Alcohols
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What is a biofuel?
Any fuel made from living organisms or their waste
How is bioethanol made?
Photosynthesis, fermentation and then it is combusted/used
What does carbon neutral mean?
No net annual emissions of carbon dioxide
Problems with biofuel
• energy required at each stage of production • growing, harvesting, fermenting and separating is energy intensive • crops are dependent on environmental conditions
Suitable oxidising agents for primary and secondary alcohols
Acidified potassium or sodium dichromate
What does the oxidation of primary alcohols produce?
Aldehydes and then when oxidised further, carboxylic acids
What happens to a primary alcohol during oxidisng?
It loses two of it’s hydrogens
Conditions required for oxidising primary alcohol to produce aldehydes
• Alcohol in excess • Product is distilled off immediately to prevent further oxidising
Conditions required to produce carboxylic acids?
Excess oxidizing agent and refluxed gently
What does the oxidation of secondary alcohols produce?
Ketones
Conditions required to produce ketones
• secondary alcohols • refluxed gently • excess oxidising agent
Conditions required to oxidise tertiary alcohols
Hot concentrated nitric acids
What colour are dichromate ions?
Orange
What colour are chromium ions?
Green
How are chromium ions produced?
Reduction of dichromate ions
What group do ketones, aldehydes and carboxylic acids belong to?
Carbonyl group (c double bonded t oxygen)
Steps to Tollens’ reagent silver mirror test
• Colourless solution of silver nitrate and dilute ammonia is added to sample and is warmed gently • If aldehydes are present they will be oxidised to carboxylic acids and silver ions are reduced to silver
Steps to Fehling solution
• contains copper ions that when aldehydes is added and it is warmed, the blue colour becomes red due to copper oxide
How to test for carboxylic acids?
Add solid or solution of sodium carbonate and the solid will disappear, producing carbon dioxide bubbles.
Functional group of aldehydes
-CHO
Functional group of ketones
-COCH3