American Journal of Engineering Research (AJER) 2013 www.ajer.us Page 21 American Journal of Engineering Research (AJER) e-ISSN: 2320-0847 p-ISSN : 2320-0936 Volume-02, Issue-02, pp-21-28 www.ajer.us Research Paper Open Access Proton spectrum analysis of 4-(ethylamino)-6-methyl-7-propylpyrido[3,4- d]pyrimidin-8(7H)-one using 1-D NOE technique and Correlation spectroscopy methodology. Prashant Dwivedi, Kartikeya Dwivedi, Nitin Saraswat, Noida International University; Greater Noida; (U.P) Maharaj Singh College ; Saharanpur (U.P) K.M.Institute of Pharmaceutical Sciences, Rourkela, Orissa Abstract: The power of Nuclear Magnetic Resonance spectroscopy (NMR) in structure elucidation derives in large part from its ability to establish bonding connectivity (via J- coupling interaction) or through space proximity (via dipolar coupling interactions) of nuclei the first is known as Correlation spectroscopy(COSY) and the second being Nuclear Overhauser effect spectroscopy(NOESY). The amount of time consumed in elucidating a structure depends on the rate at which these interaction can be detected by NMR and analyzed.1D NMR methods most often explore interactions between only few nuclei at a time: spin-spin decoupling measurements are used to demonstrate through-bond connectivity; and NOE measurements are used to probe inter-nuclear distances, 2-Dimensional NMR experiments provide much more structural information in a given time period. Keywords: NMR; Nuclear Overhauser effect; Correlation spectroscopy; NOESY;decoupling I. INTRODUCTION: The key point in all is that magnetisation transfer occurs between coupled spins. To appreciate the outcome of this in the final COSY spectrum, consider the case of two J-coupled spins, A and X, with a coupling constant of J AX and chemical shift offsets of √ A and √ x . The magnetisation associated with spin A will, after the initial 90 0 pulse, precess during t1 according to its chemical shift offset, √ A . The second 90 0 pulse then transfers some part of this magnetisation to the coupled X spin, whilst some remains associated with the original spin A. That which remains with A will then precess in the detection period at a frequency √A just as it did during t1, so in the final spectrum, will produce a peak at √ A in both dimensions, denoted (√ A , √ A ). This peak is therefore equivalent to that observed for the uncoupled AX system and because it represents the same frequency in both dimensions, it sits on the diagonal of the 2D spectrum and is therefore referred to as a diagonal peak. In contrast, the transferred magnetisation will precess in t 2 at the frequency of the new ‘host’ spin X and will thus produce a peak corresponding to two different chemical shifts in the two dimensions (√ A , √ X ). This peak sits away from the diagonal and is therefore referred to as an off-diagonal or, more commonly, a crosspeak This is the peak of interest as it provides direct evidence of coupling between spins A and X. The whole process operates in the reverse direction also, that is, the same arguments apply for magnetisation originally associated with the X spin, giving rise to a diagonal peak at (√ x , √ x ) and a crosspeak at (√ x , √ A ). Thus, the COSY spectrum is symmetrical about the diagonal, with crosspeaks on either side of it mapping the same interaction. Figure-1: Sample containing two uncoupled spins, A and X, of offsets √ A and √ X . Each produces a 2D peak at its corresponding chemical shift offset in both dimensions.