Nitration was the final step in the musk ketone

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2,6-dimethyl-acetophenone was formed. Nitration was the final step in the musk ketone synthesis. Sulfric acid was used to protonate the nitric acid that was eventually dehydrated to become nitrate, before attaching to the two open spots on the benzene ring in the final result of 4- t-butyl-2,6-dimethyl-3,5-dinitroacetophenone product. An IR spectra of the starting material showed important peaks at 3015.31 cm -1 ( C- aromatic-H), 2964.10 and 2865.80 cm -1 (Csp 3 -H), 1604.01 and 1478.75 cm -1 (Aromatic C=C),
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and 768.82 cm -1 and 706 cm -1 (meta substituted methyl groups). This starting IR spectra was used to make sure that the correct starting material was being used and to also compare future taken IR spectra. When the AlCl 3 was added to the solution a color change as well as the presence of HCl gas occurred. This ensured that the reaction was happening. The boiling point of the for 1-t- butyl-3,5-dimethylbenzene was recorded at 190°C while the literature value is 205-208°C; indicating that impurities were present within the solution. Another IR of the intermediate product was performed and resulted in the following important peaks 2963.75 cm -1 (C aromatic-H), 2867.5 cm -1 (Csp 3 -H), 1697.67 cm -1 (Ketone), 1606.35 and 1479.36 cm -1 (Aromatic C=C). This IR confirms that the Friedel-Crafts acylation step did work and that a ketone successfully formed on the aromatic ring. The various color changes that were observed and recorded in the second step of the synthesis indicated that the reaction from 1-t-butyl-3,5-dimethylbenzene to 4-t-butyl-2,6-dimethyl-acetophenone had occurred. The intermediate did not form a solid, which is an indicator that some impurities may have been present. An IR spectra of the final product was performed and the key peaks that were identified were 2975.46 cm -1 (C aromatic-H), 2928.28 cm -1 (Csp 3 -H), 1711.43 cm -1 (Ketones), 1621.13 and 1472.24 cm -1 ( Aromatic C=C), and 1539.87 and 1371.66 and 1352.33 (NO 2 groups). The confirmation of the nitration substitution correctly occurring on the benzene ring can be observed from the IR spectra. The several color changes observed within this last step of the synthesis of musk ketone as well as the formation of the precipitate indicate that the reaction of 4-t-butyl-2,6- dimethylacetophenone to the final musk ketone product had occurred. The melting point range of the final product was recorded as 220°C-229°C which is much higher than the literature value of 134-136°C. This indicates that the product that was collected was impure. Another possible
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explanation for such a high boiling point is that nitration may not have fully occurred which would lead to the presence of the previous intermediate in the final product. Also due to either the first or second step of the synthesis not occurring completely the starting material for each of these steps could have been present and then consequently caused undesired side reactions during latter steps of the synthesis. Also the presence of the 2975.46 cm -1 bond in the IR performed in the last week of the lab indicates that there is a C-H aromatic bond which should not be present in the musk ketone. Supporting the conclusion that impurities must be present within the final synthesized product.
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  • Fall '07
  • crandall
  • Organic chemistry, pH, Benzene, final product, Sulfuric acid, Electrophilic aromatic substitution, Friedel-Crafts Acylation, musk ketone

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