NMR6 Flashcards
(28 cards)
Which spectrum-method can be used to determine which signal is coupled to which signal?
A (double quantum filtered) DQF-COSY spectrum, where a spectrum of a molecule is plotted against itself.
What is a COSY-spectroscopy?
It is a type of 2D-NMR where the correlation of the cross peaks from scalar coupling is shown. With other words the spectrum is used to determine which signals are coupling to which.
What is the difference of HSQC and 2QF COSY spectroscopy?
- HSQC COSY spectra shows a 2D spectra of H1 in one dimension and C13 in another dimesion (2 isotopes).
- 2QF COSY spectra shows a 2D spectra of C13 on both dimensions. (one isotope)
2D-NMR spectra are a way to…
- waste a lot of harddisk space
- make a simple spectrum look really scientific
- visualize a correlation matrix between atoms
visualize a correlation matrix between atoms
Cross peaks are signals that…
- have different chemical shifts on the two frequency axes
- give information on a correlation between two atoms
- look like an “X”
- are on top of other signals
- have different chemical shifts on the two frequency axes
- give information on a correlation between two atoms
is this statement always true?
“The closer a CH2 group is to a ketone group, the higher the 13C chemical shift”
Yes or no
No
What is an EXSY spectra?
It stands for exchange spectrocopy and is a 2D NMR method that detects slow chemical exchange between different nuclear environments by showing cross-peaks between exchanging nuclei, typically used to investigate conformational changes, tautomerism, or binding/unbinding processes.
List the different phases of classical 2D-NMR experiments in the right order accoring to the schmatic pulse sequence:
Acquisition, evolution, preparation, mixing
preparation, evolution, mixing, acquisition
The chemical shift of the indirect dimension is encoded into the recorded signal as….
- amplitude modulation
- phase modulation
- frequency modulation
amplitude modulation
The direct dimension frequency axis is recorded during…
- preparation
- evolution
- mixing
- acquisition
acquisition
What is heteronuclear single-quantum coherence (HSQC) and heteronuclear multiple-quantum coherence (HMQC) used for?
It is used for single bond coupling (1J) and is better at observing the bonds for one H-atom bonded to one C-atom. It can also be used for more bonds but will show weak peaks. It shown large couplings.
What is HMBC used for?
It is designed to show small couplings. (2J,3J. 4J) and is able to giveyou the coupling of cross peaks.
Describe homonuclear 2D-NMR
it is a method that — it contains scalar coupling (DQF-COSY or TOCSY) and dipolar coupling
Describe homonuclear 2D-NMR
it is a method that — it contains scalar coupling (DQF-COSY or TOCSY) and dipolar coupling
What is TOCSY?
It stands for total correlation spectroscopy and is a 2D NMR technique used to observe spin systems, meaning groups of nuclei (typically protons) that are scalar-coupled (J-coupled) to each other, even across multiple bonds.
What is NOESY?
It stands for nuclear overhauser effect spectroscopy and is a 2D NMR technique that provides information about spatial proximity between nuclei in small-size molecules, typically protons. (Dipolar coupling)
What is ROESY?
stands for rotating-frame overhauser effect Spectroscopy and is a 2D NMR technique used to determine spatial proximity between protons (¹H nuclei) in medium-sized molecules. (dipolar coupling)
A 2D-NMR-spectrum that has two different isotopes on the two frequency axes, is called….
Heteronuclear, homonuclear, multinuclear, multiisotopic, mononuclear, monoisotopic
heteronuclear
A 2D-NMR-spectrum that has the same isotope on the two frequency axes, is called…..
Heteronuclear, homonuclear, multinuclear, multiisotopic, mononuclear, monoisotopic
Homonuclear
The best NMR-spectrum for fingerprinting organic molecules is the…
COSY, TOCSY, NOESY, ROESY, INEPT, 13C-1H-HSQC, 13C-1H-HMQC, 13C-1H-HMBC, 15N-1H-HSQC, 15N-1H-HMBC
13C-1H-HSQC
The best NMR-spectrum for fingerprinting proteins is the…
COSY, TOCSY, NOESY, ROESY, INEPT, 13C-1H-HSQC, 13C-1H-HMQC, 13C-1H-HMBC, 15N-1H-HSQC, 15N-1H-HMBC
15N-1H-HSQC
Which 2D-NMR spectra rely on a magnetization transfer through scalar coupling?
COSY
TOCSY
NOESY
ROESY
HSQC
HMBC
HMQC
COSY
TOCSY
HSQC
HMBC
HMQC
Do you have to enrich 13C in molecules in order to record an HSQC?
yes or no
no
Are the following statements true or false?
HSQC and HMBC provide you with the same information:
true or false
false
