Physical Organic Chemical Applications

All bond angles in adamantane are nearly 109.5 ° (see above). Theory170) predicts, therefore, that all carbon bonding orbitals should be nearly pure sp3 hydrids. The situation in norbomane is quite different. Endocyclic bond angles of this molecule are considerably less than 109.5 ° 17 l. The p character of the endocyclic carbon orbitals should be greater than that of the exocydic orbitals170). 

The differences in the hybridizations of the exocyclic bridgehead bonds of adamantane and norbomane are reflected by the bridgehead C13-H coupling constants observed for the two systems Jq1 3-H = 120 lHz for all hydrogens in adamantane 1S°) Jq 3 h = 139 1 Hz for norbomane 172). These coupling constants correspond to 24 and 28 % s character for the exocyclic bridgehead C orbitals of adamantane and norbomane, respectively 173). 

The observed trend in F19 chemical shifts may be due to an increased interaction of the nonbonded electrons of the fluorine atom with the greater p character of the endocyclic bonds in the more deformed systems 17S). A si- 

The same effect is also observed in the bicyclo[2.2.2]octyl system 175f In this system, the effect has been attributed to a substituent induced structural perturbation. The electronegative fluorine and substituent repel each other resulting in enhanced p-character of the endocyclic C-C bonds. The C-F bond order may, therefore, be enhanced as discussed above for the unsubstituted polycyclic fluorides 17S . 

---

Jahnke H, Schonbom M, Zimmermann G (1976) Organic dyestuffs as catalysts for fuel cells. In Schafer F, Gerischer H, Willig F, Meier H, Jahnke H, Schonbom M, Zimmermann G (eds) Physical and chemical applications of dyestuffs, vol 61. Springer, Heidelberg, pp 133-181... 

Certain physical or chemical characteristics of the wastestream may limit the application of precipitation. For example, some organic compounds (as well as cyanide or other ions) may form organometallic complexes with metals, decreasing the precipitation potential. 

In all of these applications, the emphasis to date has been on the use of lasers to study chemically and physically well characterized systems, that is, simple molecules in the gas phase, or in ordered phases such as molecular crystals, or in cryogenic matrices. There are exceptions to this statement, but the basic fact is that the great strides in chemical applications of lasers have been made by the chemical physics and analytical chemistry communities and largely ignored by inorganic, organic, and biological chemists. 

Third, the electron theory of valence, cultivated mainly by Anglo-American physicists and physical chemists in the first two decades of the twentieth century, offered mechanical models for chemical affinity on the molecular level. These models combined data from structural chemistry with insights about physical mechanisms involving ions and electrons from the rapidly developing work of radiation physicists and spectroscopists. The further application of this third approach is the subject of chapters 6, 7, and 8, as it was developed by specific research schools in different national traditions and became part of the fundamental framework of the new subdiscipline of physical organic chemistry. 

---