Turel and Patil (1996)  have established a rapid and selective method for the extraction of molybdenum with malachite green into nitrobenzene. The influence of solvent extraction variables on molybdenum extraction such as effect of pH, time of equilibration, solvents, effect of various anions and cations have been studied. On the basis of substoichiometric extraction method the constituent ratio of the metal-organic complexes was found as 1:1. The slope ratio method was also in agreement with the
They can impart localised structural rigidity, confer cytotoxicity by alkylation, or be secondary metabolites . The chemistry of epoxides is dominated by the reactions that involve opening of the strained three-membered heterocyclic ring by nucleophiles. Such reactions yield valuable bifunctional compounds. In nature, epoxide ring opening is catalysed by the phenolic proton of a tyrosine moiety . But in laboratory, the cleavage usually occurs in non-aqueous media in presence of a Lewis acid
Commercially and valuable side products such as butanone, formic acid, propionic acid and ethyl acetate are formed as well. The acetic acid can also be obtained by substituting butane with acetaldehyde in the above reaction. 2CH_3 CHO+O_2→2CH_3 COOH The acetic acid yield percentage can exceed 95% when using modern catalyst. Distillation process is carried out to separate them. When it comes to ethylene oxidation, the ethylene will produce acetaldehyde through Wacker process and then oxidized with the oxygen present in the air to form acetic acid.
Acidic character surrounded by benzoic acids, which have different electron releasing group . Factors that affect’s Acidity -Bronsted acids are proton donors. -Lewis acids are electron pair acceptors. Converse: proton acceptor =Bronsted base, Lewis base = electron pair donor. 1.
Different amines produce different colors. For example, α-amino acids produce a blue-purple product while secondary amines like Proline produce a yellow-orange product (Hunt, n.d.). In the Ninhydrin Test, the electron deficient polar carbonyl carbon is attacked by the nucleophilic nitrogen on the amino acid. This combines the ninhydrin to the amino acid molecule temporarily. Until the carbon originally attacked is protonated and leaves in water form, the structure stays rearranged.
The next step is nucleophilic attack by the deprotonated cysteine's anionic sulfur on the substrate carbonyl carbon. In this step, a fragment of the substrate is released with an amine terminus, the histidine residue in the protease is restored to its deprotonated form, and a thioester intermediate linking the new carboxy-terminus of the substrate to the cysteine thiol is formed. Therefore, they are also sometimes referred to as thiol proteases. The thioester bond is subsequently hydrolyzed to generate a carboxylic acid moiety on the remaining substrate fragment, while regenerating the free enzyme. 3.Mechanism of threonine protease Threonine proteases use the secondary alcohol of their N-terminal threonine as a nucleophile to perform catalysis.
ABSTRACT The Diels-Alder reaction has been an area of great research interest with regards to enhancing enantioselectivity in the reaction by use of various catalysts and reaction conditions. INTRODUCTION In organic chemistry, a Diels-Alder reaction refers to a 4, 2 cycloaddition between a diene consisting of alternating double bonds and a substituted alkene (the dienophile) resulting in a substituted cyclohexene system. The reaction is often used to reliably control regioselective and enantioselective aspects in organic synthesis. If specific conditions are applied, these reactions can be reversible, with the reverse reaction referred to as the retro-Diels-Alder reaction. Mechanism, Regioselectivity and Enantioselectivity of the Diels-Alder Reaction
In detail, the Prins cyclization of homoallylic amines takes place in a fashion similar to that of homoallylic alcohols, whereby the non bonding electrons on the nitrogen initiate the sequence of reaction steps by attacking the electrophilic site of the aldehyde activated by an acid catalyst. The key intermediate of the aza-Prins cyclization is an iminium ion, in analogy to the oxonium ion. Compared to classical Prins cyclization, examples of aza-Prins cyclization using iminium ions leading to nitrogen-containing heterocycles have been less developed in the literature due to less electrophilic nature of iminium ions compared to oxo-carbenium ions. Whereas, aza-Prins cyclization of acyclic/cyclic N-acyliminium ion intermediates to achieve piperidine ring containing mono and bicyclic compounds is well explored due to more electrophilic nature of N-acyliminium
Introduction Grignard reagent is considered as an organometallic compound or it's the composition of electrophilic and nucleophilic that electrophilic is the carbon atom of organic halide which is directly attached to the halogen, it's reactivity can be switched to the nucleophilic reactivity by conversion an organomagnesium halide. It has the general formula of (RMgX) and it has a general nomenclature which it's called magnesium alkyl halide. We can get Grignard reagent by adding one of solutions of alkyl halide to an ether, slowly. Then, garbling them that's leads to the boiling of solution and magnesium becomes disappeared so, we can get the reagent. Grignard reagent is also considered as the best known reagent of all organometallic compounds, as carbon atom is connected to a metal atom which may be
One noticeable exception is the so-called “Atwal modification” of the Biginelli reaction. In this scheme, an enone(a) is first condensed with a suitable protected urea or thiourea derivative(b) under almost neutral conditions. Deprotection of the resulting 1,4-dihydropyrimidine(c) with HCl or TFA leads to the desired DHPMs.20 Scheme-3: Shutalev et al described another approach to DHPMs synthesis. This synthesis is based on the condensation of readily available R-tosylated (thio)ureas(a) with the enolates of acetoacetates or 1,3-dicarbonyl compounds. The resulting hexahydropyrimidines(b) need not to be isolated and can be converted directly into DHPMs.