Water removing from reaction mixture using

The first step can be realized both by reaction of AA with HBr or with NMI (the reaction of NMI with HBr leads to the stable methyl ammonium bromide salt which doesn t react with AA), followed by elimination of water using microwave technical. The exchange of anion using ammonium salt is rapid (10 min in acetone). The ammonium bromide resulting from the counter-anion exchange is insoluble in acetone and, as a consequence, is easily removed from reaction mixture by a simple filtration. 

One patent describes a continuous process involving an aqueous alkah metal hydroxide, carbon disulfide, and an alcohol (82). The reported reaction time is 0.5—10 min before the mixture is fed to the dryer. The usual residence time is on the order of hours. A study ia the former USSR reported the use of the water—alcohol azeotrope for water removal from isobutyl or isoamyl alcohol and the appropriate alkah hydroxide to form the alkoxide prior to the addition of carbon disulfide (83). 

This book concerns the use of enzymes in non-aqueous media, which means that the major part of the medium surrounding the enzyme is non-aqueous. However, it is extremely difficult to remove water completely from enzymes. Even after extensive drying, a few water molecules remain tightly bound to the enzyme [6], and in most cases enzyme activity can be increased considerably by supplying an optimal amount of water to the system. It is thus very important to control the amount of water in the reaction mixtures in a proper way. 

The conversion of hexanoic acid as a function of time for the three different experiments is plotted in Fig. 8.27. For orientation, the maximally obtainable conversion if no water is removed from the mixture is also plotted (79 % under the chosen conditions). The lowest curve shows a blank experiment where the liquid flows over uncoated monoliths and reacts homogeneously. The second curve represents an experiment in the autoclave where the water removal is suppressed. The comparison of these two curves indicates that, without decreasing the water contents, the catalytic activity of the BEA cannot be used efficiently. The third (highest) curve proves the effect of reactive stripping. The reaction runs much faster and easily continues beyond the equilibrium. 

Heat a mixture of 4 g of benzoin and 14 mL of concentrated nitric acid on the steam bath for 11 min. Carry out the reaction under a hood or use an aspirator tube near the top of the flask to remove nitrogen oxides. Add 75 mL of water to the reaction mixture, cool to room temperature, and swirl for a minute or two to coagulate the precipitated product collect and wash the yellow solid on a Hirsch funnel, pressing the solid well on the filter to squeeze out the water. This crude product (dry weight 3.7-3.9 g) need not be dried but can be crystallized at once from ethanol. Dissolve the product in 10 mL of hot ethanol, add water dropwise to the cloud point, and set aside to crystallize. Record the yield, crystalline form, color, and mp of the purified benzil. 

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