Additive halogenated

Additions. Halogens, hydrogen haUdes, and hydrogen cyanide readily add to acryUc acid to give the 2,3-dihalopropionate, 3-halopropionate, and 3-cyanopropionate, respectively (21). 

Metallation of simple iodopyridines faUs °, but iodopyridines containing additional halogens metallate and rearrange to place the lithium between the two directing groups, as shown in Scheme 103. ... 

The nitrogen of phenothiazine 16 can be deprotonated and alkylated, for example, with a palladium catalyst <1985AXC1804>. When an excess of butyllithium was used for 188, an additional halogen-metal exchange occurred and the compound could be doubly silylated (Scheme 14) <20020L623>. 

The first report on a tandem / ,a-substitution of a Michael acceptor butenolide using a conjugate addition-halogenation sequence is J. L. Herrmann, M. H. Berger, R. H. Sehlessinger,./. Am. Chem. Soc. 95, 7923 (1973). 

Substitution 1 additional halogen(s) to the terminal carbon Alkylating activity decreases... 

Introduce additional halogen(s) to the terminal carbon to decrease the alkylating activity. Alkylating activity is reduced as the increased electron-withdrawing power of additional halogen(s) hinders the departure of the first halogen. 

Section III,G,2. Sequential oxidative addition, halogenation at Si, and reductive elimination provide an elegant route to pure R2SiHX derivatives (cf. Section III,C,1 and Table XII, entry 14) (453) ... 

Butyl rubber is one of the older synthetic rubbers, having been developed in 1937. Because of the saturated nature of a polyolefin elastomer, the commercial polymer is actually a copolymer of isobutylene and isoprene. The isoprene is added to provide cure sites. In addition, halogenated (bromo or chloro) derivatives are available. 

The structures which have been elucidated so far may be grouped into two general categories the first group possesses the 5,6-dichloro-2,6-dimethylocta-l,3,7-triene structure (61 R = Me, X = H) with additional halogen substituents in the dimethylal-lyl pyrophosphate-derived methyl carbon atoms, and the second group has the... 

The empirical value of s = 0.43 indicates that the increase of x with growing nucleophilic power of X is relatively small which can be expected because N2 is a very good leaving group. An estimate of the rate coefficient for the A2 reaction with attack of water in the slow step may be computed from h2o- The experimental value of is lower than the computed value. Consequently, the reaction without participation of halide must follow an A2 mechanism, also. An A1 mechanism can be operative only if its reaction rate is faster than that of the competing A2 reaction. Furthermore, if the reaction pathway of the first term in rate eqn. (47) referred to an A1 mechanism with a carbonium ion intermediate it would lead to formation of additional halogenated product iP > ( h x /feh )[X ]), in contrast to the experimental findings. 

The bimolecular nucleophilic (5nz) displacement of halide from haloalkane adjuvants and fumigants is slowed by the presence of alkyl groups or additional halogen atoms bound to the carbon at (C ), or immediately adjacent to (C g) the site of attack. Although bromide is a better leaving group... 

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