Orientation terminology

Input from A. E. Newton, especially concerning capsule orientation terminology, and from an unknown reviewer significantly improved this paper. 

Structures [VI] and [VII], respectively, are said to arise from head-to-tail or head-to-head orientations. In this terminology, the substituted carbon is defined to be the head of the molecule, and the methylene is the tail. Tail-to-tail linking is also possible. The term orienticity is also used to describe positional isomerism. 

Although Baldwin s rules can be applied to ketone enolates, additional rules were added to make the terminology more specific. The orientation of the orbital as it approaches the reactive center must be considered for determining the correct angle of approach. Diagrams that illustrate the enolate rules are... 

The heavy-end portions (usually called heavy fractions) of bitumen (e.g. asphaltenes, preasphaltenes) can exist both in a random oriented particle aggregate form or in an ordered micelle form, peptized with resin molecules (16.17). In their natural state, asphaltenes exists in an oil-external (Winsor s terminology) or reversed micelle. The polar groups are oriented toward the center, which can be water, silica (or clay), or metals (V, Ni, Fe, etc.). The driving force of the polar groups... 

Since this review is oriented towards chemists who may have very little familiarity with semiconductors, Sect. 2 attempts to provide some brief useful background not otherwise readily found in one place (much more detailed exposition can be found in textbooks such as the excellent one by Yu and Cardona [15]). It begins in Sect. 2.1 with a concise introduction to some basics aspects of semiconductors relevant to understanding terminology encountered in the literature on NMR of semiconductors. The four crystal structures adopted by the majority of important semiconductors will be summarized in Sect. 2.2, and the various methods of making semiconductors will be outlined in Sect. 2.3. 

The diagonally oriented filter (d) decomposes any incoming light into a component vibrating in the direction of d and another component in the perpendicular plane, pz. Both of these have x and y components, which are resolved by the third yz) filter in the sequence. In mathematical terminology... 

This chapter is an introduction to methods-oriented microscopy. Because the contributing authors present methods in relation to their researches, plant cell structure-function relationships as revealed by light and electron microscopies are reviewed. Much of this conceptual and terminological information is summarized in tables that are augmented with references to either photomicrographs or electron micrographs of cells and tissues. 

To simplify terminology of axial systems, gzz is defined to be g(l (the g-value observed with the symmetry axis of Cu + parallel to the applied field), and gxx (= gyy) is defined to be gA (the g-value observed with the symmetry axis perpendicular to the applied field). An elongated z-axis (depicted in Figure 11 for Cu(H20)5 +) results in gjj > gj. For axially symmetric Cu + rigidly bound in a crystal, the g-value can then vary between the minimum (gj.) and maximum (g(,), depending on orientation of the crystal within the magnetic field. However, for axial Cu + bound in a powdered clay sample, all possible orientations, and therefore all g-values between gA and gj are represented in the "powder" spectrum. Therefore, electron spin resonance occurs only for field values, H, between Hjj and H, where ... 

Now, just the same sort of rationalization can be applied to the radical addition, in that the more favourable secondary radical is predominantly produced. This, in turn, leads to addition of HBr in what is the anti-Markovnikov orientation. The apparent difference is because the electrophile in the ionic mechanism is a proton, and bromide then quenches the resultant cation. In the radical reaction, the attacking species is a bromine atom, and a hydrogen atom is then used to quench the radical. This is effectively a reverse sequence for the addition process but, nevertheless, the stability of the intermediate carbocation or radical is the defining feature. The terminologies Markovnikov or anti-Markovnikov orientation may be confusing and difficult to remember consider the mechanism and it all makes sense. 

Esters and Related Functions 57 Thus, primary electronic effects (n-n interaction) form the conjugated system of the ester function whereas secondary electronic effects (n-o interaction) are the result of the orientation of non-bonded electron pairs anti peri planar to the o C-0 bonds of the ester function. Clearly, the primary are energetically more important than the secondary electronic effects and this terminology is justified by the fact that these two effects have their origin in the same chemical principle, orientation in space of electron pairs with resultant electronic delocalization. 

This definition is more oriented to objectives than on the structure of the microcapsules. It includes a very large number of systems starting from hollow molecules such as cyclodextrin, to large solid microsphers of 2 to 3 mm. It proposes a product-oriented approach, a solution that limits debate around terminologies. 

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