Acetal Formation - nnnNJ PDF

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Acetal Formation - Synthesis of 1,1-diethoxy-cyclohexane Organic Chemistry Lab ABSTRACT: 1,1-diethoxy-cyclohexane was synthesized through carbonyl addition reaction of cyclohexanone. The product was synthesized with an 59.26% yield. Following the reaction, an FT-IR analysis of the product showed absorptions at 3,000 cm-1,1450 cm-1, 1150-1085 cm-1, and 1100 cm-1. 1H-NMR analysis showed peaks at δH 3.5 ppm, δH 1.5 ppm, and δH 1.2 ppm. The 13C-NMR analysis showed peaks at δc 110.9 ppm, δc 58.2 ppm, δc 35.8, δc 26.3, δc 27.8, and δc 15.8 ppm. KEYWORDS: 1,1-diethoxy-cyclohexane, cyclohexanone, ethanol, hydrochloric acid, carbonyl addition reaction. INTRODUCTION Carbonyl Addition Reactions are nucleophilic additions of carbonyl groups to the carbonoxygen double bond. Depending on the conditions, aldehydes react with alcohols to create hemiacetals (a functional group comprised of one —OH group and one —OR group bonded to the same carbon) or acetals (an active group made up of two —OR groups bonded to the same carbon). Acetals are benzene ring aldehydes or ketone derivatives derived by reacting two equivalents (or an excess amount) of an alcohol with water removal. Ketone derivatives of this kind were once known as ketals, but that term is no longer used. Hemiacetal forms as an intermediate during the Acetal formation process. The hemiacetal is made by combining the two reactants. When the two reactants are combined with hydrochloric acid, an acetal is formed. This reaction is dependent on HCl and ethanol. The product of this experiment is 1,1-diethoxycyclohexane.

EXPERIMENTAL Materials: cyclohexanone, ethanol, and hydrochloric acid Synthesis of 1,1-diethoxy-cyclohexane: A cyclohexanone solution (5.0g) was added to the round bottom flask. The flask was then placed on the stir plate to be heated, where Hydrochloric acid was added as a reagent. The heater, condenser, and N2 gas supply were then added to the round bottom flask so the reaction mixture could be heated through reflux. The progress of the reaction was tracked using TLC until the product was formed. This process took about 10 minutes. The solution was then put in a separatory funnel and washed with water. The aqueous layer was discarded leaving the organic layer containing the product 1,1-diethoxy-cyclohexane. With this, the FT-IR analysis was performed yielding absorptions at 3000 cm-1 indicative of C-H stretching, 1450 cm-1 indicative of –CH3, 1150-1085 cm-1 indicative of C-O, and 1100 cm-1 indicative of the C-C bond. 1H-NMR analysis was then performed yielding three significant peaks at δH 3.5 ppm, δH 1.5 ppm and δH 1.2 ppm. A 13C-NMR analysis was also done yielding six peaks at δc 110.9ppm, δc 58.2 ppm, δc 35.8 ppm δc 26.3 ppm δc 27.8 ppm and δc 15.8 ppm. RESULTS AND DISCUSSION The product formed by the reaction1,1-diethoxy-cyclohexane was consistent with the predicted product. The calculated theoretical yield was 8.775g, and the reaction produced 5.2g of 1,1-diethoxy-cyclohexane making the actual yield 59.26%. While this yield is relatively high, it is typical for all reactions to have an actual yield of less than 100% because some products are impossible to collect without some loss. Also, the occurrence of side reactions that generate other products can create inefficiencies. The FT-IR analysis of 1,1-diethoxy-cyclohexane revealed that there were absorptions at 3,000 cm-1 ,1450 cm-1, 1150-1085 cm-1, and 1100 cm-1. The 1H-

NMR analysis of the product revealed three relevant peaks at δH 3.5 ppm, δH 1.5 ppm, and δH 1.2 ppm. Peak 1 at δH 3.5 ppm represents the carbon to hydrogen bonding. Peak 2 represents the three hydrogen atoms bonded to carbon. Peak 3 at δH 1.2 ppm represents the carbon bonded to carbon. The 13C-NMR analysis revealed six relevant peaks at δc 110.9ppm, δc 58.2 ppm, δc 35.8 ppm δc 26.3 ppm δc 27.8 ppm and δc 15.8 ppm. δH 3.5 ppm corresponds to 4H of CH 2 attached to O atom. δH 1.5 ppm corresponds to 10H of CH2 groups present in the ring and δH 1.2 ppm corresponds to 6H of CH 3 attached to the OCH2 group. Finally, the mass spectrometry analysis revealed its parent peak at m/z = 173.2 amu coincides with the molecular weight of 1,1diethoxy-cyclohexane at 172.26g. CONCLUSION The product formed, 1,1-diethoxy-cyclohexane, was the intended product from alcohol hydration. 5.2g was produced, making it a yield of 59.26%. This means 40.74% of the product either failed to react or evaporated while heating. The proper functional groups were indicated by the absorptions from the FTIR analysis. The 1H-NMR analysis provided the molecular structure expected of the product. The 13C-NMR analysis confirmed the environment expected of the carbons that 1,1-diethoxy-cyclohexane consists of the peak of m/z=173.2 amu obtained through mass spectrometry confirms that the compound produced was 1,1-diethoxy-cyclohexane. These various analyses confirm that the proper compound was synthesized in this reaction.

REFERENCES Guthrie, J. Peter. "Carbonyl addition reactions: factors affecting the hydrate–hemiacetal and hemiacetal–acetal equilibrium constants." Canadian Journal of Chemistry 53, no. 6 (1975): 898-906. Naughton, Andrew B. "CHEM 244-043: Organic Chemistry II." (2019)....