Chlorine, isolation

Bible KC, M Buytendorp, PD Zierath, KL Rinehart (1988) Tunichlorin a nickel chlorin isolated from the Caribbean tunicate Trididemnum solidum. Proc Natl Acad Sci USA 85 4582-4586. 

Sings, H.L., Bible, KG., and Rinehart, K.L. (1996) Acyl tunichlorins a new class of nickel chlorins isolated from the Caribbean tunicate Trididemnum solidum. Proc. Natl Acad. Sci. USA, 93,10560-10565. 

This compound, which contains atoms arranged tetrahedrally around the boron atom, can readily be isolated from a mixture of dimethyl ether and boron trichloride. On occasions a chlorine atom, in spite of its high election affinity, will donate an electron pair, an example being found in the dimerisation of gaseous monomeric aluminium chloride to give the more stable Al2Clg in which each aluminium has a tetrahedral configuration ... 

Chlorine, bromine and iodine form halic(V) acids but only iodic(V) acid, HIO3, can be isolated. Solutions of the chloric) V) and bromic) V) acids can be prepared by the addition of dilute sulphuric acid to barium chlorate(V) and bromate(V) respectively, and then filtering (cf. the preparation of hydrogen peroxide). These two acids can also be prepared by decomposing the corresponding halic(I) acids, but in this case the halide ion is also present in the solution. 

This ion is derived from manganeseflV) chloride, MnCl4, but the latter has not been isolated. The MnCl ion is unstable, breaking down to give chlorine thus ... 

The fact that the ratios of rates were much greater in chlorination than in nitration, prompted Dewar to suggest that the actual transition state was intermediate between the Wheland model and the isolated molecule model. He accommodated this variation in the relative rates within his discussion by treating yS as a variable whose value depended on the nature of the reaction. With the notation that y ) is the... 

Like carbocations most free radicals are exceedingly reactive species—too reac tive to be isolated but capable of being formed as transient intermediates m chemical reactions Methyl radical as we shall see m the following section is an intermediate m the chlorination of methane... 

Each chlorine atom formed m the initiation step has seven valence electrons and IS very reactive Once formed a chlorine atom abstracts a hydrogen atom from methane as shown m step 2 m Figure 4 21 Hydrogen chloride one of the isolated products from... 

Ethylene was known to chemists in the eigh teenth century and isolated in pure form in 1795 An early name for ethylene was gaz olefiant (French for oil forming gas ) to describe the fact that an oily liquid product is formed when two gases—ethylene and chlorine—react with each other... 

N,]S7-bis(methoxymethyl)uron was first isolated and described in 1936 (41), but was commercialized only in 1960. It is manufactured (42) by the reaction of 4 mol of formaldehyde with 1 mol of urea at 60°C under highly alkaline conditions to form tetramethylolurea [2787-01-1]. After concentration under reduced pressure to remove water, excess methanol is charged and the reaction continued under acidic conditions at ambient temperatures to close the ring and methylate the hydroxymethyl groups. After filtration to remove the precipitated salts, the methanolic solution is concentrated to recover excess methanol. The product (75—85% pure) is then mixed with a methylated melamine—formaldehyde resin to reduce fabric strength losses in the presence of chlorine, and diluted with water to 50—75% soHds. Uron resins do not find significant use today due to the greater amounts of formaldehyde released from fabric treated with these resins. 

DAG is treated with ethanol and hydrochloric acid in the presence of inert solvent, eg, chlorinated solvents, hydrocarbons, ketones, etc. The L-ascorbic acid precipitates from the mixture as it forms, minimising its decomposition (69). Cmde L-ascorbic acid is isolated through filtration and purified by recrystallization from water. The pure L-ascorbic acid is isolated, washed with ethanol, and dried. The mother Hquor from the recrystallization step is treated in the usual manner to recover the L-ascorbic acid and ethanol contained in it. The cmde L-ascorbic acid mother Hquor contains solvents and acetone Hberated in the DAG hydrolysis. The solvents are recovered by fractional distillation and recycled. Many solvent systems have been reported for the acid-catalyzed conversion of DAG to L-ascorbic acid (46). Rearrangement solvent systems are used which contain only the necessary amount of water required to give >80% yields of high purity cmde L-ascorbic acid (70). 

Trichloroacetone [921-03-9] (13a) is prepared by chlorination of acetone. The reaction is nonselective and the required compound is isolated by distillation. The selectivity has been improved by catalyzing the reaction with iodine (31). 

Chlorine and fluorine in beryUium metal are isolated by pyrohydrolysis or by distUlation (21). Fluoride and chloride in the condensate are determined by ion-selective electrode or colorimetricaUy. 

Ureas. Chlorination of aqueous urea yields unstable A/-chloro compounds. With excess C10 decomposition yields CO2, N2O, and NCl the latter decomposes further to NO (96). Only two soHd derivatives have been isolated A/-chlorourea [3135-74-8] mp 74—76°C, and N,lSf-dichlorourea [2959-01-5] which decomposes at its mp of 83°C with evolution of NCl. As an amide, urea also undergoes the Hofmann reaction yielding hydrazine. This route to hydrazine was once employed commercially. 

The oxo-anions of chlorine are weaker oxidants than the corresponding acids. Because they are also more stable, it is not too difficult to isolate certain salts of those acids that can be obtained only in aqueous solution. Hypochlorites and chlorites are hydroly2ed in aqueous solution since HOCl and HCIO2 have acid dissociation constants of 10 and 10 , respectively however, aqueous chloric and perchloric acids are hiUy iorrhed. 

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