Formal linkages

The broken lines represent the edges of the tetrahedron formed by the four copper atoms, the apex formed by the central copper atom being tilted to show all the bonds joined to this atom. The iodine atoms are depicted on the faces of the tetrahedron in order to show their linkage to the neighboring copper atoms. Actually, they lie well above the plane of the tetrahedral faces. The iodine atom on the rear face of the tetrahedron is not shown. The unbroken lines without barbs represent covalent links those with barbs represent coordinate links. These are formal linkages, but all the Cu-I links are of course identical 36). 

Aromatic polyformals cannot be synthesized by an extension of this chemistry. Reaction of aromatic phenols or bisphenols with formaldehyde does not give the formal derivatives derived from 0-alkylation but instead produces the well known phenol-formalde-hyde resins which result from C-alkylation of the phenol (equation 3). As a result, an alternate to formaldehyde must be found to supply the methylene group of the formal linkage. Barclay first reported such an approach in 1962 when he reacted the... 

This reaction sequence offers the advantage of being able to prepare linear oligomers under simplified reaction conditions and then couple them with formal linkages to get pol3rmers with properties which are hopefully not too much different from the homopolymers themselves. 

We would like to acknowledge the work of A. Factor and W.L. Grosvenor on the oxidation of the formal linkage and E.A. Williams for obtaining and interpreting the NMR spectra. 

During the phase transfer etherification the bisphenols were slowly transferred into the reaction. This slow addition of monomer, the highly reactive haloether chain ends and the flexibility of the formal linkage lead to the formation of cyclic polyfor-mals typical yields = 20 wt%. The cyclics eluted as the low molecular weight tail in the size exclusion chromatograph. Reverse precipitation by the addition of non-solvent to a polymer solution removed the cyclic component (see Figure 2). 

Strategies to create formal linkages among programs and services... 

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