COLOC-S: A modified COLOC sequence for selective long-range X-H correlation 2D NMR spectroscopy

✍ Scribed by V. V. Krishnamurthy; John E. Casida

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 462 KB
• Volume: 25
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260251002

✦ Synopsis

The COLOC-S pulse sequence (a modification of COLOC) provides rapid and selective long-range correlation 2D NMR spectra. It combines the advantages of the COLOC and Freeman sequences. This modification is analysed in terms of the Product Operator Formalism, and its application is illustrated by spectral peak assignments of two insecticides, ryanodine and l R , cis-phenothrin.

KEY WORDS 2D NMR COLOC-S modified COLOC pulse sequence 'H evolution time, thus effecting broad-band decoupling in Fl . The sequence proposed by Bauer el aL7 (Freeman sequence) uses the TANGO" (Testing for Adjacent Nuclei with a Gyration Operator) and BIRD" (BIlinear Rotation Decoupling) pulses to discriminate between directly bound protons and long-range coupled protons. This sequence achieves proton decoupling in both the F, and F2 dimensions while retaining C-H (long-range) couplings in the F, dimension, and therefore is useful for measuring long-range C-H coupling constants. The sequence recently proposed by Reynolds et aL8 uses two BIRD pulses and is, in principle, superior to the COLOC and Freeman sequences, at least for 2J(CH) correlation. This sequence also discriminates between 2J(CH) and * V.V.K. dedicates this paper to Professor G. A. Olah (University of Southern California), on his 60th birthday.