Analog propellant

This burning rate equation has been tested by McAlevy (58) with a so-called analog propellant. [The technique was first seriously exploited by Burger and van Tiggelen (17,96). ] In one form this propellant con-... 

The modern Russian MIA flaw detectors use pulse version of the method [1-3], which peirnits to produce very portable (0.7 - 1.5 kg) and simple instruments, convenient especially for in-service testing. The objects to be tested are multilayer structures of reinforced plastics, metals and other materials honeycomb panels, antenna fairings, propellers, helicopter rotors and so on. In mentioned instruments amplitude-frequency analog signal processing is used. 

Free radicals with resonance are definitely planar, though triphenylmethyl-type radicals are propeller shaped, like the analogous carbocations (p. 225). 

Mislow, who discussed MM in some detail in his textbook (64), has performed excellent systematic studies of overcrowded methanes (3) (molecular propellers) and ethanes (4) and their metal analogs by the combination of dynamic NMR with MM calculations. Since his own reviews have been published (65,66), only very recent results are mentioned. 

Tetranitrohexahydropyrimidine (DNNC) (94) has been synthesized from the nitrolysis of the A(iV -di-fert-butylpyrimidine (93). Levins and co-workers reported the synthesis of DNNC (94) from the nitrolysis of the analogous A. V -di-wo-propylpyrimidine (92). DNNC is a high performance explosive with a detonation velocity of 8730 m/s, impact sensitivity lower than RDX and a very favourable oxygen balance. DNNC has been suggested " for use as an oxidizer in propellant compositions. This is also considered as an excellent oxidant for pyrotechnic compositions. ... 

The use of isophthalic acid-2-methyl aziridine was also reported as a bonding agent for composite propellants in the literature. Based on this fact, its analog, that is, isophthalic dimethyl oxaziridine (reaction product of oxaziridine unsubstituted on the nitrogen and isophthaloyl dichloride) also appears to be a potential bonding agent [223] but needs to be evaluated in propellant formulations. 

TNAZ (2.19) is also known as 1,3,3-trinitroazetidine (C3H4N406) and was first prepared in 1983 at Fluorochem Inc. It is reported to be more thermally stable than RDX but more reactive than HMX. Pure TNAZ is more shock sensitive than the explosives based on HMX but less sensitive than analogous PETN. It can be used as a castable explosive and as an ingredient in solid rocket and gun propellant. 

Figure 89 shows that at b = 1.2 an additional feature has appeared on the potential energy surface, which at b = 1.3 has formed a deep minimum (Figure 90). The two minima correspond to the two optical isomers of the Z)4 square antiprism (Figure 93). It may be noted that in contrast to the three-bladed propeller , which is the dominant stereochemistry for tris(bidentate) complexes (Section 2.3.3), this four-bladed propeller is only expected in tetrakis(bidentate) complexes where the bidentate ligands have exceptionally large normalized bites. At b = 1.26, the angle of twist 0 = 22.5° and the two square faces are staggered with respect to each other (Figure 93). In an analogous way to the behaviour of tris(bidentate) complexes, a decrease in b leads to a decrease in 9.

The most interesting feature of the decomposition flames is their analogy to flames of the solid monopropellants. In fact, many of these substances, which are ordinarily liquids, may support a flame directly from the liquid phase without auxiliary vaporization of the liquid. In this case, the flame supplies the necessary heat of vaporization or decomposition in exact analogy to the solid propellant flame.8 The principal usefulness of a decomposition flame is found in the simplicity of design and control of a rocket powered by such a flame, even though more powerful fuels are readily available. A recent example, which has been featured in the news, is the hydrogen peroxide attitude-control rocket used in the artificial earth satellites of the U.S.A. 

Although the above analysis of isomerism in molecular propellers with three blades has been described in terms of molecules featuring three aryl groups bonded to a central atom, it is intuitively obvious that the analysis is equally applicable to other analogous three-bladed propeller molecules. Clearly, the points of analogy are independent of parameters such as the kind or number of atoms and bonds in each molecule rather, they include such features as the symmetries of the... 

Propellers of the type A13ZX may be analyzed in an analogous manner.9) The four classes of rotational mechanisms are retained, and an additional non-rotational pathway is added inversion at Z along the Z—X bond. Such inversion changes the configuration only with respect to the center of chirality, and has no effect on the other elements of isomerism. Enantiomerization pathways for an AraZX molecule of type 3 thus must include an odd number of inversions. 

We have noted that all three-bladed propellers with D3 skeletons are in some ways structurally analogous. The analogy extends to their isomerization pathways. We will investigate the nature of this relationship by discussing the concept of stereochemical correspondence and then illustrating its application to propeller molecules. 

The rotary speed of the propellers exhibits a turning influence on the average size of the product this is similar to the results obtained by Chen et al. [165] in their investigation on an analogous problem in a stirred tank reactor and also similar to the results on the preparation of nano copper described in the previous chapter. It results from the mutual effect between macro- and micro-mixing, as mentioned before. 

Nonpolar and dipolar altitudinal rotors (compounds 2 and 3 in Fig. 17.3) have been synthesized. 19F NMR spectroscopy showed that the barrier to rotation in 3 was extremely low in solution. Both systems have then been immobilized on Au(l 11) surfaces and studied with a variety of techniques.57 The results obtained indicated that for a fraction of molecules the static electric field from the scanning tunneling microscopy (STM) tip could induce an orientation change in the dipolar rotor but not in the nonpolar analog (for a recent example of an azimuthal molecular rotor controlled by the STM tip, see Reference 58). Compound 3 can exist as three pairs of helical enantiomers because of the propeller-like conformation of the tetra-arylcyclobutadienes. For at least one out of the three diastereomers, an asymmetric potential energy surface can be predicted by molecular dynamics simulations on application of an alternating electric field.55... 

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