NMR Spectroscopy Flashcards

Describe the chemical shift range for aldehydes or ketones in C13 NMR.

The chemical shift range for aldehydes or ketones in C13 NMR is approximately 190-220 ppm.

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Describe the chemical shift range for aldehydes or ketones in C13 NMR.	The chemical shift range for aldehydes or ketones in C13 NMR is approximately 190-220 ppm.
Describe the information that can be obtained from NMR spectra.	NMR spectra can provide information about the carbon chain, the number of different environments for hydrogen atoms, and the connectivity of hydrogen atoms to other atoms in the compound.
How can IR spectra be used to identify the functional groups present in a compound?	IR spectra can be used to identify functional groups by looking for characteristic absorption peaks for specific bonds, such as C=O and O-H bonds.
Describe the process of determining the empirical formula of a compound.	The empirical formula of a compound is determined by calculating the ratio of the elements present in the compound based on their percentage composition.
What is the chemical shift range for a hydrogen bonded to an oxygen?	The chemical shift range for a hydrogen bonded to an oxygen is 0.5-5.0 ppm.
What is the chemical shift range for ethanol?	The chemical shift range for ethanol is 0.7-1.2 ppm.
Describe the appearance of a peak next to a carbon with 0 H's.	The peak will appear as a singlet.
What type of peak is observed when a hydrogen is bonded to an oxygen?	A singlet peak is observed, as hydrogens bonded to a nitrogen or oxygen usually do not couple with other protons.
Describe the relative size of the peaks in a triplet.	The relative size of the peaks in a triplet is 1:2:1.
How many peaks are observed when a peak is next to a carbon with 3 H's?	Four peaks are observed, forming a quartet.
What is the appearance of a peak with one neighboring carbon with 2 H's?	The peak will appear as a triplet.
Describe the splitting of a peak in H NMR.	The splitting of a peak in H NMR is determined by the number of inequivalent H's on neighboring C atoms plus one.
What is spin-spin coupling in H NMR?	In high resolution H NMR, each signal in the spectrum can be split into further lines due to inequivalent H's on neighboring C atoms.
What are the two main types of NMR spectroscopy?	C13 NMR and H (proton) NMR
How does the chemical shift vary for different types of protons in H NMR?	Different types of protons have different chemical shifts in H NMR, resulting in distinct positions on the NMR spectrum.
Define chemical shift in H NMR.	Chemical shift in H NMR refers to the position of a proton's signal on the NMR spectrum, which is influenced by the electron density around the proton.
Describe the relationship between the chemical shift and the electronegativity of groups near a proton in H NMR.	The chemical shift in H NMR increases with the presence of more electronegative groups near the proton.
What is the purpose of the chemical shift scale in NMR spectroscopy?	The chemical shift scale, measured in parts per million (ppm), indicates how far the frequency of the proton signal has shifted away from that of TMS. It allows for comparison and identification of different proton environments in a molecule.
Why is TMS (tetramethylsilane) used as a calibration compound in NMR spectroscopy?	TMS is used because it only gives one signal, its signal is away from all other H signals, it gives a strong signal with only a small amount needed, it is non-toxic, inert, and has a low boiling point for easy removal from the sample.
What is the difference between CCl4 and CDCl3 as solvents in NMR spectroscopy?	CCl4 is a non-polar compound and is suitable for dissolving non-polar organic molecules. CDCl3 is a polar covalent molecule and is suitable for dissolving polar organic molecules.
Describe the purpose of using solvents in NMR spectroscopy.	Solvents are used to dissolve samples and provide a medium for the NMR analysis. They should not contain any 1H atoms to avoid interference with the H NMR spectrum.
Do C13 NMR spectra or H NMR spectra have a simpler spectrum?	C13 NMR spectra have a simpler spectrum compared to H NMR spectra.
What is the ratio of equivalent hydrogen atoms in 1,3-dinitrobenzene?	1,3-dinitrobenzene has 3 sets of equivalent hydrogen atoms with a ratio of 3:2:9.
Describe the ratio of equivalent hydrogen atoms in ethanol.	Ethanol has 3 groups of different hydrogen atoms with a ratio of 6:1:2:3.
How sensitive are modern NMR machines in detecting C13 in organic molecules?	Modern NMR machines are sensitive enough to give a full spectrum for C13, even though it is present in only around 1% of organic molecules.
Define equivalent carbon atoms in a C13 NMR spectrum.	Equivalent carbon atoms in a C13 NMR spectrum refer to carbon atoms that produce the same signal (peak).
What is the integration value in an H NMR spectrum?	The integration value is the intensity of each signal, which is proportional to the number of equivalent hydrogen atoms it represents.
Describe the difference between C13 NMR and H NMR spectra.	C13 NMR spectra have one signal for each set of equivalent carbon atoms, while H NMR spectra have one signal for each set of equivalent hydrogen atoms.

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