Alcohols

Includes:

Making and using alcohol,

Properties of alcohols

Combustion and oxidation of alcohols

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  • Created by: Charlotte
  • Created on: 23-05-11 14:49

Making Ethanol

Hydration of Ethene(http://t3.gstatic.com/images?q=tbn:ANd9GcSAQZuAGh-pPxJ7vlLZxxaZlCwQyq3V6-ooqxyl2fEgT7K9TuhYug)

  • steam
  • phosphoric acid catalyst
  • This reaction is reversible, only 5% of ethene is converted to ethanol so unreacted gases are recyled to create a 95% conversion
  • Fermentation(http://t1.gstatic.com/images?q=tbn:ANd9GcS7eqlLSv-P2k8J_Ot7ZeAcKBcIhH8YUAK8_-KkqjUQd3j0AQBH)
  • Carbohydrates (sugar/starch)
  • 37ºC(so enzyme Zymase in yeast doesn't denature)
  • anaerobic(Presence of air may produce ethanal / ethanoic acid)
  • The toxicity of alcohol limits the concentration of ethanol to approx 14%.
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Uses of Alcohols

Alcohols can be used in:

  • Alcoholic drinks such as beer, wine and spirits
  • Ethanol as fuel - It can be blended with petroleum to increase the octane rating so it burns more cleanly
  • Methylated spirits - Mixed with methanol and coloured dye for use as fuel, spirit burners, camping stoves and to remove paint or ink stains
  • Methanol is highly toxic and ingestion can lead to severe organ damage and death. It is a clean-burning fuel used as an additive in racing cars.
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Physical Properties

These are influenced by ability to make H-bonds between O-H groups.

Volatility - Decreases as chain length increases

Solubility - Decreases as chain length increases

  • Only first 3 alcohols are soluble (methanol, ethanol and propanol)

This is because as the chain length increases a larger part of the molecule is non-polar and cannot form hydrogen bonds with water molecules.

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Primary Alcohol - Distillation

In these alcohols the -OH is bonded to a carbon with 1 or 0 alkyl groups.

(http://t1.gstatic.com/images?q=tbn:ANd9GcRhboPe_uCma1uplNOS-g6x7KPYtbeHmAk29l6hBjy7eKuHW2An)

 

 

 DISTILLATION: Heated gently with acidified          

potassium dichromate to produce an ALDEHYDE

(http://t2.gstatic.com/images?q=tbn:ANd9GcTiCWNgG245KG2eKEoJL7X5skmiwd4wnNJdC_qhp01waHZJkmNb)

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Primary Alcohols - Reflux

When a primary alcohol is heated more strongly with excess acidified dichromate the alcohol is completely oxidised to form a carboxylic acid.

REFLUX

(http://t0.gstatic.com/images?q=tbn:ANd9GcSWqZrALxk9WEGnrfgTYKBs5USxuESdRdR8QPIj2TnE4LWQoy7wBA)

 

Product = Carboxylic Acid

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Secondary Alcohols

In a secondary alcohol the -OH group is bonded to a carbon that has 2 other alkyl groups.

(http://www.chemistry-drills.com/icons/19.jpg)To oxidise a secondary alcohol you must use REFLUX apparatus

(http://t2.gstatic.com/images?q=tbn:ANd9GcTBW4GpElNE_GfjHbgMULcRAxTDex--1hWDjR6tYn4rDSYgrIZulw)

The product is a KETONE!

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Tertiary Alcohols

In these alcohols the -OH group is bonded to a carbon atom with 3 other alkyl groups.

Because of this the tertiary alcohols are resistant to oxidation.

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Combustion of Alcohols

  • Plenty of oxygen needed
  • Forms carbon dioxide and water
  • Incomplete combustion can form carbon monoxide

 Combustion of ethanol with plentiful supply of oxygen...

 (http://t2.gstatic.com/images?q=tbn:ANd9GcSuciIm2YcUvOMwwdOHh5QDnfl6BVCD68c8W_SYvooPNepaof976A)

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