Carboxylic Acids Flashcards
Nomenclature - ending
-anoic acid
Nomenclature - what do you count from
The C on COOH
What is the functional group
COOH
Neutral or charged
Neutral
Describe how boiling points change with increased size and branching
INCREASE AS SIZE INCREASES
- No change in hydrogen bonding
- increase in LDF give higher boiling points
HIGHER IF CHAIN IS STRAIGHT, NOT BRANCHED
- Branched chains have less surface area contact between molecules
- Fewer LDF
Describe how solubility changes with increase length
INCREASED LENGTH MEANS LOWER SOLUBILITY
- Due to longer hydrocarbon ‘tails’ getting between water molecules and carboxylic acid.
- Breaks the hydrogen bonds needed for solubility
- Stronger hydrogen bonds are replaces by weaker LDF
What are carboxylic acids soluble in and what can smaller carboxylic acids dissolve in
Dissolve in organic solvents and water
Small ones dissolve in cold water
Test for carboxylic acids
What is used?
What is positive?
Sodium bicarbonate
Fizzing occurs
Name the ways in which a carboxylic acid can be produced
Oxidation
Hydrolysis of nitriles —> Acid or Alkaline
Acyl chlorides and water
Ester hydrolysis - acidic
Equation for oxidation to produce carboxylic acids
ROH + [O] —> RCHO ~ ALDEHYDE
RCHO + [O] —> RCOOH ~ CARBOXYLIC ACID
How many times does a primary alcohol need to be oxidised to form a carboxylic acid
Twice
First to aldehyde and then carboxylic acid
Conditions for oxidation
Potassium dichromate(VI) and dilute sulfuric acid
Heated under reflux
What shows oxidation has occurred
A colour change from orange —> green
What happens to bonds during hydrolysis of nitriles to produce COOH
What is the nitrile functional group
Functional group: CN
The CN bond breaks.
The carbon atom remains part of the organic product.
The nitrogen atom becomes either ammonia or the ammonium ion.
Acid hydrolysis of nitriles to produce carboxylic acid equation
RCN + H+ + H2O —> RCOOH + NH4+
Alkaline hydrolysis of nitriles to produce carboxylic acids
1st and 2nd step required
Conditions for the second step
RCN + OH- + H2O —> RCOO- + NH3
1st step creates a carbonate ion and ammonia
Dilute acid is now added to the ion.
RCOO- + H+ —> RCOOH
Second step forms carboxylic acid
Acyl chloride and cold water to produce carboxylic acids equation
How does the product appear?
RCOCl + H2O —> RCOOH + HCl
White misty fumes of HCl gas are produced.
Mechanism for Acyl chlorides and water forming COOH
Check on oneNote
Equation for ester hydrolysis - acidic
What is different about this reaction
R1COOR2 + H2O <—> R1COOH + R2OH
It is reversible
Conditions for ester hydrolysis to form COOH
Done under reflux in dilute HCl or H2SO4 (catalyst)
Name the reactions Carboxylic acids can do
Reduction
Halogenation
Salt formation
Esterification
Reduction of COOH equation
RCOOH + 4[H] —> ROH + H2O
Carboxylic acid + hydrogen —> alcohol + water
Reduction of COOH conditions
LiAlH reagent is used in dry ether
Can carboxylic acids be reduced to aldehydes
NO
Only alcohols
Equation for the halogenation of carboxylic acids
List products
RCOOH + PCl5 —> RCOCl + POCl3 + HCl
Forms acyl chloride and phosphorus trichloride oxide.
Misty fumes visible due to HCl product
Conditions for the halogenation of COOH
PCl5 is used as a reagent
Must be anhydrous conditions as both the reagent and acyl chloride react with water.
How can POCl3 and the acyl chloride be separated
Fractional distillation
Salt formation from COOH equation
RCOOH + NaOH —> RCOO- Na+ + H2O
Conditions or reagent used
Aqueous alkali and complete neutralisation produces COOH
E.g. NaOH
Esterification of COOH equation
What is important about this equation
R1COOH + R2OH <—> R1COOR2 + H2O
It is reversible
The opposite produces carboxylic acids!
What is required for the esterification of carboxylic acids
An acid catalyst
Salts of carboxylic acids functional group
COO-
Nomenclature - ending for salts of carboxylic acids
What is placed in front
-oate
The metals name
What must be remembered about the displayed structure for the COO and Na bond
Why is this the case
It is shown as COO- Na+ with no bond drawn.
It is ionic bonding not covalent
