, although it can dissolve many small molecules (9). It was once believed that CO2 had solvent properties similar to those of hexane based on solubility parameter calculations but in fact, McFann et al. have shown that the quadrapole moment of CO2 serves to inflate the calculated solubility parameter by 20% (10,11). Consequently, using the solubility parameter as a sole determination of solubility could be misleading. The polarizability/volume has been suggested as a better parameter on which to estimate the solvent power of CO2, but the polarizability/volume of CO2 indicates that it is a weak solvent (11). Other properties of CO2 include low polarizability and electron accepting capacity, since CO2 is a Lewis acid. 

Mendeleev s reluctance toward reduction was not widely shared. One of the codiscoverers of the periodic system, the German Lothar Meyer, accepted the possibility of primary matter and supported Prouf s hypothesis. He was also happy to draw curves through numerical data, including his famous plot of atomic volumes that showed such remarkable periodicity that it helped in the acceptance of the periodic system. Nonetheless, prior to Thomson s discovery of the electron, no accepted model of atomic substructure existed to explain the periodic system, and the matter was still very much in dispute. 

Patel et al., 1974), but no effect is observed for neutral (Group IV) impurities in Ge or Si. Also, impurities that are electron-donors soften both Ge and Si at temperatures above about 450 °C whereas accepter type impurities soften Ge, but not Si. Another important point is that small impurity concentrations have little effect. The effects begin at concentrations of about 1018/cc. Since the atomic volume of Si is 20 A3, the critical ratio of impurity to Si atom is about 2 x 10 5. Therefore, the average lineal distance between impurity atoms is about one every 270 A. 

---