Iron chloride, anhydrous 2- hydrate

A 5.012-g sample of an iron chloride hydrate was dried in an oven. The mass of the anhydrous compound was 3.195 g. The compound was dissolved in water and reacted with an excess of AgNOs. The precipitae of AgCl formed weighed 7.225 g. What is the formula of the original compound ... 

This method makes anhydrous iron(IIl) chloride. Anhydrous means without water of crystallisation. Anhydrous iron(III) chloride is dark brown. If left in air it absorbs moisture and turns yellow. It has become hydrated iron(III) chloride, with the formula FeCl3.6H20. 

The sulphate of soda may be procured in hydrated crystals—Na 0 S0 , 10 HO—by exposing the solution to a low temperature or, in an anhydrous state as an opaque precipitate, by concentrating the solution at the boiling point. In. either case the chloride of iron remains in the mother-liquor. 

Iron dissolves in aqueous HC1, and solids such as [Fe(H20)6]Cl2 and [Fe(H20)4Cl2] can be crystallised. The anhydrous chloride can be obtained by heating the hydrate in a stream of HC1, or by treatment with SOCl2 which reacts with coordinated H20 to give S02 and HC1. Such wet methods are obviously inapplicable to halides which undergo hydrolysis in water, e.g. BeCl2, A1C13. 

Anhydrous iron(II) chloride has been prepared by passing hydrogen chloride over iron, by reducing iron(III) chloride with hydrogen, and by dehydrating one of the hydrates of iron(II) chloride. A new procedure is outlined here.1,2... 

Copper(II) salts are familiar oxidants in organic chemistry [204, 205], but they have been little used by transition-metal chemists. They are commercially available with various counter-anions as anhydrous or hydrates (CuCh is also simply obtained by heating CUCI2 2H2O in thionyl chloride) [206]. They have been used in CH2CI2 and MeCN to cleave metal-carbon bonds in 18-electron iron (11) and ruthenium (II) complexes. The first step of this reaction is a single-electron oxidation [207]. 

Iron(III) trichloride is commercially available both as the anhydrous or hydrate form which can also be refluxed in thionyl chloride to generate the anhydrous form (purified by sublimation) most often used [209], Anhydrous iron trichloride is about as strong as ferrocenium salts, but it is not necessarily innocent. It is sometimes used to recover functionalized metal-free hydrocarbon derivatives which have been transformed by temporary complexation and activation on a transition-metal center [210]. 

Section 11-5 33. Analysis of a hydrate of iron(lll) chloride revealed that in a 10.00-g sample of the hydrate, 6.00 g is anhydrous iron(lll) chloride and 4.00 g is water. Determine the formula and name of the hydrate. 

Some salts could not be dehydrated in THF. Iron(III) chloride for example, polymerizes THF and must be prepared using neat trimethylchlorosilane. Cobalt(II) chloride dihydrate gave a similar result requiring neat trimethylchlorosilane. In both cases, nearly quantitative yields of the anhydrous salt were obtained. Hydrated zinc chloride, which we prepared by adding 10 wt % water to the anhydrous chloride because well-defined hydrates are not commercially available, was very efficiently dehydrated in neat trimethylchlorosilane to give a 96% yield of zinc chloride. In contrast, the THF/trimethylchlorosilane mixture afforded a comparatively modest 71% yield of the tetrahydrofuranate. Chromium(III) chloride hexahydrate, on the other hand, could not be completely dehydrated in neat trimethylchlorosilane and required THF for an efficient reaction giving 89% yield of chromium(III) chloride tris(tetrahydrofuran). Our results are summarized in Table I. 

Iron(lll) chloride exists in two forms, the covalent anhydrous chloride and the ionic hydrated chloride. 

As for the role of bipy and py, subsequent work has established that they are not essential for the oxygenation (dehydrogenation) to occur. Iron(III) salts, like chloride, nitrate or perchlorate, hydrated or anhydrous, are effective catalysts for 3,5-DTBC oxidation in THF or DMF [108]. 3,5-DTBQ is the predominant product but intradiol cleavage to 15, DBMUA and 53 (Scheme 7) also takes place. Additives like py. 

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