carboxylic acid Flashcards
what does carboxylic acids contain
the carboxyl functional group, -COOH
formula for carboxylic acid
CnH2n+1COOH which can be shortened to just RCOOH
why is the intermolecular forces that carboxylic acids experience be high
because carboxylic acids contain two polarised groups C=O and O-H and they will have relatively high melting points and boiling points
what does the presence of O-H bond in carboxylic acid allow
exhibit hydrogen bonding
Not only does this contribute to the high melting and boiling points, it also contributes to the solubility in water
carboxylic acids can be formed from the oxidation of….
primary alcohols and aldehydes by either acidified K2Cr2O7 or acidified KMnO4 and reflux
what do the oxidising agents get reduced to
K2Cr2O7
KMNO4
In K2Cr2O7 the orange dichromate ions (Cr2O72-) are reduced to green Cr3+ ions
In KMnO4 the purple manganate ions (MnO4-) are reduced to colourless Mn2+ ions
carboxylic acids can be prepared from the hydrolysis of …
hydrolysis of nitriles using either dilute acid or dilute alkali followed by acidification
what does the hydrolysis of nitriles by dilute acid result in
formation of a carboxylic acid and ammonium salt
what does the hydrolysis of nitriles by dilute alkali result in
formation of a sodium carboxylate salt and ammonia; Acidification is required to change the carboxylate ion into a carboxylic acid
what does partial ionisation of carboxylic acids mean
that carboxylic acids are weak acids
This means that the position of the equilibrium lies to the left and that the concentration of H+ is much smaller than the concentration of the carboxylic acid
what do carboxylic acids ionise to form
low concentrations of hydronium ions and alkanoate ions
what is a test for the presence of carboxylic acid
NaHCO3 / Na2CO3 - effervescence / bubbles limewater turn milky
add alcohol should turn into ester and distinctive smell
what do carboxylic acid undergo when reacted with LIAlH4
undergo reduction when they react with a reducing agent such as lithium tetrahydridoaluminate, LiAlH4
what is Carboxylic acid reduced to
primary alcohol
Addition of water at the end will destroy any excess lithium tetrahydridoaluminate
what does carboxylic acids form when reacted with bases such as metals alkalis and carbonates
metal oxides: metal salt and hydrogen gas
alkalis: alt and water are formed in a neutralisation reaction
carbonates: metal salt, water and carbon dioxide gas are produced
what is formed when carboxylic acid reacts with solid phosphorus(V) chloride
acyl chloride
what will propanoic acid (PCl5) react with phosphorus chloride to form
physical observations?
propanoyl chloride, phosphorus trichloride oxide and hydrogen chloride
CH3CH2COOH (l) + PCl5 (s) →
CH3CH2COCl (l) + POCl3 (l) + HCl (g)
steamy fumes of HCl are produced
what is formed when carboxylic acid reacts with alcohol
an ester is formed
what are esters
compounds with an -COOR functional group and are characterised by their sweet and fruity smells
how are esters formed
condensation reaction between a carboxylic acid and alcohol with concentrated H2SO4 as catalyst
This is also called esterification
how do you name an ester
The first part of the ester’s name comes from the alcohol and the second part of the name comes from the carboxylic acid
e.g. ethyl propnaoate
what is the reverse of esterification and what is this useful for
hydrolysis of Esters for creating biodegradable plastics
how can esters be hydrolysed
by using either dilute acid (e.g. sulfuric acid) or alkali (e.g. sodium hydroxide) and heat
what happens when ester heated under reflux with alkali
irreversible reaction as the ester is fully hydrolysed and the reaction goes to completion
The carboxylic acid produced reacts with excess alkali to form a carboxylate salt and alcohol
The sodium carboxylate salt requires further acidification to turn into a carboxylic acid
what are acyl chlorides
derivatives of carboxylic acids by substitution of the -OH group by a chlorine atom
how can acyl chlorides be named
Acyl chlorides are named by identifying the parent hydrocarbon chain and adding the suffix -oyl chloride
They can also be named by removing the -oic acid from the carboxylic acid and adding -oyl chloride
what are acid anhydrides
erivatives of carboxylic acids formed by substitution of the -OH group by an alkanoate
how can acid anhydrides be named
Acid anhydrides are named by identifying the parent hydrocarbon chain and adding the suffix -oic anhydride
They can also be named by removing the -oic acid from the carboxylic acid and adding -oic anyhydride
what are examples of nucleophilic addition elimination reactions
Hydrolysis
Reaction with alcohols to form esters
Reaction with ammonia and primary amines to form amides
what does hydrolysis of acyl chlorides form
carboxylic acid and HCl molecule
what is the nucleophilic addition elimination reaction of the hydrolysis of acyl chlorides
A water molecule adds across the C=O bond
A hydrochloric acid (HCl) molecule is eliminated
explain the nucleophilic addition-elimination reaction for the formation of esters
Acyl chlorides can react with alcohols to form esters
The alcohol adds across the C=O bond
A HCl molecule is eliminated
A HCl molecule is eliminated
what do acyl chlorides form when reacted with primary amines and concentrated ammonia
amides
how can acyl chlorides form amides with primary amine or concentrated ammonia
The nitrogen atom in ammonia and primary amine has a lone pair of electrons which can be used to attack the carbonyl carbon atom in the acyl chlorides
The product is an amide (when reacted with ammonia) or N-substituted amide (when reacted with primary amines)
This is also an example of a nucleophilic addition-elimination reaction as
The amine or ammonia molecule adds across the C=O bond
A HCl molecule is eliminated
how are addition polymers made
They are made using monomers that have C=C double bonds joined together to form polymers such as polyethene
what are condensation polymers
reaction whereby a polymer is produced by repeated condensation reactions between monomers
Natural condensation polymers are all formed by elimination of water
how is polyester formed
by the reaction between dicarboxylic (2 -COOH groups) acid monomers and diol monomers ( 2 -OH groups)
linking these monomers with ester bonds / links
When the polyester is formed, one of the -OH groups on the diol and the hydrogen atom of the -COOH are expelled as a water molecule (H2O)
can you form polyesters with one monomer
A single monomer containing both of the key functional groups can also be used
These monomers are called hydroxycarboxylic acids
They contain an alcohol group (-OH) at one end of the molecule while the other end is capped by a carboxylic acid group (-COOH)
three differences in the esterification reaction when acyl chloride used instead of carboxylic acid
- the reaction is irreversible compared to reversible (1)
- hydrogen chloride is the by-product rather than water (1)
- the reaction is very fast/occurs at room temperature so
an acid catalyst is not needed (1)
compare contrast two methods of hydrolysis for esters
acid/alkali
(similarity)
* both make the (same) alcohol / pentan-1-ol
(differences)
acid hydrolysis is reversible, alkaline hydrolysis is irreversible
(1)
(1)
acid hydrolysis produces the carboxylic acid/ ethanoic acid and
(ion)
alkaline hydrolysis produces the carboxylate / ethanoate
(1)
the acid is a catalyst and the alkali is a reactant
3 differences between esterfication reaction when you use ethanoyl chloride vs ethanoic acid
(with ethanoyl chloride)
the reaction is irreversible compared to reversible (1)
hydrogen chloride is the by-product rather than water (1)
the reaction is very fast/occurs at room temperature so
an acid catalyst is not needed (1)
