Experimental Measurement of Rates

Batch vs Continuous Reactions:

• Batch: Monitoring progress of reaction at time intervals. e.g. photolysis (conc vs time)

• Continuous: Continuous measurement of reaction. e.g. tubular reactor (conc vs l)

Ex-situ Analysis:

• Monitors any physical changes occurs outside the reaction medium.

• Techniques like titration, GC/LC, and MS analyze samples after quenching reactions.

• Limitations: sampling time restricts to timescales » 1s

In-situ Analysis:

• Monitors any physical changes in the reaction medium.

• Measures parameters like pressure, volume, conductivity, pH, and polarimetry, absorbance, luminescene, in real-time.

• This is critical for fast reactions and offers more instantaneous data.

Specialist Techniques:

• Pump-Probe Methods: Initiate with a short pulse, allowing monitoring of rapid reactions e.g. femtochemistry

• Lifetime Methods: NMR spectroscopy

Beer’s Law & Spectrophotometry:

• Relationship: Absorbance A = -log10(I/I0) relates concentration, path length, and light absorbance.

• By plotting absorbance vs. concentration, one can create standard curves for accurate determination of unknowns.