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Measure the amount of starting reactants that become useful products.
Condensation reactions:
atom economy: <100%
Two molecules join together to create a larger molecule and a small molecule is eliminated.
rearrangement and addition reactions:
atom economy: always 100% (no molecules are lost in the reaction)
Substitution reactions:
atom economy: <100%
one functional group is 'swapped' for another, meaning there will always be a small, unwanted molecule left over.
Elimination reactions:
atom economy: <100%
Atoms are removed from a molecule - for example, dehydration of an alcohol.
rearrangement & addition > substitution & condensation > elimination
Infra-red light is shone through a material. Some wavelengths are absorbed in the material, and these show as troughs on a graph of absorption against wavenumber (the inverse of wavelength)
Only certain wavelengths of infra-red light are absorbed. This is because the wavelengths that are absorbed cause the bonds between certain atoms, such as carbon and hydrogen, to be raised quantized energy levels and vibrate more. This energy corresponds to the frequency of the light absorbed, so only some frequencies of light can be absorbed by a particular bond.
The scale usually reads from 4000 to 0. The region from around 1500-0 is called the fingerprint region, and unique for each molecule - this can tell you precisely what the molecule being tested is, by comparing the fingerprint region to a database of fingerprint regions for different molecules.
A technique used by chemists to determine the structure of molecules.
Process
A sample is vapourized and enters the mass spectrometer via the sample inlet.
In the first chamber, it is ionized by a stream of electrons, so it becomes positively charged.
In the second chamber, the ions are accelerated to the negative plate at the other end of the chamber so they have the same kinetic energy.
In the third chamber, the ions race each other across a vacuumed space, whereupon they reach the detector. Smaller ions travel faster, so this enables the Mr of the ion to be calculated.
Question: Why is the space a vacuum?
Fragmentation
Separates mixtures of molecules.
Can also be used to identify various substances.
1) draw a thin pencil line about 2cm away from the bottom of the chromatography plate.
2) add a small drop of mixture to the baseline, numbering each one to avoid confusion.
3) place in a solvent, making sure the solvent doesn't reach the base line.
4) rest the beaker in a place of quiet and peace and calm, and wait until the solvent has climbed to almost the top of the paper.
5) remove the plate from the solvent and make a thin pencil line to show where the solvent has reached.
6) spray some identifier spray to see the separated mixture: mark where each one has travelled to.
7) you can calculate the Rf value and compare it to a database value to help identify the chemical.