a. Does the 1H NMR spectrum reveal if the final product contained any unreacted reactant? Estimate the mole ratio of the cis isomer to the trans isomer in the original reactant. Explain your reasoning and show your calculations.
b. Based solely on three bond coupling, what multiplicity (number of peaks) is expected for the signal due to the CHOH proton in the reactant alcohols.
c. What three alkenes can confidently be assessed to be in the Product 1H NMR spectrum? What is a possible identity for the fourth alkene signal? Explain your reasoning.
d. Which alkene appears to be the major product from the reaction? What is the mole fraction for the major alkene product compared to all alkenes in the Product 1H NMR spectrum? Explain your reasoning and show your calculations.
e. Suggest why products arising from the most stable carbocation are not the major products from the reaction you performed.
a. The 1H NMR spectrum can reveal if the final product contained any unreacted reactant by showing the presence of peaks corresponding to the reactant. If peaks corresponding to the reactant are observed, it indicates that some of the reactant did not react and remained in the final product.
To estimate the mole ratio of the cis isomer to the trans isomer in the original reactant, we can compare the peak integrations of the cis and trans isomers in the 1H NMR spectrum. The mole ratio can be estimated using the following equation:
Mole ratio = integration of cis peak / integration of trans peak
b. Based solely on three bond coupling, the signal due to the CHOH proton in the reactant alcohols is expected to exhibit a triplet multiplicity (three peaks). This is because the CHOH proton will couple with the adjacent protons on the carbon, resulting in a splitting pattern of 1:2:1.
c. The three alkenes that can confidently be assessed to be in the Product 1H NMR spectrum can be identified based on the presence of double bond signals (peaks) in the spectrum. However, without more information or specific peaks in the spectrum, it is not possible to confidently identify the fourth alkene signal.
d. The major alkene product can be determined by comparing the peak integrations of the alkene signals in the 1H NMR spectrum. The alkene with the highest peak integration will be the major product. The mole fraction for the major alkene product can be calculated using the following equation:
Mole fraction = integration of major alkene peak / (integration of all alkene peaks)
e. The products arising from the most stable carbocation are not the major products from the reaction because the reaction conditions may favor the formation of other carbocations that are less stable but undergo faster reaction kinetics. Additionally, the presence of other reaction pathways, such as rearrangement reactions, can lead to the formation of different products.