Ch.13

Question 1

Nuclear Magnetic Resonance spectroscopy

Answer 1

a form of spectroscopy that measures the absorption of radio-frequency by nuclei in a magnetic field. The energy absorbed causes nuclear spin transitions

Question 2

Magnetic moment

Answer 2

the magnitude of a nuclear magnetic field

Question 3

Chemical shift

Answer 3

the difference between the resonance frequency of the proton being observed and that of tetramethylsilane

Question 4

_________ atoms deshield atoms and they move more downfield

Answer 4

electronegative

Question 5

the farther the distance from the electronegative group, the ______ the effect

Answer 5

smaller

Question 6

deshielded

Answer 6

when a nucleus is bonded to a group that withdraws part of the electron density from the bond, moving the absorption more downfield

Question 7

What does the pi bonding in aromatic protons cause?

Answer 7

more deshielding and a farther downfield shift

Question 8

what does pi bonding do in aldehyde protons?

Answer 8

deshield

Question 9

what does the triple bond in acetylenic protons do?

Answer 9

shields the electrons

Question 10

shielded

Answer 10

when a nucleus is surrounded by electrons whose induced magnetic field opposes the externally applied magnetic field

Question 11

Hydrogen-bonded protons

Answer 11

hydrogen bonding will deshield the protons, lowering the field

Question 12

carboxylic acid protons

Answer 12

the protons are deshielded by both the oxygen and the carbonyl group which will lower the field

Question 13

chemically equivalent

Answer 13

atoms that can not be distinguished chemically

Question 14

accidentally equivalent

Answer 14

atoms that are not equivalent by NMR yet absorbed at nearly the same chemical shift and are not resolved

Question 15

Integration

Answer 15

the measurement of the area under a peak, proportional to the number of protons giving rise to that peak

Question 16

spin-spin splitting

Answer 16

the interaction of the magnetic fields of two or more nuclei, usually through the bonds connecting them

Question 17

What is the 3 bond rule?

Answer 17

protons within 3 bonds of each other will couple

Question 18

N+1 Rule

Answer 18

if a signal is split by N equivalent protons, it is split into N+1 peaks

Question 19

When will a proton split each other

Answer 19

1. Nonequivalent
2. Bonded to the same carbon, or adjacent carbons

Question 20

Coupling Constant (J)

Answer 20

the distance (Hz) between two adjacent peaks of a multiplet

Question 21

If the J distance is the same, two molecules are _______

Answer 21

coupled

Question 22

Complex Splitting

Answer 22

splitting by two or more different kinds of protons with different coupling constants