Spectroscopy

Question 1

What happens to an organic compound in a mass spectrometer?

Answer 1

it loses an electron and forms a positive ion - the molecular ion

Question 2

What does a mass spectrometer detect?

Answer 2

the mass-to-charge ratio (m/z) of the molecular ion which gives the molecular mass

Question 3

What is the molecular ion?

Answer 3

the positive ion formed when a molecule loses an electron

Question 4

How do you determine the molecular mass from a mass spectrum?

Answer 4

the molecular ion peak is the largest no. peak

Question 5

What is the symbol for the molecular ion peak?

Answer 5

M+

Question 6

What is the M+1 peak?

Answer 6

a very small peak after M+ peak due to Carbon 13 or other isotopes

Question 7

What is fragmentation?

Answer 7

in the mass spectrometer, some molecular ions break down into smaller pieces called fragments

Question 8

What does fragmentation break a molecular ion up into?

Answer 8

a fragment ion and a radical

Question 9

What is the m/z value of CH2OH+ fragment ion?

Answer 9

31

Question 10

What is the m/z value for CH3+?

Answer 10

15

Question 11

What is the m/z value for C2H5+ fragment ion?

Answer 11

29

Question 12

What is the m/z value for C3H7+ fragment ion?

Answer 12

43

Question 13

What is the m/z value for C4H9+ fragment ion?

Answer 13

57

Question 14

What is the m/z value for CH3CH2O+ fragment ion?

Answer 14

45

Question 15

How does infrared spectroscopy work?

Answer 15

covalent bonds posses energy and vibrate naturally
the amount of vibration increases with increasing temperatures
theses bonds can absorb infrared which makes them bend ans stretch more

Question 16

What does the amount a bond streches or bends depend on?

Answer 16

the mass of the atoms in the bond = heavier—> slower vibration
the strength of the bond = stronger —-> faster vibration

Question 17

How does global warmbing occur due to IR radiation?

Answer 17

greenhouse gases absorb IR radiation because it has the same natural frequency of their bonds
the vibrating bonds re-emit this energy as radiation
resulting in increasing the temp of the earth

Question 18

What is infrared spectroscopy used for?

Answer 18

identifying the functional groups present in organic molecules

Question 19

What does an infrared spectrum show?

Answer 19

the frequencies that have been absorbed by the bonds

Question 20

What is the fingerprint region?

Answer 20

peaks below 1500 wavenumber - (dont need to indentify these peeks)

Question 21

What does an OH alchohol bond peak on infrared spectrum look like?

Answer 21

tall and broad, no spiking

Question 22

What does a C-H bond look like on an infrared spectrum?

Answer 22

small spikes

Question 23

What does a caroxyl OH infrared peak look like?

Answer 23

broad but has C-H spikes on the right side

Question 24

What is the application of infrared spectroscopy?

Answer 24

used to identify pollutants - CO, CO2 and hydrocarbons
breathalysers for the presence of ethanol

Question 25

What is element analysis?

Answer 25

use of % composition data to determine the empirical formula

Question 26

What is mass spectrometry?

Answer 26

use of the molecular ion peak from a mass spectrum to determine the molecular mass; use of fragment ions to identify sections of a molecule

Question 27

What is infrared spectroscopy?

Answer 27

use of absorption peaks from an infrared spectrum to identify bonds and functional groups present in the molecule