Spin--lattice relaxation and hydrogen bonding in methanol--solvent mixtures

Journal Article · Wed Oct 01 04:00:00 EDT 1975 · J. Phys. Chem., v. 79, no. 21, pp. 2307-2312

DOI:https://doi.org/10.1021/j100588a016· OSTI ID:4146678

Inlow, R O; Joesten, M D; Van Wazer, J R

Nuclear spin-lattice relaxation times, T$sub 1$, of the hydrogen nuclei in CD$sub 3$OH and CH$sub 3$OH have been measured as a function of concentration in solvents of varying hydrogen bonding ability. CD$sub 3$OH--CCl$sub 4$, CD$sub 3$OH--(CD$sub 3$$)$$sub 2$CO, CD$sub 3$OH--CD$sub 3$OD, CD$sub 3$OH--(CD$sub 3$$)$$sub 2$SO, CH$sub 3$OH--CCl$sub 4$, and CH$sub 3$OH--(CD$sub 3$$)$$sub 2$CO mixtures were studied over the entire range of concentration at 31$sup 0$. The results show that T$sub 1$ reaches a minimum in all solvents at approximately 0.9 mole fraction alcohol. This is interpreted in terms of the structure of pure liquid methanol being disrupted by insertion of small amounts of solvent. Extrapolation of the spin--lattice relaxation time to infinite dilution, T$sub 1$$sup 0$, gives an indication of the strength of the alcohol--solvent hydrogen bond. T$sub 1$$sup 0$ is shortest in CCl$sub 4$ and increases in the order: (CD$sub 3$$)$$sub 2$CO less than CD$sub 3$OD greater than (CD$sub 3$$)$$sub 2$SO. This behavior is explained by the hindrance of rotation of the alcohol as a result of the formation of hydrogen bonds of increasing strength with the solvent. At large mole fractions of methanol, relaxation is interpreted to be a mixture of dipole--dipole and spin--rotation interaction; while in dilute solutions the spin- -rotation mechanism seems to predominate. (auth)

• Research Organization: Vanderbilt Univ., Nashville
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-000076
• OSTI ID: 4146678
• Journal Information: J. Phys. Chem., v. 79, no. 21, pp. 2307-2312, Journal Name: J. Phys. Chem., v. 79, no. 21, pp. 2307-2312; ISSN JPCHA
• Country of Publication: United States
• Language: English

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