Organic analysis
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What is the test for alkenes?
Add bromine water and shake, orange to colourless if alkene present
What is the test for haloalkenes?
Add NaOH, warm and acidify with HNO3 and add AgNO3
What are the results for halide ions with AgNO3?
AgCl = white AgBr= cream Agl= yellow precipitate
What is the effect of ammonia on silver halides?
Dilute NH3 dissolves AgCl, concentrated NH3 dissolved AgBr; AgI does not dissolve
What is the test for primary and secondary alcohols?
Add acidified K2Cr2O7 and warm, orange to green if present
Can acidified K2Cr2O7 test distinguish between primary and seconary alcohols?
No, further tests are needed
Fehling’s/Benedicts test result?
Aldehyde: blue to brick red precipitate Ketone: no change
Tollen’s reagent result?
Aldehyde forms silver mirror, ketone does not react
Test for carboxylic acids?
Add Na2CO3 and bubbles formed if present (CO2)
What is the limitation of the carboxylic acid test?
Any acid gives the positive result
What is the test for H2 gas?
Lit splint, squeaky pop
What is the test for CO2?
Bubble through limewater, turns cloudy
What is the test for O2?
Glowing splint relights
What is the test for SO2^2- ions?
Add BaCl2, white precipitate
What is the test for Co3^2- ions?
Add acid, bubbles
What is the molecular ion peak?
Peak with the largest m/z value
What does molecular ion m/z equal?
Mr of the molecule
Why are fragments useful?
Help distinguish molecules with same Mr
What are the two ionisation methods?
Electron impact and electrospray ionisation
What is the difference between electron impact and electrospray?
Electron impact produces fragments whereas electrospray doesnt and instead forms MH+
How to find Mr from electrospray?
Mr = (MH+) - 1
What is the bromine isotope ratio in Br2 spectrum?
1:2:1
What is the chlorine isotope ratio in Cl2?
9:6:1
Why is high resolution mass spectrometry useful?
Distinguishes molecules with the same Mr (to 1 d.p.)