REACTIONS OF ALCOHOLS C 2 7 Alcohols Carboxylic
REACTIONS OF ALCOHOLS C 2. 7 Alcohols & Carboxylic Acids
MAKING ALCOHOLS RECAP The hydration of ethane: CH 2 =CH 2(g) + H 2 O (g) ⇄ CH 3 CH 2 OH (g) Conditions: 300 o C, 60 -70 atmospheres, phosphoric acid catalyst. Fermentation (e. g. glucose): C 6 H 12 O 6 2 C 2 H 5 OH + 2 CO 2 Conditions: 35 o C, yeast, no oxygen
DEHYDRATION REACTIONS Dehydration reaction: This type of reaction is an elimination reaction in which water is formed as a product. For alcohols the dehydration results in the formation of an alkene. The acid catalysts normally used are either concentrated sulphuric acid (H 2 SO 4 ) or concentrated phosphoric acid (H 3 PO 4 ). One alternative, non-acidic, catalyst could be aluminium oxide (Al 2 O 3 ) Usually some heat is also required. Around 180 o C CH 3 CH 2 OH Al 2 O 3 180°C CH 3 CH=CH 2+ H 2 O
KNOWLEDGE CHECK 1. Write an equation for the dehydration of ethanol to give ethene. 2. Write an equation for the dehydration of cyclohexanol to give cyclohexene 3. Predict the three possible isomers formed in the dehydration of butan-2 -ol (Hint: E/Z isomers) 4. State the necessary conditions for each reaction.
ALCOHOL OXIDATION REACTIONS Oxidising agents are used to oxidise alcohols In reactions the oxidising agent is given the symbol [O]. The most common oxidising agent is acidified potassium dichromate (K 2 Cr 2 O 7 and H 2 SO 4 ) The oxidation also requires heat.
ALCOHOL OXIDATION REACTIONS Primary alcohol + [O] Aldehyde + [O] Carboxylic acid ORANGE GREEN Secondary alcohol + [O] Ketone ORANGE GREEN Tertiary alcohol + [O] NO REACTION ORANGE
ALDEHYDES In aldehydes, the C=O group will appear at the end of the carbon chain. RCHO They have the suffix ‘-al’. No numbering is needed as it will always be on the first carbon atom.
KETONES In ketones, the C=O group will appear in the middle of the carbon chain. Ketones have the suffix ‘-one’ RCOR If there are 5 or more carbon atoms in the chain you will always have to say where the carbonyl group is in the chain.
KNOWLEDGE CHECK Complete the worksheet on the reactions of alcohols.
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