Chapter 12

Question 1

Spectroscopy: technique used to determine the ______ of a compound, most techniques are _______

Answer 1

structure
nondestructive

Question 2

The _______ (v) of a wave is the number of complete wave cycles that pass a fixed point in a second

Answer 2

frequency

Question 3

_______ (λ) is the distance between any 2 peaks of the wave

Answer 3

wavelength

Question 4

frequency and wavelength are _______ proportional

Answer 4

inversely

Question 5

Low E has _______ v and _______ λ

Answer 5

low
long

Question 6

High E has _______ v and _______ λ

Answer 6

high
short

Question 7

Infrared spectroscopy (___): used to determine _______ present in a molecule

Answer 7

IR
functional groups

Question 8

Bond stretching frequencies:
1) frequency _______ with increasing atomic mass
2) frequency _______ with increasing bond energy (strength)

Answer 8

1) decreases
2) increases

Question 9

Which has higher frequency on IR, stretching or bending

Answer 9

stretching

Question 10

1) Stronger bonds absorb at _______ wavenumbers
2) Bonds to smaller mass absorb at _______ wavenumbers

Answer 10

higher
higher

Question 11

IR-active: vibrations must change the overall _______ of the molecule

Answer 11

dipole moment

Question 12

Each molecule has a _______ resulting spectrum of IR

Answer 12

unique

Question 13

Where is the magic line in IR?

Answer 13

3000 cm-1

Question 14

Conjugations _______ the frequency

weaker bonds

Answer 14

lower

Question 15

IR in hydrocarbons experience C-C _______

Answer 15

stretch

Question 16

IR in hydrocarbons experience C-H _______

Answer 16

stretch

Question 17

A greater percent of S character in the hybrid orbitals will make the C-H bond _______ leading to _______ wavenumber

Answer 17

stronger
Higher

Question 18

When an alkene has approx frequencies at 990, and 910 cm-1 then you can assume its _______

Answer 18

monosubstituted

Question 19

Because alcohol (O-H) bond can participate in hydrogen bonding, the IR appearance is _______ and centers around _______

Answer 19

broad
3350

Question 20

Because carboxylic acid (CO2H) bond can participate in a lot of hydrogen bonding, the IR appearance is _______ and centers around _______

Answer 20

ultra broad
3000

Question 21

1° RNH2 has _______ appearance on IR

Answer 21

2 weak bends

Question 22

2° R2NH has _______ appearance on IR

Answer 22

1 weak bend

Question 23

3° R3N has _______ appearance on IR

Answer 23

NA

Question 24

Conjugation in carbonyl compounds _______ the position of IR by _____-_____ cm-1

Answer 24

lowers
20-40

Question 25

If C of the C=O is in a 5 membered ring or smaller, IR shifts to _______ position by _____ cm-1

Answer 25

higher ~30

Question 26

MS measures _______, which can then be used to determine molecular formula

Answer 26

molecular weight

Question 27

In MS, a beam of high-energy electrons breaks the molecule apart by "_______" an electron out of it

Answer 27

knocking

Question 28

MS is a _______ technique: the sample cannot be recovered

Answer 28

destructive

Question 29

Fragmentation gives a mixture of two fragments, a _______ and a _______

Answer 29

cation and radical

Question 30

MS only detects the _______ charged fragments!

Answer 30

positively

Question 31

What are the two important terminology in MS?

Answer 31

1) parent ion [M+] 2) base peak

Question 32

Parent ion [M+]: _______ of the molecule (minus one electron lost)

Answer 32

mass

Question 33

Base peak: ______ peak in the spectrum (molecule in greatest abundance)

Answer 33

tallest

Question 34

What are the 3 elements where Isostope ratios have distinctive appearance on MS?

Answer 34

1) C (100:1) 2) Cl (3:1) 3) Br (1:1)

Question 35

What is the nitrogen rule in MS?

Answer 35

- an odd numbered molecular ion usually means that the unknown compound has 1 or 3 nitrogen atoms - an even numbered molecular ion usually means that the unknown compound has 0 or 2 nitrogen atoms

Question 36

Rank the 3 possiblilities for initial electron loss in order from highest energy to lowest energy

Answer 36

1) NB electron 2) pi electron 3) sigma electron

Question 37

_______: the molecular ions may be unstable and will fragment

Answer 37

fragmentation patterns

Question 38

_______ fragmentation: radical cation loses a small, neutral molecule (H2O)

Answer 38

type 1

Question 39

In type 1 fragmentation, after the loss of an electron from the alcohol, it gains an H from the _______ carbon via homolytic cleavage

Answer 39

alpha - one away

Question 40

_______ fragmentation: the bond in the radical cation where the initial electron was lost breaks to give two molecules: a cation and a radical

Answer 40

type 2

Question 41

type 2 fragmentation: the bond in the radical cation where the initial electron was lost breaks to give two molecules: a _______ and a _______

Answer 41

cation radical

Question 42

fragments that are _______ stable are more likely to exist

Answer 42

more - C+ and C. stabilized by 3°>2°>1°>methyl

Question 43

What are the common fragments lost in type 2: 1) CH3 2) CH3CH2 3) CH3CH3CH2 4) CH3CH3CH3CH2

Answer 43

1) 15 2) 29 3) 43 4) 57

Question 44

In type two fragmentation, the MS gives _______-stablized cations whenever possible

Answer 44

resonance

Question 45

_______ fragmentation: a bond elsewhere in the radical cation (often alpha), does homolytic cleavage yielding two molecules each with a radical

Answer 45

type 3

Question 46

Type 3 fragmentation often yields an additional pi bond along with a ______ charged O or N

Answer 46

positively charged

Question 47

a triple bond Oxygen+ (O+) connected to a Carbon is called a ________ ion

Answer 47

acylium