5 Alcohol

ALCOHOL

The Alcohol Family1. One of member of homologous series which contain carbon,

hydrogen and oxygen.

2. General formula for alcohol is CnH2n+1OH. [n=1,2,3..]

3. Alcohol contains the hydroxyl group, -OH as their functional group. [notes: not hydroxide ion, OH- , alcohol not is alkaly ]

4. Alcohol is neutral compound.

5. Alcohol are named by replacing -e for alkane with –ol.

1

6. Structural formula and molecule for few alcohol.

n Name Mr Molekul Formula

Structural formula

1 Methanol12+3+16+1= 32

CH3OH@

CH4O

H |H— C — OH | H

2Ethanol

very important

12x2 + 5 +16 + 1 =

46

C2H5OH@

C2H6O

H H | |H— C — C — OH | | H H

3Propan-1-

ol60 C3H7OH

H H H | | |H — C— C — C — OH | | | H H H

4Butan-1-

ol74 C4H9OH

5Pentan-1-ol

88 C5H11OH

6Hexan-1-ol

102 C6H13OH

2

Q: Give names for this alcohol.

OH

CH3 CH2 CH CH2 CH2 CH3

Formula: C6H13OH

Name : HEXAN-3-OL

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Naming Alcohol 1. Find the longest continous carbon chain containing –OH.2. Number the carbon beginning at the end nearer to the – OH,

write the number in front of the ending –ol. 3. Locate the alkyl group (branch chain), give number to the

carbon and named the alkyl group. Put the number in front of the group. CH3 : methyl

C2H5 atau CH2CH3 : ethyl C3H7 atau CH2CH2CH3 : propyl

4. Complete the name for the alcohol

(ii)

OH

CH3 CH2 C CH2 CH2 CH3 | CH3

Formula: C7H15OHName : 3-methyl hexan-3-ol

4

(iii)

OH

CH3 CH2 CH CH CH2 CH3 | CH3

Formula : C7H15OHName : 4-methyl hexan-3-ol

(iii)

OH

CH3 CH CH CH CH2 CH2 | | | CH3 CH3 CH3

Formula : C9H19OHName : 2, 4 – dimethyl heptan-3-ol

5

(iv)

C2H5 OH

CH3 CH2 CH CH2 CH CH2 ─ CH3

Formula : C9H19OHName : 5-ethyl heptan-3-ol

Physical Properties1. Liquid at room temperature. (pg. 62) [ no gas]2. Simple alcohol are very soluble in water, infinite solubility. Methanol, ethanol dan propan-1-ol is miscible in all proportions (terlarut campur dengan air dalam semua kadaran). The rest of the alcohol less soluble or insoluble.

Isomerism Similar to alkenes, isomerism in alcohol results from the

branching of the carbon chain and the different location of the hydroxyl group.

You only have to know the isomerism in propanol dan butanol.

Q : Draw 2 isomers for propanol and 4 isomers for butanol, and dan named the isomers.

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Propanol

Butanol

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Propanol

H H H │ │ │H ─ C ─ C ─ C ─ OH │ │ │ H H H

H H H │ │ │H ─ C ─ C ─ C ─ H │ │ │ H OH H

Molecular formula: C3H7OH

Name: Propan-1-ol

Molecular formula: C3H7OH

Name: Propan-2-ol

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Butanol

9

Molecular formula: C4H9OH

Name: Butan-1-ol

Molecular formula: C4H9OH

Name: Butan-2-ol

H H H H │ │ │ │H ─ C ─ C ─ C ─ C ─ OH │ │ │ │ H H H H

H H H H │ │ │ │H ─ C ─ C ─ C ─ C ─ H │ │ │ │ H H OH H

H H H │ │ │H ─ C ─── C ─── C ─ OH │ │ │ H H─C─H H │ H

Molecular formula: C4H9OH

Name: 2-methylpropan-1-ol

H OH H │ │ │H ─ C ─── C ─── C ─ H │ │ │ H H─C─H H │ H

Molecular formula: C4H9OH

Name: 2-methylpropan-2-ol

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ETHANOL1. Preparation of ethanol.

i. Laboratory preparation (fermentation)ii. Industrial production (hydration process)

Making Ethanol Fermentation1. Two stages;

i. Fermentation ii. Purification

- through fractional distillation at 78 oC ( boiling point of ETHANOL)

Fermentation of Glucose1. Yeast is added to sugar or starch.

2. Anaerobic process ( takes place in the absence of oxygen).

3. Yeast releases enzymes. These enzymes break down the sugars/starch into glucose, C6H12O6.

4. Zymase slowly decomposes the glucose to form ethanol and carbon dioxide.

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Zymase @ C2H5OH @ C2H6O C6H12O6 (aq) 2CH3CH2OH (l) + 2CO2 (g)

30 oC

When the concentration of ethanol reach 15%, the yeast dies.

Q: How to produce pure alcohol?

A: Purified the ethanol through fractional distillation.

Purification of Ethanol1. Ethanol produced from the fermentation process is impure,

because its mix with the glucose solution.

Q : Draw labeled diagram to carry out the purification of ethanol through fractional distillation process.

Delivery tube

Lime water

Beaker

Glucose + yeast

Conical flask

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Q: Why the solution/filtrate in rounded conical must heated at 78oC.

A: The boiling point of ethanol is 78 oC.

Q: Ethanol produced may still contains of some water. What should be done to be sure that ethanol is 100% pure?

A: Anhydrous calcium oxide or anhydrous calcium chloride is add/put into the ethanol.

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Thermometer

Fractioning collum

Liebig condenser

Water in

Water out

Product from fermentation Porcelain

chips

Retort stand with clamp

Distillate (Ethanol)

Bunsen burner

Rounded conical

Water

Wire gauge

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Q: What is the function of;- thermometer- porcelain chips- Liebig condenser

A: thermometer is used to ensure that temperature is always at 78 oC.

B: Porcelain chips is used to avoid the solution jumped/ effervesence (breaking bubbles)

C: To cooled the ethanol vapour to become liquid.

Q: Named the process in Liebig condenser.

A: Condensation

Q: What is the properties of ethanol

A: Properties;- colourless- volatile- good organic solvent- miscible with water- highly flammable- antiseptic- chemically reactive

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Q: What is the uses of ethanol

A: Uses;- 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.

Industrial production of ethanol

Ethene is mix with steam is passed through concentratedphosphoric acid (catalyst) at 300 oC (temperature) and 60 atmosphere (pressure).

H3PO4 @ C2H4 concentrsted C2H5OH CH2 = CH2 + H2O —————→ CH3CH2OH

300 o C, 60 atm

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Chemical Properties

1. Combustion

i. Alcohol are very flammable sustances. ii. Ethanol burns with non-smoky and blue flame and releases lot of heat. Suitable for use as fuel, described as clean fuel.

Q: Write combustion equation for hexanol

2. Oxidationi. Ethanol can be oxidised into ethanoic acid by an oxidising agent.

[Ethanoic acid is a family of carboxilic acids]

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C2H5OH + 3O2 2CO2 + 3H2O Ethanol Oxygen Carbon Water dioxide

C6H13OH + 9O2 6CO2 + 7H2O hexanol Oxygen Carbon Water dioxide

CH3CH2OH + 2[O] CH3COOH + H2O Etanol Ethanoic acid

Q: Show the structural formula for the equation above.

Q: Named 2 solutions are commonly used as oxidising agent.

(i) Acidified potassium manganate(VII), KMnO4 (purple to colourless / decolourised)

(ii) Acidified potassium dichromate(VI), K2Cr2O7 (orange to green)

Q: Draw a labeled diagram for the process.

H H H O | | | ║ H — C — C — OH + 2[O] → H — C — C — OH + H2O | | | H H H

Heat

Ethanol + potassium dikromat(VI) + dilute sulfuric acid

Cold water

Distillate (ethanoic acid)

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Distillate (ethanoic acid)

- Colourless- Vinegar smell - Blue litmus paper turns red (acidic properties)

3. Dehydration

ALCOHOL → ALKENE

1. Converted ethanol into ethene and a molecule of water.

2. The elimination of water results the formation of a carbon-carbon double bond.

3. Dehydration occur when a. ethanol vapours is passed over a heated catalyst such as.

i- Porous pot / porcelain chipsii- Purnice stone / aluminium oxide, Al2O3 /alumina

b. Ethanol is heated under reflux at 170 oC with excess concentrated sulphuric acid.

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CH3CH2OH CH2 = CH2 + H2O Ethanol Ethene

- H2O

Q : Draw the structural molecule for the process

Q : Draw labeled diagram.

Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.com

Heat

Glass wool soaked with ethanol

Heat

Ethene gas

Water

Porcelain chips

Retort stand with clamp

Test tube

Delivery tube

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H H H H | | | | H — C — C — H → H — C ═ C — H + H2O | | H OH