3.3.6 - Organic analysis

Question 1

Test for primary/secondary alcohol + result

Answer 1

• Add acidified potassium dichromate (K2Cr2O7)
• Orange to green (Cr3+)

Question 2

Fehling’s test for aldehydes/ketones

Answer 2

Aldehydes = blue to brick red precipitate
Ketones remain blue

Question 3

How do you make Tollens reagent? (3)

Answer 3

1. Silver nitrate solution
2. Drops of NaOH
3. Drops of dilute ammonia

Question 4

Tollens reagent test

Answer 4

Tollens + water bath
Aldehyde = silver mirror

Question 5

Test for alkenes

Answer 5

Bromine water turns orange to colourless

Question 6

Test for carboxylic acids + result

Answer 6

• React with solid sodium carbonate
• Produces a gas that turns lime water cloudy (CO2)

Question 7

What is the last peak on a mass spectrometry graph?

Answer 7

Molecular ion peak

Question 8

What is the fingerprint region?

Answer 8

• Unique to all compounds
• Compare the IR spectra against a database of known pure compounds to identify the compound.

Question 9

Greenhouse gases (3)

Answer 9

Carbon dioxide, methane, water vapor

Question 10

3 Main ways of distinguishing between two compounds

Answer 10

1. Boiling points (Hydrogen bonding vs dipole-dipole)
2. NMR (peaks at ___PPM)
3. IR (C=O bond = 1680-1750 cm-1)

Question 11

Tests for halides + results

Answer 11

Silver nitrate
Chloride - white ppt
Bromide - cream ppt
Iodide - yellow ppt