A simple Norrish Type II actinometer for flow photoreactions

Area of Science:

• Photochemistry
• Chemical Engineering
• Organic Synthesis

Background:

• Flow photochemistry lacks standardized methods for determining quantum efficiency.
• Product yields are often reported without measuring light exposure, hindering reproducibility.
• Accurate measurement of light is crucial for understanding photoreaction kinetics.

Purpose of the Study:

• To develop and present a flow actinometer for measuring light intensity in photochemical reactions.
• To provide a practical tool for researchers in organic laboratories.
• To enable accurate determination of quantum yields in flow photochemistry.

Main Methods:

• A flow actinometer based on the photochemistry of valerophenone was designed.
• The actinometer was integrated into a photoreactor setup using Teflon tubing and low-pressure UV lamps.
• Irradiance was measured under specific experimental conditions.

Main Results:

• The developed flow actinometer successfully measured irradiance in the UV region.
• An example measurement for UVB lamps showed an irradiance of 1.1 × 10⁻⁴ einstein L⁻¹ s⁻¹.
• The photoreactor design is adaptable for different geometries and light sources.

Conclusions:

• The valerophenone-based flow actinometer is a readily implementable tool for quantifying light in flow photochemistry.
• This method addresses a critical gap in standardizing photoreaction yield measurements.
• The approach can be extended to other spectral regions and reactor designs.