3.6 Organic analysis Flashcards
What is the test for alkenes?
Bromine water
Orange to colourless
What is the test for haloalkanes?
- Add aqueous NaOH
- Acidify with HNO3
- Add AgNO3
- Add dilute ammonia
- Add conc ammonia
A white cream or yellow precipitate will form if Cl, Br or I is present
AgCl will dissolve in dilute ammonia
AgBr will dissolve in conc ammonia
What is the test for 1 or 2 degree alcohols?
Add acidified K2Cr2O7
Heat
Solution will turn orange to green
What is the test for aldehydes?
Warm with feihlings or tollens solution
F - Blue solution turns to brick red ppt
T- Silver mirror forms
What is the test for a carboxylic acid?
Add Na2CO3
Effervescence as CO2 given off
What is the test for H2 gas?
Lit splint
A squeaky pop
What is the test for CO2 gas?
Bubble through lime water
Will turn cloudy
What is the test for O2 gas?
Apply a glowing splint
Splint will relight
What is the test for sulphate ions?
Add BaCl2 solution
A white precipitate will form
What is the test for halide ions?
Add HNO3 then AgNO3
Cl - white ppt
Br - cream ppt
I - yellow ppt
What is the test for CO3 2- ions?
Add any acid
Effervescence
What is infrared spectroscopy used to identify?
The functional group of an organic molecule
What kind of frequency do strong bonds have?
High frequency
What kind of frequency do weak bonds have?
Low frequency
How does infrared spectroscopy work?
Infrared energy is absorbed by bonds which makes bonds vibrate
The bonds vibrate at the same frequency as the infrared energy
Describe the process which happens in an IR spectrometer
- A beam of IR light is passed through a sample
- Some of the frequencies of the IR are absorbed, many are not absorbed so pass through
- The light that emerges on the other side is missing the frequencies that were absorbed
- A computer then plots a graph called transmittance
What are the peaks on a spectra graph called?
Absorptions
What does the absorption of a O-H (alcohol) bond look like?
Broad
Smooth
Mitten shaped
What does the absorption of a O-H (carboxylic acid) bond look like?
Broad
Jagged
Glove shaped
How does global warming occur?
The OH bonds in water, C=O bonds in CO2 and C-H bonds in methane absorb infrared radiation
The IR emitted by the earth is trapped and not allowed to escape into the atmosphere
What is the fingerprint region?
The area of the spectrum below 1500 cm-3
How can IR spectroscopy be used to confirm that a compound is definitely ethyl butanone?
Compare the fingerprint region to a known spectrum from a database, it should be an exact match
What is the peak with the largest m/z value called?
Molecular ion peak
What can you find from the molecular ion peak?
The m/z value
Why does carbon have a relative moleccular mass of 12?
12C is the standard reference
