Carboxylic Acids and Derivatives
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What is the functional group of a carboxylic acid?
COOH
How is a carboxylic acid named?
Suffix -oic acid.
Describe the physical properties of carboxylic acids.
Can form hydrogen bonds with water. Carboxylic acids up to and including 4 carbons are completely soluble in water. High melting points Ethanoic acid smells like vinegar
What are esters derived from?
Carboxylic acids.
Functional group of an ester?
COO
Describe the properties of esters.
Short chain esters are fairly volatile and have pleasant fruity smells. Esters used in flavourings and perfumes. Used as solvents and plasticisers. Fats and oils are esters Low boiling points
How is the carboxylic acid functional group polarised?
The slightly positive C is open to attack from nucleophiles. The slightly negative O of the C=O may be attacked by H+ The slightly positive H may be lost as H+ (in this case the compound is acting as an acid)
If the H of the O-H group is lost in a carboxylic acid, what is formed.
Carboxylate ion
How are esters formed?
Carboxylic acids react with alcohols to form an ester and water. The reaction is speeded up by a strong acid catalyst. This is esterification. This is done under reflux.
What is the non-systematic name of propane-1,2,3-triol?
Glycerol
What is the difference between fats and oils?
Oils are liquids at room temperature and are unsaturated. Fats are solids at room temperature and they are saturated.
How can you hydrolyse oils/fats?
Boiling with NaOH. The products are glycerol and a mixture of sodium salts.
What are the carboxylate salts used as?
Soaps and cleaning products
Describe glycerol.
Alcohol so forms hydrogen bonds so soluble in water. Used as a solvent in many medicines. Used as a solvent in food colourings. Used to plasticise materials making the material flexible and smooth. Attracts water so is used to prevent ointments and creams from drying out.
What is common between all acid derivatives?
All have a C=O group.
List alcohols, water, primary amines and ammonia in order of most to least reactive.
Primary amine > Ammonia > Alcohol > Water
Describe the mechanism for forming a carboxylic acid from an acyl chloride.
1) Arrow from lone pair on oxygen of water molecule to carbon (in C=O). 2) Arrow from carbon (in C=O) to O. 3) Arrow from lone pair of O to C-O bond. 3) Arrow from C-Cl bond to Cl. 4) Arrow from H (in H2O) to O.
What are the advantages of ethanoic anhydride over ethanoyl chloride as an acylating agent?
Cheaper Less corrosive Less vulnerable to hydrolysis Safer - byproduct is ethanoic acid rather than hydrogen chloride (harmful fumes). Ethanoyl chloride is dangerous to use
How are carboxylic acids formed from alcohols?
Oxidation under reflux
Describe carboxylic acids as acids.
Weak acids that slightly dissociate when in solution forming a H+ ion and a carboxylate ion.
What is formed when a carboxylic acid reacts with carbonates?
CO2 + H2O + Carboxylate ion
What is ester hydrolysis?
Reverse reaction to esterification. Converting esters back into carboxylic acids and alcohols using water.
What is formed when an ester reacts with a base?
A carboxylate salt and an alcohol
What is the production of a carboxylate salt called?
Saponification