Spectroscopy

Question 1

Nuclear Magnetic resonance principles

Peaks

Answer 1

Each peak on NMR spectroscopy represents hydrogens that are chemically equivalent

Question 2

Nuclear Magnetic resonance principles

Calibration

Answer 2

NMR usually calibrated by a compound called TMS whose shift is at 0 ppm

Question 3

Nuclear Magnetic resonance principles

Shielding

Answer 3

Shielding decreases with electron-withdrawing groups due to increasing influence of the magnetic field

Question 4

Nuclear Magnetic resonance principles

Splitting

Answer 4

of peaks = (# of neighboring H within 3 bonds) + 1

Also called spin-spin coupling.
Adjacent hydrogens cause magnetic interference resulting in splitting of peaks on NMR spec.

Question 5

Nuclear Magnetic resonance principles

Electron groups

Answer 5

Electron-donating groups increase shielding and are located more upfield (right).
Electron-withdrawing groups decrease shielding and are located more downfield (left).

Question 6

Infrared spectroscopy peaks

C=O

range and peak shape

Answer 6

1750
Sharp

Question 7

Infrared spectroscopy peaks

C=C

range and peak shape

Answer 7

1600-1680
Weak

Question 8

Infrared spectroscopy peaks

C≡C or C≡N

range and peak shape

Answer 8

1900-2200
Medium

Question 9

Infrared spectroscopy peaks

N-H

range and peak shape

Answer 9

3300
Sharp

Question 10

Infrared spectroscopy peaks

O-H

range and peak shape

Answer 10

3000-3300
Broad

Question 11

Nuclear Magnetic Resonance peaks

Shifts of Hydrogens of sp3 carbons

Answer 11

0 to 3

Question 12

Nuclear Magnetic Resonance peaks

Shifts of Hydrogens of sp2 carbons

Answer 12

4.6 to 6

Question 13

Nuclear Magnetic Resonance peaks

Shifts of Hydrogens of sp carbons

Answer 13

2 to 3

Question 14

Nuclear Magnetic Resonance peaks

Shifts of Hydrogens of aromatics

Answer 14

6 to 8

Question 15

Nuclear Magnetic Resonance peaks

Shifts of Aldehyde hydrogens

Answer 15

8 to 10

Question 16

Nuclear Magnetic Resonance peaks

Shifts of -OH group hydrogens

Answer 16

1 to 5

Question 17

Nuclear Magnetic Resonance peaks

Shifts of Carboxylic acid hydrogens

Answer 17

10 to 12

Question 18

Mass Spectroscopy peaks

Molecular ion peak

Answer 18

Represents the molecule of interest

Question 19

Mass Spectroscopy peaks

Base peak

Answer 19

The tallest peak and represents the most abundant ion

Question 20

Mass Spectroscopy peaks

M+1 peak

Answer 20

A smaller peak to the right of the molecular ion peak.
Represents the abundance of carbon

Question 21

Mass Spectroscopy peaks

M+2 peak

Answer 21

Represents the abundance of Br or Cl

Question 22

Mass Spectroscopy peaks

m/z ratio

Answer 22

The x-axis represents the m/z ratio, or the ratio of mass to charge
Signal intensity represents the quantity of particles at a given m/z ratio

Question 23

Spectroscopy Types

Infrared spectroscopy

Answer 23

Based on absorption of infrared light and the principle that vibration or rotation of bonds causes a net change in dipole moment
Useful for determining functional groups

Question 24

Spectroscopy Types

Ultraviolet spectroscopy

Answer 24

Based on absorption of UV light, comparing absorption of a compound in a solvent with the reference as the solvent alone.
Most useful for conjugated π-bond systems

Question 25

Spectroscopy Types

Mass spectrometry

Answer 25

Mass spectrometry is based on electron collisions that result in ionization of compounds.
Used for determining molecular structure or weight of a compound.

Question 26

Spectroscopy Types

Nuclear magnetic resonance spectroscopy

Answer 26

Measures nuclear spin using a magnetic field.
Used for determining the functional groups of a compound.