## TRANSFERABILITY OF ELECTRO-OPTICAL PARAMETERS FOR INFRARED INTENSITIES OF NORMAL PARAFFINS

##### Publisher:

Ohio State University##### Abstract:

The intensity of infrared absorption for the i-th normal mode $\theta_{1}$ depends on $\left( \frac{\vec{\partial M}}{\partial Q_{i}} \right)^{\circ}$ where $\vec{M}$ is the total dipole moment of the molecule. $\left( \frac{\vec{\partial M}}{\partial Q_{i}} \right)^{\circ}$ can be expressed as $${\left( \frac{\vec{\partial M}}{\partial Q_{i}} \right)}^{\circ} = {\Sigma_{m}} {\left( \frac{\vec{\partial M}}{\partial R_{m}} \right)}^{\circ} \qquad L_{mi}$$, where $R_{m}$ is an internal coordinate, or as $$ \left( \frac{\vec{\partial M}}{\partial Q_{i}} \right)^{\circ} = {\Sigma_{m}} \left\{ {\Sigma_{k}} {\left( \frac{\partial _{\mu^{k}}}{\partial R_{m}} \right)}^{\circ} \quad {\vec{e^{ko}}} + {\Sigma_{k}} \mu^{ko} {\left( \frac{\vec{\partial e^{k}}}{\partial R_{m}} \right)}^{\circ}\right\} \quad L_{mi} $$ where $\mu^{ko}$ and $\vec{e}^{ko}$ are the equilibrium bond dipole moments and equilibrium bond directions, respectively. ${\left( \frac{\partial \mu^{k}}{\partial R_{m}} \right)}^{\circ}$ and $\mu^{ko}$ are usually referred to as electrooptical parameters. The ${\left( \frac{\vec{\partial M}}{\partial R_{m}} \right)}^{\circ}$ can be transferred to isotopic derivatives only when $\vec{M^{\circ}}$ = 0; otherwise, they must be corrected for the rotational contributions. On the contrary the electrooptical parameters can be transferred to isotopic derivatives also when $\vec{M^{\circ}} \neq 0;$ moreover, since they refer to groups of atoms in the molecule, they seem more apt to be transferred to chemically similar molecules. Results will be presented of an ``overlay"" least squares refinement of the electrooptical parameters on the experimental intensity data of $CH_{4}, C_{2}H_{6}, C_{3}H_{8}$ and their isotopic derivatives. The same set of parameters successfully reproduces the infrared spectrum of polyethylene.

##### Description:

Author Institution: Istituto di Chimica delle Macromolecole del CNR

##### Type:

article##### Other Identifiers:

1976-WD-4Items in Knowledge Bank are protected by copyright, with all rights reserved, unless otherwise indicated.