Carboxylic acids and derivatives

what is a carboxylic acid?

a molecule with an alcohol group bonded to a carbonyl group (CARBOXYL GROUP)

what is a carboxyl group?

COOH

what groups do all carboxylic acid derivatives have?

acyl group (carbonyl group)

suffix for saturated carboxylic acids?

-anoic acid

suffix for unsaturated carboxylic acids?

-enoic acid if alkene functional group is present

test for carboxylic acids?

add an equal amount of sodium carbonate, fizzes and bubbles produced. CO2 produced bubbled through limewater turns it cloudy.

2 physical properties of carboxylic acids?

• meth,eth,prop and butanoic acid are completley soluble in water

• higher melting points

how are carboxylic acids completley soluble in water?

they have many opportunities to form hydrogen bonds WITH WATER as they have a delta positive hydrogen on the OH group and a delta negative oxygen on the O group

why do carboxylic acids have higher melting points?

they form dimers which are twice as big as a single carboxylic acid molecule

what is a dimer?

two monomers bonded together, carboxylic acids bond together with HYDROGEN bonds

t/f: carboxylic acids react similarly to other functional groups

true x

carboxylic acid + metal -> ? + ?

salt + hydrogen

carboxylic acid + metal oxide -> ? + ?

salt + water

carboxylic acid + hydroxide -> ? + ?

salt + water

carboxylic acid + metal carbonate -> ? + ?

salt + water + carbon dioxide gas

in a reaction, what ions do carboxylic acids ionise into?

carboxylate ions, e.g. ethanoate, propanoate, butanoate

(found in salts produced when they react)

when do molecules act as acids in terms of functional groups?

molecules act as acids when they have a carboxyl group, but not when they have separated alcohol and carbonyl group

why are carboxylic acids acidic but alcohols arent if they both have a H+ ion from the OH?

in a carboxylate ion, the extra electron in delocalised over 3 atoms (O,C,O-), making the atom stable, so it doesnt reform COOH, allowing H+ to act as the acid thing;

alcohols immediatley attract a proton as soon as its lost, as its unstable (due to O-)

ester functional group?

R1 COO R2

what can R1 be?

CH3, H

what can R2 be?

CH3

why must R2 begin with a carbon and not a hydrogen?

if it was a hydrogen, that would make a carboxylic acid functional group

2 reactants used to form esters?

carboxylic acid + alcohol -> ester + water

reaction requirements to make esters from carboxlyic acids and alcohol?

1 strong acid catalyst (H2S04)

2 heat

how to name esters?

alcohol first, acid second (carboxylic acid is used for the main parent chain)

propanol + propanoic acid -> propyl propanoate + water

butanoic acid + octanol -> octyl butanoate + water

why is the part of the molecule from the carboxylic acid used for the main carbon chain?

higher priority functional group than alcohols

functional groups from the highest priority to lowest?

(alkane, alkene, halogenoalkane, alcohol, aldehyde, ketone, nitrile, carboxylic acid)

1 carboxylic acid (and derivatives)

2 nitrile

3 aldehyde

4 ketone

5 alcohol

6 alkene

7 halogenoalkane

8 alkane

hydrolysis of esters in acidic conditions reaction?

ester + water ⇌ carboxylic acid + alcohol

can reach equilibrium because it’s reversible

requirements for hydrolysis of esters in acidic conditions?

only hydrolysed in the presence of a strong acid catalyst

does amount of acid affect point of equilibrium?

no since its a catalyst

hydrolysis of esters in alkaline conditions reaction?

ester + (excess)alkali -> salt + alcohol

why is the alkali in excess?

ester is completley converted if theres enough alkali since the reaction is NON-reversible

difference between hydrolysis of esters under alkali and acidic conditions?

alkali: not reversible, alkali is consumed, produces a salt and an alcohol

acid: reversible, acidic catalyst (isnt consumed), produces an acid and an alcohol

name of a molecule with 2 hydroxyl groups?

diol

name of a molecule with 3 hydroxyl groups?

triol, like glycerol

glycerol's IUPAC name?

propane-1,2,3-triol

4 uses of glycerol?

1 moisturiser

2 gloopy: used in medicine

3 plasticiser: cling film

4 solvent

ethanoic acid smells of vinegar due to COOH

difference between fats and oils?

fats are solid at room temperature, oils are liquid at room temperature

how do plants use esters?

compact energy in seeds for germination and further growth

how are soaps formed from esters?

hydrolysis of esters (often found in animal fats and vegetable oil) in alkaline conditions

what is biodiesel made up of?

a mixture of methyl esters;

made from long chain carboxylic acids and alcohols with short chains

what is biodiesel?

diesel replacement fuel made of a mixture of methyl esters which produces less pollution, can be mixed with ordinary diesel to reduce pollution

how are biodiesels produced?

ester (vegetable oil) + methanol -> glycerol + methyl ester (biodiesel)

conditions required to make biodiesel?

strong alkali catalyst present (OH-)

what is an acyl chloride?

-Carboxylic acid derivative where -OH group is replaced by a Cl

general formula of acyl chlorides?

RCOCl

reaction to form acyl chlorides from carboxylic acids and sulfurous dichloride?

carboxylic acid (l) + sulfurous dichloride (SOCl2)(l) -> acyl chloride + SO2 (g) + HCl (g)

why is the reaction irreversible? what happened to entropy?

SO2 (g) + HCl (g) lost as a gas,

entropy has increased as 2 gases are produced from 2 liquids

shape of sulfurous dichloride (SOCl2)?

107 degrees, 6 valence, 4 used for covalent bonding, 2 lone pairs

suffix for naming acyl chlorides?

-anoyl chloride

butanoyl chloride

what are acid anhydrides?

Derivatives of carboxylic acids formed by substitution of the -OH group by an alkanoate

general formula for acid anhydrides?

RCOOCOR

how are acid anhydrides formed?

dehydration of acid molecules (-H20) -> acid anhydride and water

why is the formation of acid anhydrides reversible?

water can be added back (hydrated) to form acid molecules again

how to name acid anhydrides?

replace 'acid' with anhydride,

first is the acid it’s derived from,

e.g. propanoic anhydride

2 properties of acid anhydrides and acyl chlorides?

1 smell of the acids from which they are derived from

2 react w/water (acyl chlorides react more violently in water)

acid anhydrides + water -> ?

2 carboxylic acids

acyl chloride + water -> ? + ?

carboxylic acid + HCl

what type of reaction is acyl chlorides with water?

acylation, nucleophilic addition elimination reaction

what is acylation?

loss of a hydrogen and added to an acyl group

mechanism of acyl chlorides and water?

1 H20 nucleophile, C-O covalent bond forms, C=O pi bond breaks, both e- go to oxygen = negative charge

alcohol + acyl chlorides -> ? + ?

ester + HCl

why does this nucleophilic addition-elimination acylation reaction occur in anhydrous conditions?

acyl chlorides react with water

acyl chloride + alcohol mechanism?

same as water

EXCESS ammonia + acyl chloride -> ? + ?

amide + ammonium chloride (NH4Cl)

amide functional group?

-amide

what type of reaction is ammonia + acyl chlorides?

nucleophilic addition elimination acylation reaction

what is produced if ammonia is not in excess?

HCl is produced instead of ammonium chloride

what are the 2 molecules of ammonia use for in this reaction?

1 forms the amide, other forms ammonium chloride during acylation

excess primary amides + acyl chloride -> ? + ?

amide, ammonium salt (RNH3+X- ,e.g. C3H7NH3+Br-)

what type of mechanism is primary amide + acyl chloride?

nucleophilic addition elimination acylation

what is a primary amine?

nitrogen with a lone pair, covalently bonded to 2 hydrogen atoms and one alkyl group

acid anhydride + alcohol -> ? + ?

ester + carboxylic acid

(COOH produced instead of HCl due to double bonded O and O and no Cl) (acylation)

acid anhydride + water -> ?

2 carboxylic acids (acylation)

acid anhydride + ammonia -> ? + ?

amide + carboxylic acid (acylation)

acid anhydride + excess ammonia -> ? + ?

amide + ammonium carboxylate (acylation)

acid anhydride + excess primary amine -> ? + ?

amide + carboxylate salt (acylation)

what reactions are nucleophilic addition elimination acylations?

acyl chloride + alcohol/water/ammonia/primary amides;

acid anhydrides + alcohol/water/ammonia/primary amides

order of reactivity for carboxylic acids, acyl chlorides and acid anhydrides?

1 acyl chlorides (most reactive)(no catalyst needed to react with alcohol)(more violent reaction in water)

2 acid anhydrides (no catalyst needed to react with alcohol)

3 carboxylic acids (least reactive) (do not react in water, need a catalyst to react with alcohol)

why are carboxylic acids the least reactive?

lone pair on oxygen is donated throughout the functional group, increasing stability as the delta positive charge on carbon is reduced, reducing reactivity

why are acid ahydrides least reactive than acyl chlorides?

electronegativity is split between 2 carbonyl groups, so the delta positive carbon charge is reduced a LITTLE;

little donation from Cl in acyl chlorides as outer e- do not delocalise well

how is aspirin made?

ethanoic anhydride + salicylic acid -> aspirin + ethanoic acid

where is salicin found?

willow trees

why is ethanoic anhydride used instead of acyl chloride for manufacturing of aspirin?

1 less exothermic = safer and easier to control

2 less dangerous by-products (acyl chloride produces HCl gas)

3 cheaper and easier to recycle