Intermolecular nuclear relaxation and molecular pair distribution in liquid mixtures

Abstract

ABSTRACT7 Li and 23 Na relaxation times in aqueous solution of Li+ and Na+ in the presence of an increasing amount of Mn2+ are reported. From these measurements the cation-cation pair distribution function has been calculated. A distance ofapproach between Li+ (or Na +)and Mn 2 + of ~4.5A has been found.The intermolecular proton relaxation rates of the acids CH 3 COOD, CH 3 CD 2 COOD, and CD 3 CH 2 COOD dissolved in water (D 2 0) are presented and from these data simple acid-acid pair distribution functions are constructed. Association has been detected from excess intermolecular proton-proton interactions. In the solution of propionic acid the association is stronger as seen from the methylene group than from the methyl group.In the pure alcohols CD 3 0H and C 2 D 5 0H and their mixtures with inert solvents intermolecular proton relaxation is entirely of rotational character and permits conclusions concerning the depth of the potential characterizing the pair distribution function.

Group-Structure of Rotational Correlation Functiong2(t) of Flexible Molecule (EtOH) Produced by Addition of Strongly Interacting Components

“…Considering the composition of the system (II) we obtain the result that the OH... HO relaxation should be to 70% of intermolecular nature which we treat here as being of pseudointramolecular character. So again we obtain the result which has been found already several times [7,9,21] that the interaction strength obtained experimentally with the intermolecular or pseudo-intramolecular relaxation rates is markedly closer to the value predicted by geometry than in the intramolecular case. However, if we are considering the OH relaxation rate as being caused entirely by the water intramolecular relaxation, then we would have to use the proton-proton distance of 1.52 A and the aA coefficient would also go down to a value of 0.24.…”

Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride

“…By the oxygen-17 substitution method we were able to separate intramolecular and intermolecular relaxation rates, and then using the former we calculated the reorientational correlation times T°h of the OH bond in liquid methanol, which were in good agreement with those obtained from computer simulations [12,13]. In the past there existed two difficulties in obtaining the correct reorientational correlation time r°H as in the case of proton relaxation in CD3OH [14] the reorientational vector is not strictly defined, and in the case of deuteron relaxation in CH 3 OD [4,15,16] the quadrupole coupling constant is not known. The quadrupole coupling constants of D and 17 0 in the liquid are though expected to be intermediate between the ice and gas values, but their exact values so far were unknown.…”

Internal Motion in Liquid Ethanol and some Other Alcohols, Separation of Contributions by Added Glycerol

“…Thus, if the coefficients wj in Eq. (1) The path we are following up in the present paper is different from the conventional one. We wish primarily to answer the following two questions: (i) Is the effective correlation time expressable as a sum of terms as given in Eq.…”

“…reff is a weighted sum of a number of time constants Tj, Tet( = T Wf, (1) where the t/s characterize the rotation of the group about the respective intramolecular axis and the diffusive motion of the whole molecule about different axes fixed in the molecular frame. Now in a liquid like ethanol at room temperature the time constants xi as derived from the experimental results have very small values, i.e.…”

“…We wish primarily to answer the following two questions: (i) Is the effective correlation time expressable as a sum of terms as given in Eq. (1)? and (ii), if so, is the relation (2) fulfilled for the molecule in question here, i. e. ethanol ?…”