Spectroscopy and Chromatography
- Created by: Acacia Sheppard
- Created on: 08-06-13 19:46
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- Spectroscopy and Chromatography
- UV and microwave radiation
- UV has a lot of energy so can cause homolytic fission to form free radicals
- Cl2 is split into 2Cl' (very reactive)
- Destroys the ozone: Cl'+O3-> ClO'+O2 ClO'+O3-> Cl'+2O2
- The termination step occurs when 2 free radicals combine.
- Also occurs with methane
- Destroys the ozone: Cl'+O3-> ClO'+O2 ClO'+O3-> Cl'+2O2
- Cl2 is split into 2Cl' (very reactive)
- Microwave ovens heat food by passing through the food molecules and producing an electric field
- the polar molecules try to align themselves with the field by rotating and collide with each other producing heat.
- Solids heat up less quickly than liquids as the molecules are less mobile
- Microwaves are used in the chemical industry to head substances directly, by surgeons to kill cancer cells and to dry wood.
- UV has a lot of energy so can cause homolytic fission to form free radicals
- Mass spectrometry
- The sample is bombarded with electrons to create a +ve ion
- A mass spectrum is produced, showing the relative amounts of each ion.
- The peak second from the left is the M peak (molecular mass of the sample)
- The highest peak is the base peak, caused by a particularly stable ion
- NMR spectroscopy
- Protons have spin (causing a tiny magnetic field), which is normally in random directions and so cancel each other out.
- When an external magnetic field is applied, they align either against (high energy) or with (low energy) the field.
- They can move between energy levels by emitting or absorbing radio waves.
- Protons in different environments absorb different frequencies
- They can move between energy levels by emitting or absorbing radio waves.
- When an external magnetic field is applied, they align either against (high energy) or with (low energy) the field.
- Chemical shift is measured relative to TMS (peak furthest right)
- Number of peaks = number of hydrogen environments.
- Area under peaks = ratio of hydrogen enviroments
- Peaks are split by spin-spin coupling (n+1 rule)
- This shows the number of protons the hydrogen is adjacent to
- Used in an MRI machine (safer than X rays)
- Used to test the purity of samples (each chemical has a 'fingerprint')
- Protons have spin (causing a tiny magnetic field), which is normally in random directions and so cancel each other out.
- Infrared spectroscopy
- IR is absorbed by the bonds in a molecule
- Each bond will absorb a different wavelength of IR
- Each peak represents a bond, compare to the data book for identification
- Used to track reactions in industry
- Degree of polymerisation (presence of the double bond)
- Oxygen in polymers (causes cracking)
- IR is absorbed by the bonds in a molecule
- Chromatography
- Gas Chromatography
- Stationary phase: oil mobile phase : nitrogen (HEATED)
- Detected by heat absorption, and the retention time recorded.
- Used fto check the purity of a continuous process
- HPLC
- Stationary phase: silica + carbon compounds Mobile phase: water+methanol
- Not heated, so used for chemicals with a high bp, or ones that will decompose on heating
- Detected by UV
- Used to check purity of drugs- VERY sensitive.
- Gas Chromatography
- UV and microwave radiation
- Destroys the ozone: Cl'+O3-> ClO'+O2 ClO'+O3-> Cl'+2O2
- The termination step occurs when 2 free radicals combine.
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