Flashcards on Introduction to Two-Dimensional NMR Spectroscopy
Introduction to 2D NMR Spectroscopy: A Student's Guide
Tap to flip · Swipe to navigate
Two-dimensional Nuclear Magnetic Resonance (2D NMR)
15 cards
Card 1
Question: What is the basic effect of a 90° pulse on nuclear magnetization in NMR?
Answer: It tips the excess spin population (magnetization) from the direction of the applied magnetic field into the xy plane, producing the FID.
Card 2
Question: What does FID stand for and what produces it?
Answer: FID = Free Induction Decay; it is produced by transverse magnetization (M) in the xy plane and decays as that magnetization diminishes after resonance
Card 3
Question: What are the three main stages shown in the ONE-PULSE 2D NMR experiment layout?
Answer: Preparation, Evolution, and Detection.
Card 4
Question: Give the pulse sequence timing for a basic 1H–1H COSY ONE-PULSE 2D experiment.
Answer: (90°)x — t1 — (90°)x — t2, where the first 90° pulse is preparation, t1 is evolution, the second 90° pulse, and t2 is detection.
Card 5
Question: In a 2D experiment schematic, what does 'n' represent when processing 2D data?
Answer: n is the number of increments in the indirect dimension (t1) used for constructing the 2D dataset.
Card 6
Question: List major types of 2D NMR experiments grouped as autocorrelated and cross-correlated.
Answer: Autocorrelated: Homonuclear J-resolved, 1H–1H COSY, TOCSY, NOESY, ROESY, INADEQUATE. Cross-correlated (heteronuclear): Heteronuclear J-resolved, 1H–13
Card 7
Question: In a 1H–1H COSY spectrum, what feature lies on the diagonal and what does it indicate?
Answer: The diagonal corresponds to f1 = f2 and shows the same resonances in both dimensions (self-correlation).
Card 8
Question: What cross-peak types (bond relationships) can appear in a 1H–1H COSY?
Answer: Geminal (2-bond), vicinal (3-bond), 4-bond correlations, and diagonal peaks; examples include allylic correlations.
Card 9
Question: What does the INADEQUATE experiment correlate and why is it challenging at natural abundance?
Answer: INADEQUATE correlates C–C (13C–13C) pairs via double-quantum transfer; it's challenging because the natural abundance probability of adjacent 13C–13C
Card 10
Question: What is the purpose of suppressing the 13C single-quantum signal in INADEQUATE?
Answer: To detect double-quantum signals (DQ) that report on 13C–13C connectivities by removing dominating single-quantum 13C signal.