Introduction Arynes are reactive intermediates derived from substituted arenes which participate in some aromatic nucleophilic substitutions and some cycloaddition reactions. It is non isolable very reactive species with the hexagonal planar ring structure with six pi delocalizing and 2 additional pi electrons. The additional 2 pi electrons do not affect the aromatic character of ring as it does not interfere with the Huckel number. Arynes are so highly reactive that they exist as stable species only at very low temperatures, e.g., 8 K for benzyne. Arynes may be derived from substituted benzenes, fused arenes and pyridines. Structure of Benzyne The sp 2 orbitals involved in the ‘triple bond’ are at 90 o to the p-orbitals of the aromatic pi-system Instead of an overlap between two 2p orbitals (as in an alkyne) the “triple bond” is formedthrough overlap of two adjacent sp2 orbitals in the plane of the ring (i.e., at right angles to, and completely independently of, the aromatic
Fractional Crystallization/ Fractional crystallization of all salts/ Fractional crystallization of NaCl and NH4Cl.
Fractional crystallization of NaCl and NH4Cl Fractional Crystallization Principle: The impurities are more soluble when the temperature increases in the liquid medium. The refining materials are more likely to get easily in fractions. It is all done due to the solubility differences. Material Required : China dish, wire gauze, filter paper, tripod stand, beaker, stirrer, Bunsen burner, distilled water, funnel, weight machine, solution of two salts which have to separate by crystallization (i.e. NaCl and NH 4 Cl). The technique of preparing NaCl and NH 4 Cl solution or salt solution : Take 4g of NaCl and 7g of NH 4 Cl (you may use the salts of your own choice that you want to crystallize). Add the two in distilled water. And mix them at room temperature. The amount of distilled water is 15mL. Procedure: Take the china dish and pour the solution of two salts into it. · Put the filled china dish on the wire gauze which is already present on a tripod stand. · Turn o