Adds, alcohol exchange reactions

As we pointed out in the previous section, thiols have a markedly greater tendency to add to carbonyl groups than do water and alcohols. The equilibrium constant for the exchange reaction 8.46 is estimated84 to be about 2.5 x 104. 

The complexes trani-[IrX(NO) (P(C6H5)3 2]BF4(X = Cl, Br) are dark red crystalline solids with n(NO) = 1902 cm i. The chloro complex exhibits limited transition metal basicity and oxidative-addition reactions it does not bind with O2 but adds various donor molecules, especially coordinating anions. The complex hydrolyzes in water to give the hydroxy complex and undergoes an exchange reaction in alcohols which yields the alkoxy derivatives. The complexes are presumably square-planar with NO coordinated as NO+.6... 

Dowex, a common cation-exchange resin, is widely used as catalysts in esterification (Vahteristo et al., 2009). In 2005, Kulawska, et al. investigated the esterification of maleic anhydride with octyl, decyl or dodecyl alcohol over Dowex 50Wx8-100, and the kinetic data were measured in the tempjerature range of 403-433 K (Coalc/Coma =5 1). Based on the data, a first order reaction was foimd- first order with resp>ect to add and zero order with resp>ect to alcohol. The reaction rate can be described as follows. 

A whole network of synthetic pathways to the tefluthrin alcohol 363 (Reaction scheme 245, 246) adds another fascinating facet to the diverse chemistry embraced by pyrethroid chemistry. One parent compound is tetrafluoro terephthaloyl chloride 364. All chlorine atoms are activated, thus allowing facile and complete chlorine-fluorine exchange with potassium fluoride [755]. From 364 several synthetic lines develop to Reaction scheme 245. 

A halogen-lithium exchange in the reaction of BuLi and 2-bromopropene (41) affords 2-lithiopropene (42) which then adds to the carbonyl double bond. After aqueous workup, alcohol 22 is obtained as a mixture of isomers. 

Since both the stereochemical results and the exchange experiments are inconclusive regarding competition of the two reaction routes for the cis isomer, the dissection of the reaction into the contributions of the two routes requires the isolation or the estimation of the intermediate. Under suitable conditions, 9-toluenesulphonylacetylene is the main product from bromo-(ll), while it is only detected by infrared spectroscopy during the reaction of chloro-(ll). Dissection of the overall substitution rate constant (k ) into contributions from elimination-addition ( eUm) and addition-elimination (k i,) is possible when the rate of the alkoxide-catalysed addition of alcohol to the intermediate acetylene ( add) the concentrations of the latter during the reaction are known. Such analysis for cis-(11) and (12) (Table 10) shows that at 0° the contributions of the two processes to the overall rate are nearly equal, but the importance of the elimination-addition route increases with the temperature, fceUm/ 9ub = 3-0 and T4for (11) and (12) respectively at 25° (DiNunno... 

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