A simple and efficient process for the chlorination of industrially important aromatic compounds using NaCl/p-TsOH/NCS in aqueous media under mild conditions is described. The addition of NaCl increases the yield of chlorinated product and decreases the reaction time in the presence of p-toluenesulphonic acid (p-TsOH) and N-chlorosuccinimide (NCS). The present method furnishes higher selectivities and yields of chlorinated products under mild reaction conditions in a short reaction time. Organic solvent-free conditions, a feature of green chemistry, was successively used not only for the reactions but also for the isolation of products at the end of the reaction, which seems to be the most promising methodology from the viewpoint of a green approach to organic synthesis.

No abstract

A new, simple, and practical aromatic bromination process is disclosed wherein NaBr/NaIO4 combination in acidic medium was efficiently utilized for the first time in the bromination of deactivated aromatic compounds, thus, affording the corresponding bromo-derivatives of deactivated aromatics in good yields and purity.

The existing classification systems like canine-guided and group function are insufficient to classify all clinical conditions and chances of subjective variations are always there, as there is no standardization in examination method. Hence a study was planned to find out the frequency of tooth contacts in different lateral positions and to assess whether existing occlusal schemes like canine protection and group function can classify all occlusal guidance in the natural dentition. 100 systematically healthy undergraduate students between the age group of 18 to 25 years were selected. Occlusal contacts were examined with shim stock in lateral positions, 0.5, 1, 2, and 3 mm from the maximum intercuspation. Frequency of tooth contacts in different lateral positions was examined. The SPSS version 15.0 statistical software and Chi- Square test were used for statistical analysis. Out of all the four lateral positions, 0.5 mm position showed maximum contacts which progressively decreases for further positions. Out of all teeth, canine showed consistent contact frequency throughout all four positions. Most contact patterns belonged to group function, and a few to canine protection. Majority of the contact patterns were those other than canine protection and group function and were unclassifiable. On the basis of the results of this study, it does not seem appropriate to describe and classify the patterns of occlusal contact using only existing classification system. A clear description regarding the position of mandible should be included in definition for research as well as clinical situations. Here an attempt is made to classify eccentric occlusal contact at different lateral positions so as to get consistent result for future studies.

An instantaneous method for the bromination of bisphenol A has been reported using potassium tribromide for the first time as an efficient brominating agent affording the corresponding tetrabromobisphenol A in a reaction time of only 5−10 min at ambient temperature in high yields (99%) and purity (>99%), free from reaction byproduct and having very low ionic impurities. Mild reaction conditions and simple workup provide a practical and commercially viable route for the synthesis of the largest selling flame retardant. The generated HBr during the bromination reaction is used either in the preparation of value-added brominated products or is disposed of as waste, causing serious environmental problems. An environmentally acceptable method for an inbuilt recycling of HBr by its neutralisation, thereby generating additional amounts of metal bromide and recovering the solvent from the liquid mixture has been designed and developed. The KBr used for the preparation of potassium tribromide can be recovered, regenerated in additional amounts, and reused without any significant loss.