Linear structure series

I) The segments selected from each parent structure should retain the additional symmetry elements (if there are any) in addition to the minimal symmetry (see 3.3.). These additional elements should be perpendicular to the stacking direction for a linear structure series, perpendicular to the mosaic plane for a two-dimensional series and in the case of a three-dimensional stoicture series the segments should contain the symmetry centre or/and symmetry axes. 

These requirements have been formulated on the basis of a systematical study of linear structure series. The requirements i) and ii) apply to the linear homogeneous structure series. In the description of the inhomogeneous series the requirements iii) and iv) have to be added. It may be possible, that in two- and three-dimensional structure series the segments must conform to additional requirements. 

NUMERIC CODE NOTATION FOR THE MEMBERS OF LINEAR STRUCTURE SERIES... 

THE APPLICATION OF THE ONE-DIMENSIONAL OR LINEAR SYMMETRY GROUPS TO THE SYSTEMATIZATION OF LINEAR STRUCTURE SERIES AND THEIR REPRESENTATIVES... 

TABLE 1. Symmetry, numeric codes and structures of selected inhomogeneous linear structure series with Q = 1... 

Grin, Yu.N. Akselrud, LG. (1990). Use of inhomogeneous linear structure series for the crystal-chemiceil description of the superconducting oxides. Acta Cryst. A46 Suppl., C-338. 

Pharmaceutical development traditionally involves a linear, sequential series of structured events. This is true on both a macro (program) level as well as... 

A series of heteroatom substituted carbodiphosphoranes C PR2ECH(CF3)2 2 have been prepared in the last 10 years by various groups as shown in Fig. 6. The main synthetic approach consists of the reaction of hexafluoroacetone or thioacetone with the related diphosphines R2P-CH2-PR2 [25, 26]. The bent structure with a P-C-P angle (140°) confirms the double ylidic nature [27] and a related chemistry to C(PPh3)2 is expected however, no reports about coordination activities were reported so far. Theoretically, double alkylation at the heteroatoms of the dianion in Fig. 9 would lead to the substituted carbodiphosphoranes. The amino derivative C(P NMe2 3)2 has a linear structure and was not investigated further [28]. 

The structural variety of the compounds that form fibers is as diverse as their chemistries. From glasses (fiberglass), and partially crystalline materials (carbon), to special three-dimensional arrays, including polymers, the small, elongate solids may have aspect ratios up to 5000. From our research and compilation (Appendices 1, 2) we noted many mineral and synthetic compounds that have structures characterized by basic linear units. Amphi-boles, the major mineral group mined as asbestos, are characterized as doublechain structures. Many of the minerals in Appendix 1 are polymorphic (di-or trimorphs), and where one member of a mineral series has been described as fibrous the others in the same series are likely to be able to grow as fibers as well. Probably all compounds with similar structures and compositions, mineral or synthetic, can form fibers, even though they are not presently listed. It is also clear that fibrous formation is not confined to compounds with linear structural units indeed the variety of crystalline structure patterns is remarkably diverse. 

It is worthwhile analyzing whether the same conclusion holds when the water dimer structure is considered. A series of calculations have been performed for a linear structured water dimer, the values are listed in Table II. 

An obvious difficulty arises with this rather elaborate rationale when phosphoramidate and aryl phosphoramidate monoanions are compared for example, the dissimilarity of the dioxan effect yet the identity of product distribution observed in methanol-water competition experiments. Preliminary studies in the author s laboratory have revealed striking differences in the hydrolytic behavior between a series of phosphoramidafes derived from primary aliphatic amines and the above aryl systems. No linear structure-reactivity relationship between the logarithmic rate of hydrolysis of the monoanion species and the pKa of the amine is observed19. Moreover, the rate of hydrolysis of phosphoramidate monoanions derived from aliphatic amines is at least 104 times slower than those formed from aryl amines. In contrast, only a thirtyfold decrease in rate is observed for the corresponding ApKa in the O-phos-phate monoester series. The suspicion that mechanism (1), even with the above proposed modification, is not an accurate description of phosphoramidate monoanion hydrolysis derives some further support from the observation that the monoanion is subject to nucleophilic attack by substituted pyridines al-... 

Individual sequential covalent bond formation in a series of reaction-isolation steps. Bond formation usually involves only one or several connections per step. The method can be used to construct one-dimensional linear structures (e.g., polypeptides/polynucleic acids) where chronological sequencing can be used to introduce desired side groups or chirality by this linear covalent method. 

The planar configuration of ethylene and the linear structure of acetylene are supported by experimental data. In Table XX are given the values obtained by electron diffraction measurements for the valency angle of a series of carbon compounds containing double bonds. It will be seen that the values are all close to 120°. 

The question of whether the phosphonitrilic chlorides have cyclic or linear structures has been frequently discussed in the literature. The structural evidence will be considered in Section lY, where it will be seen that the cyclic formulation is established beyond doubt for the trimer and tetramer, and is highly probable for the higher soluble polymers it will meanwhile be assumed for all compounds of formula (PNX2) . For reasons considered in Section II, C the petrol-insoluble fraction (PNCUln PCls is believed to consist of a mixture of linear polymers. The two series are related, in that the linear compounds of low molecular weight are intermediates in the formation of the cyclics by the ammonolysis of phosphorus pentachloride. 

Cadmium UPD deposition was studied by Bondos et al. They monitored this process on Cu( 111) and Au(l 11) surfaces and observed a (4x4) structure on the copper electrode, while on gold electrode they imaged a series of linear structures. They explained the formation of these stmctures by coadsorption of sulfate anions. 

---