BROMINE CONTAINING Subject

While fluorine-substituted retinoids can be handled in a conventional manner, chlorine-containing and bromine-containing retinoids are reported to be very much less stable. The isomeric 10-chlororetinaldehydes (459) and (460) were obtained from the carbenoid (456) and the aminoaldehyde (457) via the imonium perchlorate (458), which was subjected to alkaline hydrolysis to give a mixture of the 9E and 9Z aldehydes (459) and (460), It was possible to separate these isomers by chromatography (Kobrich et al., 1967). 

The dominant species of Ce(IV) existing under the reaction conditions is 00(804)3 and the activated complexes for the two paths must have compositions 0(804)2 Br and 00(804)261 . The latter path is subject to chloride-ion catalysis of the form = A q-1-A [OI ] which suggests an activated complex 0e(804)201Br2 . 8I0W oxidative breakdown of the complexes containing bromide gives Oe(III) and Br atoms or -BrJ. The latter go on to form molecular bromine however, their presence has been detected in this reaction from their ability to add to butadiene to form dibromooctadienes . 

Once ignited they produced considerable amounts of heat and smoke. Flame retarded flexible PU foams became available in 1954-55, i.e. within a few years of flexible PU foams becoming available in commercial quantities(22). These FR PU foams contained trichloroethyl phosphate or brominated phosphate esters and resisted ignition from small flame sources. Unfortunately they may burn when subjected to a larger ignition source or when covered by a flammable fabric and may then produce as much heat and more smoke than the standard grade of PU foam(3). This was identified by UK room tests in the early 1970 s and has been confirmed more recently by furniture calorimeter tests at the NBS(21). 

It seems obvious that electron-withdrawing groups enhance nucleophilic addition and inhibit electrophilic addition because they lower the electron density of the double bond. This is probably true, and yet similar reasoning does not always apply to a comparison between double and triple bonds.70 There is a higher concentration of electrons between the carbons of a triple bond than in a double bond, and yet triple bonds are less subject to electrophilic attack and more subject to nucleophilic attack than double bonds.71 This statement is not universally true, but it does hold in most cases. In compounds containing both double and triple bonds (nonconjugated), bromine, an electrophilic reagent, always adds... 

A hydrobromic acid solution is prepared in a 5-I. round-bottom flask by the reduction of 1000 g. of bromine in the presence of 1100 g. of cracked ice. Experimental details have been given under (A) Hydrobromic Acid. A mixture of 2075 g. of aqueous (48 per cent) hydrobromic acid and 600 g. of concentrated sulfuric add may be used in place of the above reduction mixture. After the addition of 500 g. of ordinary 92 per cent ethyl alcohol, the flask is attached to a long condenser set ready for distillation and 1000 g. of concentrated sulfuric acid are slowly added through a separatory funnel. Because of the volatility of ethyl bromide, the mixture is not heated under reflux, but is subjected instead to slow distillation. The end of the condenser is provided with an adapter tube, and the distillate Is collected in a flask containing ice water. The crude... 

Flame Resistance. Blends with nitrile rubbers (Table III) containing at least 10% bromine passed the comparatively stringent Underwriters Subject 94 test. Graft blends having 7-10% bromine failed the Underwriter s test only because of dripping. They passed the ASTM D-635 test, as did all the nitrile rubber blend types. 

Similar to petroleum-derived cracking the fractions from plastics pyrolysis can contain a significant concentration of unsaturated hydrocarbons (especially a-olefins) [9]. The mono- and diolefin content makes the diesel fuel prone to instability due to polymerization and the formation of deposits (i.e. gums). Since the plastic-derived diesel fuel has an appreciable olefins content it is important to subject it to a hydrogenation step (e.g. hydrogenation over PCI/AI2O3 at 300-320°C and 3 MPa H2) which lowers the bromine number from typical values of 22-28 g Br2/100 g to less than 0.5 g Br2/100 g [9]. 

The preparations of 1,2,4-thiadiazoles and 1,2,4-thiadiazolidines from thioureas are well known and have been summarized in three reviews those of Bambas, Sherman, and Kurzer. Contained in these reviews are discussions of the controversies that surrounded some of the products, notably Hector s bases, which resulted from oxidation of substituted thioureas.Subjects covered in the above reviews, but too extensive to outline in detail here, are the oxidation of amidinothioureas to 3,5-diamino-l,2,4-thiadiazoles (71), the oxidation of phenylthiourea and of substituted amidinothioureas to 3,5-diimino-1,2,4-thiadiazolidines (72, Hector s bases), the reaction of thiopseudoureas with trichloromethanesulfenyl chloride to form 3-alkylthio-5-chloro-l,2,4-thiadiazoles (73), the reaction of thiopseudoureas with sodium thiocyanate and bromine and the oxidation... 

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