Meehir Palit

Fluorinated phosphonium ylides: versatile in situ Wittig intermediates in the synthesis of hydrofluorocarbons

Abstract A simple and convenient technique has been developed for the synthesis, characterisation and isolation of hydrofluoro/hydrohalofluorocarbons such as chlorodifluoromethane (CF2ClH), difluoromethane (CF2H2), bromodifluoromethane (CF2BrH) and dibromofluoromethane (CFBr2H) as possible chlorofluorocarbon (CFC) alternatives. The Wittig reaction of carbonyl compounds with in situ generated triphenylphosphonium ylides in DMF forms terminal fluoroolefins. However, in the absence of the carbonyl moiety these ylides undergo decomposition. The high reactivity of fluoromethylene triphenylphosphonium ylides in DMF in the absence of the carbonyl moiety has been exploited for the first time to design the synthesis of hydrofluorocarbons.

N, N'-Dichloro bis(2,4,6-trichlorophenyl) urea (CC-2) : an efficient reagent for synthesis of dialkyl chlorophosphates

An efficient and simple method is described for the preparation of dialkyl chlorophosphates by the use of new positive chlorine bearing reagent namely N, N′-dichloro bis(2,4,6-trichlorophenyl) urea.

Surface-mediated solid phase reactions : a simple, efficient and base-free synthesis of phosphonates and phosphates on Al2O3

Al2O3-supported solvent free condensation of alkylphosphonic dichlorides with alcohols at room temperature yielded phosphorus esters in excellent yields.

SYNTHESIS OF 2-PHENYLPERFLUOROPROPENE AND 1,1,1,3,3,3-HEXAFLUORO-2-PHENYLPROPANE

Abstract We describe the optimisation of reaction conditions for the synthesis of 2-phenylperfluoropropene and its HF addition product 1,1,1,3,3,3-hexafluoro-2-phenylpropane from 1,1,1 -trifluoroacetophenone by the reaction with sodium chlorodifluoroacetate and triphenylphosphine in dimethylformamide. The formation of olefin and the addition product has been studied over a range of temperature ( 50–150 °C ) as a function of time.

Synthesis, characterisation and mass spectrometric fragmentation of O-(chlorodifluoroacylated) alcohols

Abstract An indirect and uncatalysed esterification of chlorodifluoroacetic acid with polyfluoro and hydrocarbon alcohols has been developed. The method which involves the reaction between sodium chlorodifluoroacetate and alcohols in dimethylformamide (DMF) is particularly facile with polyfluorinated alcohols resulting in esters in 71–85% yield. The esters have been characterised on the basis of 1 H and 19 F NMR and mass spectral data. The electron impact (EI) mass spectrometric fragmentation of these polyfluorinated esters have shown some interesting features which have been substantiated by using tandem mass spectrometry.

Analysis of Chemical Neutralization Products of Phosphonothiolates by Gas Chromatography Mass Spectrometry

A series of phosphonothiolates, including the highly toxic O-Ethyl-S-(2-diisopropylamino) ethyl methylphosphonothioate (VX), have been subjected to chemical neutralization reaction with metallic sodium. The phosphonothiolates decompose to their respective phosphonic and phosphonothioic acids and this results in the detoxification of VX. GC/MS technique in both EI and CI mode has been applied for reaction monitoring and final identification of the neutralization products formed in this reaction.

Mass spectral studies on synthetic analogs of organophosphorus toxin occurring in dinoflagellate algae

A series of organophosphorus compounds related to PB-1 toxin [O,O-diphenyl N-cyclooctylphosphoramidate] occurring in dinoflagellate algae as fish toxin have been synthesized and subjected to mass spectral studies under electron ionization. The fragmentation pattern obtained for the compounds has been substantiated by performing tandem mass spectrometry experiments in product ion scan mode.

Time-dependent comparative evaluation of some important biomarkers of acute cyanide poisoning in rats: an aid in diagnosis

Abstract Objective: The study focuses on time-dependent comparative evaluation of various biomarkers of acute cyanide poisoning in rats. Methods: Blood gas (analyzer), lactate, pyruvate, cyanide, thiocyanate (spectrophotometer) and 2-amino-2-thiazoline-4-carboxylic acid (ATCA; gas chromatography–mass spectrometry) in plasma or urine, and various physiological parameters (polygraph) were measured. Results: Cyanide poisoning was characterized by elevated lactate, cyanide, thiocyanate and ATCA concentrations in plasma up to 15 min, 4, 16 and 24 h, respectively, while high urinary thiocyanate and ATCA levels were measured between 4 and 24 h. Conclusion: ATCA concentration in plasma and urine was found to be more reliable indicator of cyanide poisoning.

Isotope dilution mass spectral studies on capsaicin analogues

A series of capsaicin analogues have been synthesised as probable tear gas compounds. These compounds were subjected to mass spectral studies under electron ionization (EI) for their total identification. The fragmentation patterns observed in ortho- and para-substituted compounds have been substantiated by performing isotope dilution experiments and daughter-ion scans using tandem mass spectrometry.