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Background: During the last two decades, horizon of research in the field of Nitrogen Heterocyclic Carbenes (NHC) has widened remarkably. NHCs have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods: By manipulating structural features and selecting appropriate substituent groups, it has been possible to control the kinetic and thermodynamic stability of a wide range of NHCs, which can be tolerant to a variety of functional groups and can be used under mild conditions. NHCs are produced by different methods, such as deprotonation of Nalkylhetrocyclic salt, transmetallation, decarboxylation and electrochemical reduction. Results: The NHCs have been used successfully as catalysts for a wide range of reactions making a large number of building blocks and other useful compounds accessible. Some of these reactions are: benzoin condensation, Stetter reaction, Michael reaction, esterification, activation of esters, activation of isocyanides, polymerization, different cycloaddition reactions, isomerization, etc. The present review includes all these examples published during the last 10 years, i.e. from 2010 till date. Conclusion: The NHCs have emerged as versatile and powerful organocatalysts in synthetic organic chemistry. They provide the synthetic strategy which does not burden the environment with metal pollutants and thus fit in the Green Chemistry.

Degenerate Cope rearrangements of bullvalene, semibullvalene, and barbaralane and their all-phospha analogues, namely decaphosphabullvalene (P 10 -bullvalene), octaphosphasemibullvalene (P 8 -semibullvalene), 9H-nonaphosphabarbaralane (P 9 -barbaralane), P 9 -barbaralan-9-onium ion and P 9 -barbaralane-9-phosphinic acid have been investigated theoretically at the DFT (B3LYP/6-31+G * ) level. The CH/P exchange causes remarkable lowering of the activation enthalpies, H # for the degenerate Cope rearrangements. On the basis of the optimized geometries and the activation enthalpies, P 8 -semibullvalene, and P 9 -barbaralan-9-onium ion are predicted to show bishomoaromatic character.

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Every year several disasters, natural as well as man-made, strike across the globe causing loss of humanlives as well as property. So, the country facing disaster events is pushed many years back due to thedestruction of property and infrastructure. Due to environmental changes number of disaster events areincreasing every year posing challenge to the world regarding prevention, mitigation and management ofdisaster operations. Being unpredictable all natural disasters cannot be prevented completely but by theeffective use of technology, the loss in life and property can be reduced to a greater extent. In this modernera, social media platforms have become a part of daily life and the number of social media users iscontinuously increasing. General public can report the incidents related to disaster events through socialmedia and thus contribute in monitoring of disasters. Effective disaster management is essential to mitigateand minimise the loss of life and property during disaster. Relevant information from social media increasesthe effectiveness of disaster management and hence reduces the impact of natural disasters. In this study aliterature review is conducted on the role of social media in effective disaster management.