Carboxylic Acids

Question 1

General Formula

Answer 1

CnH2nO2

Question 2

Functional Group

Answer 2

Carboxyl
-COOH

Question 3

Name with/without double bonds

Answer 3

-anoic
-enoic

Question 4

Properties

Answer 4

sharp irritating odour
short chain = liquids
short chain = soluble in water
WEAK acids

Question 5

Formation from oxidation of Primary Alcohls/aldehydes

Answer 5

primary alcohols undergo prolonged mild oxidation
oxidised first to aldehydes then to carb acids

o agent usually acidified potassium dichromate

Question 6

Formation of CA from Hydrolysis of Esters

Answer 6

acidcatalysed hydrolysis - acid and alcohol produced
ester heated under reflux w/ dilute HCl

base catalysed hydrolysis - salt of acid and alcohol produced
ester heatedunder reflux w/ NaOH solution

CA could be regenerated by adding dilute mineral acid to salt

Question 7

Formation from Hydrolysis of Nitriles

Answer 7

acid or base

first stage: formation of amide (-CONH2)
second stage: formation of acid with removal of ammonia

Acid-Catalysed: CA and ammonium salt of acid
Base Catalysed: salt of CA and Ammonia

Question 8

Reaction of OH group with PCl5

Answer 8

RCOOH + PCl5 -> RCOCl + POCl3 + HCl (g)

misty fumes, vigorous, heat produced

identity hcl confirmed with conc ammonia on glass rod

Question 9

Esterification of OH group

Answer 9

• COO

condensation products of CA react w/ alcohol

RCOOH +R1OH -> RCOOR1 + H2O

R=alkyl group

Question 10

Reaction w/ Sodium Carbonate as a Weak Acid

Answer 10

forms salt, CO2 and H2O

bubbles of gas produced, solid Na2CO3 disappears
2CH3COOH +NaCO3 -> 2CH3COONa + CO2 + H2O

Question 11

Reaction w/ Sodium Hydroxide as a Weak Acid

Answer 11

release heat, no other obsv
all solutions colourless

CH3CH2COOH + NaOH -> CH3CH2COONa + H2O

Question 12

Reaction w/ Ammonia as a Weak Acid

Answer 12

form sol of ammonium salt and heat released
all solutions colourless

CH3COOH + NH3 -> NH3COONH4

no suitable indicator - pH meter used

Question 13

Reduction Reaction of CA

Answer 13

heating under reflux with LiAlH4 in dry ether

Aldehyde can be distilled off if required

CH3COOH + 2[H] -> CH3CHO + H2O

CH3CH2COOH + 4[H] -> CH3CH2CH2OH + H2O

Question 14

Preperation from Primary Alcohol

Answer 14

-add water and conc H2SO4 to pear shaped flask
-swirl solution and cool flask
-add potassium dichromate
-add anti-bump granules
-add the alcohol slowly with a vertical condenser in place and cool the reaction vessel in a water bath
-heat the mixture under reflux
-distil off acid