Organic analysis

Question 1

On an infra-red spectrograph what is below the 1500cm-1 region called? What is the region between?

Answer 1

Fingerprint region

500-1500

Question 2

What does the fingerprint region do in IR spectrographs?

Answer 2

Gives a unique match to every compound including isomeric forms of alcohols

Question 3

What must you do with an unknown sample on a spectrograph?

Answer 3

Must be matched against a known spectrograph database (e.g. using the fingerprint region even propane-q-ol can be separated by propan-2-ol)

Question 4

How do you get an exact identification using the spectrograph method?

Answer 4

Both the functional group and fingerprint region should match the unknown sample and not just one or other half of the spectrograph

Question 5

What must you write in an answer to get marks on the spectrograph?

Answer 5

The entire range of the wavelength
Name of the absorption/ peak

e.g. C-0 at 1000-1300 cm-1

Question 6

What way do wave numbers decrease?

Answer 6

Left to right

Question 7

What can peaks and the graph of infrared spectrometry be used for?

Answer 7

Give identification to functional groups

Question 8

What does an absence of a peak signify?

Answer 8

A structure

Question 9

What else can Infra Red spectrographs be used for?

Answer 9

To test the purity of a substance

Question 10

What can mass spectrometry be used for to find?

Answer 10

• Detecting banned drugs in sports
• Detect toxins in food
• Identify the country of origin of diamonds

Question 11

What is mass spectrometry used for?

Answer 11

To find the mr of a compound

Question 12

Molecular ion (M+) is formed when

Answer 12

A molecule loses an electron

Question 13

M+ produces ____ _____ ____ on mass spectrum of compound

Answer 13

molecular ion peak

Question 14

Mass/charge (m/z) value of molecular ion peak =

Answer 14

molecular mass of compound

Question 15

What does high resolution mass spectrometry measure?

Answer 15

Measures atomic and molecular masses extremely accurately

Question 16

What is high resolution mass spec used for?

Answer 16

Identifying compounds that have the same mr when rounded to the nearest whole number

Question 17

Describe how infrared spectroscopy works

Answer 17

1. Beam of IR radiation is passed through sample of the chemical
2. IR radiation absorbed by covalent bonds in the chemical = vibrational energy
   
   1. Bonds between different atoms absorb different frequencies of IR radiation
   2. Bonds in different places in molecules absorb different frequencies too (e.g. O-H group in alcohol and O-H in carboxylic acid absorb different frequencies)

Question 18

What does an infrared spectrometer produce & what does this show?

Answer 18

Infrared spectrometer produces graph that shows what frequencies of radiation molecules are absorbing

Question 19

Impurities produce …. in infrared spectroscopy

Answer 19

Extra peaks in the fingerprint region

Question 20

Describe how infrared radiation absorption is linked to global warming

Answer 20

1. Some electromagnetic radiation emitted by Sun reaches Earth and is absorbed
   
   • Earth re-emits some of its infrared radiation (heat)
2. Molecules of greenhouse gases (CO2, CH4, water vapour) in atmosphere absorb IR radiation (it’s bonds of these molcules that absorb it)
   
   • & re-emit some of it back towards Earth = keeps us warm
   • Called greenhouse effect
3. Human activities, burning fossil fuels & leaving rubbish to rot in landfill sites, caused rise in greenhouse gas concentrations
4. Means more heat being trapped and Earth getting warmer = global warming