carboxylic acid Flashcards by Rehaan Khaleqi

what does carboxylic acids contain

the carboxyl functional group, -COOH

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formula for carboxylic acid

CnH2n+1COOH which can be shortened to just RCOOH

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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

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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

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carboxylic acids can be formed from the oxidation of….

primary alcohols and aldehydes by either acidified K2Cr2O7 or acidified KMnO4 and reflux

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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

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carboxylic acids can be prepared from the hydrolysis of …

hydrolysis of nitriles using either dilute acid or dilute alkali followed by acidification

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what does the hydrolysis of nitriles by dilute acid result in

formation of a carboxylic acid and ammonium salt

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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

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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

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what do carboxylic acids ionise to form

low concentrations of hydronium ions and alkanoate ions

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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

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what do carboxylic acid undergo when reacted with LIAlH4

undergo reduction when they react with a reducing agent such as lithium tetrahydridoaluminate, LiAlH4

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what is Carboxylic acid reduced to

primary alcohol

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

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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

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what is formed when carboxylic acid reacts with solid phosphorus(V) chloride

acyl chloride

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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)