Addition mixed ’ halogens

Table 7. Chlorinated and Mixed Halogen Additive Flame Retardants...

Bromine vapor forms CgBr [12079-58-2] by direct addition to weU-oriented graphite. Other halogen and mixed halogen compounds have been prepared. 

In addition to 6,14-dibromopyranthrone, there are some mixed halogenated pyranthrone derivatives which exhibit equally useful pigment properties. 

This stereochemical character is shared by all addition reactions involving a halonium ion, so that mixed halogens e.g. Br-F [8g], Br Cl [go], I Cl [gi] and I F [g2]), and also reagents like hypobromous acid (Br-OH) [gs], acetyl hypobromite (CH3CO OBr) [g4] and iodine isocyanate (I NCO) [gs] lead to diaxial addition products, with the... 

Mixed additions of halogen and methoxide, or benzoate, give the trans adducts preponderantly, although halomethoxylation of tri-0-... 

The mode of addition of hydrogenphosphonates to fluorinated ketones can also be complex. The addition of dialkyl, diphenyl or bis(trimethylsilyl) hydrogenphosphonates to methyl trifluoromethyl ketones occurs in the expected manner, but this contrasts with the behaviour of aryl perfluoralkyl ketones in the presence of triethylamine at room temperature, when the products, obtained even under such mild conditions, are phosphate esters (reaction 6), a situation which represents lack of stability of the hydroxyphospho-nate rather than novelty of the reaction under identical conditions, the corresponding alkyl aryl ketones fail to react. The same reaction with mixed-halogen ketones is still more involved, and the nature of the products depends on the reaction conditions if these are of a mild nature, and with catalysis by triethylamine or pyridine (depending on the particular ketone), the product is the expected (hydroxyalkyl)phosphonate 177, whereas with... 

Polyacetylene reacts with chlorine rapidly to give a white polymer that is equivalent to poly(l,2-dichloroethylene) and no stereospecificity has been reported on the chlorinated polymer. The addition of halogens is an important general reaction of carbon-carbon double bonds in a stereospecific and regiospecific sense. For instance, the electrophilic additions of chlorine to ethylene, buta-1,3-diene and hexa-l,3,5-triene have been shown to proceed by 1,2-trans (anti), 1,4-cis (syn) and 1,6-trans (anti) attack, respectively. This stereospecificity has been rationalized with a mixing rule of a-n orbital interaction. The reaction of a long conjugated polyene like polyacetylene with chlorine may produce an atactic chlorinated polyene, because random l,2n additions occur to result in a random addition product. ... 

A significant increase in the study of the relationship between phospha(V)zenes and phospha(III)zenes has been noted for this time period. In addition to the expected products observed in the photolysis of MesP(O)CMSjNj in the presence of MejS, products derived from the capture of the intermediate phosphonamidate, MesP(0)=NCMe3, are observed. The trihalogenophosphine imides Mes N=PXj(X=C ,Br) are obtained nicely by oxidation of the phosphorus(III) precursor by Cl, Brj or PhIC . Mixed halogen species are also available, including Mes N=PC 2l, from the disproportion reaction of the... 

The results of halogenation remain unchanged if reactions proceed in the dark, with addition of catalysts or inhibitors of radical processes. These data, as well as the strict regiospecificity on addition of mixed halogens (in the derivatives of bicyclo[3,2,l]octadienes the more electropositive halogen turns out to be on C ) corroborate the ionic character of the reactions studies. 

The mixed halogens ICl, IBr, and BrCl also add to alkenes. White and Robertson found third-order kinetics for the reaction and determined the relative reactivities to be BrCl > ICl > Br2 > IBr > l2- The l ge reactivity of BrCl means that addition of BrCl can occur when alkenes react with mixtures of Br2 and Cl2. The regioselectivity of addition of mixed halogens was reported by Ingold and Smith. Addition of ICl to propene gave 69% of 2-chloro-l-iodo-propane (30) and 31% of l-chloro-2-iodopropane (31), and addition to styrene gave more than 95% of l-chloro-2-iodo-l-phenylethane. ... 

Mixed fluorohalides can be obtained by addition of halogen to PF3 (4.265). They are thermally unstable colourless gases which tend to dissociate, the bromine componnd being the least stable (4.266). Phosphorus tetrafluorochloride can be made in about 52% yield by a reaction between PFj and BCI3 at low pressure (4.267). 

Another source of flame retardancy for flexible vinyls can be found in dioctyl tetra-bromophthalate (BrDOP). BrDOP imparts excellent flame retardancy with relatively low smoke production. Also its structure is reported to be very stable (5 percent weight loss at 290 °C), well beyond the processing range of most vinyl compounds) with low volatility (Table 9.6). BrDOP is used for plenum grade vinyls and other high-end FR-PVC applications. One manufacturer claims that mixed halogen (bromine and chlorine) phthalate esters have improved mechanical properties in addition to excellent FR properties (Table 9.6). ... 

Phosphoms forms weU-defined halogen compounds of the types PX, PX, POX, and PSX, all of which except the pentaiodide and the oxy- and sulfoiodides are known. In addition to the binary haUdes, a few of the many possible mixed haUdes, eg, PX2Y and PX2Y2, have been prepared. The commercially important phosphoms haUdes are phosphoms trichloride [7719-12-2] phosphoms oxychloride [10025-87-3] phosphoms pentachloride [10026-13-8] and phosphoms sulfochloride [3982-91-0]. A few other phosphoms haUdes, eg, PI, PR13) marketed as reagent... 

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