3.9 Carboxylic Acids 1 Flashcards
Why do Esters have Lower Boiling Points than their Carboxylic Acids?
Esters do not form Hydrogen bonds
Properties of Esters?
|> Sweet Smelling Liquids (occur naturally in fruits)
|> lower boiling points than carboxylic acids
|> less soluble in water than carboxylic acids
Define: Condensation reaction
Chemical reaction in which Two Molecules are Joined together with the Elimination of a Small Molecule
Carboxylate salts of fatty acids formed from the hydrolysis of triglycerides can be used as ____ ?
Soaps
Esters occur naturally in ____ ?
Fruits
Why are Esters less soluble in water than Carboxylic Acids?
Do not form Hydrogen Bonds
What is the IUPAC name of Glycerol?
Propane-1,2,3-triol
Can Esters be formed by reacting a Carboxylic acid + Acid Anhydride?
No
Acid + Metal |> ?
Salt + Hydrogen
Define: Hydrolysis
The Breaking of a Bond using Water
Functional Group: Amides
R-C(=O)-NH₂
Acid + Carbonate |> ?
Salt + Water + Carbon Dioxide
Acid + Base |> ?
Salt + Water
Define: An Acid
A substance that donates H⁺ ions
What state is an Oil at room temperature?
Liquid
What state is a Fat at room temperature?
Solid
Functional Group: Acyl Chlorides
R-C(=O)-Cl
Why don’t Carboxylic Acids with a high Mr dissolve in water?
Have a long Carbon chain that won’t dissolve
What kind of Carboxylic Acids are Soluble in Water?
Those with a low Mr
Why are Carboxylic Acids with a low Mr soluble in water?
Hydrogen Bonding to Water Molecules
Type of Reaction: Acid + Carbonate
Neutralisation
Carboxylic Acids react to form ___ salts?
Carboxylate Salts
Carboxylate salts are ____ in water because they are ____ ?
Soluble
Ionic
Test for Carboxylic Acids?
Add Na₂CO₃
Fizz due to CO₂
Functional Group: Carboxylic Acids
R-C(=O)-OH
Can Esters be formed by reacting Acyl Chloride + Acid Anhydride?
No
Can Esters be formed by reacting Acid Anhydride + Alcohol?
Yes
Triglycerides found in Oils often contain ____ fatty acids?
Unsaturated
Define: Hydrolysis
The Breaking of a Bond using Water
Why do Carboxylic Acids have relatively High Melting Points and Boiling Points?
Form Hydrogen bonds between the Molecules
What kind of isomers are Esters & Carboxylic Acids?
Functional Group isomers
General Equation: Obtaining Carboxylic Acid from Carboxylate Salt
RCOO⁻Na⁺ + HCl |> RCOOH + NaCl
Functional Group: Acid Anhydrides
R-C(=O)-O-C(=O)-R
General Equation: Acid Anhydride + Alcohol |> Ester
(RCO)₂O + R’OH |> R-C(=O)-O-R’ + RCOOH
General Formula: Carboxylic Acid
CₙH₂ₙO₂
Type of Reaction: Acid + Base
Neutralisation
General Formula: Esters
CₙH₂ₙO₂
General Equation: Hydrolysis of Triglycerides
H-C-((H₂C-O-C(=O)-R)₂)-O-C(=O)-R + 3NaOH |>
HC-((H₂C-OH)₂)-OH + 3 RC(=O)-O⁻Na⁺
Where R is a long chain fatty acid
General Equation: Acyl Chloride + Alcohol |> Ester
R-C(=O)-Cl + R’OH |> R-C(=O)-OR’ + HCl
General Equation: Acid Hydrolysis of Esters
R-C(=O)-O-R + H₂O R-C(=O)-OH + R’OH
General Equation: Carboxylic Acid + Alcohol |> Ester
R-C(=O)-OH + R’OH |> R-C(=O)-OR’ + H₂O
Type of Reaction: Acid + Metal
Redox
General Equation: Alkaline Hydrolysis of Esters
R-C(=O)-O-R’ + NaOH R-C(=O)-O⁻Na⁺ + R’OH
Functional Group: Esters
R-C(=O)-O-R’
General Equation: Manufacture of Biodiesel
H-C-((H₂C-O-C(=O)-R)₂)-O-C(=O)-R + 3CH₃OH |(KOH)>
HC-((H₂C-OH)₂)-OH + 3 RC(=O)-O-CH₃
Where R is a long chain fatty acid
Conditions: Acid Hydrolysis of Esters
Reflux with HCl or H₂SO₄
Conditions: Alkaline Hydrolysis of Esters
Reflux with NaOH(aq) or KOH(aq)
Products: Acid Hydrolysis of Esters
Carboxylic Acid & Alcohol
Products: Alkaline Hydrolysis of Esters
Carboxylate Salt & Alcohol
Conditions: Carboxylic Acid + Alcohol |> Ester
Heat
Conditions: Acid Anhydride + Alcohol |> Ester
Gently Warm
Conditions: Acyl Chloride + Alcohol |> Ester
Room Temp
Catalyst: Carboxylic Acid + Alcohol |> Ester
Conc. Sulfuric Acid
Why do Carboxylic Acids have Higher Boiling Points than Alcohols?
Forms More Hydrogen Bonds so more Energy is required to break
How are Esters Named?
Parent Alcohol followed by Parent Carboxylic Acid
E.g. Ethanoic Acid + Methanol |> Methyl Ethanoate
To make Biodiesel, ____ ____ are reacted with ____ in the presence of a catalyst?
Vegetable Oils
Methanol
Why is Ethanoic Anhydride used instead of Ethanoyl Chloride to make Aspirin?
|> Cheaper
|> Less Corrosive
|> Safer (Doesn’t produce toxic HCl(g) )
|> Reacts less readily with water
Uses of Esters?
|> Food Flavourings
|> Perfumes
|> Solvents
|> Plasticisers
Three Methods of Preparing Esters?
Carboxylic Acid + Alcohol
Acid Anhydride + Alcohol
Acyl Chloride + Alcohol
Equation to make Aspirin from Carboxylic Acid & Acid Anhydride?
2-hydroxybenzoic Acid + Ethanoic Anhydride |>
Aspirin + Ethanoic Acid
Triglycerides found in Fats often contain ____ fatty acids?
Saturated
Conditions: Hydrolysis of Triglycerides
Reflux
Products: Hydrolysis of Triglycerides
Glycerol
Carboxylate salts of Fatty Acids
Catalyst: Manufacture of Biodiesel
KOH or NaOH
alkaline
Why does the Alkaline Hydrolysis of Esters have a Better Yield than the Acid Hydrolysis?
Is not Reversible
The reaction of a Carboxylic acid with an Alcohol to form Esters is ____ ?
Reversible
The process of making Biodiesel from Triglycerides is called ____ ?
Transesterification
Where do Triglycerides occur naturally?
Animal Fats
Vegetable Oils
Why must you use conc. Sulfuric acid in the reaction between Carboxylic acid & Alcohol to form Esters?
Weak Acid has Water in so Equilibrium would shift Left
Biodiesel is a mixture of ____ ____ of long chain carboxylic acids?
Methyl Esters
Why are Carboxylic acids Weak acids?
Only Partially Ionise in Aqueous Solution
