Deuterium bromide

Bromine (7 ml) is added dropwise to a mixture of white sand (14 g) and red phosphorus (3 g, dried at 165° under vacuum) moistened with 5 ml of deuterium oxide. The apparatus is fitted with an exit tube to allow the liberated deuteriobromic acid to pass through two U-tubes and into a receiving flask. The first trap contains glass beads and is cooled in an ice-salt slurry. The second contains glass beads and red phosphorus moistened with deuterium oxide. The deuterium bromide gas is collected in the appropriate solvent at ice bath temperature. A small amount of phosphorus pentoxide should be added to remove any deuterium oxide if anhydrous reagent is required. 

Tiffeneau ring enlargement of 5a-deuterio ketone (59) gives the required 3yS-hydroxy-B-homo-5a-deuteriocholestan-7-one acetate (60). The 6a-bromo-3 -hydroxy-B-homo-5a-deuteriocholestan-7-one acetate (61) obtained by bromination is then treated with lithium bromide in dimethylformamide to give the deuterium free a,j5-unsaturated ketone (62). The loss of deuterium bromide proves that bromination takes place at C-6 and that the carbonyl group must therefore be located at C-7. 

According to Cram 88a>, the stereochemical course of several polar addition and substitution reactions at the bridge position of the [2.2]-paracyclophane system is best explained on the basis of a species similar to 96 Reaction of [2.2]paracyclophane-l-ene (32) with bromine or deuterium bromide is postulated to lead exclusively to the cis-addition products 97 and 99, which retain configuration on acetolysis. The reaction of cis-l,2-dibromo[2.2]paracyclophane (cis- 97) with lithium bromide in... 

Cabaleiro and Johnson (1967) report that the addition of chlorine to -methyl cinnamate in chloroform or acetic acid is syn-selective, SS 0-75, in chloroform and acetic acid acetoxychloro derivatives are produced as well. Again, Dewar and Fahey (1964) argue that the normal course of addition of hydrogen halides onto olefins is a polar electrophilic process involving classical carbonium ions as intermediates and leading mostly but not exclusively to cis-adducts. A syn-preference was found in the additions of deuterium bromide to acenaphthylene, indene, and cis- and fraws-phenylpropene. In the case of indene, phenylpropene and methyl cinnamate, which are styrene analogs, concerted syn addition is symmetry-allowed (see bottom of p. 273). 

If exo-2-bromonorbomane, which is stereospecifically deuteriated in the exo-P-position to the halogeno substituent, is treated with a base, then an elimination reaction occurs. However, in the carbon product there is no deuterium, i.e. deuterium bromide has been eliminated. Account for this observation. 

In several preparations of deuterium labeled analogs, elimination of deuterium bromide was much slower than that of hydrogen bromide, suggesting an EicB mechanism for the elimination. Thus, in the preparation of cis- and rans -l,2-dimethyl-3-methylenecyclopropane (17), formation of the dideuteromethylene analogs took 7 days at room temperature, as opposed to 14 hours for the unlabeled compounds. In the case of endo- and exo-2-methyl-6-methylene-bicyclo[3.1.0]hexane (19), the dideutero analog also required heating to 45°C to complete the reaction. ... 

Methylation of cyclopropylidenetriphenylphosphorane (1) can be achieved by reaction with iodomethane in tetrahydrofuran, while protonation (or deuteration) of 1 is performed with anhydrous hydrogen bromide (or deuterium bromide) in inert solvents. ... 

The additions of HCl or HBr to norbornene are interesting cases because such factors as the stability and facile rearrangement of the norbornyl cation come into consideration. (See Section 4.4.5 to review the properties of the 2-norbornyl cation.) Addition of deuterium bromide to norbornene gives ejco-norbornyl bromide. Degradation to locate the deuterium atom shows that about half of the product is formed via the bridged norbornyl cation, which leads to deuterium at both the 3- and 7-positions. ° The exo orientation of the bromine atom and the redistribution of the deuterium indicate the involvement of the bridged ion. 

Deuterium bromide is obtained from D20 and thionyl bromide15 in the same way (for preparation of liquid DBr from the elements see Kalinatchenko et al.16). Its addition to carbon-carbon multiple bonds has been used mainly for the preparation of various deuterium-labeled halogeno-ethanes and -ethyl-enes,4a 17,18 for not only is the DBr readily added but also the bromine can be removed selectively from the products e.g. ... 

Liquid deuterium bromide has proved a solvent well suited for isotope exchange and it is also a powerful deuteron-donor.106 The hydrogen of polycyclic aromatic hydrocarbons is rapidly exchanged at 20° the hydrogen of... 

Further acceleration of isotope exchange, by three to four powers of ten, can be achieved116-118 by working in liquid deuterium fluoride, particularly if it contains BF3.108-110 The properties attaching to deuterium bromide apply also to this system. For toluene, equilibrium is reached in 15 minutes,108 and, as in exchange in DBr, only the hydrogen atoms attached directly to the aromatic ring are replaced, even in presence of BF3. 

Isomerization of n-Butane in the Presence of Aluminum Bromide-Deuterium Bromide Catalyst... 

In order to test the validity of the postulated mechanism of isomerization, deuterium bromide-aluminum bromide instead of hydrogen bromide-aluminum bromide was used as an isomerization catalyst (Pines and Wackher, 23). The reactions were carried out under controlled conditions using a high-vacuum technique. The experimental conditions are summarized in Table XIV. 

It was found that by treating either n-butane or isobutane with 10 mole % deuterium bromide-aluminum bromide catalyst for 20 hours at 25°, no isomerization of the butanes occurred and only 6 and 9.5% of the deuterium exchanged with n-butane and isobutane, respectively. When, however, 0.1 mole % butenes was added to n-butane and the isomerization reaction was carried out under the same experimental conditions, over 40% of the butane isomerized to isobutane and 92% of the deuterium underwent an exchange reaction. These results indicate clearly that olefins take an active part in isomerization. The results obtained are in agreement with the proposed mechanism of isomerization. 

The exchange reaction occurring in the presence of aluminum bromide between deuterium of the deuterium bromide and hydrogen of butanes, when small amounts of olefins are present, can be represented by the equations ... 

Deuterium bromide is stored either as a liquid at a low temperature or as a gas in a sealed glass flask. Pure DBr reacts with Hg only on long exposure. 

Deuterium bromide solution 47% [ HJEr, w/w, in deuterium oxide. 

Dissolve the 4-methoxyphenyIethylamine hydrochloride from step 12 in 3.7 mL of 47% deuterium bromide and reflux the solution under a nitrogen atmosphere for 2 h. 

The addition of deuterium bromide to both cis- and tra s-2-butene proceeds in a stereospecific trans manner at low temperature. The dx-olefin yields three while the trans gives the eryihro bromide. Similarly, the addition of HBr to isomeric 2-bromo-2-butenes is stereospecific at low temperature and in excess of HBr. The stereospecificity decreases as the temperature of the reaction is increased. At room temperature, both olefins yield the same mixture of products. Goering and Larsen first suggested that two different conformations are involved as intermediates from ds- and trons-olefins. The lifetime of these two conformations is so short that they cannot interconvert prior to the chain transfer step, which takes place from the less hindered side. At room temperature, however, these can obtain equilibrium rapidly because of easy C-C bond rotation, which results in the same mixture of meso- and d,l-2,3-dibromobutanes. Another reason may be that the addition of bromine radical (Br ) to noncyclic olefins is often reversible and may lead to nonstereospecific products. The second mechanism assumes a tr-complex formation between olefin and HBr. A bromine atom then collides with the complex leading to its attachment and simultaneous breaking of the HBr bond, which explains the decrease in stereospecificity with rising temperature (Scheme 4.53). 

Ikram A, Tortie BH, PoweU BM (1993) Strucmres of solid deuterium bromide tmd deuterium iodide. Mol Phys 79 1037-1049... 

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