(O) Topic 26 - Carboxyl Groups
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What does: Optically Inactive mean?
When a mixture has no effect on the direction of a plane of polarised light as it passes through the mixture. (usually means the mixture is a racemix)
What is the test for: Aldehydes? (there are 2)
• Tollens Reagent - mix organic mixture with Tollens Reagent (Ag(NH3)2NO3) and heat in a water bath. If aldehyde is present a silver mirror will form. • Fehlings solution - Add to the organic solution, mix and heat. If Aldehyde is present the blue solution will form a red precipitate. (Cu2+ -> Cu+)
what is [O]
An acidified oxidising agent such as Potassium Manganate or Potassium Dichromate. Acidified means it is part of a solution with an acid such as sulfuric acid.
what are lipids made up of?
3x fatty acids and a glycerol joined by ester bonds
Draw: Equation and Diagram for Saponification
Refer to notes for answers should include: * Lipid + 3KOH under heat and reflux produces * 3 salts of fatty acids (K+)(fatty acid) * Glyercol molecule
Draw: Equation and diagram for production of biodiesel
Refer to notes for answers should include: Lipid + 3x methanol produces (with KOH catalyst) 3 methyl esters of fatty acids and glycerol Biodiesel is a renewable fuel and potentially carbon neutral
To Practice
Nucleophilic additon with NaBH4 (aqueous conditions)
To Practice
Nucleophilic Addition with KCN (dilute acid and aqueous) • this process is very toxic (both KCN and possible formation of HCN)
To Practice
Nucleophilic Addition-Elimination on acyl chloride with nucleophiles including water, alcohols and ammonia (not primary amines, this is in later topic)
what are the two types of acylation and their mechanisms
Friedel-Crafts Acylation - Electrophilic substituion with aromatics Acylation - nucleophilic addition elimination with acyl chloride and acid anhydrides
what are the 3 ways to make esters
• acyl chloride + alcohol -> ester + HCl • Acid Anhydride + alcohol -> ester + carboxyllic acid • Carboxyllic acid + alcohol -> ester + water
Pros and Cons of esterfication with acyl chloride
Pros: occurs at room temperature, faster Cons: corrosive, often reversible, form strong HCl acid, vulnerable to hydrolysis, more expensive
Pros and Cons of esterfication with acid anhydride
pros: often irreversible, not corrosive, forms weak carboxyl acids, not vulnerable to hydrolysis, still faster then carboxylic acid cons: requires heat to speed it up, slower
Pros and Cons of esterfication with carboxyllic acid
Pros: no toxic fumes Cons: reversible, low % yield, requires sulfuric acid catalyst and heat, slow