Melts, reactions

The rigid and soft blocks used in polyesteredier diermoplastic elastomers (polyesteretlier TPEs) are typically PBT and poly(oxyteti amethylene) (PTMO), respectively, witii block number-average molar mass varying between 1000 and 3000. They are obtained by the melt reaction between dimethyl terephthalate, butanediol, and dihydroxy-terminated PTMO in the conditions typical of a PBT syndiesis. 

Melt reaction mechanisms of tertiary aliphatic amine catalyzed phenolic-epoxy reactions were proposed to begin with a trialkylamine abstracting a phenolic hydroxyl proton to form an ion pair (Fig. 7.36). The ion pair was suggested to complex with an epoxy ring, which then dissociated to form a /1-hydroxycther and a regenerated trialkylamine.87... 

Synthesis of hydrolytically stable siloxane-urethanes by the melt reaction of organo-hydroxy terminated siloxane oligomers with various diisocyanates have been reported i97,i98) -yhg polymers obtained by this route are reported to be soluble in cresol and displayed rubber-like properties. However the molecular weights obtained were not very high. A later report56) described the use of hydroxybutyl terminated disiloxanes in the synthesis of poly(urethane-siloxanes). No data on the characterization of the copolymers have been given. However, from our independent kinetic and synthetic studies on the same system 199), unfortunately, it is clear that these types of materials do not result in well defined multiphase copolymers. The use of low molecular weight hydroxypropyl-terminated siloxanes in the synthesis of siloxane-urethane type structures has also been reported 198). 

Controlled synthesis of ABA type poly(2-ethyl-2-oxazoline)-b-PDMS block copolymers was obtained by the melt reaction of a,c -benzyl halide terminated PDMS oligomers and the oxazoline monomer 291 as shown in Reaction Scheme XX. 

Mixed O, N donor molecules are truly extensive and structurally diverse, and only a few selected examples will be presented. In line with other 2-substituted pyridine analogs reported in this chapter, it is worthwhile noting the chemistry of 2-pyridone (or 2-hydroxypyridine, Hopy), which can form O-bonded monodentate complexes such as Co(Hopy)4(N03)2, but as the monoanion is an effective chelate ligand, forming Co(opy)2 and Co(bpy)(opy)2 compounds.454 An unusual solid state melt reaction with Co(OAc)2 yields the dodecanuclear cluster Co12 (OH)6(OAc)6(opy )12.455... 

PBT has also been blended with styrene-maleic anhydride (SMA) copolymers giving materials similar to the ABS blends. Impact modification appears to be more difficult, and one must always be attentive to possible melt reaction with the anhydride, or its ring-opened acid forms, and the PBT resin. 

Platinum(iv).—Group VII Donors. Simple syntheses of hexafluoro-complexes of some noble metals have been reported, including K2[PtF ]. The method involved the melt reaction between KHFj and K2[PtXg] (X = Cl, Br, or I), which has the advantage of not requiring corrosive reagents such as fluorine or BF3- The stepwise stability constants K have been measured for the bromoaquo-complexes [PtBr , (H20)-7 ] "" (n = 4, 5, or 6) formed in... 

Pure soHd-state reactions are more frequently waste-free than melt reactions with increased risk of incompleteness or side reactions. We select here only... 

Melt or intermediate melt reactions are excluded from this review as much as possible because these do not (fully) profit from the initial crystal packing. They can nevertheless be of preparative importance or be preferable in particular instances if the products crystalhze directly from the melt during reaction and thus produce a quantitative yield [2]. Nevertheless, these different types of solvent-free reactions should be sharply separated for the sake of consistent wording. Solid-solid should not only mean that the reactants were sohds but also that profit was made from the crystal packing, which is only possible if there were no liquids upon mixing and during the reaction period. 

The racemization of Diels-Alder adducts in the solid state appears to proceed via diradical or complete cycloreversion. For example, (-l-)-96 racemizes in the solid state from 130 to 155 °C (AH =40.0 kcal mol AS =14 cal mol K ) to give (-)-96 (Scheme 9), whereas the melt reaction (eutectic temperature is 165 °C) from 176 to 194 °C has much lower activation parameters (AfJ =... 

Eliminations belong to one of the most diverse reaction types [76] and numerous solvent-free pyrolyses (sometimes quantitative melt reactions) provided useful syntheses [58,81-87]. However, quantitative solid-state eliminations are rare (examples are found in the halogenations of 110,112, and 114 (Scheme 12)). If an elimination reaction cannot be performed purely thermally or photo-chemically, usually a catalyst or other auxiliary has to be added and it is then no longer waste-free. 

An interesting synthetic approach to cyclic enamine ketones is provided by waste-free and quantitative solid-state reaction of the anilines 236 with cyclic 1,3-diketones such as 332 or enolized 334 (Scheme 52). The enamine ketones 333c-h are quantitatively obtained in the solid state by milling at room temperature. The melt reaction (80 °C) for 333a is not quantitative, but 333b arises with 100% yield from the melt reaction [10]. All of the solid-state reactions give 100% yield, as usual. 

By comparison, melting of incongruent minerals produces not only melt but also minerals, and such a melting reaction process can be expressed as... 

As another example, at 10 kbar, melting of a spinel peridotite has the following melting reaction in mass units (Kinzler and Grove, 1992)... 

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