Grignard Reaction - Synthesis of Substituted Benzoic Acids

A convenient preparation of substituted benzoic acids from Grignard additions to solid carbon dioxide. Students create a library of carboxylic acids by using differentially substituted, commercially available aryl bromides, which can be used as the starting materials for a multistep synthesis. This is a modification and improvement of a very popular undergraduate organic chemistry experiment.

I. Configurational stability and redistribution equilibria in organomagnesium compounds. II. Redistribution equilibria in organocadmium compounds

I. CONFIGURATIONAL STABILITY AND REDISTRIBUTION EQUILIBRIA IN ORGANOMAGNESIUM COMPOUNDS

The dependence of the rate of inversion of a dialkylmagnesium compound on the solvent has been studied.

Examination of the temperature dependence of the nuclear magnetic resonance spectrum of 1-phenyl-2-propylmagnesium bromide in diethyl ether solution indicates that inversion of configuration at the methylene group of this Grignard reagent occurs with an approximate rate of 2 sec^-1 at room temperature. This is the first example of a rapid inversion rate in a secondary Grignard reagent.

The rates of exchange of alkyl groups between dineopentylmagnesium and di-s-butylmagnesium, bis-(2-methylbutyl)-magnesium and bis-(4, 4-dimethyl-2-pentyl)-magnesium respectively in diethyl ether solution were found to be fast on the nmr time scale. However, the alkyl group exchange rate was found to be slow in a diethyl ether solution of dineopentylmagnesium and bis-(2-methylbutyl)-magnesium containing N, N, N', N'-tetramethylethylenediamine. The unsymmetrical species neopentyl-2-methylbutyl-magnesium was observed at room temperature in the nmr spectrum of the solution containing the diamine.

II. REDISTRIBUTION EQUILIBRIA IN ORGANOCADMIUM COMPOUNDS

The exchange of methyl groups in dimethylcadmium has been studied by nuclear magnetic resonance spectroscopy. Activation parameters for the methyl group exchange have been measured for a neat sample and for a solution in tetrahydrofuran. The exchange is faster in the basic solvent tetrahydrofuran relative to the neat sample and in tetrahydrofuran solution is retarded by the solvating agent N, N, N’, N’-tetramethylethylenediamine and greatly increased by cadmium bromide. The addition of methanol to a solution of dimethylcadmium in tetrahydrofuran appears to have very little effect on the rate of exchange. The exchange was found to proceed with retention of configuration. The rate-limiting step for the exchange of methyl groups in a basic solvent appears to be the dissociation of coordinating solvent from dimethylcadmium.

The equilibrium between methylcadmium bromide, dimethylcadmium and cadmium bromide in tetrahydrofuran solution has also been studied. At room temperature the interconversion of the species is very fast on the nmr time scale but at -100° distinct absorptions for methylcadmium bromide and imethylcadmium are observed.

The species ethylmethylcadmium has been observed in the nmr spectrum.

The rate of exchange of vinyl groups in a solution of divinylcadmium in tetrahydrofuran has been found to be fast on the nmr time scale.

Phenolics in sugar cane juice : potential degradation by hydrogen peroxide and Fenton's reagent

The presence of colour in raw sugar plays a key role in the marketing strategy of the Australian raw sugar industry. Some sugars are relatively difficult to decolourise during refining and develop colour during storage. A new approach that might result in efficient and cost-effective colour removal during the sugar manufacturing process is the use of an advanced oxidation process (AOP), known as Fenton oxidation, that is, catalytic production of hydroxyl radicals from the decomposition of hydrogen peroxide using ferrous iron. As a first step towards developing this technology, this study determined the composition of colour precursors present in the juice of cane harvested by three different methods. The methods were harvesting cane after burning, harvesting the whole crop with half of the trash extracted and harvesting the whole crop with no trash extracted. The study also investigated the degradation at pH 3, 4 and 5 of a phenolic compound, caffeic acid (3,4–dihydroxycinnamic acid), which is present in sugar cane juice, using both hydrogen peroxide and Fenton’s reagent. The results show that juice expressed from whole crop cane has significantly higher colour than juices expressed from burnt cane. However, the concentrations of phenolic acids were lower in the juices expressed from whole crop cane. The main phenolic acids present in these juices were p-coumaric, vanillic, 2,3–dihydroxybenzoic, gallic and 3,4–dihydroxybenzoic acids. The degradation of caffeic acid significantly improved using Fenton’s reagent in comparison to hydrogen peroxide alone. The Fenton oxidation was optimum at pH 5 when up to ~86 % of caffeic acid degraded within 5 min.

Phenolics in sugar cane juice : potential degradation by hydrogen peroxide and Fenton’s reagent

The presence of colour in raw sugar plays a key role in the marketing strategy of the Australian raw sugar industry. Some sugars are relatively difficult to decolourise during refining and develop colour during storage. A new approach that might result in efficient and cost-effective colour removal during the sugar manufacturing process is the use of an advanced oxidation process (AOP), known as Fenton oxidation, that is, catalytic production of hydroxyl radicals from the decomposition of hydrogen peroxide using ferrous iron. As a first step towards developing this technology, this study determined the composition of colour precursors present in the juice of cane harvested by three different methods. The methods were harvesting cane after burning, harvesting the whole crop with half of the trash extracted and harvesting the whole crop with no trash extracted. The study also investigated the degradation at pH 3, 4 and 5 of a phenolic compound, caffeic acid (3,4–dihydroxycinnamic acid), which is present in sugar cane juice, using both hydrogen peroxide and Fenton’s reagent. The results show that juice expressed from whole crop cane has significantly higher colour than juices expressed from burnt cane. However, the concentrations of phenolic acids were lower in the juices expressed from whole crop cane. The main phenolic acids present in these juices were p-coumaric, vanillic, 2,3–dihydroxybenzoic, gallic and 3,4–dihydroxybenzoic acids. The degradation of caffeic acid significantly improved using Fenton’s reagent in comparison to hydrogen peroxide alone. The Fenton oxidation was optimum at pH 5 when up to ~86% of caffeic acid degraded within 5 min.

Biopharming the SimpliRED™ HIV diagnostic reagent in barley, potato and tobacco

This is the first report of an antibody-fusion protein expressed in transgenic plants for direct use in a medical diagnostic assay. By the use of gene constructs with appropriate promoters, high level expression of an anti-glycophorin single-chain antibody fused to an epitope of the HIV virus was obtained in the leaves and stems of tobacco, tubers of potato and seed of barley. This fusion protein replaces the SimpliRED™ diagnostic reagent, used for detecting the presence of HIV-1 antibodies in human blood. The reagent is expensive and laborious to produce by conventional means since chemical modifications to a monoclonal antibody are required. The plant-produced fusion protein was fully functional (by ELISA) in crude extracts and, for tobacco at least, could be used without further purification in the HIV agglutination assay. All three crop species produced sufficient reagent levels to be superior bioreactors to bacteria or mice, however barley grain was the most attractive bioreactor as it expressed the highest level (150 μg of reagent g-1), is inexpensive to produce and harvest, poses a minuscule gene flow problem in the field, and the activity of the reagent is largely undiminished in stored grain. This work suggests that barley seed will be an ideal factory for the production of antibodies, diagnostic immunoreagents, vaccines and other pharmaceutical proteins.

Silicon Tetrachloride/Sodium Iodide as a Convenient and Highly Regioselective Ether Cleaving Reagent

Abstract is not available.

Pyridinium poly(hydrogen fluoride). A versatile fluorinating reagent preparation and characterization of nonmetal and metal complex fluoro salts

Abstract is not available.

New reagents 3: aluminium iodide - a highly regioselective ether-cleaving reagent with novel cleavage pattern

AlI3 is an easily accessible and versatile ether-cleaving reagent.

Synthesis of Thioesters from Carboxylic Acids via Acyloxyphosphonium Intermediates with Benzyltriethylammonium Tetrathiomolybdate as the Sulfur Transfer Reagent

An efficient protocol is reported for the synthesis of thioesters from carboxylic acids with use of acyloxy phosphonium salts as intermediates and benzyltriethylammonium tetrathiomolybdate as the sulfur transfer reagent.

Pyridinium poly(hydrogen fluoride)- a reagent for the preparation of hexafluorophosphates

Pyridinium poly(hydrogen fluoride) has been found to be an efficient and versatile reagent for the preparation of hexafluorophosphates. Pyridinium hexafluorophosphate has been prepared by the reaction between phosphorus (V) halides (POCl3, POBr3, PSCl3, PCl5, PBr5) and pyridinium poly(hydrogen fluoride). This in turn is used to prepare the hexafluorophosphates of ammonium, sodium, potassium, rubidium and cesium in good yield and high purity.

Hydrazinium thiocyanate as a reagent for determination of copper

Hydrazinium thiocyanate, N2H5SCN, has been used for the determination of copper in copper salts. The reagent reduces the copper ions to the cuprous state and precipitates cuprous thiocyanate Cu2(SCN)2, quantitatively.

Synthesis of Thioesters by Simultaneous Activation of Carboxylic Acids and Alcohols Using PPh3/NBS with Benzyltriethylammonium Tetrathiomolybdate as the Sulfur Transfer Reagent

A new and simple route for the synthesis of thioesters starting from carboxylic acids and alcohols is reported by using tetrathiomolybdate as the key sulfur transfer reagent. Triphenylphosphane and N-bromosuccinimide were used for the activation of the carboxylic acid and alcohol in the same pot followed by the transfer of sulfur from tetrathiomolybdate. Thioesters were obtained in good to moderate yields. Primary alcohols show excellent reactivity and gave good yields of the corresponding thioesters, whereas secondary alcohols gave moderate yields and tertiary alcohols were very less reactive and gave poor yields of the corresponding thioesters.

Folin-Ciocalteu reagent for the estimation of siderochromes

1. A simple method has been devised for the estimation of siderochromes based on their reaction with Folin-Ciocalteu reagent to give a blue complex under alkaline conditions. 2. The applicability of the method to biological systems has been tested with N. crassa and concentrations in the ranges 5–50 μg and 1–10 μg can be accurately estimated with an over-all recovery of 95%.

Potassium phosphate as a reagent for the gravimetric estimation of lithium

Previous attempts for the quantitative estimation of lithium as orthophosphate, employing an alkali metal phosphate, have not been successful. A method, is described for the estimation of lithium as trilithium phosphate from 60% ethyl alcohol solution at 65° to 70° C., employing potassium phosphate reagent, at pH 9.5. The method is applicable in the presence of varying amounts of sodium and/or potassium cations and chloride, sulfate, nitrate, and phosphate anions.