The objective of this experiment was to synthesize an alpha-acylated cyclohexanone at relative
purity and at a reasonable percent yield via the nucleophilic enamine intermediate
This short sequence
of reactions included the reaction of a carbonyl compound with a secondary amine to form the enamine,
and subsequent acid-catalyzed hydrolysis to form the acylated cyclohexanone.
In the first step,
pyrrolidine was the cyclic secondary amine added in the presence of toluene solvent and an organic acid
catalyst, para-toluenesulfonic acid, for the formation of enamine and water.
During this reaction, water
was azeotropically distilled with toluene in order that the products were favored.
This new technique is
fully discussed in the introduction section.
Subsequently, acetic anhydride was added to form an
intermediate with a formal positive charge on nitrogen.
This reaction developed for one week unto
completion, after which the synthesis was resumed.
The intermediate iminium ion was hydrolyzed with
water and hydrochloric acid to yield the final product and regenerate the pyrrolidine used as a reagent.
The techniques employed in this experiment included enamine formation, column chromatography,
extraction, evaporation, heating under reflux, infrared spectroscopy, and azeotropic distillation.
The results of this experiment can be summarized as follows
0.2793 g of 2-acetylcyclohexanone
was synthesized with 32.10% efficiency, based on a theoretical yield of 0.87 g.
The purity of the final
product can only be discussed in terms of the lack of other characteristic peaks on the infrared spectrum,
since no experimental melting point was taken.
Edition, has provided ideal NMR
spectra for analysis of relative keto-enol content of the product, although no experimental spectra were
The experimental IR spectrum confirms formation of relatively pure 2-acetylcyclohexanone, as
evidenced by the presence of a carbonyl absorption and corresponding C (sp
)-H stretches at their proper
locations, 1760 cm
and slightly below 3000 cm
, on an otherwise empty spectrum.
In conclusion, the
desired product was formed at an acceptable percent yield with no obvious or measurable impurity based
on the characterization tests performed (further testing is needed to generate a more specific conclusion)
Figure 43.1—Overall Reaction of Cyclohexanone via Enamine to Form 2-Acetylcyclohexanone