The content of this thesis is divided into two chapters, based on the results of experimental works carried out during the entire course of the research period. The first chapter of the dissertation is again divided into two parts, Part I and Part II. Most of the processes that currently work for the bromination of aryl compounds use toxic corrosives and expensive molecular bromine.
Aminocarbonyl compounds and their derivatives, which are the adducts of the aza-Michael reaction, have been used as building blocks for many nitrogen-containing biologically important compounds such as -aminoalcohols, 1,2-diamines and -lactams. It was seen that the inherent acidity of the catalyst would facilitate the conjugate addition reactions. After third cycle, the activity of the catalyst decreases due to leaching of the catalyst.
This part contains the details of the development of a general, economical and environmentally friendly method for the preparation of isothiocyanate from the corresponding dithiocarbamic acid salt by using cheap and readily available reagent molecular iodine in the presence of triethylamine in acetonitrile solvent at room temperature (Scheme 4). In comparison with the existing methods for degradation of the dithiocarbamic acid salts, our procedure is perhaps the simplest but most efficient method for the synthesis of isothiocyanates.
A One-pot Preparation of Cyanamide from Dithiocarbamate Using Molecular Iodine
The mechanism proposed in the scheme has been verified by isolation and characterization of all intermediates. The influences of different operating conditions on the degree of extraction of nitrobenzene are described in the thesis. Initial concentration of NB: 100 mg/l, pH: 6.0. The effects of temperature on the efficiency of nitrobenzene extraction are shown in Fig.
The performance of solvent extraction to recover surfactant from the dilute phase has been described in detail in the thesis. In particular, heterogeneous catalysis addresses the goals of green chemistry by providing easy separation of product and catalyst, thereby eliminating the need for separation through distillation or extraction.5 The invention of a newer clean and suitable catalyst for a chosen transformation is extremely very important, and for this, a clear understanding of the chemistry of a potential catalyst or catalytic system, as well as the transformation to which the catalyst is to be applied, is an essential prerequisite. TBATB has been shown to be a convenient reagent for α-bromination of ketones, but when reacted in the presence of ethylene glycol, ketoprotection was simultaneously observed (Scheme IA.
The dibromoderivate of enone is eliminated in the presence of K2CO3, whereby α-bromoenones are formed (Scheme IA.5.3.4.).55. Due to their synthetic and biological importance, many methods for the preparation of isothiocyanates from amines are described in the literature. As turbidity is approached, the solubilization of nonpolar solubilizers increases, probably due to an increase in the aggregation number of micelles.
Both temperature effects cited here are consistent with changes in the space available for solute molecules in micelles.190.
Chapter II describes the surfactant mediated cloud point extraction of nitro benzene from water
Thus the use of molecular iodine overcomes many of the problems associated with isothiocyanate preparation. It was also observed that for a particular TX-100 concentration, the extraction percentage decreases with increasing NB concentration. Variations of TX-100 extraction with NB and TX-100 feed concentration are shown in Figure IIA.3.2.1.
It can be observed from the figure that the surfactant extraction efficiency increases with the initial surfactant concentration for all NB concentrations. Since the concentration of TX-100 in the dilute phase remains almost constant (at lower surfactant concentration just above the CMC) at constant temperature and NB concentration, the extraction efficiency of TX-100 increases with increasing concentration of TX-100 feed. It is clear from the figure that the extraction of nitrobenzene increases with temperature and concentration of TX-100.
Therefore, the solubilizing ability of the micellar solution increases with temperature, leading to an increase in the extraction of nitrobenzene. Changes in the extent of surfactant extraction with respect to temperature are shown in Figure IIA.3.3.3. It can be seen from the figure that the extraction of surfactant increases with temperature and.
The effects of solution pH on the extent of nitrobenzene extraction are shown in Figure IIA.3.4.1. The variation of NB extraction using TX-100 with temperatures at different initial NB concentrations has been discussed in previous sections. It can be seen from the figure that the value of ∆G0 increases linearly with temperature and decreases with TX-100 concentration.
From the figures it can be seen that the value of ΔH0 increases with the concentration of TX-100 but decreases with the concentration of NB. Cloud point extraction has been successfully used for the removal of NB using TX-100 as a non-ionic surfactant. On the other hand, in the same ratio, the extraction efficiency decreases with increasing TX-100 feed concentration.
The increase in yield with the volume ratio between the solvent and the dilute phase is due to the greater distribution of the TX-100 molecule in the heptane phase. Murad, Goodman and Gilman's The Pharmacological Basis of Therapeutics, 7th edition, Pergamon Press, New York.
Substrates: An Eco-friendly and Practical Protocol
