Spectroscopy

Question 0

Uv spec is most useful for detecting ?

Answer 0

Conjugated alkenes

Question 1

Mass spectroscopy results in the separation of fragments according to ?

Answer 1

Mass to charge ratio

Question 2

How does water effect alcohols with the NMR spectra

Answer 2

The hydroxyl exchanges protons with the water , preventing it from coupling

Question 3

The isotope c12 is not useful for NMR because ?

Answer 3

It has no magnetic moment. Only elements with an odd number of electrons can have magnetic moments

Question 4

Chemical shifts of a proton for these functional groups in the NMR spectrum

Alkyl
Aromatic
Aldehyde
Carboxyl

Answer 4

1ppm
7ppm
9.5ppm
11ppm

Question 5

Ir spec is most useful for distinguishing ?

Answer 5

Double and triple bonds

Question 6

The process of measuring the frequencies of electromagnetic radiation absorbed by a molecule

Answer 6

Spectroscopy

Question 7

IR spectroscopy measures?

Answer 7

Molecular vibrations

Stretching bonding rotation

Question 8

The useful numbers of infrared light occur in frequency range from 400 to 4000 cm called ?

Answer 8

Wave numbers

Question 9

Fingerprint region ?

Answer 9

Between 400 and 1500 cm which is unique to a molecule , complex vibrations

Question 10

In order for IR light to be absorbed , the vibration of the molecule must result in ?

Answer 10

A change in the bond dipole moment

Ex o2 and br2 do not

Question 11

Characteristic absorption frequencies ?

Single bonds
Double bonds
Triple bonds

Answer 11

1200
1600
2200

Question 12

Functionalgroup/1700-1750/3100-3500

Alcohol
Aldehyde/ketone
Carboxylic acid
Amine

Answer 12

No Yes (broad)
Yes No
Yes. Broad peak
No. Sharp peak

Question 13

Gives areas of absorption the appearance of valleys on the spectrum.

Answer 13

Percent transmission (the inverse of absorption) vs frequency

Question 14

Nuclei whose magnetic moments are aligned with the field vs against the field (NMR)

Answer 14

Alpha (lower energy )

Beta (higher energy )

Question 15

If the nuclei are exposed to electromagnetic radiation , some in lower energy of alpha will be excited into the beta state

Answer 15

Resonating

Question 16

Chemical shift is represent by the sigma symbol and with units ?

Answer 16

Parts per million (ppm)

Question 17

A peak further to the left in NMR is said to be shifted

Answer 17

Downward

Question 18

NMR is most commonly used to study ? But can also be used for ?

Answer 18

Protons /H1 nuclei and C13 nuclei

Any nucleus with an odd atomic number or odd mass number

Question 19

Proton NMR size of the peaks , the areas underneath correspond to ?

Answer 19

The number of protons producing each peak

Question 20

If a proton is next to a electron withdrawing atom , it is called ___ because ?

Answer 20

Deshielding

Pulling the electron cloud away from the nucleus moving it’s resonance to the left

Question 21

Electron donating atoms will ____ the nucleus in an H NMR spectrum . This will move it to the ?

Answer 21

Shield

Right

Question 22

TMS appears on which spectrum ?

Answer 22

NMR H1

Question 23

Peak splitting/coupling for NMR H1 ?
Number of peaks ?
Area ratios?

Answer 23

If two magnetically different protons are within 3 bonds of each other.

Number of adjacent hydrogens +1

^ number related to the triangle of numbers

Question 24

Other hydrogens influence Ha. Causes slight upfield and downfield shifts. Thus this will cause a ?

Answer 24

Dublet

Question 25

If a Ha is influenced by two nearby Hb, this causes it to have ___ different states

Answer 25

4 Alpha beta Alpha alpha Beta alpha Beta beta

Question 26

Alpha beta and beta alpha have resonance frequencies occurring at ? Alpha alpha and beta beta have frequencies ?

Answer 26

The same frequency Different from each other and the above alpha beta /beta alpha Results in 3 peaks instead of 4!!!

Question 27

The number of peaks that appears when splitting occurs is ?

Answer 27

N hydrogen atoms couples to give n+ 1

Question 28

For C NMR , does coupling occur between the carbon atoms ? | Where does it occur ?

Answer 28

No | Between carbon and hydrogen atoms directly attached to then

Question 29

The ability for a C NMR to record a spectrum without the coupling of adjacent protons ,

Answer 29

Spin decoupling This just shows how the carbon atoms are affected by their adjacent functional groups

Question 30

For uv spectroscopy the higher the ___ in solution , the greater the absorbance

Answer 30

Concentration

Question 31

Uv spectrum is often used to identify ?

Answer 31

The presence or absence of a compound by measuring the absorbance at a characteristic wavelength

Question 32

The means of determining the molecular weight and structure of a molecule based on how it ionizes and decomposes under specific conditions

Answer 32

Mass spectrometry

Question 33

Mass spectrometry differs from others in 2 ways

Answer 33

No absorption of electromagnetic radiation | It's a destructive technique

Question 34

Mass spectrometers ionize the sample with a high speed of ?

Answer 34

Electrons

Question 35

First ion formed for mass spectrometry is the ?

Answer 35

+1 cation

Question 36

Graph of mass spectrometry ?

Answer 36

Abundance(y) vs mass/charge (x)

Question 37

Tallest peak belonging to the most common ion in mass spectrometry ?

Answer 37

Base peak This is assigned the abundance value of 100 percent

Question 38

The peak with the highest m/c ratio is almost always the ___ and from which the molecular weight can be obtained

Answer 38

Parent ion peak