Organic synthesis using clay catalysts: Clays for "green chemistry"

A review. An important family of catalysts that has received significant attention is derived from the soil, the most noteworthy ones being clays and zeolites. Clays are solid acidic catalysts which can function as both Bronsted and Lewis acids in their natural and ion-​exchanged form. Some of the org. reactions that have been conducted using clays as catalysts for reducing environmental pollution are described. Chem. modified clays are considered to be potentially the most cost-​effective nanomaterials, and it is estd. that hundreds of millions of dollars worth of clays will be marketed by 2010. The structure and properties of montmorillonite clay are described. The range of reactions that have been successfully conducted on clay catalysts includes addn., elimination, addn.-​elimination, substitution, rearrangement, Diels-​Alder reactions, and oxidn.-​redn

Electronic effects in the cyclocondensation of benzil

Electronic effects are important directing forces in the course of chem. reactions. Small differences in these effects can bring about considerable changes in the results of very similar reactions. Thus, although the ambident nucleophiles urea, o-​phenylenediamine and dibenzyl ketone are expected to take comparable double condensation pathway in their resp. reaction with benzil, urea reacts differently by causing benzil-​to-​benzilic acid type rearrangement. This is attributed to the reduced availability of the lone pair of electrons on nitrogen in urea that is needed for assisting the dehydration of the intermediate

Liquid fuels from plants: Can we meet our petroleum needs from plants?

A review with no refs. of plant-​derives liq. fuels such as vegetable or fatty oils, alc. (EtOH)​, and liq. hydrocarbons

An appreciation of free radical chemistry. Part 4. Free radicals in atmospheric chemistry

The earth is unique in having a blanket of atm., which has helped the evolution and sustenance of life. For a layman, the atm. seems a simple, just some air that we breathe, with clouds and rain at times. But actually what is atm. and what happens within it in chem. terms is unimaginably complex. Even small changes in its compn. can greatly affect the life processes. Though different kinds of chem. reactions take place in the atm., the most dominant ones involve free radicals. A brief discussion on this aspect is presented

An appreciation of free radical chemistry. Part 5: Free radicals in organic synthesis

A good understanding of the free radical reaction mechanism has led to the realization of unprecedented control over the chemo-​, regio-​, and diastereospecificity. The free radical chem. has transformed from the intractable to the predictable. In certain systems, radical chem. can deliver results that are far superior to those obtained from conventional ionic or organometallic methods. Some of the syntheses involving free radicals are presented

Jacobus Henricus van't Hoff. A short biographical sketch

A biog. for J H van't Hoff, considered as one of the greatest chemists of all time, is presented. He started his career as an org. chemist. He solved the vexing problem of optical isomerism by proposing an asym. tetrahedral carbon bonded to form different groups. He extended this to include geometric isomerism, and to compds. with heteroatoms in place of asym. carbon. Thus he established the 'chem. in space' or stereochem. He moved on to work on reaction kinetics, equil., thermodn. properties of dil. solns. and related areas. He laid the foundation for phys. chem. through these discoveries and was awarded the first Nobel Prize in Chem. in 1901. Van't Hoff died of tuberculosis at a relatively early age of 59

An appreciation of free radical chemistry 6. Experiments involving free radicals

In the previous five parts, we have seen how the ubiquitous free radicals touch our lives in many ways. In this part, four expts. involving free radical intermediates are described. They are very simple, economical and practical, and can be easily carried out in labs. with meagre resources. They can, therefore, be adapted for MSc chem. practicals as part of free radical chem. course

An epitome of K Venkataraman's chemistry

Some of the significant contributions of Krishnaswami Venkataraman's to the chem. of flavones and other natural products and dyes are presented. The initiative taken by Venkataraman for research and the support to establish dyestuff industry that found success within a short period, earned him the nickname "the father of dyestuff research in India". He developed several new synthetic procedures, chromatog. sepn. techniques, and simple, practical methods for the characterization and estn. of dyes. He also discovered that naphthols could be estd. by pptg. them by acidifying their alk. soln. in water or aq. alc. and weighing the ppt

Organic synthesis under solvent-​free condition: an environmentally benign procedure - I

A review. The growing concern to minimize the environmental pollution caused by solvents and the increasing interest in solid-​solid reactions have led to the development of methodologies for solvent-​free reactions with considerable success. Solvent-​free or solid state reaction may be carried out using the reactants alone or incorporating them in clays, zeolites, silica, alumina or other matrixes. The principles and disadvantages of solvent-​free org. synthesis are discussed. Illustrative examples representing a no. of org. syntheses performed under both thermal and photochem. conditions are described

Solvent-free reactions using cetyltrimethylammonium permanganate and cetyltrimethylammonium dichromate-cis-1,2-dihydroxylation of alkenes, oxidation of alcohols and regeneration of aldehydes and ketones from oximes

Cetyltrimethylammonium permanganate (CTAP) and cetyltrimethylammonium dichromate (CTAD) have been known to be good oxidizing agents in organic solvent media. This homogeneous solution phase procedure itself is a useful advantage over oxidation reactions carried out employing inorganic manganese salts (e.g., KMnO4) or chromium salts (e.g., Kr2Cr2O7) performed under heterogeneous conditions. Now we have found that oxidation reactions using CTAP or CTAD do not require a solvent medium, and can be performed under completely solvent-free conditions. We have carried out 1,2-dihydroxylation of olefins with CTAP, oxidation of alcohols to aldehydes/ketones with CTAD, and regeneration of aldehydes and ketones from their oxime derivatives using either reagent, essentially under solid phase conditions. The results are excellent. As a dihydroxylating agent the CTAP is so good that it should be able to replace the highly toxic and expensive OsO4 for this reaction. © 2009 King Saud University