Anhydrous copper sulfate

Cmde diketene obtained from the dimeriza tion of ketene is dark brown and contains up to 10% higher ketene oligomers but can be used without further purification. In the cmde form, however, diketene has only limited stabHity. Therefore, especiaHy if it has to be stored for some time, the cmde diketene is distiHed to > 99.5% purity (124). The tarry distiHation residue, containing trike ten e (5) and other oligomers, tends to undergo violent Spontaneous decomposition and is neutralized immediately with water or a low alcohol. Ultrapure diketene (99.99%) can be obtained by crystallization (125,126). Diketene can be stabHized to some extent with agents such as alcohols and even smaH quantities of water [7732-18-5] (127), phenols, boron oxides, sulfur [7704-34-9] (128) and sulfate salts, eg, anhydrous copper sulfate [7758-98-7]. 

FIGURE D.l Blue crystals of copper(ll) sulfate pentahydrate (CuS04 5H20) lose water above 150°C and form the white anhydrous powder (CuS04) seen in this petri dish. The color is restored when water is added and, in fact, anhydrous copper sulfate has such a strong attraction for water that it is usually colored a very pale blue from reaction with the water in air. 

The composition and properties of the ions contained in the solution are not the same as those of ions contained in the ionic crystal lattice. It is already known that anhydrous copper sulfate (CuS04) is colorless. This implies that Cu2+ and SCT ions that make up the crystal lattice of the sulfate are colorless. When the Cu2+ ions combine with water molecules during dissolution they turn blue (the color characteristic of copper salt). This color is therefore due to hydrated ions of copper, i.e., ions connected with the water molecules. 

D-Ribono-1,4-lactone (1) readily condenses with acetone, under acidic catalysis with mineral acids or anhydrous copper sulfate, to give 2,3-0-isopropylidene-D-ribono-1,4-lactone (16a), which was employed for the synthesis of 5-deoxy and 5-0-substituted derivatives of D-ribono- 1,4-lactone and D-ribitol (24). Acid removal of the 1,3-dioxolane protecting group gave products having probable inhibitory activity of arabinose 5-phosphate isomerase (25). Other applications of 16a for the synthesis of natural products will be discussed later. 

One borderline circumstance, which should be considered as intentional chemistry for purposes of managing chemical reactivity hazards, is hydration. For example, anhydrous copper sulfate is a white solid with the formula CuS04. When it is crystallized from water, a blue crystalline solid with the formula CuS04-5H20 results, and the water molecules are an integral part of the crystal (Parker 1997). 

Mix 16.7 g potassium sulfate, 0.6 g titanium dioxide, 0.01 g anhydrous copper sulfate, and 0.3 g pumice and grind fine in a crucible. The mixed catalyst powder is stable under usual laboratory storage conditions at room temperature. Avoid moisture to prevent from caking. Commercially premixed tablets are also available. 

The dimethylformamide was dried and purified by distillation from anhydrous copper sulfate. 

When hydrates are heated, the water is driven off. If you heat blue crystals of CuS04 5 H20 above 350°C, for example, you ll observe formation of anhydrous copper sulfate, CuS04, a white compound (Figure 14.13). 

When 1-methylcyclohexanol is heated with anhydrous copper sulfate, two products P2 and P3 are isolated in a 85 15 ratio. The NMR spectra of these products are shown in Figures 11.26 and 11.27. The appearance of signals in the olefinic region of both products indicates that both are elimination products. Furthermore the major product has an intact methyl group (s, 1.635, 3 H) whose chemical shift indicates it is likely allylic. The vinyl signal integrates for a single... 

This process is reversible adding water to the white anhydrous copper sulfate salt will rehydrate the salt and regenerate the blue pentahydrate. 

Determine the weight of the anhydrous copper sulfate (7) and the weight of the water lost (8). 

To isolate the new D-galactosan, Hann and Hudson converted the accompanying levogalactosan to its monoisopropylidene derivative by condensing the acetone-soluble portion of the pyrolysis sirup with acetone in the presence of anhydrous copper sulfate. After concentration of the reaction solution the bulk of the 3,4-isopropylidene-D-galactosan < 1,5 > /8-... 

In subsequent work Levene and Stiller91 showed that condensation of D-ribose with methanol and acetone in the presence of anhydrous copper sulfate and sulfuric acid gave methyl 2,3-isopropylidene-D-ribo-furanoside (Cl) which was identified by conversion to XCVIII, then to XCIX and, finally, to the crystalline p-bromophenylosazone of XCIX, identical with the derivative previously prepared from XCVII. When these authors166 attempted to acetonate methyl D-ribopyranoside (CIV),... 

In the course of a study of the condensation of D-ribose with acetone, Levene and his coworkers61 88 found that an anhydroisopropylidene-D-ribose, melting at 93-94°, was obtained when hydrogen chloride was used as a catalyst, while an isomeric compound, melting at 61-62°, resulted when a mixture of sulfuric acid and anhydrous copper sulfate was employed. The structure of neither of these anhydrides has received further attention. 

Dean-Stark trap. During this period the yellow reaction mixture turned first crimson and then dark brown. Toluene was removed under reduced pressure and the residual enamine crystallized from acetone as discolored crystals (8 g). The enamine (10 g) was treated with concentrated HC1 (1 ml) in methanol (200 ml). The crimson solution was evaporated and the residual dark oil crystallized from acetone, yielding the intermediate ketopyran (8.4 g, yellow needles from acetone). The crystals were added to methanol and an excess of sodium borohydride was gradually added to the solution, yielding on standard workup 7.47 g of the hydroxypyran. The crystalline hydroxy intermediate was well mixed with 4.5 g of anhydrous copper sulfate and heated to 150-160°C in a carbon dioxide current for 10 min. Upon cooling, the product was extracted into methylene chloride. Removal of the solvent under reduced pressure gave 6.3 g of discolored solid that was decolorized with carbon and recrystallized from acetone (melting point not reported). 

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