Titanium IV bromide

Titanium(IV) bromide may be prepared by passing bromine vapor over a heated mixture of titanium(IV) oxide and carbon or by the action of hydrogen bromide on titanium(IV) chloride heated just below its boiling point. The following directions are for the former method. 

An apparatus as shown in Fig. 8 is constructed. A and B are two gas-washing bottles containing concentrated sulfuric acid and 180 g. of dry bromine, respectively. The pyrex combustion tube C surrounded by an electric furnace leads to a 500-ml. distilling flask E, which is provided with a mercury well for taking temperature readings during subsequent purification of the product. 

An intimate mixture of 40 g. of titanium(IV) oxide and 24 g. of sugar charcoal (synthesis 20) is distributed in a layer in the combustion tube at the center point of the furnace. With the furnace at a temperature of 300°, dry carbon dioxide (or nitrogen) is passed through the apparatus until the reaction mixture is thoroughly dry. Any 

At the end of the reaction, the excess bromine is removed by a current of carbon dioxide. Then the drying tube attached to F is removed and replaced by an air condenser, which in tium is attached to a suitable container. After the apparatus has been flushed out with carbon dioxide, the 

Titanium(iV) bromide is a hygroscopic, crystalline, amber-yellow substance 3.25 m.p. 39°. b.p. 230°.. It 

Submitted by Role B. Johannesen and Chables L. Gobdon Checked by Kabl H. GATEBf and Lawbence BALASHf 

The apparatus for the reaction consists essentially of a two- or three-necked 100-ml. round-bottomed flask, heated 

In cleaning up the apparatus, titanium (IV) bromide may be satisfactorily dissolved in cold water if the aqueous solution is promptly discarded. Titanium(IV) chloride is better dissolved in hydrochloric acid (2 N or stronger) to avoid deposition of insoluble oxides of titanium. Both halides react vigorously with water and dilute acids, and it is necessary to exercise caution and preferable to work in a hood. 

Titanium (IV) bromide is readily soluble in most organic solvents and in Br2, AsBrs, and SbBra, and can be recov- 

While not a strong oxidizing agent, titanium (IV) bromide can be reduced by a number of reducing agents to bromides of Ti(III) or Ti(II) or to metallic titanium. 

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A. Diisopropoxytitanium(lV) dibromide (Note 1). A 50-mL, two-necked, round-bottomed pre-weighed flask equipped with a magnetic stirring bar, a rubber septum, and an argon inlet is charged with 20 mL of hexane (Note 2) and titanium(IV) bromide (7.3 g, 20 mmol) (Note 3). To the red-brown suspension is added titanium(IV)... 

In early work [165] on the synthesis of the pentasaccharide (236), the azide (237) was condensed with (238) [an intermediate in the preparation of (237)]in the presence of silver perchlorate and polyvinylpyridine to give the a-linked disaccharide (239) in 60 % yield and this on acetolysis gave the disaccharide (240) which contains the potential terminal disaccharide unit of the Forssman antigen. Compound (240) was converted into the glycosyl bromide with titanium(IV) bromide under carefully controlled conditions [182] and condensed with l,6-anhydro-2,4-di-0-benzyl-D-galacto-pyranose in the presence of silver carbonate to give the potential terminal trisaccharide (241) of the Forssman antigen. 

Acetolysis of (241) and subsequent treatment of the 1,6-di-O-acetate produced with titanium(IV) bromide gave the a-glycosyl bromide (247). This was condensed with the lactose derivative (248) (substitution with deuterated benzyl groups made it possible to interpret the NMR spectra [185]) in the presence of silver carbonate — silver perchlorate to give the a-linked pentasaccharide (249) in 38 % yield, and this was deprotected to give (236). 

In addition to these three classes of Lewis acids, certain compounds (notably halides) in which the central atom may hold more than an octet of electrons may show acidic properties. Typical of these are tin(IV) chloride, titanium(IV) bromide, and molecular iodine. In such acids, the acidic atom is always beyond the first eight-membered group in the periodic table. 

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