1. Investigation of a Regioselective and Stereoselective Markovnikov Addition of
Water to (1R)-(-)-Nopol, a Bicyclic Sterically Hindered Alkene
Daniel Joaquin, Scotty Squire, Richard Ratto, Dr. Kerensa Sorensen-Stowell
INTRODUCTION
METHODS & MATERIALS
RESULTS DISCUSSION
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
• Set up a reflux condenser.
• Mix 2.73 mL nopol, 4.8 g mercury(II) acetate, 20
mL distilled H2O, and 20 mL THF in a round
bottom flask.
• Prepare in a separate flask a 0.57 M NaBH4
solution in 3.0 M NaOH.
• Reflux the nopol mixture, while stirring, for 7-10
hours or until solution is clear and little to no
precipitate is present.
• Neutralize the reaction with NaBH4 solution and
extract the organic layer.
• Purify the organic layer via column
chromatography using a 50-50 ethyl
acetate/hexane solution as the mobile phase in a
silica gel column
Dr. Kerensa Sorensen-Stowell
Dr. Mike Wood
BYU-I Chemistry Department
Figure 2. (a) 1H NMR of (1R)-(-)-nopol. (b) IR of (1R)-(-)-nopol.
Figure 1. Overall reaction.
(a) (b)
Through TLC analysis the formation of several products is observed.
Unreacted nopol was successfully removed via column
chromatography. IR spectra of products suggest the reaction may
have taken place, but the limited amount of recovered product
prevented successful 1H and 13C NMR characterization. As a result,
verification of the formation of the desired product was not
achieved.
Figure 3. (c) Structure and 1H NMR of predicted product, (d) Structure and 13C of predicted product.
(c)
(d)
(e)
Figure 4. (e) TLC demonstrating multiple products. (f) TLC demonstrating separation of products. 50-50
Ethyl acetate/hexane solution mobile phase.
A two-part reaction involving nopol, a sterically
hindered bicyclic alkene, was tested for
regioselectivity and stereoselectivity via the
oxymercuration-demercuration reaction. Mercuric
acetate was used to form an organomercuric
intermediate. Sodium borohydride was used to
reduce the remaining mercuric functional group
leaving behind a hydrogen in its place. The
expected alcohol product is conformationally
stable. Characterization of the resultant molecule
involved infrared (IR) spectroscopy, and nuclear
magnetic resonance (1H and 13C NMR). The findings
will lead a reaction that is both regioselective and
stereoselective.
The procedure used in this reaction was based on a procedure by
Smith, et. al. They used 1-octene as their alkene source, which did not
contain a primary alcohol like nopol. In our reaction, the cyclic
mercury intermediate does appear to have added to the double bond
as well as cause an SN2 reaction with the primary alcohol. We observed
the formation of metallic mercury after the addition of NaBH4
suggesting that coupling did take place.
The TLC plate analysis and IR spectra of the products appear to
demonstrate that both reactions took place to an extent. We have
attempted to purify the products via column chromatography with
silica gel as the stationary phase and 50-50 hexane/ethyl acetate as
the mobile phase. The samples obtained after chromatography were
contaminated with unreacted nopol when 1H, 13C NMR, and IR spectra
were obtained. At this point in this project, it’s impossible to
differentiate each of the stereoisomeric products from one another. In
the future a less polar mobile phase will be used to better separate the
products.
Purification with a column was sufficient to properly separate the
products from the unreacted nopol; however, individual products were
not separated from the mixture. There is evidence to support the
successful addition of the hydroxyl group to the alkene. Further
investigation is needed to properly substantiate the success of steric
hindrance influencing stereochemical product formation.
Buinova, É , Yaremchenko, N., Urbanovich, T. R., & Izotova, L. V. (1979).
Oxymercuration-demercuration of car-3-ene. Chemistry of Natural
Compounds, 15(5), 565-568.
Smith, M. E., Johnson, S. L., & Masterson, D. S. (2013). Regioselective
hydration of an alkene and analysis of the alcohol product by remote
access NMR: A classroom demonstration. Journal of Chemical
Education, 90(1), 99-101.
(f)
Rf:
0.45
0.38
0.28