Alcohols

Notes

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  • Created by: Georgina
  • Created on: 03-04-12 09:19

General

Alcohols have a general formula CnH2n+1OH

They are either Primary, Secondary or Tertiary.

To determine which of these the alcohol is, look at whic Carbon the OH group is bonded to.

If bonded to:

  • The first Carbon, it is Primary.
  • The Second Carbon, it is Secondary.
  • The Third Carbon, it is Tertiary.
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Hydrogen bonds in alcohols

The OH group in alcohols is polar, this means that it can form hydrogen bonds.

Because the hydrogen bonding is the strongest type of intermolecular force, it gives alcohols a high bioling point.

Alcohols have a relatively low volatility. 

Volatility is the tendency of something to evaporate into a gas.

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Making ethanol

There are 2 ways to make ethanol:

1. Hydration of ethene

  • Requires a H3PO4 catalyst
  • 300'C
  • 60atm

2. Fermentation of glucose - exothermic

  • Warm - 30'C - 40'C
  • Yeast
  • anareobic conditions
  • at 15% ethanol, the yeast dies
  • Fractional distilation is used to increase conc of ethanol
  • cheap
  • low tech
  • stll has to be purified
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Uses of alcohols

  • Alcoholic drinks
  • Solvents - Methylated spirits - Ethanol +methanol +purple dye - UNDRINKABLE
  • Fuel
  • Unleaded petrol
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Alcohols can form alkenes

BY DEHYDRATION!!

C2H5OH ---->CH2=CH2 +H2O

DEHYDRATION REACTION

  • Acid catalyst - CONC H2SO4 OR CONC H3PO4
  • 170'C
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CARBOXYLIC ACID + ETHANOL

PRODUCES ANN ESTHER!!

  • warm ethanol with a carboxylic acid and a strong acid catalyst
  • forms an esther
  • OH bond is broken by a esterification reaction.

ethanol + ethanoic acid ----------------------------->ethyl ethanoate

                                        strong acid catalyst

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Comments

Maleficent

Incorrect definition of a tertiary alcohol. It's when the -OH group is attached to a C which isn't attached to any H. Also, the -OH in a secondary alcohol doesn't have to be attached to the second carbon, it just has to be attached to a C attached to two alkyl groups, e.g. in pentan-3-ol.

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