The Studies of Microwave Effects on the Chemical Reactions

Abstract

Microwave heating involves direct absorption of energy by functional groups tbat bear ionic conductivity or a dipole rotational-effect, and this energy is then released into the surrounding solution. This absorption of energy causes the functional groups involved to have higher reactivity to other surrounding reactants than when they are simply incubated with the reactants at the same temperature. In other word the enhanced rate of the reaction can be due to the reactant stirred by the molecular dipole rotation and molecules themselves acting as a stirring bar. In contrast to conventional heating, the salient feature of "dipole rotation" constitutes one efficient form of "molecular agitation" or "molecular stirring" many aspects of which can be explore in chemical reactions. We will discuss some of the useful applications of this "molecular agitation" by means of microwave irradiation. Using this unique technology, we have developed: 1) a method to control the cleavage sites of peptide bonds, especially those bonds connected to aspartic acid residues inside the native peptides and proteins, 2) a method to increase coupling efficiency in solid-phase peptide synthesis using a common microwave oven, 3) a novel procedure that increases the rate of alcalase-catalyzed reactions using microwave irradiation in peptide-bond formation with proline as a nucleophile and selective benzoylation of a pyranoside derivative, 4) a procedure to solubilize and hydrolyze retrograded starch, 5) a novel procedure to enhance the rate of saponification in a serum sample for very long chain fatty acid analysis. 169

Microwave-assisted acid hydrolysis of proteins combined with liquid chromatography MALDI MS/MS for protein identification

“…Selective hydrolysis of aspartyl peptide bond of peptides has been studied [31]. Enhancement of alcalase-catalysis reaction rate by microwave irradiation has been demonstrated [32]. More recently, Pramanik and co-workers have illustrated the use of microwave to enhance Akabori reaction for peptide analysis [33,34] and to accelerate proteolytic cleavage of proteins for peptide mass mapping by MALDI MS and ESI LC/MS [35].…”

Rapid Synthesis of 1,4-Diaryl Thiosemicarbazides using Microwave Technology

“…As we know, the application of microwave techniques for chemical synthesis has attracted considerable interest in the last decade. [5][6][7] The reason is that technology can enhance the selectivity and reactivity, 8,9 increase the chemical yields and shorten the reaction time. 10,11 Today, it has been widely used in a variety of organic reactions.…”

Peptide and glycopeptide dendrimers. Part II

“…If necessary, coupling steps should be repeated using different activating agents (DCC/HOBt, BOP, PyBOP, HBTU etc. ), solvents (DCM, DMF, NMP and mixtures such as 'magic mixture' [33]), increased temperature [34,35], microwaves [36] etc.…”