4-Tert-Butylcyclohexanone Lab Report

explanatory Essay
1799 words
1799 words

The goal of this two week lab was to examine the stereochemistry of the oxidation-reduction interconversion of 4-tert-butylcyclohexanol and 4-tert-butylcyclohexanone. The purpose of first week was to explore the oxidation of an alcohol to a ketone and see how the reduction of the ketone will affect the stereoselectivity. The purpose of first week is to oxidize the alcohol, 4-tert-butylcyclohexanol, to ketone just so that it can be reduced back into the alcohol to see how OH will react. The purpose of second week was to reduce 4-tert-butylcyclohexanol from first week and determine the effect of the product's diastereoselectivity by performing reduction procedures using sodium borohydride The chemicals for this lab are sodium hypochlorite, 4-tert-butylcyclohexanone …show more content…

In this essay, the author

  • Explains the purpose of the two week lab, which was to examine the stereochemistry of oxidation-reduction interconversion of 4-tert-butylcyclohexanol.
  • Explains the purpose of oxidation reaction, which is to reduce the alcohol to a ketone so it can be observed how the oh will act.
  • Describes the three reduction conditions that can be used to reduce the 4-tert-butylcyclohexanone: nabh4, mpv, and l-selectride.
  • Explains that the cis and trans products in figure 2 show the alcohol oh group in axial and equatorial positions, respectively.
  • Explains that kmno4 will be used to stain the tlc plate since the starting material and product will not show up under uv light.
  • Explains that nabh4, mpv, and l-selectride have cis and trans isomers, whereas the proton is free to attack the carbonyl oxygen in a frontside attack.
  • Explains that ir spectroscopy can be used to determine the functional group in compound. the hydride reduction product shows a broad peak at 3300 cm-1, indicating the presence of an alcohol o-h.
  • Explains that the percent yield for oxidation was calculated to be 53% but it is not certain of how much of the ketone has been formed since there are impurities according to tlc.
  • Explains the stereoselectivity of various hydride reducing agents. the reduction of 4-tert-butylcyclohexanone was studied in detail.

Depending on which face of carbonyl the hydride attacks, the ketone could result in two different diastereomers of product. Since the two ketone faces are nonequivalent, there will be stereo selectivity in reduction which means that one diastereomer will be more prevalent than the other. There are three reduction conditions can be used to reduce the 4-tert-butylcyclohexanone : NaBH4, MPV , and L-selectride. For NaBH4, the hydride attach itself to the carbonyl oxygen to become the hydroxyl group and it more likely from the top because the hydride isn’t blocked by a bulky group (Fig mech prez). Both sodium borohydride and lithium aluminum hydride are less bulky hydride reducing agents so it is expected that they will be able to attack from the top face of the molecule since the bulky tert-butyl group will not hinder the attack. For L-selectride mechanism is similar to NaBH4, the L-selectride is a source of hydride for the carbonyl oxygen but there are bulky groups that block the hydride. Since L-selectride is much larger and bulkier hydride reagent so likely not be able to attack from the top face in the presence of the bulky tert-butyl group (fig 1 and 2 like web) For MPV, the ketone is reduced with aluminum isopropoxide in isopropanol. The carbonyl oxygen attack the aluminum which causes the carbonyl oxygen to have a +1 charge, a hydrogen as …show more content…

The ratios for NaBH4, MPV, and L-selectride are 24.2:75.8, 43.6:56.3, 91.3:.86 respectively. According to analysis of the 1H-NMR spectrum, it is shown that the trans product formed over the cis. The mechanism for L-selectride is very similar to that of NaBH4, but NaBH4 primarily yields the more trans isomer whereas the L-selectride primarily the cis isomer. The reason for this is because in NaBH4, the hydride is not being blocked when convert to OH so it’s free to do a top attack to make a lot more of the the trans isomer. Whereas the L-selectride has bulky groups that block from the carbonyl oxygen which means that it must perform bottom attack and because of this, the isomer that gets made is the cis at 91%. In MPV, the proton is free to attack the carbonyl oxygen in a frontside attack to give more of the trans isomer The MPV reaction using aluminum isopropoxide gives reversible reduction of ketones and aldehydes and the cis or trans can revert back to starting ketone. Each step in the mechanism is reversible so the reaction is driven by the formation of the more stable product which favored thermodynamic. Overall, the stereoselectivity of reaction is affected how the hydride is opened was when it was attacking the carbonyl

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