Temperature halogen derivatives

Halogen derivatives of silanes can be obtained but direct halogena-tion often occurs with explosive violence the halogen derivatives are usually prepared by reacting the silane at low temperature with a carbon compound such as tetrachloromethane, in the presence of the corresponding aluminium halide which acts as a catalyst. 

Above 100°C, most polyolefins dissolve in various aHphatic and aromatic hydrocarbons and their halogenated derivatives. For example, polybutene dissolves in benzene, toluene, decalin, tetralin, chloroform, and chlorobenzenes. As with other polyolefins, solubiHty of PB depends on temperature, molecular weight, and crystallinity. 

Halogen derivatives also form when the silanes are allowed to react with anhydrous hydrogen haUdes, ie, HCl, HBr, or HI, in the presence of an appropriate aluminum haUde catalyst (25,26). The reactions are generally quite moderate and can be carried out at room temperature or slightly above, ie, 80-100°C ... 

Halogen derivatives are hardly inflammable. Their behaviour depends on the halogen rate that is present in the molecule and its nature (brominated derivatives are less inflammable than chlorinated) as well as the temperature to which they are exposed. So some of them that used to be used as extinguishing... 

A large number of ethylene halogen derivatives peroxidise easily at ambient temperature, by forming peroxides and polyperoxides that are particularly dangerous. 

A trichloroethylene/potassium mixture detonates around 100 C apart from when the superoxide KO2 layer that covers potassium is removed beforehand. The danger is therefore assumed to come from the oxidising property of this oxide. However, it seems surprising that pure potassium is inactive vis-a-vis this halogen derivative at such a temperature. 

When the lactone was introduced, the temperature reached 165 and then 180 C very quickly even though an attempt was made to cool the medium. The reactor detonated and a fire broke out. It seems obvious that the temperature rise is due to the high reactivity of lactone, but the main factor in this accident seems to be related to the behaviour of dichlorophenoi, which in such conditions gives rise to an aromatic nucleophilic substitution reaction that leads to the formation of a dichlorodioxin (see halogen derivative on p.283). 

Another method of preparation is as follows 1 33 parts of fluorescein are dissolved in 5 parts of ether and treated with 25 parts of selenium chloride in the same solvent. A yellowish-red precipitate separates, and after long stirring at the ordinary temperature the ether is distilled off. The residue is stirred with water, the mixture filtered and the residue now dissolved in sodium hydroxide. After further filtration the filtrate is treated with hydrochloric acid, which precipitates seleno-fluorescei n. Further purification is effected by solution in alkali and reprecipitation. A reddish-brown powder is obtained, soluble with fluorescence in alcohol, but insoluble in water. In concentrated sulphuric acid it dissolves to give an orange solution. Its alkali salts are very soluble in wrater, giving red solutions. This process may also be applied to phthalins, which are obtained by the reduction of phthaleins and their halogen derivatives. If the selenium chloride is replaced by the oxychloride similar products are obtained.2 In place of the phthalins specified in the patents quoted, their O-acetyl compounds or O-acetyl compounds of the phthaleins may be used in indifferent solvents. The products are different from those obtained by the action of selenium on fluoresceins in aqueous alkali solutions.3... 

We have computed the surface areas, IT, halogenated derivatives, some of which also bear other functional groups. These data are listed in Table 4, along with experimentally determined boiling points and critical temperatures. 

Butyl rubber is produced at very low temperature (below — 90°C) to control the rapid exotherm, and to provide high molecular weight. The process consists of charging isobutylene along with isoprene (2-4%) with an inert diluent such as methyl chloride to a reactor to which a Friedel-Crafts catalyst is added. The polymerization is very rapid, and the polymer forms in a crumb or slurry in the diluent. Heat is removed via the reactor jacket. The slurry is steam-stripped to remove all volatiles. The catalyst is neutralized, and antioxidants are added to the slurry prior to drying.53 The halogenated derivatives are produced by the direct addition of the halogen to a solution of the isobutylene-isoprene polymer. 

The photolysis of aniline at high temperatures results in N-H and C-N clea-vage, but at room temperature the major reaction is fluorescence. Below 2800 A some photodecomposition takes place the lifetime and dissociation probability of excited aniline molecules have been calculated Flash photolysis of aniline followed by kinetic mass spectroscopy failed to reveal the presence of dissociation products. Irradiation of halogen derivatives of aniline between 2480 and 2562 A produces halide ions in measurable yields . Positive mesomeric effects increase, and negative mesomeric effects decrease... 

The maiin domain of oxidation with dimethyl sulfoxide is the conver-sionofprimary alcoholsinto aldehydes andofsecondaryalcoholsintoketones. These reactions are accomplished under very mild conditions, sometimes at temperatures well below 0 °C. The reactions require the presence of acid catalysts such as acetic anhydride [713, 1008, 1009], trifluoroacetic acid [1010], trifluoroacetic anhydride [1011, 1012, 1013], trifluorometh-anesulfonic acid [1014], phosphoric acid [1015, 1016], phosphorus pentox-ide [1006, 1017], hydrobromic acid [1001], sulfur trioxide [1018], chlorine [1019, 1020], A -bromosuccinimide [997], carbonyl chloride (phosgene) [1021], and oxalyl chloride (the Swem oxidation) [1022, 1023, 1024], Dimethyl sulfoxide also converts sufficiently reactive halogen derivatives. into aldehydes or ketones [998, 999] and epoxides to a-hydroxy ketones at -78 °C [1014]. 

Although sulfonation resembles nitration and halogenation in many respects, there are certain important differences. The two most noticeable of these differences are the reversibility of sulfonation processes and the striking sensitivity of orientation to changes in the reaction temperature. Amino derivatives offer a further complication in that considerable amounts of ortho and para derivatives are often obtained. Thus at low temperatures, aniline gives a mixture of 0, m, and p-amino-benzenesulfonic acid,48 whereas dimethylaniline gives an almost equal... 

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