Pre-lab Questions – Answers
1. Figure 1 below shows the chemical structure of Dibutylboron trifluoromethanesulfonate (Dibutylboron trifluoromethanesulfonate, Wikipedia.com). This compound is considered extremely air and moisture sensitive because of the presence of numerous highly electronegative elements of oxygen. Such a compound will allow an immediate hydrogen bonding to form once exposed to water.
Fig. 1 Chemical structure of Dibutylboron trifluoromethanesulfonate.
2. Figure 2 below shows the structures of the 4 stereoisomer pairs that can form from this aldol reaction.
Fig. 2 Enantiomers for aldol substrate
3. Yes, enantiomers can be separated by column chromatography. This method used chiral chromatography wherein it uses chiral additives that is on the mobile phase, or through derivatization of the sample so that a diastereomeric product of the enantiomers may be formed (Robards et al.).
4. Yes, diastereomers can also be separated by column chromatography. This will all depend on looking for the perfect mobile phase for it.
5. The best way to know whether the reaction proceeded forwards is by understanding the values of the chemical shifts for the different types of protons that were initially present on your reactants, and the types of protons that you will be expecting in your products. A comparison should be made based on the appearance and disappearance of a particular peak in an NMR spectrum both on the reactant and expected product side.
6. The TLC solvent conditions that would be best used for this experiment is the 1:1 mix of acetone and hexane. This is because there is a balance in terms of the intermolecular forces that exist between the reactants and the products.