3.3.6 - Organic Analysis

Question 1

How do you test for an alkene?

Answer 1

Shake with bromine water.
Pos - turns colourless solution
Neg - remains orange solution

Question 2

How do you test for a haloalkane?

Answer 2

1. Dilute HNO3
2. Add AgNO3
   Pos - White/cream/yellow ppt
   Neg - no ppt
3. Confirm halide ion with adding ammonia solution (firstly dilute and then concentrated)

Question 3

How do you test for an alcohol?

Answer 3

Add acidified K2Cr2O7 and gently heat.

Primary/secondary alcohol - orange to green colour change of solution (also for aldehydes)

Question 4

How do you test for aldehydes?

Answer 4

Warm with Fehling’s solution or Tollen’s reagent

Question 5

How do you test for carboxylic acids?

Answer 5

Add NaHCO3 (aq) -> produces CO2 (g)

Question 6

Mass spectrum graph - x vs y axis labels?

Answer 6

x - m/z ratio

y - % abundance

Question 7

In infrared spectroscopy, stronger bonds vibrate at a ______ frequency and heavier atoms cause the bonds to vibrate at a ______ frequency.

Answer 7

Stronger bonds = higher frequency vibration

Heavier atoms = lower frequency vibration

Question 8

How does infrared spectroscopy work? x3

Answer 8

• Shine a beam of infrared radiation through a sample
• Bonds in sample absorb radiation of same frequency as that bond vibrates
• So spectrum that comes from sample misses frequencies of vibration that have been absorbed by those bonds

Question 9

Frequency of bond vibration units?

Answer 9

cm^-1 (wavelength)

Question 10

Infrared spectrum axes?

Answer 10

y - % transmittance

x - wavenumber/cm^-1

Question 11

Where do you find the fingerprint region on an infrared spectrum?

Answer 11

Below 1500cm^-1 wavenumbers