Non‐coincidence effect in methyl ethyl ketone: a solvent‐dependent Raman study

Abstract The wavenumber shift of the isotropic and anisotropic profiles of the CO stretching mode of methyl ethyl ketone (MEK) was measured in several polar and non‐polar solvents at different concentrations. The anisotropy shift function F = δ ν (2ε + n 2 ) 2 ε −1 was plotted as a function of solute concentration (ϕ). A discontinuity around 50% appears to be present in many solvent systems. The variation of shift with concentration may arise as a result of several interactions such as dipole–dipole, dipole–quadrupole, quadrupole–quadrupole and higher multipole interactions in the solute–solvent systems. The plot of ln F against ϕ is linear over the entire range. It may be inferred from the data that repulsive‐type intermolecular forces play a significant role in these molecular systems. The steric effects may be responsible for the discontinuity in the F vs ϕ plot apart from the atomic quadrupole effects and other intermolecular forces. Copyright © 2004 John Wiley & Sons, Ltd.

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