Gutmann–Beckett method

In chemistry, the Gutmann–Beckett method is an experimental procedure used by chemists to assess the Lewis acidity of molecular species.

In 1975, Viktor Gutmann [de] used 31P-NMR spectroscopy to parameterize Lewis acidity of solvents by acceptor numbers (AN).

[1] In 1996, Michael A. Beckett recognised its more generally utility and adapted the procedure so that it could be easily applied to molecular species, when dissolved in weakly Lewis acidic solvents.

Acceptor numbers can be calculated from AN = 2.21 x (δsample – 41.0) and higher AN values indicate greater Lewis acidity.

The Gutmann-Beckett method is based on a single parameter NMR chemical shift scale but is in commonly used due to its experimental convenience.