LEARNING OUTCOMES

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LEARNING OUTCOMES

• Explain the reactions of alcohol with reference
  to
• Oxidation with KMnO4/H, K2Cr2O7/H, CrO3/H and
  PCC/CH2Cl2
• Explain the identification tests to distinguish
  classes of alcohols
• Lucas reagent, i.e. concentrated HCl/ZnCl2
  (between 1?, 2? and 3? alcohol )
• KMnO4/H or K2Cr2O7 /H (between 1? and 3?, and
  2? and 3? alcohols)
• Explain iodoform test, i.e. I2/NaOH(aq) to
  identify methyl alcohol group.

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Oxidation reaction of alcohol

• Oxidation of methanol (simplest alcohol) using
  KMnO4 and K2Cr2O7 can produce methanoic acid
  (carboxylic acid), CO2 and water.
• - Oxidation methanol using PCC can produce
  methanal (an aldehyde)

Video 1
3

• The reagant commonly used are KMnO4, K2Cr2O7 (as
  a strong agents) give carboxylic acid and PCC as
  a weak agent give an aldehyde.

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(No Transcript)
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Example
O CH3CH
PCC/CH2Cl2
1
aldehyde
6
Example
KMnO4/H,?
1
carboxylic acid

• Observation purple colour solution turns to
  colourless

Video 2
7
KMnO4/H,?
CH3CHCH3
2

• Observation purple colour solution decolourised

8
KMnO4/H,?
3

• Observation purple colour solution remains

9
Identification tests to distinguish classes of
alcohols

• Lucas reagent, i.e. concentrated HCl/ZnCl2
  (between 1?, 2? and 3? alcohol )
• KMnO4/H or K2Cr2O7 /H
• (between 1? and 3?, and 2? and 3? alcohols)
• refer to oxidation reaction of alcohol.

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Lucas Test to classify alcohols

• Lucas Reagent a mixture of concentrated HCl and
  zinc chloride (HCl/ZnCl2)
• primary alcohol does not turn cloudy
• secondary alcohol - the solution turn cloudy
  within 5 minutes
• tertiary - the solution turn cloudy immediately

Video 3
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Example
does not turn cloudy
No observable change

• Observation solution does not turns cloudy

12
Cl
Turn cloudy within 5 minute

• Observation solution turns cloudy within 5
  minutes

13
Cl
turn cloudy immediately

• Observation solution turns cloudy immediately

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Oxidation reaction to classify alcohol
K2Cr2O4/H,?
1

• Observation orange colour solution turns to
  green.

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K2Cr2O4/H,?
CH3CHCH3
2

• Observation orange colour solution turns to green

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K2Cr2O4/H,?
No observable change
3

• Observation orange colour solution remains

17
Haloform Reaction

• Methyl carbinol cleavage to give Carboxylic acids
  and Haloform

H
X2
, H

H
C
OH
HCX
CH
C
H
3
3
OH-
O
OH
H
X2
, H

HCX
C
OH
R
CH
C
R
3
3
OH-
O
OH
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IODOFORM TEST
OH
base (OH-)
CH3CH2CCH3 3I2 2-butanol
CH3CH2COO- CHI3? yellow
precipitate (iodoform)

• Observation yellow precipitate formed