Molecule wedge-like

A second general rule specifies that soaps of monovalent metal cations tend to produce O/W emulsions, while those of polyvalent metal cations will tend to produce W/O emulsions. Figure 7.3 illustrates the concept. In the example shown, the calcium ions each coordinate to two surfactant molecules that are aligned with their polar groups near the metal ion. This forces the hydrocarbon tails into a wedge-like orientation. The hydrocarbon tails in a close-packed interfacial layer are most easily accommodated if the oil phase is the continuous phase. Thus, the oriented-wedge... 

Besides the divergent synthesis where the molecules are built up shell-by-shell starting from the centre, a convergent approach has been developed In which wedge like subunits, so called dendrons , are employed. The dendrons are prepared first and become assembled to the final dendrlmer via a multifunctional core (Scheme 3) [15,359]. The dendrons are versatile building blocks for molecules with a distinct tertiary structure (Scheme 4). 

Fig. 15 The molecules with wedge-like structures (a) can stack to form columns where for the columnar phase the molecules are disordered relative to the column axis, with the columns organised into rectangular or hexagonal arrays (b).

Fig. 8.1 Schematic presentation of strategies for the construction of hydrogen bonded organic nanotubes. Nanotubes from unimolecular, a helical, b tubular molecules, supramolecular, c bundles of rod-like molecules, d the stacking of macrocyclic molecules, and e aggregation of wedge-like molecules. The dotted red lines represent hydrogen bonding...

Now that we understand what the dash and wedge mean, let s consider what the molecule would look like from a slightly different angle ... 

There is an entirely different way to draw stereocenters (instead of using regular bond-line drawings with dashes and wedges). Fischer projections are helpful for drawing molecules that have many stereocenters, one after another. These drawings look like this ... 

Practically all dendrimers [ 1 ] known today have cores with a few, typically three to six functional groups to which the corresponding number of dendrons (dendritic wedges) are attached. The fact that these dendrons are connected to one another by a small, almost dot-like molecule results in considerable steric congestion in the space around the core. This congestion is a unique structural feature and has one led to view dendrimers, specifically those of high genera-... 

Thus complete intercalation of the aromatic PAH between the bases of DNA, in the manner described above for flat molecule such as proflavine, did not seem to be a likely mechanism for the carcinogenic action of these compounds. Since alkylation and intercalation are not simultaneously possible for steric reasons, and since one molecule is wedge-shaped and the other is flatter, it was considered more likely that the action of these compounds arose from their alkylating ability they could alkylate a base of DNA and then, since the bulky aromatic hydrophobic group would possibly not remain protruding into the hydrophilic environment, it is possible that the aromatic PAH group could then lie in one of the grooves of DNA. 

Organic molecules are three-dimensional, so showing structures on paper in two dimensions can give a misleading picture of what the molecule actually looks like. This has led to the use of wedged line notation, which provides a simple way of showing organic molecules to Indicate their three-dimensional nature. 

The ionic phosphonates like NTMP are effective hydration inhibitors because they can form an insoluble complex with the oxide surface. They are useful as epoxy adhesive couplers in cases where the adhesive and its curing cycle are compatible with the adsorbed phosphonate molecule. (14) Wedge test results indicate that in two epoxy-aluminum systems studied, certain organosilanes tend to both increase the epoxy-metal bond durability and maintain hydration resistance. The results of anodic polarization experiments further suggest that these silane films are effective against localized pitting. 

These results are simply explained in the patterns of Figure 9 in the compact complex, the marker (M) is wedged in between the polymer sequences and its mobility is low. In the gel-like structure the mobility of the marker is not affected, because the marker is mainly surrounded by sovlent molecules since the cross-linking between macromolecules is very low. Polarized luminescence results lead to confirmation of the complex structure proposed from visco-metry studies. 

Figure 5.4 Self-assembly of wedge-shaped molecules (modified from Zeng et al 2004). (a) Dendrons with fewer tethered chains adopt a flat slice-like shape (X is a weakly binding group), (b) The slices stack up and form cylindrical columns, which assemble on a two-dimensional hexagonal columnar (Col ) lattice (c). (d) Dendrons with more end-chains assume a conical shape, (e) The cones assemble into spheres, which pack on three different three-dimensional lattices (f) with different symmetries.

Fischer projection formulas are also used for compounds like aldohexoses that contain several stereogenic centers. In this case, the molecule is drawn with a vertical carbon skeleton and the stereogenic centers are stacked one above another. Using this convention, all horizontal bonds project forward (on wedges). 

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