Lithium chloride temperatures, effect

The Diels-Alder reaction of nonyl acrylate with cyclopentadiene was used to investigate the effect of homochiral surfactant 114 (Figure 4.5) on the enantioselectivity of the reaction [77]. Performing the reaction at room temperature in aqueous medium at pH 3 and in the presence of lithium chloride, a 2.2 1 mixture of endo/exo adducts was obtained with 75% yield. Only 15% of ee was observed, which compares well with the results quoted for Diels-Alder reactions in cyclodextrins [65d]. Only the endo addition was enantioselective and the R enantiomer was prevalent. This is the first reported aqueous chiral micellar catalysis of a Diels-Alder reaction. 

The salt effect parameter ko is plotted in Figure 2, and the data for lithium chloride and lithium bromide reported in the previous paper (3) are also plotted for the purposes of comparison. It can be seen from Figure 2 that ko depends markedly on the solvent composition. The values of ko decrease and in the extremely water-rich region k0 is negative at 50° and 25°C. In other words, 2-propanol is salted in by the addition of lithium perchlorate. The salting-in effect of 2-propanol increases with reduction in temperature. 

Zinc chloride has also been observed to have a significant influence on the enantiose-lectivity of these reactions. But several other important parameters have been pointed out, such as the temperature (best performances are obtained at very low temperatures), the solvent (HMPA is often required) or the concentration of the lithium amide96. As underlined above about the stereoselectivity of the deprotonation, the formation of lithium amides-lithium chloride mixed aggregates (1 1 or 2 1) has been proposed to rationalize the important salt effects (Scheme 20), the amide homogeneous dimer being supposed to provide only mediocre enantioselections. With diamines, the intramolecular chelation would provide a fairly rigid system. 

In general, the increase in conductivity is largest for the addition of alkali metal chloride with the smallest cation. Thus, lithium chloride will favor the conductivity most. Benhenda (1980) determined the conductivity of ZnCl2-LiCl mixtures in the temperature range from 320 to 450°C. Furthermore, the effect of FiCl addition to ternary mixtures of ZnCl2, KCl, and NaCl on the conductivity was determined by Driscoll and Fray (1993). A significant increase in conductivity was reached when 20 mole % LiCl was added. 

Catalytic hydrogenation of nitrosamines to A, A-di substituted hydrazines is effected in water or aqueous alcohol with 10% palladium-charcoal, 10% platinum-charcoal, or 5% rhodium-charcoal as catalyst,132 in the presence of a salt (e.g., calcium chloride, ammonium acetate, or lithium chloride) at temperatures between 25° and 60° for example, 0.2 mole of 4-nitrosomorpholine in a solution of 30 g of calcium chloride in 150 ml of water is stirred with 2 g of 10% palladium-charcoal under a hydrogen pressure of 3-4 atm for 22 hours at 60°, thereby affording an 82.7% yield of 4-aminomorpholine. 

The generality of this methodology was documented using several other functionalized alkyl chlorides. Orthoester (carboxyl) functionalization was effected by termination of PSLi (Afn= ITOOgmoC ) with 4-chloro-l,l,l-trimethoxybutane in benzene at room temperature. In the absence of lithium chloride, the orthoester-functionalized polystyrene was obtained in 88% yield, while a 96% yield was isolated when... 

Lithium chloride, Uthiurn bromide, and copper chloride were foimd to be effective in reducing the melting temperature of polyamides. The reduction of the melting temperature of Nylon 6 by the addition of lithium chloride is shown in Table 5.8. 

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