Bromoalkane

Bromination. 1-Bromoalkanes are produced commercially by the anti-Markovnikow free-radical addition of HBr to a-olefins. These are further reacted with dimethyl amine to produce alkyldimethyl amines, which ultimately are converted to amine products for household cleaning and personal care. 

Mixed sulfides are prepared in the flavor industry by the reaction of thiols, 2inc oxide, and a bromoalkane (39). Some of these mixed sulfides are constituents of allium, asafetida, coffee, and meat flavors. A representative reaction is represented in equation 24. 

Fluoro- or 2,2-difluoro-l-bromoalkanes readily undergo nucleophilic substitution in the presence of sodium thiophenoxide [45] (equation 41)... 

The alkylation process possesses the advantages that (a) a wide range of cheap haloalkanes are available, and (b) the substitution reactions generally occur smoothly at reasonable temperatures. Furthermore, the halide salts formed can easily be converted into salts with other anions. Although this section will concentrate on the reactions between simple haloalkanes and the amine, more complex side chains may be added, as discussed later in this chapter. The quaternization of amines and phosphines with haloalkanes has been loiown for many years, but the development of ionic liquids has resulted in several recent developments in the experimental techniques used for the reaction. In general, the reaction may be carried out with chloroalkanes, bromoalkanes, and iodoalkanes, with the reaction conditions required becoming steadily more gentle in the order Cl Br I, as expected for nucleophilic substitution reactions. Fluoride salts cannot be formed in this manner. 

A bromoalkane is formed from an alkane when a bromine atom replaces a hydrogen atom. Decide whether the bromoalkanes (a) CH3CH,CHBrCH3 and (b) CH3CHBrCH are chiral. 

Non-activated n-alkylbromides react non-selectively under radical conditions, because the radicals formed at the step of chain growth, actively abstract hydrogen atoms from bromoalkane alkyl chain. 

The descriptors used should not be highly collinear with each other, for two reasons. First, this can lead to statistical instability and overprediction, and second, collinearity makes mechanistic interpretation difficult. For example, Cronin and Schultz [41] have pointed out that although a good correlation could be obtained between the skin sensitization potential and the hydrophobicity of a series of bromoalkanes, a correlation between skin sensitization potential and molecular weight had exactly the same statistics, because hydrophobicity and molecular weight are very highly correlated in homologous series. 

C09-0076. Draw Lewis structures of all possible stmctural isomers of the bromoalkanes with formula C4 Hg Br. 

Shochat E, 1 Hermoni, Z Cohen, A Abeliovich, S Belkin (1993) Bromoalkane-degrading Pseudomonas strains. Appl Environ Microbiol 59 1403-1409. 

In previous chapters we have considered the relative reactivity of numerous series of compounds in specific reactions—such as nucleophilic displacement by EtOe in the series of bromoalkanes below (cf. p. 86)-... 

The electrochemistry of cobalt-salen complexes in the presence of alkyl halides has been studied thoroughly.252,263-266 The reaction mechanism is similar to that for the nickel complexes, with the intermediate formation of an alkylcobalt(III) complex. Co -salen reacts with 1,8-diiodo-octane to afford an alkyl-bridged bis[Co" (salen)] complex.267 Electrosynthetic applications of the cobalt-salen catalyst are homo- and heterocoupling reactions with mixtures of alkylchlorides and bromides,268 conversion of benzal chloride to stilbene with the intermediate formation of l,2-dichloro-l,2-diphenylethane,269 reductive coupling of bromoalkanes with an activated alkenes,270 or carboxylation of benzylic and allylic chlorides by C02.271,272 Efficient electroreduc-tive dimerization of benzyl bromide to bibenzyl is catalyzed by the dicobalt complex (15).273 The proposed mechanism involves an intermediate bis[alkylcobalt(III)] complex. 

Observations A white precipitate (soluble in dilute ammonia) indicates a chloroalkane. A cream precipitate (insoluble in dilute ammonia but soluble in concentrated ammonia) indicates a bromoalkane. A yellow precipitate (insoluble in both dilute and concentrated ammonia) indicates an iodoalkane. 

A spectacular example of the influence of steric factors on the fragmentation pattern involves the behavior of chloro- and bromoalkanes. If the hydrocarbon chain is unbranched, peaks of C4H8Hal+ ions dominate in the homologous series of fragment ions CnH2nHal+ (Scheme 5.9). Any substitute in the carbon chain sharply decreases the competitiveness of this process. 

Method A The bromoalkane (0.39 mol) is refluxed in Me2CO (30 ml) with Amberlyst A-23 resin (in HC02 form) (3.87 g equivalent to 3.65 mmol formate per g) for 72 h. The mixture is filtered and the filtrate is evaporated to yield the formate ester, HC02R (e.g. 

TBA),-HP207 (0.68 g, 0.75 mmol), obtained from Na2H2P207 by exchange on a Dowex 50W-X8 (H+ form) column followed by neutralization (to pH 7) with TBA-OH, is added to the bromoalkane (0.75 mmol) in MeCN (6 ml) and the mixture is stirred at room... 

The preparation of thiols by nucleophilic displacement reactions using aqueous potassium or sodium hydrogen sulphide under catalytic conditions is not particularly effective. A limited number of simple alkane thiols have been obtained under mild and neutral conditions in moderate yield (70-80%) from the reaction of bis(n-butyltin) sulphide with bromoalkanes in the presence of a ca. twofold amount of tetra-n-butylammonium fluoride [1], but there has been no exploitation of this procedure. 

In a similar manner, saccharin has been A-alkylated and A-acylated (Table 5.17) [31, 32], There is good evidence that the kinetic O-alkylated product is initially formed and it is converted into the thermodynamically more stable A-alkyl derivative upon prolonged heating [31, 32], The reaction fails with secondary haloalkanes and is most successful with primary bromoalkanes [31, 32]. 

The acidities of sulphonamides are considerably greater than those of the carboxamides and, as a consequence, their A. A -dialkylation proceeds extremely easily [3]. Generally, use is made of a basic solid.liquid two-phase system and yields are usually greater than 80%, except when secondary bromoalkanes are used (Table... 

Method A The bromoalkane (20 mmol) in PhH is added dropwise over 1.5 h with stirring to Ph2PONH2 (4.34 g, 20 mmol), TBA-HS04 (0.34 g, 1 mmol), aqueous NaOH (50%,... 

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