Orientation unusual

Figures 11.11 through 11.13 illustrate the type of metal loss responsible for a dozen tube leaks over a 3-month period. Note the highly localized character of the metal loss, as well as the unusual shapes and random orientations of the eroded sites. The sites were located at the inlet end and resulted from the lodgment of debris at the mouth of the tube. Highly localized turbulence created by this debris caused the erosion.

For centrifugal compressors, nozzle orientation must be specified. If the compressor is on an elevated foundation, the down-nozzle orientation makes maintenance much easier, because major piping does not have to be removed to lift the casing upper half. Figure 11-1 shows an unusual case where all the nozzles are in the upper casing half. 

The revision leads to a difference of 0.06 A. between the interatomic distance in the normal oxygen molecule and the sum of the double-bond radii. This may be attributed to the presence of an unusual structure, consisting of a single bond plus two three-electron bonds. We assign this structure both to the normal 2 state, with ro = 1.204 A., and to the excited 2 state, with ro = 1.223 A., the two differing in the relative spin orientations of the odd electrons in the two three-electron bonds. We expect for the double-bonded state the separation n 1.14 A. 

Unusual orientation has been reported for amination with halomines and with NCI3 in the presence of AICI3. For example, toluene gave predominately meta amination. It has been suggested that initial attack in this case is by Cl and that a nitrogen nucleophile (whose structure is not known but is represented here as NHJ for simplicity) adds to the resulting arenium ion, so that the initial reaction is addition to a carbon-carbon double bond followed by elimination of HCl ... 

In some cases, chemical substituents can bring about unusual monotropic liquid crystalline phases which only exist upon heating or cooling. The diphenyl-diacetylenes are examples in this category [22]. Early theoretical connections between molecular electronic structure and orientational order... 

In contrast to the above case, addition of HCl to 1,1-dimethylallene at —78°C gives at least two thirds and possibly exclusively l-chloro-3-methyl-2-butene, 33, although these results are complicated by rearrangement of the allene to isoprene and the addition of HCl to the isoprene (65). No satisfactory explanation was offered (65) and none is readily available within the carbonium framework to account for the unusual orientation in this addition. Certainly the tertiary carbonium ion, 34, should be more stable than the primary carbonium ion, 35, since neither is stabilized by the adjacent perpendicular n center. This result is all the more surprising since tetramethylallene, 36, behaves as expected... 

Stretched Polymers MF membranes may be made by stretching (Fig. 20-68). Semicrystalline polymers, if stretched perpendicular to the axis of crystallite orientation, may fracture in such a way as to make reproducible microchannels. Best known are Goretex produced from Teflon , and Celgard produced from polyolefin. Stretched polymers have unusually large fractions of open space, giving them very high fluxes in the microfiltration of gases, for example. Most such materials are very hydrophobic. 

Orientational disorder is also present if a molecule or part of a molecule occupies two or more different orientations in the crystal, even without performing unusual vibrations. For example, tetraethylammo-nium ions often occupy two orientations that are mutually rotated by 90°, in such a way that the positions of the C atoms of the methyl groups coincide, but the C atoms of the CH2 groups occupy the vertices of a cube around the N atom, with two occupation probabilities. 

---