Development of Novel NMR Methodology and the Investigation of Challenging Chemical Problems

Abstract

The thesis is entitled as quotDevelopment of Novel NMR Methodology and Investigation of Challenging Chemical Problems quot. The research work reported in this thesis is mainly carried out in two directions. The initial focus being the design of new pulse sequence by manipulating the spin dynamics to precisely measure the scalar couplings of the selected proton from the complex NMR spectrum. The developed novel pulse sequence efficiently suppresses the evolution of unwanted couplings and eradicates the uninformative intense axial peaks that are inherent in the selective refocusing experiments, thereby yielding the clean spectrum devoid of any type of artefacts. In the other part, the one and two dimensional NMR spectroscopic has been extensively employed to address challenging and interesting chemical problems, such as, chiral analysis where a new ternary ion-pair protocol has been developed for the spectroscopic configurational assignment of various chiral acids and esters, and the two- and three-centered hydrogen bonding interactions in molecules of pharmacological importance. It has been indubitably established that the strength of intramolecular hydrogen bond is controlling the conformational populations in one set of the investigated molecules and the geometrical constraints in addition to the cooperativity between the individual hydrogen bonds of another set of bifurcated molecules imparts full rigidification to the molecular structure making the system relatively very stable and hindering the breaking of hydrogen bond by even the high polarity solvent DMSO.