The extinction coefficient ratio (ECR) of coordinatively bonded pyridine (Lpy) and protonated pyridine (Bpy) was determined in situ by diffuse-reflectance FTIR spectroscopy (DRIFTS), by exposing sulfated zirconia (SZ) containing chemisorbed pyridine to water vapor. Both pure and KBr-diluted SZ samples were analyzed. The linearity with concentration of the Kubelka−Munk transformation was verified for pyridine interacting with the undiluted SZ samples. The portability of published ECR values between transmission and diffuse-reflectance IR spectroscopy, as well as between different types of materials, was found questionable. For the SZ samples analyzed, following a statistical analysis of the data, an Lpy/Bpy ECR value of 2.05 ± 6.3% was determined, resulting in the calculation of an initial Lewis/Brönsted acidity ratio value of 1.1 in the freshly activated material. This ECR determination method should be applicable to other similar solid acids that have a window of relative transparency in the 1600−1400 cm -1 range and are capable of retaining chemisorbed pyridine upon exposure to water vapor.
No takes yet. Share an insight, caveat, or question.
Platon et al. (2003) studied this question.
Synapse has enriched 4 closely related papers on similar clinical questions. Consider them for comparative context: