3.3.9 carboxylic acid and derivatives

Question 1

Carboxylic acid functional group

Answer 1

COOH

The carbon atom on the functional group is counted as part of the carbon chain
benzenecarboxylic acid (This is still often called benzoic acid).

Question 2

Physical properties of carboxylic acids

Answer 2

Can form hydrogen bonds
Up to 5C soluble in water
Higher bp and mp than alkanes
Way of identifying carboxylic acids by melting point

Question 3

Other carboxylic acids facts

Answer 3

Can be identified by specific smells (ethanoic acid as vinegar)
hexanoic and octanoic acids are caproic and capryllic acid respectively - used in goat fat - unpleasant smell

Question 4

Measuring a carboxylic acid melting points

Answer 4

put a section of a sample in a cappilary tube

Question 5

Ester functional group

Answer 5

RCOOR
- replace the H on the carboxylic acid with a r group

Derived from carboxylic acids
Hydrogen replaced by a hydrocarbon group (alkyl or aryl)
Short chains - volatile - have a fruity smell - used in flavourings and perfume ( and as solvents and plasticisers)
Fats and oils are ester with long carbon chains

Question 6

Ester naming

Answer 6

Based of the name of the parent acid
Name begins with alkyl group

Question 7

Reactivity of carboxylic acids

Answer 7

the c and the h is a delta pos the o are delta neg

C is open to attacked by nucleophiles
O may be attacked by a pos charged species
H+ may be lost - behaving as an acid

carboxylate ion is a carboxylic acid without a proton

Neg charge shared over the whole carboxylate group - delocalisation makes the resulting ions more stable
Weak acid - eq to left
Distinguished as react with NaHCO3 - release CO2

Question 8

Reactions of acids

Answer 8

Carboxylic acids are proton donors
Form ionic salts with more reactive metals
Salts general name is carboxylates

Question 9

Formation of esters

Answer 9

Carboxylic acids react with alcohols to form esters
Catalysed by a strong acid catalysts

Question 10

Hydrolysis of esters (acid catalyst)

Answer 10

Water acting as a weak nucleophile

With acid catalyst
reversible reaction
Does Not go to completion
Creates an equilibrium mixture containing the ester, water , acid, and alcohol
Room temp

Question 11

Hydrolysis of esters ( base catalyst)

Answer 11

Salt produced rather than the acid
Removes the acid form the mixture - meaning no eq meaning goes to completion

reversible reaction
to a full on reaction with naOH

Question 12

Uses of esters

Answer 12

Animal and vegetable oils - esters of propane 1,2,3 triol
- fats and oils can be hydrolyzed in acidic conditions - to give glycerol and fatty acids
- can be hydrolyzed by boiling with NaOH - produces glycerol and sodium salts of the acids

the sodium salts formed are ionic and dissociate to form Na+ and RCOO- = allows them to work as cleaning agents

Question 13

propane -1,2,3-triol (glycerol)

Answer 13

Can form hydrogen bonds and is very soluble in water
Used ub pharmaceuticals and cosmetic preparation
Used as a solvent in medicine
Solvent in the food industry
Used as a plasticiser

Question 14

What is acylation

Answer 14

Where an acyl group is introduced into another molecule

the acyl group is a carbon with a double bond and an r group

Question 15

Acid derivatives

Answer 15

Have the acyl group in their structure

ester
acyl chloride
acid anhydride

Question 16

Nucleophilic acyl substitution

Answer 16

Reaction takes place because of the polarisation leaving the carbon susceptible to nucleophilic attack
The z group is replaced therefor the nucleophile has been acylated

Factors that effect
1. The magnitude of the charge on the carbon group which depends on the electron releasing or attacking power of z
2. How easily z is lost
3. How good the nucleophile is

Question 17

Order of reactivity for nucleophiles in acylation

Answer 17

The nucleophiles are neutral so they must loose a hydrogen ion during the reaction

water more than alochol more than ammonia more than primary amine

Question 18

Polarisation of acid derivatives

Answer 18

Acid chlorides and acid anhydrides withdraw electrons
Meaning they are both good acylating agents as the z is easily lost

Question 19

Products of addition elimination reactions

Answer 19

ammonia - amide
amine - n-substituted amide
alcohol - ester
water - carboxylic acid

Question 20

Mechanism for nucleophilic addition elimination reactions

Answer 20

the nucleophile attcks the pos carbon eith the = o attached

arrow breaks the double bond electrons move to o - o- lone pair

then the o lone pair move back in to the bond

the nucleophile is attached with a pos charge

then the carbon with halogen attched bond collapes and cl- removed

then the h colappses into the pos part of nucleophile

Question 21

Ethnic anhydride vs ethanoyl chloride

Answer 21

Its is cheaper
It is less corrosive
It does not readily react with water
Its is safer as no HCl byproduct
Important in the production of aspirin