Reaction Monitoring System using Surface-Enhanced Raman Spectroscopy for Flow Synthesis Process

Introduction

Organic synthesis is conventionally carried out by batch methods, but continuous-flow synthesis has recently been attracting attention because it is easy to scale up chemical reactions and allows stable production of the desired compound.

We have developed a new measurement system using the compact JASCO Palmtop Raman spectrometer to monitor flow synthesis.

Reaction monitoring using JASCO Palmtop Raman spectrometer

Aldol reactions were monitored under batch conditions to ensure that reactions were traceable.

Result

Decrease in starting compound and increase in products were observed.
The smaller the intensity of the peak of interest, the smaller the Signal-to-noise ratio in the time variation graph.

Reaction monitoring was confirmed to be possible using the JASCO Palmtop Raman spectrometer

Signal enhancement by SERS under flow conditions

Result

Using rhodamine 6G (R6G), which is widely used for SERS, Raman spectra were acquired under flow conditions. Signal enhancement was clearly identified.

Spectra and peak intensity ratios obtained with and without a SERS substrate for dilute solutions of 2-benzylidene-1-tetralone (2B1T), which is the product of the reaction in first Experiment, are shown below.

Solvent: EtOH, Sample: 0.012 M 2B1T in EtOH (1 mL)

Conclusion

A new measurement system that incorporates SERS under flow conditions was developed. This system is expected to contribute to on-line monitoring of reaction systems.

References

Adamo, R. L. Beingessner, M. Behnam, J. Chen, T. F. Jamison, K. F. Jensen, J.M. Monbaliu , A. S. Myerson, E. M. Revalor, D. R. Snead, T. Stelzer, N. Weeranoppanant, S. Y. Wong, P. Zhang: Science, 352, 61-67 (2016).
Porta, M. Benaglia, A. Puglisi: Org. Process Res. Dev., 20, 2-25 (2016).
B.Laroche, Y. Saito, H. Ishitani, S. Kobayashi: Org. Process Res. Dev., 23 (5), 961-967 (2019).

Acknowledgement

This work was supported by the Japan Agency for Medical Research and Development (AMED) under project number JP24ak0101189.

Poster Session at RSC-JAIMA Symposium on Analytical Chemistry 2024 (September 5 – 6, 2024, in Makuhari Messe, JAPAN)
Sarina Mine¹, Tomoaki Sakamoto², Takuji Shoda², Hiroyuki Takei³, Koji Inada⁴, Kohei Tamura¹, Satoko Suzuki¹, Shinichiro Fukuda⁴, Kenichi Akao¹
¹ JASCO Corporation, ² National Institute of Health Sciences, ³ Faculty of Life Sciences, Toyo University, ⁴ JASCO Engineering