Mahesh Ramniklal Gandhi

Kappaphycus alvarezii as a source of bioethanol.

The present study describes production of bio-ethanol from fresh red alga, Kappaphycus alvarezii. It was crushed to expel sap--a biofertilizer--while residual biomass was saccharified at 100 °C in 0.9 N H2SO4. The hydrolysate was repeatedly treated with additional granules to achieve desired reducing sugar concentration. The best yields for saccharification, inclusive of sugar loss in residue, were 26.2% and 30.6% (w/w) at laboratory (250 g) and bench (16 kg) scales, respectively. The hydrolysate was neutralized with lime and the filtrate was desalted by electrodialysis. Saccharomyces cerevisiae (NCIM 3523) was used for ethanol production from this non-traditional bio-resource. Fermentation at laboratory and bench scales converted ca. 80% of reducing sugar into ethanol in near quantitative selectivity. A petrol vehicle was successfully run with E10 gasoline made from the seaweed-based ethanol. Co-production of ethanol and bio-fertilizer from this seaweed may emerge as a promising alternative to land-based bio-ethanol.

An alternative method for the regio- and stereoselective bromination of alkenes, alkynes, toluene derivatives and ketones using a bromide/bromate couple

Mixtures of NaBr and NaBrO3 in two different ratios have been used for highly stereoselective bromination of alkenes and alkynes, and regioselective bromine substitution at the α-carbon of ketones and at the benzylic position of toluene derivatives. The reactions were conducted in an aqueous acidic medium under ambient conditions. The solid reagents were prepared from the intermediate obtained in the “cold process” of bromine manufacture and are stable, non-hazardous and inexpensive to prepare. This procedure provides an efficient and practical alternative to conventional procedures using liquid bromine directly or indirectly.

Clean synthesis of crystalline p-nitrobenzyl bromide from p-nitrotoluene with zero organic discharge

2 : 1 : 3 NaBr-NaBrO3-NaCl (obtainable as a low cost and eco-friendly reagent from an alkaline bromine intermediate) has been utilized previously in a number of bromination reactions. One such reaction is the conversion of p-nitrotoluene (PNT) to p-nitrobenzyl bromide (PNBBr) used widely for functional group protection. In the present work, selective cold (0–5 °C) crystallization of PNBBr from the reaction mixture containing ca. 2.5 M PNBBr along with 2.5–5.0 M PNT in ethylene dichloride (EDC) was found to be a winning move which led to gains in two fronts. It allowed the bromination reaction to be carried out cleanly and also enabled direct recycling of the mother liquor in the subsequent batch. Para NO2-Ph-CHBr2 impurity, which built up gradually in the reaction mixture over 8 batches, was converted into PNBBr/PNT through treatment of the mother liquor with NaBH4, thereby helping to recycle the liquor perpetually and eliminate organic waste. EDC was the sole solvent in the entire process and its losses were minimal. The combined yield of isolated and recoverable PNBBr was 98.30% with respect to PNT consumed. The reagent utilization efficiency was 98.26%.