Ch. 12

Question 1

Absorption Spectroscopy

Answer 1

the measurement of the amount of electromagnetic radiation by a compound as a function of the wavelength

Question 2

What are the 3 types of absorption spectroscopy

Answer 2

Infrared (IR), Nuclear magnetic resonance (NMR), ultraviolet (UV)

Question 3

How are frequency and wavelength related?

Answer 3

Inversely

Question 4

As energy increases, wavelenth _______, and frequency _____

Answer 4

Wavelength shortens, frequency increases

Question 5

How does IR spectroscopy work

Answer 5

light causes molecular vibrations in the molecule

Question 6

Wavenumber (v)

Answer 6

the number of wavelengths that fit into one centimeter that is proportional to the frequency

Question 7

When a bond is stretched a restoring force _______; when a bond is compressed, a restoring force _______.

Answer 7

Pulls the two atoms together
Pushes the two atoms apart

Question 8

Heavier atoms vibrate _______ than lighter atoms

Answer 8

slower

Question 9

Stronger bonds stretch or compress better/worse than weaker bonds

Answer 9

worse

Question 10

Stronger bonds usually vibrate ______ than weaker bonds

Answer 10

faster

Question 11

Simple stretching vibration region(IR)

Answer 11

most common area for characteristic and predictable vibrations between 1600 and 3500

Question 12

IR-Active

Answer 12

a vibration that changes the dipole moment of the molecule and thus can absorb infrared light

Question 13

IR-Inactive

Answer 13

a vibration that does not change the dipole moment of the molecule and thus cannot absorb infrared light

Question 14

A molecule that is stretched has an _____ dipole moment. A molecule that is compressed has an ______ dipole.

Answer 14

Decreased
Compressed

Question 15

Infrared Spectrometer

Answer 15

a device that measures a compound’s absorption of infrared light as a function of frequency or wavelength

Question 16

How long does dispersive IR take? How long does FT-IR take?

Answer 16

Dispersive takes a long time, FT-IR takes seconds

Question 17

Why doesn’t a tertiary amine show up on a spectrometer? (IR)

Answer 17

Because there is no N-H bonds

Question 18

Does resonance raise or lower carbonyl frequencies

Answer 18

lowers

Question 19

Mass spectrometry

Answer 19

method to determine the molecular mass and other valuable information about the molecular formula

Question 20

Mass spectrometer

Answer 20

An instrument that ionizes molecules, sorts the ions according to their masses and records the abundance of ions of each mass

Question 21

Electron impact ionization

Answer 21

A sample is bombarded by a beam of electrons; an electron may ionize a molecules by knbocking out an additional electron forming a radical cation

Question 22

Fragmentation

Answer 22

the breaking apart of a molecular ion upon ionization

Question 23

Only __________ fragments are detected by the mass spectrometer

Answer 23

positively charged

Question 24

How does the separation of ions of different masses occur?

Answer 24

magnetic deflection

Question 25

What is a base peak? (massspec)

Answer 25

the strongest peak in a mass spectrum

Question 26

What is a parent peak? (massspec)

Answer 26

the highest peak that is observed due to the fact that the molecule did not fragment

Question 27

What does an even number of Ns in CHN tell about the parent? An odd number? (massspec)

Answer 27

An even numb er will have an even parent, an odd number will have an odd parent \

Question 28

High-resolution mass spectrometers can measure masses in 1 part to _______

Answer 28

20,000

Question 29

How many peaks will bromine have? What are their characteristics? (massspec)

Answer 29

two peaks, (M+, M+2) they will have equal heights

Question 30

How many peaks will chlorine have? What are their charactersitcs? (massspec)

Answer 30

two peaks (M+ M+2) The M+2 peak will be a third of the height of the M+ height

Question 31

What peaks will Iodine have? (massspec)

Answer 31

Iodine will have a large gap and a peak at 127

Question 32

What peak(s) will Nitrogen have? (massspec)

Answer 32

an odd number M+ peak

Question 33

How many bonds do you break to find a fragment (massspec)

Answer 33

one

Question 34

What is alpha clevage (massspec)

Answer 34

breaking the carbon-carbon bond adjacent to the carbon bearing a specified functional group; happens with ethers and amines

Question 35

What do alcohols lose during mass spectra? What peak does it create?

Answer 35

water, creates a corresponding water peak at M-18