Organic analysis Flashcards
On an infra-red spectrograph what is below the 1500cm-1 region called? What is the region between?
Fingerprint region
500-1500
What does the fingerprint region do in IR spectrographs?
Gives a unique match to every compound including isomeric forms of alcohols
What must you do with an unknown sample on a spectrograph?
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)
How do you get an exact identification using the spectrograph method?
Both the functional group and fingerprint region should match the unknown sample and not just one or other half of the spectrograph
What must you write in an answer to get marks on the spectrograph?
The entire range of the wavelength
Name of the absorption/ peak
e.g. C-0 at 1000-1300 cm-1
What way do wave numbers decrease?
Left to right
What can peaks and the graph of infrared spectrometry be used for?
Give identification to functional groups
What does an absence of a peak signify?
A structure
What else can Infra Red spectrographs be used for?
To test the purity of a substance
What can mass spectrometry be used for to find?
- Detecting banned drugs in sports
- Detect toxins in food
- Identify the country of origin of diamonds
What is mass spectrometry used for?
To find the mr of a compound
Molecular ion (M+) is formed when
A molecule loses an electron
M+ produces ____ _____ ____ on mass spectrum of compound
molecular ion peak
Mass/charge (m/z) value of molecular ion peak =
molecular mass of compound
What does high resolution mass spectrometry measure?
Measures atomic and molecular masses extremely accurately
What is high resolution mass spec used for?
Identifying compounds that have the same mr when rounded to the nearest whole number
Describe how infrared spectroscopy works
- Beam of IR radiation is passed through sample of the chemical
- IR radiation absorbed by covalent bonds in the chemical = vibrational energy
- Bonds between different atoms absorb different frequencies of IR radiation
- 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)
What does an infrared spectrometer produce & what does this show?
Infrared spectrometer produces graph that shows what frequencies of radiation molecules are absorbing
Impurities produce …. in infrared spectroscopy
Extra peaks in the fingerprint region
Describe how infrared radiation absorption is linked to global warming
- Some electromagnetic radiation emitted by Sun reaches Earth and is absorbed
- Earth re-emits some of its infrared radiation (heat)
- 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
- Human activities, burning fossil fuels & leaving rubbish to rot in landfill sites, caused rise in greenhouse gas concentrations
- Means more heat being trapped and Earth getting warmer = global warming
