MIR-Spectroscopic Reaction Monitoring

Importance of the Topic

Monitoring chemical reactions in the mid infrared region provides direct insights into reaction kinetics and end points It reduces the need for manual sampling which is labor intensive error prone and limited in temporal resolution Real time spectroscopic data support process optimization quality control and fundamental mechanistic studies

Objectives and Study Overview

This work demonstrates the use of a flow through attenuated total reflection ATR based FT IR setup for continuous reaction monitoring The esterification of acetic acid with ethanol to form ethyl acetate serves as a model reaction Temperature was controlled to study its influence on reaction rate and a fully automated measurement protocol captured spectral changes over time

Methodology and Instrumentation

• FT IR spectrometer Bruker ALPHA II equipped with a temperature controlled diamond ATR unit
• Custom stainless steel flow through cell with tungsten carbide brazed diamond crystal and Kalrez O rings for high chemical resistance
• Reaction medium recirculated across the ATR crystal enabling measurements every five minutes with potential temporal resolution down to five seconds
• Data acquisition and evaluation via OPUS software Reaction Monitoring function

Main Results and Discussion

Spectral analysis focused on carbonyl stretching vibrations the acetic acid band at 1710 cm 1 decreased while the ethyl acetate band at 1740 cm 1 increased Data at 879 cm 1 tracked carbonic acid dimers A temperature step from 40 to 60 C accelerated the reaction as revealed by steeper concentration change curves OPUS provided both 2D and 3D visualization of spectral evolution

Benefits and Practical Applications

• High chemical robustness of the diamond ATR flow cell supports aggressive or particulate reaction media
• Automated continuous monitoring minimizes operator intervention and sampling artifacts
• Enhanced temporal resolution allows kinetic profiling and rapid end point determination
• Applicable to academic research process development and routine quality assurance

Future Trends and Opportunities

• Integration with flow chemistry platforms for fully automated synthesis monitoring
• Coupling with advanced data analysis schemes including chemometrics and machine learning for predictive control
• Expansion toward more complex multistep reactions catalytic processes and industrial scale operations
• Development of miniaturized portable ATR FT IR systems for in situ field or process line analysis

Conclusion

The described mid IR ATR flow through approach offers a reliable cost effective solution for detailed real time reaction monitoring The combination of temperature controlled diamond ATR and automated software evaluation delivers valuable kinetic data and process insights enhancing both research and industrial applications

Reference

• Application Note AN M111 MIR Spectroscopic Reaction Monitoring Bruker Optics 2021