Forensic Application of 1D-NMR

FIGURE 19.2 Research preparation of BEG by mild hydrolysis of crack cocaine. 

Pedersoh et al. [6] started from a sample of crack cocaine and hydrolyzed the methyl ester using hot water. The metabohte was synthesized and characterized by 2D-NMR using three advanced techniques for a very thorough study of BEG by NMR (Eigure 19.3). Details of the study were kindly supphed by Prof. Roberto Rittner of The Physical Organic Chemistry Laboratory, Chemistry Institute, State University of Campinas, Campinas, SP, Brazil. 

Structure It was optimized at B3LYP/cc-pVDZ level of theory. 

After this analysis of the overall NMR spectra of BEG, the forensic apphcation depends on the resonance of the protons (No. 14 on the structural formula) at 2.54 ppm due to the A-methyl substituent. That peak is strong enough and in a sufficiently unique region to be observable from a urine extract sample or a suitable bowel sample from a newborn infant. One interesting structural observation from the paper is that the carboxyl H is attracted to the N lone pair forming an internal 

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