Allerhand-Schleyer scale

A Polarity Scale Based on IR Spectroscopy. Allerhand and Schleyer (34/) observed a nice correlation between the stretching frequencies of various X = 0 vibrators and the px-h stretching frequencies of X—H B hydrogen-bonded systems in a variety of solvents. This experimental result was taken as proof that solvent interacts in a similar manner with the X = 0 and X—H — B stretching frequencies. These effects were attributed to variations in polarity and used to construct a polarity scale, G, defined as ... 

Infrared Spectral Correlations vntbv. Certain infrared spectral vibration frequencies and parameters derived therefrom show good linearity with the w scale and may also qualify as 7r -type properties. That linear solvation energy relationships (LSERs) apply to ir spectra was first pointed out by Allerhand and Schleyer (34/), who reported that solvent shifts of various types of ir stretching frequencies are proportional to one another. Based on this proportionality, they proposed an empirical LSER for the correlation of solvent sensitive ir vibration frequencies. 

The solvent dependence of the vibration of the O—H involved in hydrogen bonding was used by Allerhand and Schleyer [A163] to establish a solvent strength scale. More recently, Arnett et al [Ar 74] attempted to utilize the shift of the O—H vibration of p-fluorophenol caused by a solvent to characterize the donor strength of the solvent. 

Allerhand and Schleyer formd that a proportionality exists between the stretching frequencies of vibrators of the type X=0 (with X = C, N, P or S) and the corresponding stretching If equencies in situations involving hydrogen bonds of the X-H- B type in a variety of solvents. They thought these results to be indicative that the solvents studied interacted in a non-specific manner with both types of vibrator, in contradiction with the specific interaction-only approach advocated by Bellamy et al. They used this information to construct a solvent polarity scale that they called the G scale . Allerhand and Schleyer used an empirical linear fi ee-energy equation to define G ... 

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