analytical techniques Flashcards
Describe how infared spectroscopy works
Covalnet bonds vibrate (and absorbe energy) at specific natural frequencies, different for each different bond and envirmonet. An IR spectrometer passes IR radiation of a range at a sample, detecting which frequencies the sample’s bonds absorb and vibrate to. Producing a spectrum graph.
Describe the atmospheric absorbtion of IR radiation and it’s consequences
-The suns solar rays are absorbed by the earth and re emitted as longer wavelength Infared radiation.
-Greenhouse gasses such as water vapour, CO2 and methane absorb said longer wavelength infared radiatin through their covalent bonds.
- These vibrating bonds re-radiate heat energy, increasing the atmosphere’s temperature, leading to global warming.
What are governments doing to reduce global warming via IR radiation?
Governments are offering incentives to households and companies to use renewable soucres of energy which do not produce major greenhouse gasses.
Where is the fingerprint region and what is it for?
On an infared spectrum the finger print region is found between 1500 to 500 cm⁻¹. The finger print region produces a unique pattern for each different molecule and can be used with a database of regions.
What peak do most organic compounds have and why?
Roughly 3000 cm⁻¹ due to most organic molecules containing a C-H bond.
What are the two applications of IR spectroscopy?
- Breathalysers
- Atmospheric monitoring
How do breathalysers work?
Breathalysers pas a beam of IR radiation through a sample of breath, and measure the intensity of ethanols C-H peaks generated.
What do atmospheric monitors do?
Measure the levels of pollutant gasses such as CO and CO2 in the atmosphere.
What is mass spectrometry used to find?
Mass spectrometry is used to find the molecular mass of an organic compound.
How is the M/Z value made and what does it stand for?
When an organic compound is placed in a mass spectrometer it loses an electron forming a positive ion (the molecular ion). The mass spectrometer detects the charge to mass ratio (m/z) of the ion to find the molecular mass of the compound.
What is the M+ peak and what does it show?
The M+ peak is the molecular ion peak, which is the further clear peak to the right, showing the molecular mass of the molecular mass of a compound.
What is the M+1 peak and why does it exist?
The M+1 peak is a small peak after the molecular ion peak, created from the 1.1% of carbon which exists as carbon-13, which has a higher molecular mass by 1, increasing the m/z.
How are fragment ions created and what do they show?
When the molecule passes through the mass spectra it often breaks appart creating fragment ions, these fragment ions are useful as they can show more about the molecules structure.
What fragment ion has a m/z of 15?
CH3+
What fragment ion has a m/z of 29?
C2H5+
