Organic Analysis Flashcards
(14 cards)
What happens during mass spectrometry
A beam of electrons is fired at the alkane which causes it to loos an electron
What is the m/z ratio
It tells us the ration between mass an charge,
However almost every molecular ion has a 1+ charge so it basically tells us the mass of the molecular ion
What is the M+1 peak
A little peak to the right of the M+ peak that is due to the presence of the isotope carbon-13
(ignore it)
Why is bond vibration important for infrared spectroscopy
Stronger bonds vibrate faster than weaker bonds,
These vibrating bonds can absorb radiation which has the same frequency as the bond vibration
What type of radiation do organic molecules absorb
Infrared
What happens if you pass infrared radiation through an organic molecule sample
The bonds will absorb specific frequencies and you can produce an absorption spectrum
What is the fingerprint region
A complex series of peaks that are specific to the molecule being studied, from 1500–>
How do you test for an alkene
Shaken with bromine water, an addition reaction will take place and the orange solution will decolourise
How do you test for an alcohol
Add an oxidising agent (acidified potassium dichromate solution) and shake well, then place in a water bath for a few minutes
If primary or secondary alcohols are present it will change from orange to green, if tertiary then nothing will happen
How do you test for an alcohol with metal
Add a small piece of metallic sodium to alcohol, it produced hydrogen gas which is shown by the squeaky pop test
How do you test for an aldehyde with Fehlings
Fehling’s solution contains copper (II) ions which when warmed with an aldehyde it is oxidised to a carboxylic acid and the Cu2+ ions are reduced to Cu+ ions
The clear blue solution turns opaque due to the formation of a red precipitate (Copper (I) oxide)
Ketones cannot be oxidised so give a negative test when warmed with Fehling’s
How to test for an aldehyde with Tollens
It is an aqueous alkaline solution of silver nitrate in excess ammonia solution
When warmed with an aldehyde it is oxidised to a carboxylic acid and the Ag+ ions are reduced to Ag atoms
Which form a silver mirror on the inside of the tube
How do you test for a carboxylic acid
Mix sodium carbonate with the carboxylic acid
Collect the gas produced and bubble through limewater, it will turn cloudy if a carboxylic acid is present
How do you test for a halogenoalkane
Warm with sodium hydroxide solution
Acidify with dilute nitric acid and then add silver nitrate solution
A silver halogen precipitate will then form
