................DR ANTHONY MELVIN CRASTO Ph.D ( ICT, Mumbai) , INDIA 25Yrs Exp. in the feld of Organic Chemistry,Working for GLENMARK GENERICS at Navi Mumbai, INDIA. Serving chemists around the world. Helping them with websites on Chemistry.Million hits on google, world acclamation from industry, academia, drug authorities for websites, blogs and educational contribution
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Thursday, 10 September 2015
Figure 6. Recrystallized 1,5-bis(4'-methoxyphenyl)penta-1,4-dien-3-one (Product B).Figure 7 depicts the 1H NMR spectrum of 1,5-bis(4'-methoxyphenyl)penta-1,4-dien-3-one, confirming the loss of the reactive methyl centre in Product A following the reaction with p-anisaldehyde. In this case also, the 2D J-resolved and COSY experiments are used to interpret the downfield resonances between 6.82-8.02ppm (Figures 8 and 9).
Figure 7. 1H NMR spectrum of 1,5-bis(4'-methoxyphenyl)-1,4-pentadien- 3-one (Product B) in CDCI3.The J-resolved spectrum (Figure 8) differentiates 8.6Hz doublet and 16.4Hz doublet, centered at 6.90ppm. It also identifies a 16.0 Hz doublet at 7.73ppm and an 8.9Hz doublet at 7.57ppm further downfield. This data is used to determine the two spin systems in the COSY spectrum (Figure 9), one between 6.90-7.57ppm and the other between 6.90-7.73ppm. The alkene protons on C- 1/C-5 and C-2/C-4 can be allocated as 7.73ppm and 6.90ppm, respectively, while the promatic protons on C-2' and C-3' can be assigned as 7.57ppm and 6.90ppm, respectively. The magnitude of the coupling constants of H-1/H-5 and H-2/H-4 confirms the alkene’s E-geometry.
Figure 8. 2D J-resolved spectrum of 1,5-bis(4'-methoxyphenyl)-1,4-pentadien-3-one (Product B) in CDCI3.
Figure 9. COSY spectrum of 1,5-bis (4'-methoxyphenyl)-1,4-pentadien-3-one (Product B) in CDCI3.