Thermochemical hydrogen-deuterium isotope effects

"The heats of solution at 25.0 ± 0. 1°C for each member of hydrogen-deuterium isotopic pairs (chloroform/chloroform-d, acetone/acetone-d₆, methanol/methanol-d₁, ethanol/ethanol-d₁, and water/heavy water) have been determined as a function of molality in a variety of solvents. The heats for most of the systems could be described as a linear function of average molality with an average deviation in fit of less than one per cent. Using these linear equations, heats of solution at infinite dilution were obtained by extrapolation to zero molality. The heats of solution at infinite dilution of the hydrogen containing compounds were subtracted from those of the corresponding deuterium containing compounds to yield isotope effects on heats of solution. These isotope effects were interpreted in terms of hydrogen bonding and an empirical equation for the prediction of enthalpies of formation of hydrogen bonds. It was concluded that for a given isotopic pair the deuterium isomer is both more strongly and more extensively hydrogen bonded to bases than the hydrogen isomer. Heats of solution of water and heavy water were determined in each other as solvents and in the equimolar mixture as solvent. Considering the formation of HOD to be entirely responsible for the heat effect and using K = 3.8 =X_HOD²/ (X_H₂OX_D₂O) where X represents mole fraction gave 7. 88 ± 0.05 cal/mole for the heat of formation of HOD in mixtures of water and heavy water at 25°C. With the experimental results at 25°C for the mixing of different pairs in the set (methanol, methanol-d₁, water, heavy water), near infinite dilution of one component, the enthalpy change for the complete hydrogen-deuterium transfer between methanol (one mole) and heavy water (one-half mole) has been calculated. Values of -95 and -97 cal/mole were obtained for this transfer by two independent schemes. The studies performed in this work have yielded some of the first definitive data concerning the effect of deuterium versus hydrogen on intermolecular interactions. The results have not only demonstrated that isotope effects on heats of solution are measurable but also that they are amenable to meaningful interpretation"--Abstract, pages iii-iv.

Name thesis:degree_name

Ph. D. in Chemistry

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Duer, Wayne C.

• Chemistry

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/2035

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-3037