alcohols
DESCRIPTION
chemistry spmTRANSCRIPT
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ALCOHOLS
• -non-hydrocarbons• Contain hydroxyl group (-OH)• Can derived from an alkene• General formula: CnH2n+1OH
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NAMING ALCOHOLS
1. Obtain the name of alkane2. Replace the ending –e from alkane with –ol3. Example: methane : methanol
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Draw:1. Ethanol2. Propan-1-ol3. Butan-1-ol4. Butan-2-ol
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ISOMERS OF ALCOHOL
Draw the isomers and name these alcohols:• C3H7OH (2 isomers)
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• C4H9OH (4 isomers)
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INDUSTRIAL PRODUCTION OF ETHANOL
1. By fermentation- Yeast is added to sugar or starch and left in a warm place for
several days in the absence of oxygen (anaerobic)
C6H12O6 2 CH3CH2OH + 2 CO2
Glucose Ethanol + carbon dioxide
Temperature : 18-200CCatalyst : zymase from yeastOther condition: Absence of oxygen
*ethanol then purified by fractional distillation
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2. By hydration
ethene + water ethanolCH2=CH2 + H2O CH3CH2OH
temperature : 3000Cpressure :60 atmCatalyst : phosphoric acid
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PHYSICAL PROPERTIES OF ALCOHOLS
• Liquid at room condition• Colourless• Has a sharp smell• Completely miscible in water• Low boiling point• Highly volatile
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CHEMICAL PROPERTIES OF ETHANOL1. Combustion
- Complete combustion, produce carbon dioxide and water- C2H5OH + 3 O2 2 CO2 + 3 H2O
2. Oxidation- Alcohols can easily oxidised to carboxylic acids, (-COOH group) with presence of
oxidising agents such as acidified potassium dichromate (VI) solution and acidified potassium manganate (VII) solution
- acidified potassium dichromate (VI) solution: orange to green- acidified potassium manganate (VII) solution: purple to colourless
CH3CH2OH + 2[O] CH3COOH + H2O
3. Dehydration- Involve removal of water- Ethanol ethene + water (draw!!)- Two methods to carry out :
(a) Ethanol is passed over a heated catalyst such as unglazed porcelain chips, porous pot, pumice stone, or aluminium oxide
(b) Ethanol is heated under reflux at 1700C with excess concentrated sulphuric acid
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USES OF ALCOHOLS
• As a solvent in perfumes/cosmetics• As a thinner in varnish, ink• As a cleaner for compact disc.• As a fuel for transport• As a raw material for the manufacture of
vinegar,• As a raw material to make industrial product
such as antiseptic and cough syrup.
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CARBOXYLIC ACIDS
• General formula: CnH2n+1COOH• -COOH group is called carboxyl group as the
functional group of carboxylic acid• Naming for carboxylic acid:
~anol change to ~anoic acidExample: methanol : methanoic acid
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STRUCTURAL FORMULA
• Draw the structural formula for:– Methanoic acid
– Ethanoic acid
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• Propanoic acid
• Butanoic acid
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• 2-methylpropanoic acid
• 3-methylpentanoic acid
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Preparation of ethanoic acid
• Heating the mixture of ethanol and acidified potassium dichromate (VI), K2Cr2O7 under reflux (oxidation reaction)
• C2H5OH + 2[O] CH3COOH + H2OEthanol ethanoic acid
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Physical Properties of Ethanoic Acid
• Colourless liquid at room temperature• Has a sharp and pungent smell• High melting and boiling point compare to
other covalent• Soluble in water• Changes the moist blue litmus paper to red• Has a pH of 3-4 (weak acid)
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Chemical Properties of Ethanoic Acid
• Ethanoic acid is a weak acid. Ethanoic acid can ionized partially in water to produce low concentration of hydrogen ion, H+
• Weak monoprotic acid• Ethanoic acid can react with:– Base– Metal carbonate– Metal– Alcohol
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i) REACTION OF ETHANOIC ACID WITH A BASE (neutralization)
CH3COOH + NaOH CH3COONa
ethanoic acid sodium ethanoate
ii) REACTION OF ETHANOIC ACID WITH METAL CARBONATE
CH3COOH + CaCO3 (CH3COO)2Ca + H2O + CO2
ethanoic acid calcium ethanoate
ii) REACTION OF ETHANOIC ACID WITH METAL
CH3COOH + Mg (CH3COO)2Mg + H2
ethanoic acid magnesium ethanoate
Iv) REACTION OF ETHANOIC ACID WITH ALCOHOL (esterification)CH3COOH + c2H5OH CH3COOC2H5 + H2
ethanoic acid ethyl ethanoate
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USES OF CARBOXYLIC ACIDS• Carboxylic acid widely found in nature
Ethanoic acid (acetic acid) : VinegarMethanoic acid : AntsPropanoic acid : MilkButanoic acid : ButterLactic acid : Sour milk
• Uses of carboxylic acidi- make food flavouringii- preserve foodiii- manufacture foods such as vinegar and yogurtiv- manufacture of soft drinks
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34ETHANOIC ACID,CH3COOH
Sodium ethanoate,CH3COONa
+Hydrogen, H2
Iron (III) ethanoate,
Fe(CH3COO)3
+Carbon dioxide,
CO2
+ Water, H2O
Calcium ethanoate,Ca(CH3COO)2
+ Water, H2O
Methyl ethanoate, CH3COOCH3
+Water, H2O
Base, Ca(OH)2
Metal, Na
Alcohol, CH3OH
Metal carbonate, Fe2(CO3)3