Sheet structures compounds

Production Considerations Structural Foam Injection Molding Sheet Molding Compound... 

A compound with an unusual polymeric sheet structure of [Cp2PbCp(TFIF)Na]3 rings is obtained from the... 

Phyllosilicates are clay-related compounds with a sheet structure such as talc, mica, kaolin, etc. for which the nucleation mechanism of PET is known to be heterogeneous, although still uncertain. 

For sheet-layered compounds, the forces holding together the various sheets can be substantially less than the forces within the individual sheets. Similar to graphite, such structures may be easily cleaved parallel to the sheets. Examples of such materials are mica, kaolinite, and talc. 

Several insulating inorganic solids possessing sheet structures, for example, silicates belonging to the pyrophyllite family (Thomas, 1982), and acid phosphates (Alberti Constantino, 1982 Clearfield, 1981) of some tetravalent metals form intercalation compounds with a variety of donor molecules in these cases, intercalation does not involve a redox process, unlike in the cases of transition metal chalcogenides and... 

Hormones related to oxytocin and vasopressin occur in most vertebrates, the compound vasotocin shown in Fig. 30-4 being the most common. Substitution of phenylalanine for isoleucine at position 3 gives arginine vasopressin, the vasopressin found in our bodies. Structure of oxytocin and related hormones82 are also shown in Fig. 30-4. Like somatostatin, vasopressin and oxytocin may also form antiparallel pleated sheet structures with P turns. The structural requirements for hormone activity have been studied intensively. Both the macrocyclic hexapeptide ring and the tripeptide side chains are necessary for maximal activity.83... 

The formation of infinite two-dimensional sheet structures in copper(I) compounds (Figure... 

Fig. 13. Illustration of the Jfi-sheet structure generated by the template compound 26. (Reproduced with the permission of Ref. 25)...

On the other hand, the group of No wick [29] developed polyurea templates with the general structure 35 in order to nucleate parallel /1-sheet structures. They reported that in a model compound (36) the urethane carbonyls are hydrogen bonding to the adjacent NH and that the orientation of the bonding interactions is controlled by the size of the end substituent, in this case a phenyl group. They also recently prepared 37 and showed by NMR that it adopts mostly the proposed parallel /1-sheet conformation in chloroform [30]. 

Recently Sands et al.97) and Methven et al. 98) developed sheet molding compounds (SMC) and sandwich structures based on polyester syntactic foams. 

Porphyrin and nonporphyrin metals associated with asphaltenes have not been easy to identify in terms of molecular structure. This is partly due to the fact that the characteristics (i.e., spectra) of all possible model nonporphyrin compounds have not been studied. Nonporphyrin metals are probably small polar molecules that precipitate as asphaltenes (Filby, 1975) or complex at defect sites in large aromatic sheet structures of the type shown in Fig. 10. Porphyrins with increased aromaticity and systems with low aromaticity due to discontinued ring conjugation are both characterized as nonporphyrin species. These compounds do not have the characteristic visible absorption spectra and hence are not readily identified. It is also possible that some of the porphyrin in the residuum may not be extracted and identified due to intermolecular association with the asphaltene-generating molecules. 

Figure 3 Inclusion compound of (S )-isopropyl phenyl sulfoxide by 1 (a) perspective view of crystals (b) sheet structure of 1 (c) CPK model. For clarity, phenyl groups of 1 and guest are unshaded and gray, respectively.

A sheet structure was formed in THF-included crystals of (M)-(l -naphthyl)gly-cyl-(M)-phcnylglycinc (2) [16]. The THF-included compound of 2 formed on... 

Figure 6 (a) The sheet structure of dipeptide backbones of the inclusion compound... 

Figure 8 Inclusion compound of ( )-methyl lactate and 2. (a) Host-guest hydrogen bonding (A), (b) Sheet structure of dipeptide backbone, (c) Packing (CPK model) of the inclusion compound.

Thus, the arrangement of the host (2) molecules in the inclusion compound is governed by the size or shape of a-hydroxy esters (guest) to form optional sheet structures with adjustable cavities for highly enantiomeric inclusion. 

The inclusion compounds of 1 and 2 were obtained by crystallization from an appropriate solvent system containing a guest (vide infra). (R) -1 hen y I <21 y cy I - (A1) - pheny lg I y cine (1) molecules self-assemble to form a layer structure and (.V)-isopropyl phenyl sulfoxide molecules are stereospecifically included in the void between the layers (Figure 4)7 A sheet structure was also observed in THF-included crystals of (/ )-(l-naphthyl)glycyl-(/ )-phenylglycine (2), which were formed by crystallization of 2 from a mixed solvent of tetrahydrofuran (THF) and... 

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