The Cyclohexanol Cycle and Nylon Synthesis
CHE 233L Section 302
Department of Chemistry, DePaul University, 1110 W. Belden Avenue, Chicago, IL 60614 email@example.com
May 8th, 2013
The first three labs of this organic chemistry experiment involved carrying out the first three parts of the Cyclohexanol Cycle. The cyclohexanol was first converted to cyclohexene and water by simple distillation (product: 6.5395g, 79.75% recovery). The cyclohexene then underwent a bromination reaction by addition of concentrated HBr and a 30% H2O2 solution, followed by an extraction of the aqueous phase. This produced trans-1,2-dibromocyclohexane (product: 12.8886g, 67.34% recovery). The trans-1,2-dibromocyclohexane was reduced by zinc metal to cyclohexene. The reaction was conducted in water, first allowing the reaction to reflux and then isolating the cyclohexene by distillation (product: 4.2144g, 95.89%).
This experiment carries out a series of steps to carry out the Cyclohexanol Cycle. The Cyclohexanol Cycle is a multistep process that involves reacting and recycling the same product. Cyclohexanol is the starting material and ultimately is the ending material as well. The final step involves converting the cyclohexanol to nylon 6,6 (Dintzner 262). The experiment in its entirety was carried out following the major principles of green chemistry. Green chemistry is the philosophy of doing chemistry in such a way that reduces or eliminates the use and production of hazardous substances (Dintzner 262).
In the dehydration of cyclohexanol, Montmorillonite K10 clay was used as an acid catalyst, which promoted dehydration. Cyclohexanol was refluxed in the presence of the catalyst. During distillation the cyclohexene product distilled from the reaction mixture along with water, and was dried with MgSO4.
In the bromination of cyclohexene, Br2 was generated in situ from HBr and H2O2. The formation of the Br2 was apparent by a color change of the reaction mixture to dark red-brown. The temperature of the reaction mixture was kept cool to avoid any unwanted side reactions. This procedure in particular kept in the lines of green chemistry because it avoided the direct handling of molecular bromine, a very caustic substance. The bromination reaction involved the addition of the two molecular bromines on adjacent carbons to synthesize trans-1,2-dibromocyclohexane.
The debromination of trans-1,2-dibromocyclohexane was facilitated by the addition of zinc metal, water, and heat. Zinc metal acts as a reducing agent to aid in the conversion from a dibromide to an alkene. The reaction is conducted in water to allow the mixture to reflux, and followed by a simple distillation. MgSO4 was used as a drying agent and then vacuum filtered. The reaction caused an E2-like elimination product. This procedure also followed green chemistry because water was the solvent and the byproduct ZnBr2 is recyclable.
Figure 1: Cyclohexanol Cycle
Figure source: DePaul University’s D2L: Chem 233L site page
The above table illustrates the Cyclohexanol Cycle. The experiment thus far has completed the first three steps in the cycle: the dehydration of cyclohexanol (79.75% yield) which utilized Montmorillonite K10 and heat as reagents, the bromination of cyclohexane (67.34% yield) which utilized HBr, H2O2, and H2O as reagents, and the debromination of trans-1,2-dibromocyclohexane (95.89% yield) which utilized Zinc, H2O, and heat as reagents.
Figure 2: Product Mass and Percent Yield
Mass of Product (g)
Percent Yield (%)
Dehydration of Cyclohexanol
Bromination of Cyclohexene
Debromination of trans-1,2-dibromocyclohexane
The above table demonstrates the mass of product and calculated percent yields for the first three reactions in the Cyclohexanol Cycle. Dividing the theoretical yield by the actual yield and multiplying...
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