Determination of the enthalpy and reaction volume changes of organic photoreactions using photoacoustic calorimetry

Separating Enthalpy and Volume Contributions in Photothermal Experiments: A Perspective

“…The relative magnitudes of the enthalpy and volume contributions to the photothermal signal cannot be varied sufficiently to achieve resolution. In 1989, Herman and Goodman (8) reported the use of aqueous/organic solvent mixtures and aqueous micelle solutions to factor the photoacoustic signals into enthalpy and volume components for three organic photoreactions: the photodissociation of 2,3diazabicyclo[2.2.1 ]hept-2-ene, the photodissociation of diphenylcyclopropenone and the photoisomerization of transstilbene. The reaction volumes were determined to be -50, 60 and 5 mL/mol, respectively.…”

Characterization of Carbon Monoxide Photodissociation from FeIILPO with Photoacoustic Calorimetry

“…In addition, volume changes in the system of interest resulting from a photoinitiated reaction also contribute to the acoustic wave/ refractive index change. The resulting acoustic signal can be expressed as: 27,31 where S is the acoustic signal, K is an instrument response parameter, E a is the number of Einsteins absorbed, and ∆V th and ∆V nonth are the volume changes due to thermal expansion/ contraction and nonthermal volume changes (due to the conformational changes and electrostriction) per mole of photons absorbed, respectively. The volume change due to thermal expansion/contraction is related to the heat released to the solvent, Q, and is expressed as:…”

Time‐Resolved Photoacoustic Calorimetry of Tri‐ and Tetraphenylethylenes. Do S0 and T1 Energy Surfaces Cross?*

“…A well-known possible problem, for example, is the importance of any intrinsic change of volume (7)(8)(9)(10). Photoacoustic calorimetry measures the acoustic signal resulting from expansion of the system following the laser pulse.…”