DEPTkäyrät

DEPTkäyrät, which translates to DEPT curves in English, are a specialized NMR (Nuclear Magnetic Resonance) technique used in organic chemistry. DEPT stands for Distortionless Enhancement by Polarization Transfer. This technique is an extension of standard broadband decoupled 13C NMR spectroscopy and provides valuable information about the type of carbon atoms in a molecule. Specifically, DEPT experiments differentiate between primary (CH3), secondary (CH2), tertiary (CH), and quaternary (C) carbons.

There are typically three variations of DEPT experiments: DEPT-45, DEPT-90, and DEPT-135. In a DEPT-45 experiment, all carbons, including quaternary carbons, give a positive signal. The DEPT-90 experiment shows signals only for CH and CH3 carbons, and these signals are positive. CH2 carbons typically give a negative signal in DEPT-90, while quaternary carbons are absent. The DEPT-135 experiment provides positive signals for CH and CH3 carbons, and negative signals for CH2 carbons. Quaternary carbons are also absent in DEPT-135.

By analyzing the spectra from these different DEPT experiments alongside a standard 13C NMR spectrum, chemists can confidently assign signals to specific carbon types. This is particularly useful for structural elucidation of unknown compounds or for confirming the structure of synthesized molecules. The ability to distinguish between different CHn groups greatly simplifies complex spectra and aids in the identification of functional groups and molecular skeletons. DEPT is a powerful tool in the arsenal of analytical chemists.