Question 1

Each proton NMR spectra contains signals that represent different types of ___ from the sample molecule.&#10;A) Carbon&#10;B) Oxygen&#10;C) Hydrogen&#10;D) Single bonds&#10;E) Covalent bonds

Accepted Answer

Proton NMR detects the presence of different types of hydrogen atoms. It will also detect Phosphorous, Fluorine and other elements with a spin of 1/2.

Question 2

In a proton NMR sample, which hydrogen functional group(s) will appear between 2 and 4 ppm on the specta?&#10;A) unsubstituted alkane&#10;B) alkene&#10;C) alkyne&#10;D) aromatic hydrogen

Accepted Answer

Alkyne hydrogens typically appear between 2 and 4 ppm in proton NMR due to the electron-withdrawing effect of the sp-hybridized carbon.

Question 3

A ___ proton has more electron density surrounding it and the proton will appear ___ .&#10;A) Shielded, upfield&#10;B) Shielded, downfield&#10;C) Deshielded, upfield&#10;D) Deshielded, downfield

Accepted Answer

Protons that are shielded by electron density absorb at a higher magnetic field strength and appear upfield in the spectra. Deshielded protons do not have as much electron density surrounding them and will absorb at a lower magnetic field and appear downfield in the spectra.

Question 4

Each signal produced in an NMR spectra has 3 variables. Those variables are ___ .&#10;A) Signal strength, signal splitting and signal height&#10;B) Signal strength, signal shift and signal height&#10;C) Signal shift, signal splitting and signal strength&#10;D) Signal shift, signal splitting and signal integration

Accepted Answer

Signal shift is shown by the location from 0-10 on the graph. Signal shift tells what functional group is next to the hydrogen. Signal splitting is shown by the number of lines that the signal produces. Signal splitting tells how many hydrogens are next to the hydrogen. Signal integration is shown by the area under the curve. Signal integration shows how many hydrogens each signal represents.

Question 5

What would be the splitting of the indicated hydrogen?  &#10;A) I&#10;B) II&#10;C) III&#10;D) IV

Accepted Answer

The answer of What would be the splitting of the...

Question 6

What would be the splitting of the indicated hydrogen?  &#10;A) I&#10;B) II&#10;C) III&#10;D) IV

Accepted Answer

The answer of What would be the splitting of the...

Question 7

What would be the splitting of the indicated hydrogen?  &#10;A) I&#10;B) II&#10;C) III&#10;D) IV

Accepted Answer

The answer of What would be the splitting of the...

Question 8

In a carbon NMR sample, which carbon atoms will appear between 100 and 200 ppm on the specta?&#10;A) carbon of an alkene&#10;B) carbon of an alkyne&#10;C) carbon of an aromatic ring&#10;D) carbon of a ketone&#10;E) a, b and c&#10;F) a, c and d&#10;G) all of the above&#10;H) none of the above

Accepted Answer

Carbons of alkenes, aromatic rings, and ketones typically appear between 100 and 200 ppm in carbon NMR spectra. Alkyne carbons usually appear below 100 ppm.

Question 9

___ carbon NMR spectra allow you to determine whether a carbon is a CH, CH₂, CH₃ or CH. A) broadband proton decoupled B) DEPT C) COSY D) HETCOR

Accepted Answer

DEPT (Distortionless Enhancement by Polarization Transfer) NMR spectra are used to distinguish between CH, CH2, and CH3 groups by showing different signal intensities or phases for each type of carbon.

Question 10

In a mass spectrum of a compound, the following data (intensity) is given. M⁺ = 80, M⁺ +1 = 8.8, M⁺ +2 = 26. This compound will have ___ carbons and will contain a ___ . A) 8, sulfur B) 9, silicon C) 10, chlorine D) 11, bromine

Accepted Answer

For carbons, 8.8/80 × 100 = 0.11 × 100 = 11 %/1.1 = 10 carbons. For other atoms, 26/80 × 100 = 0.325 × 100 = 32.5 %. For M⁺ +2, Si = 3.35%, S = 4.4 %, Cl = 32.5% and Br = 98 %. Therefore, this contains chlorine.

Deck 9: Nuclear Magnetic Resonance and Mass Spectrometry