Carboxylic Acid

Question 1

Physical properties of carboxylic acid

Answer 1

Carboxylic acids contain two polarised groups
C=O and O-H
This means that the intermolecular forces that carboxylic acids experience are high and they will have relatively high melting points and boiling points
The presence of the O-H bond means that they can exhibit hydrogen bonding
Not only does this contribute to the high melting and boiling points, it also contributes to the solubility in water and other polar solvents of the shorter chained carboxylic acids
However, solubility falls as the length of the hydrocarbon chain in the carboxylic acid increases
The hydrocarbon chains are forcing their way between water molecules and so breaking hydrogen bonds between those water molecules
Carboxylic acids with more than eight carbon atoms will be solids at room temperature and are very slightly soluble in cold water, but will be more soluble in hot water

Question 2

HYDROLYSIS OF NITRILE
Acidic hydrolysis forms
Heating under reflux with acidified KMnO4 and K2CR2O7

Answer 2

Carboxylic acid + ammonium salt
Propanitrile +HCI + 2H2O —> propanoic acid + ammonium chloride salt

Question 3

HYDROLYSIS OF NITRILES
alkaline hydrolysis forms
Heating under reflux with acidified KMnO4 or K2CR2O7

Answer 3

Carboxylate salt and ammonia
Then acidification for change to carboxylic acid

Propaneitrile +NaOH +H2O —> CH3CH2CO(O-)(Na+) +NH3

acidification

CH3CH2CO(O-)(Na+) = CH3CH2COOH

Question 4

Carboxylic acid reaction with LiAlH4 reduction reaction

Answer 4

Carboxylic acid + lithium tetrahydridoaluminate (LiAlH4) in dry ether

CH3CH2COOH(l) + 2(H) —> CH3CH2CH2OH(l) + H2O (l)

Addition of water at the end will destroy any excess lithium tetrahydridoaluminate

Question 5

Carboxylic acid reaction with anhydrous condition and phosphorus (V) chloride

Answer 5

Form acyl chloride

CH3CH2COOH(l) + PCL5(S) —> CH3CH2COCl(l) +POCl3(l) +HCl (g)

HCl steamy fume

Products : propanol chloride, phosphorus trichloride oxide and hydrogen chloride

Question 6

Carboxylic acid with alcohol

Answer 6

Requirement : concentrated H2SO4 as a catalyst
Esterification

Ester is formed ((COO)

Alcohol then carboxylic acid

Question 7

ACYL CHLORIDE HYDROLYSIS forms

Answer 7

Carboxylic acid and HCL

HC3CH2COCL + H20 —> CH3CH2COOH + HCL

Question 8

ACYL CHLORIDES WITH ALCOHOL FORMS

Answer 8

Esters

CH3CH2COCL + CHECH2OH —> CH3CH2COOCH2CH3 + HCL

Propanol chloride + ethanol -> ethyl propanoate

Question 9

ACYL CHLORIDE WITH CONC AMMONIA SOLUTION

Answer 9

amide (CONH2)

Ethanoyl chloride + ammonia = Ethanamide +HCl

CH3COCL + NH3 = CH3CONH2 +HCL

Question 10

Reaction with concentrated ammonia product can react together to form

Answer 10

NH3 + HCL = NH4

Question 11

ACYL CHLORIDE REACTION WITH AMINE

Answer 11

N-substituted amide

PROPANOYL CHLORIDE + METHYLAMINE —> METHYL PROPAMIDE + HCL

CH3CH2COCL + CH3CH2 = CH3CH2CONHCH3 + HCL

Question 12

Physical properties do esters

Answer 12

Colourless and Low melting point and boiling

And insoluble to water

Question 13

HYDROLYSIS OF ESTER - ACID forms
Requirements

Answer 13

Ester = carboxylic acid and alcohol

Requirements: dilute acid (sulfuric acid) or alkali (sodium hydroxide)
Heat under reflux

Equilibrium is established/doesn’t go to completion

Question 14

HYDROLYSIS OF ESTER - ALKALINE
Forms

Answer 14

Carboxlylate salt and alcohol

Requirements: heating the ester under reflux with dilute alkali (sodium hydroxide)

Reaction is irreversible/ goes to completion

Sodium carboxlate salt requires further acidic action to turn into carboxylic acid

Question 15

Polyester

Answer 15

Formed by the reaction between dicarboxylic acid monomer no diol monomer
—> ester bond