Alkyl bromides pyrolysis

It is a known fact that the gas-phase pyrolysis kinetics of alkyl bromides have not been extensively investigated due to the experimental difficulties as well as to the complexity of concurrent unimolecular and radical chain mechanisms. However, when these organic bromides are pyrolyzed under maximum inhibition, the reaction in the presence of a free radical suppressor is a molecular elimination. Sometimes, these organic bromides are pyrolyzed under maximum catalysis with HBr gas, and the process may proceed by an autocatalytic molecular mechanism. 

Pyrolysis of alkyl bromides can also take place by direct unimolecular decomposition, and this reaction has been studied by Maccoll et al. 2. 

For rate studies of pyrolysis of some p-alkyl substituted ethyl bromides, see Chuchani, G. Rotinov, A. Dominguez, R.M. Martin, I. Int. J. Chem. Kinet., 1987, 19, 781. 

Uses/Sources. Manufacture of organic and inorganic bromides reducing agent, catalyst in oxidations alkylation of aromatic compounds can be generated during the pyrolysis of a variety of materials... 

It is also possible to produce covalently bonded alkyl MLs on Si(l 11) surfaces using a variety of chemical reactions with passivated H-terminated Si(l 11), but the preparation methods are more complex than the immersion strategy in part due to the higher reactivity of silicon. This is a major achievement because it allows direct coupling between organic and bio-organic materials and silicon-based semiconductors. Both pyrolysis of diacyl peroxides (Linford Chidsey, 1993) and Lewis acid-catalyzed hydrosilylation of alkenes and direct reaction of alkylmagnesium bromide (Boukherroub et al, 1999) on freshly prepared Si(lll)-H produce surfaces with similar characterishcs. These surfaces are chemically stable and can be stored for several weeks without measurable deterioration. Thienyl MLs covalently bonded to Si(l 11) surfaces have also been obtained, in which a Si(l 11)-H surface becomes brominated, Si(lll)-Br, and is further reacted with lithiated thiophenes (He etal, 1998). 

Vinyl chlorides The anion can be alkylated by alkyl iodides (HMPT) or benzylic bromides in high yield. On pyrolysis at 160°, the products are converted into vinyl chlorides (cis- and trans-isomers). 

Preparation.—From Amines or Alcohols. Katritzky has reviewed mechanistic and preparative aspects of the conversion of primary amino to other functional groups mediated by pyrilium cations according to the general Scheme 34, where nucleophiles include the halide anions (cf. 4,157) and carboxylates (c/. 4,138), Other recent publications in this area have included full details of the preparation of primary alkyl and benzyl fluorides by this route using 2,4,6-triphenylpyrilium salts (4,157). The conversion of primary amines to the corresponding bromides has now been improved, either by a modified pyrolysis procedure but still... 

In all cases, the starting material has been the bromide (3). The first method of synthesis via the diester (156) was originally developed on the basis of the 3-desmethoxy analog of the bromide (3) as early as 1934 [275, 276] and was improved in 1951 [195]. The ketodiester (156) was formed by the alkylation of the bromide (3) with the diester of )S-oxoadipic acid its cyclization and hydrolysis led to the diacid (157). Pyrolysis of the latter over lead carbonate enabled the 18-nor derivative (158) to be obtained. ... 

---