Alkylene dihalides

HN —R —NH —R ),. Hydrophilic polar substances formed by reacting alkylene polyamines or simple amines with alkylene dihalides. Used as flocculants, for, e.g. cellulose fibre and mineral ore suspensions. 

Hie reaction of dicarboxylic acid cesium or potassium salts with alkylene dihalides is another method of polyester preparation in relatively mild conditions... 

Poly(ethyleneimine)(PEI) bridged by alkylene dihalide has been used as a chelating resin for Cu and Co68. Dingman et al,69 studied the adsorption of metal ions on PEI resins crosslinked with toluene diisocyanate. The amount of metal ions adsorbed decreases with the degree of crosslinking. These crosslinked PEI resins... 

At this stage, however, addition takes place between the cydotelluio-pentane and alkylene dihalide, forming two complex telluronium bromides. 

Reaction of asymmetric (2-butene-l,4-diyl)magnesium with a,to-alkylene dihalides usually gives two isomeric products. For example, treatment of (2-phenyl-2-butene-l,4-diyl)magnesium with 1,3-dibromopropane at — 78°C, followed by warming to room temperature, resulted in the generation of two five-membered carbocycles, 1-phenyl-1-ethenylcyclopentane and a-cyclopentylstyrene, with a ratio of 77 23, in a 76% isolated yield. 

In contrast with the general 1,2-cyclizations of symmetric (2-butene-l,4-diyl)magnesium complexes with a,a>-alkylene dihalides, reactions of both symmetric and asymmetric (2-butene-l,4-diyl)magnesium complexes with diorganosilyl dichlorides yield exclusively overall 1,4-additions, generating silicon-containing five-membered rings. Some of these results are summarized in Table 5. 

Von Braun reaction. The reaction between phosphorous pentahalide and an /V-substituted benz-amide to give an alkylene dihalide and benzonitrile. 

The earliest preparation of the poly(alkylene sulfides) was by polycondensation of a divalent metal sulfide or bis-mercaptide with alkylene dihalides. Poly(ethylene sulfide) was first prepared in 1839 by Loewig and Weidmann [40] and the polymer was later studied by Crafts [41] and Meyer [42]. The latter polymer was prepared from ethylene dibromide and potassium sulfide as shown in Eq. (14). 

Cyclizations of (1,4-Diphenyl-2-butene-1 -diyl)magnesium with a,co-Alkylene Dihalides... 

Table 43 Cyclization of (1,4-diphenyl-2-butene-1,4-diyl)magnesium with owa-alkylene dihalides. ...

The dihaloalkanes having the same type of halogen atoms are named as alkyUdene or alkylene dihalldes. The dihalo-compounds having same type of halogen atoms are further classified as geminal halides (halogen atoms are present on the same carbon atom) and vicinal halides (halogen atoms are present on the adjacent carbon atoms). In common name system, pem-dihalides are named as aUq Udene halides and uic-dihalides... 

The four major methods of preparation of poly(alkylene sulfides) involves the polymerization of episulfides (thiiranes), addition of dithiols to olefins, reactions of dithiols with carbonyl compounds, and reaction of dithiols with dihalides and these will be discussed in this section. Other methods will be mentioned in Section 5 (Miscellaneous Preparations). 

The foregoing relationships of chain length to extent of reaction would then be expected to apply to such step polymerizations as are involved in the synthesis of poly(alkylene sulfides) from a dihalide and sodium polysulfide (polycondensation) or in the formation of the urethane polymers from glycols and diisocyanates (polyaddition). The polysulfide reaction is actually carried out in a suspension of the dihalide in an aqueous solution of the polysulfide, using a surfactant to stabilize the resulting polymer suspension. 

In the late 1950 s a project was started to make other polyethers from bisphenois, especially bisphenol A, and alkylene dichlorides and aromatic dihalides. One goal was improved hydrolytic stability over the polyesters and polycarbonates known at that time. A second goal was high thermal stability with that of diphenyl ether being the ultimate target. 

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