Russell, Glen A. published the artcileDirective effects in aliphatic substitutions. III. The photobromination of branched-chain hydrocarbons; the dark reaction of bromine with tertiary alkyl bromides, Recommanded Product: 2,3-Dibromo-2,3-dimethylbutane, the publication is Journal of the American Chemical Society (1955), 4025-30, database is CAplus.
The photobromination of hydrocarbons in the liquid phase is highly selective and constitutes an excellent method for the preparation of tertiary bromides from hydrocarbons which contain only primary and tertiary H atoms. The presence of secondary or an addnl. tertiary H atom in the adjacent position leads to the formation of considerable amounts of dibromides. It is proposed that these dibromides arise from an ionic or mol. reaction of Br with the tertiary bromide formed in the initial photochem. reaction. The dark reaction of Br with Me3CBr exhibits 3rd order kinetics. No evidence could be obtained of a measurable equilibrium between olefin and hydrogen halide in solutions of Me3CBr and Me3CCl in refluxing SO2 or of Me2CBrCMe3 (XVII) in CCl4 at 76°. Yet Br reacts rapidly with the tertiary halides under these conditions. These results are consistent with a reaction mechanism in which a Br mol. brings about the ionization of the tertiary bromide, followed by reaction of a 2nd Br mol. with the high-energy π-complex form of the carbonium ion. Me3CCHMe2 (XVIII), b745 80.3°, nD20 1.3895 (1 mol) irradiated with a 150-w. clear light bulb (1 in. from the flask) and treated 1.5 h. with 0.25 mol Br at 80°, 25 g. XVIII distilled off, the residue cooled, and the nearly solid crystalline mass (57 g.) washed with 50 cc. cold XVIII gave 36 g. XVII, m. 149-50° (sealed tube), and 10 g. XVIII by vacuum sublimation at 80°/25 mm. Cumene (XIX) (1 mol), b740 151.4-5°, nD20 1.4915, brominated similarly 0.5 h. with 0.5 mol Br at 60°, and the mixture bubbled with N to remove the HBr and analyzed for total and hydrolyzable Br (80% EtOH at 25°) showed that 73% of the Br was present as the tertiary bromide. A similar run with 0.25 mol Br/mol XIX gave during 1.5 h. at 0° a product containing 94% of the Br as tertiary bromide; the bromide could not be crystallized from the solution at -80° and attempts to distil below 1 mm. resulted in dehydrobromination. Br (0.5 mol) added under illumination to 0.5 mol XIX in CH2Cl2 at 0° until the Br color persisted 2 min. after the addition of 1 drop Br and the product rectified gave 111 g. MePhCBrCH2Br, b16 120-20.5°. Br (0.5 mol) added to 2 mol (Me2CH)2 (XX), nD20 1.3749, at 55° during 6 h. at such a rate that the hydrocarbon remained colorless through the reaction, the mixture cooled, and the crystalline deposit (65 g.) sublimed at 95-100°/5 mm. gave 54 g. (Me2CBr)2 (XXI), m. 169-71° (sealed tube). Br (0.5 mol) added dropwise at 60° during 8 h. to 2 mol Me2CHPr (XXII), nD20 1.3714, at such a rate that the solution was nearly colorless at all times, and the mixture fractionated gave 64 g. mixture of 92% Me2CHBrPr and 8% secondary bromides from XXII, and 10 g. material, b40 92-2.5°, containing 64.5% Br, largely as Me2CBrCHBrEt. XVII (0.075 mol) in 100 g. CCl4 treated 40 h. at 25° with 0.076 mol dry Br, the CCl4 removed, the mixture sublimed in vacuo to remove 2 g. unchanged XVII, and the residue distilled gave 10.3 g. dibromide, b10 88.5-9.5°, presumably BrCH2CMeBrCMe3, and 3 g. tribromides, b3 107-10°. Br (0.25 mol) and 0.25 mol Me2CBrEt in 120 cc. CCl4 held 40 h. at 25° in the dark and the mixture distilled gave 34 g. Me2CBrCHBrMe, b30 72.5-73°, nD20 1.5095, and 8.5 g. tribromide, b15 110-14°. Me2C(OH)CHMe2 (XXIII), b100 65.5, nD20 1.4182, (10.2 g.) as a 2M solution in CCl4 treated with Br 60 h. in the dark and the product crystallized and rectified gave 18.2 g. XXI, m. 168-9°, 2.1 g. unchanged XXIII, 1 g. tribromide, b25 140-50°, and traces of a lachrymator. A similar run with 16 g. Br and 10.2 g. XXIII in the presence of 10 g. finely divided CaCO3 showed only 80% reaction of the Br in 72 h. and gave 10 g. dibromide, 5 g. XXIII, and 4 g. high-boiling material, presumably a tribromide. Me3CBr (40 g.) and 46 g. Br held 42 h. at 0° in the dark and the mixture distilled gave 43 g. Me2CBrCH2Br, b. 146-9°, and 6 g. higher-boiling material, probably the tribromide. Br (15.984 and 13.700 g. Me3CBr diluted to 100 cc. at 0° with CCl4, 5-cc. samples sealed in ampuls, stored in ice, and 1-cc. aliquots titrated with standard Na2S2O3 at appropriate intervals gave the kinetic data for the bromination; average k3 × 102 l.2/mol2/h. 0.52. Photobrominations at 25° were carried out with 5 mol % solutions by degassing the appropriate hydrocarbon with N, vaporizing dry Br in a stream of N, passing the Br-N mixture during 1 h. into the hydrocarbon, removing the HBr with N, and analyzing the mixture (the Br used, the total bromide, and the tertiary bromide, all in moles, given): XIX, 0.055, 0.0541, 0.0541; XVIII, 0.050, 0.0486, 0.0457; XXII, 0.051, 0.0492, 0.0443; XX, 0.051, -, 0.0214 (some dibromide crystallized during the bromination); XX, 0.031, 0.0302, 0.0238; XX (0°), 0.038, 0.0371, 0.0326. Me3CCl (5 cc.) added during 6 h. to 15 cc. SO2 refluxing at -12.5 ± 0.5°, and 100 cc. vapor removed under standard conditions and analyzed in a mass spectrometer showed that not more than 0.001% Me3CCl had been dehydrochlorinated. Me3CBr (5 g.) treated 6 h. with 25 cc. SO2 refluxing at -14 ± 0.5°/722 mm. was less than 0.001% dehydrobrominated. XVII (500 cc. 0.2M solution in CCl4) rectified at atm. pressure, 400 cc. CCl4 removed during 24 h., all gases formed passed into aqueous NaOH, and the distillate extracted with H2O indicated the complete absence of acidic materials or bromide ion. Me2CBrEt (5 cc.), 25 cc. CH2Cl2, and 2 g. iodine refluxed at such a pressure that the temperature was 25°, and 100 cc. vapor removed under a high reflux ratio during 6 h. and analyzed showed less than 0.001% dehydrobromination.
Journal of the American Chemical Society published new progress about 594-81-0. 594-81-0 belongs to bromides-buliding-blocks, auxiliary class Bromide,Aliphatic hydrocarbon chain, name is 2,3-Dibromo-2,3-dimethylbutane, and the molecular formula is C6H12Br2, Recommanded Product: 2,3-Dibromo-2,3-dimethylbutane.
Referemce:
https://en.wikipedia.org/wiki/Bromide,
bromide – Wiktionary