Brominated cycloalkanes

Two additional brominated cycloalkanes are currently used as additive BFRs. l,2-dibromo-4-(l,2-dibromoethyl)cyclohexane (TBECH) and 1,2,5,6 tetrabromocyclooctane (TBCO) are produced for use in textiles, paints, and plastics. TBECH can exist as four diastereomers (designated a, fl, y, and 8), and TBCO can exist as two diastereomers. Chiral separations of TBECH and TBCO enantiomers have not yet been reported. These BFRs exhibit some of the same analytical challenges as HBCDs, and LC—MS approaches offer the most promise for the development of robust methods. 

Bromination and chlorination of alkanes and cycloalkanes can also take place by an electrophilic mechanism if the reaction is catalyzed by AgSbFs. " Direct chlorination at a vinylic position by an electrophilic mechanism has been achieved... 

PART 3 ALKANES, CYCLOALKANES AND RELATED COMPOUNDS WITH CHLORINE, BROMINE, OR IODINE SUBSTITUENTS... 

Bromination and chlorination of alkanes and cycloalkanes can also take place by an electrophilic mechanism if the reaction is catalyzed by AgSbF. "2 Direct chlorination at a vinylic position by an electrophilic mechanism has been achieved with benzenescleninyl chloride PhSe(0)Cl and AIC13 or AIBr3. n However, while some substituted alkenes give high yields of chloro substitution products, others (such as styrene) undergo addition of Cl2 to the double bond (5-26).113 Electrophilic fluorination has already been mentioned (p. 690). 

Exercise 12-17 Use the heats of combustion to liquid water given in Table 12-3 and appropriate bond energies to calculate AH° (vapor) for ring-opening of the cycloalkanes with bromine in the range n = 2 to n = 6 ... 

PV2M010O40 has usually been used in the acid form. H5PV2M010O40 catalyzes aerobic oxidative cleavage of cycloalkanes, 1-phenylalkanes, and ketones. For example, the oxidation of 2,4-dimethyl cyclopentanone and 2-methylcyclo-hexanone gives 5-oxo-3-methylhexanoic acid and 6-oxoheptanoic acid, respectively, in yields higher than 90% [285, 286). Bromination of arenes with HBr [287), oxidative dehydrogenation of cyclohexadiene [288, 289) and a-terpinene [290), oxidation of 2,4-dimethylphenol [291) and sulfides [292) are other examples. 

AgSbF6/Cl2/CH2Cl2 at -IS to 4 3S C is reported to be a convenient and effective reagent for the electrophilic chlorination of tertiary alkanes and cycloalkanes. Adamantane was sufficiently reactive to undergo uncatalyzed electrophilic bromination at 80 Substrates with adjacent tertiary C—H bonds... 

Perfluorinated alkanes, alkenes or cycloalkanes show a high thermal stability, heating to temperatures over 1000 C results in radical cleavage to give short chains or alkenes.However, C C bonds which contain quaternary and tertiary carbons are cleaved at lower temperatures than those between secondary carbons. In the presence of bromine, chlorine or toluene, cleav age products are isolated, e.g.Rp—Rp - 2 RpBr Other examples involve pyrolyses. ... 

The first step was the bromination of the oxime with bromocuccinimide to yield a bromonitroso compound on which the oxidation of hydrogen peroxide with nitric acid was transformed into bromonitro compound. The latter by acting with sodium borohydride furnished a secondary nitro compound with a yield of 33-80%. The method was particularly suitable for the formation of nitro derivatives of nitro cycloalkanes. The method is unsuitable for aromatic ketoximes and aldoximes. However, Barnes and Patterson [73] extended the method to aldoximes by using ozone as an oxidizing agent on gem-chloro ... 

Other examples of nitroxyl radicals such as TEMPO [3Id, j] have been used successfully in several examples of environmentally friendly liquid-phase oxidations with. oxygen. Sheldon et al. have reported on the use of N-hydroxysaccharin as an alternative to NHPI in the oxidation of cycloalkanes to dicarboxylic acids [31h]. Other examples include the aerobial oxidation in the presence of NHPI, o-phenanthroline and bromine, in an acetonitrile/CCU solvent and in the absence of metals, at 100 °C. The selectivity was 75% to AA and 22% to cyclohexanone, at 48% cyclohexane conversion [31i]. 

Alkanes and cycloalkanes can also react with a halogen (usually chlorine or bromine) in a reaction called halogenation. Halogenation is a substitution reaction, that is, a reaction that results in the replacement of one group for another. In... 

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