3.3.9 Carboxylic acids and derivatives (A2) Flashcards
what is the functional group of carboxylic acids?
R-COOH
what is the pH of carboxylic acids?
weak acids - pH 3-6
what is the name of a carboxylic acid which includes a benzene ring?
benzanoic acid
can carboxylic acids form H bonds with water? what does this mean?
yes
carboxylic acids with up to and including 4 carbons are completely soluble in water
when can carboxylic acids form H bonds with eachother?
in the solid state
what do the H bonds account for in terms of properties?
much higher boiling point than their counterpart alkanes
what is mechanism is likely to happen in carboxylic acids? why?
nucleophilic addition
delta positive carbon is very susceptible to nucleophilic attack and addition reactions are likely to happen as there is an area of unsaturation
what happens to carboxylic acids in solution?
partially ionised
forms carboxylate ion and a proton (H+)
what is the chemical reactivity of carboxylic acids?
despite being weak acids, any carboxylic acid will still react with sodium hydrogencarbonate (NaHCO3)
what happens in the reaction between sodium hydrogen carbonate (NaHCO3) and a carboxylic acid?
releases carbon dioxide
we would see bubbling
what can we use to distinguish between carboxylic acids and alcohols?
sodium hydrogencarbonate
carboxylic acid bubbles
alcohol gives no reaction
what do we use the test with sodium hydrogencarbonate to do?
distinguish between carboxylic acids and alcohols
carboxylic acids bubble - release of CO2
and alcohols give no reaction
what are carboxylic acids in a reaction?
proton donors
what are the salts produced by the reactions of carboxylic acids called generally?
carboxylate salts
what would a reaction of a ethanoic acid produce as a salt?
ethanoate salts
what salt would be produced from a reaction involving methanoic acid?
methanoate salts
what does the reaction of ethanoic acid and sodium hydroxide produce?
sodium ethanoate and water
what does a reaction between propanoic acid and aqueous sodium carbonate produce?
sodium propanoate
water
carbon dioxide
do carboxylic acids ionise partially or completely in water?
partially ionise in solution
what is the charge on a carboxylate ion called?
delocalised electron charge
what is the functional group of an ester?
RC=OO-R’
what are esters used for?
cleaning products, perfumes, flavourings
how do we form an ester?
carboxylic acid + alcohol
what is the equation for forming an ester?
carboxylic acid + alcohol –> ester + water
how would we get a higher yield of ester from the carboxylic acid + alcohol reaction?
increase volume of carboxylic acid / alcohol
remove water is it is formed
how can we get the carboxylic acid and alcohol back from the ester?
hydrolysis
what does an addition elimination reaction of an ester form?
carboxylic acid
alcohol
what conditions does an addition elimination reaction involving an ester?
room temperature
acid catalyst
what do we obtain after addition elimination of esters? how do we obtain the desired product?
mixture of carboxylic acid, water, ester and alcohol
fractional distillation
other than an acid catalyst for addition elimination, what else can be used to hydrolyse an ester?
bases
when we use a base to hydrolyse an ester, what are the products?
alcohol and salt of the carboxylic acid (carboxylate salt)
what happens when we use a base to hydrolyse an ester?
products are carboxylate salt and alcohol
because this is removing the carboxylic acid from the mixture, an equilibrium is NOT REACHED so reaction goes to EQUILIBRIUM
what type of mechanism is the hydrolysis of esters?
addition elimination
what is the use of esters as plasticisers?
added to plastics to make them more flexible
why are esters used as plasticisers?
ester (small molecule) can get in between the long chain molecules of plastic and allow them to slide over each other
what is the reaction for making fats and oils a reaction between? what does it form?
glycerol (alcohol) + fatty acids (carboxylic acids)
forming triglyceride (triester of glycerol)
what can we add to triglyceride (ester) to form glycerol (alcohol) and fatty acids (carboxylic acid)?
3 water molecules
what happens in the hydrolysis of fats?
boil fats / oils with sodium hydroxide
glycerol and 3 sodium carboxylate salts produced
what is produced from the hydrolysis of fats?
glycerol (alcohol) and sodium carboxylate salts
how is sodium carboxylate salt used?
soap
how many molecules of NaOH are added to a triglyceride to hydrolyse it?
3
how do the carboxylate ions arrange themselves around an oil droplet in water? why? what is this used for?
arrange themselves with hydrophilic head in the surrounding water and hydrophobic tail in the oil. this leads to separation of the oil and water, used for soaps
what is used to produce biodiesel from triglyceride (triester)?
methanol
what are the mixture of fatty esters produced by the combination of triglyceride and methanol used for?
biodiesel
what is produced by the reaction between triglyceride and methanol?
mixture of fatty esters (biodiesel)
glycerol
what is the formula of an acyl group?
RC=O
what is acylation?
addition of an acyl group to a nucleophile
what is the ending when naming acyl chlorides?
(ethan)oyl chloride
what is Z called in RC(O)Z?
Z= leaving group
what are some examples of leaving groups?
Cl, OR’, OCOR’
what does the speed of acylation reaction depend on?
depends how delta + the central carbon is
depends how stable the Z (leaving group) is
depends how strong the nucleophile is
what is the relationship between the rate of the acylation reaction and the charge of the central carbon?
the more delta + the central carbon is, the quicker the reaction
what is the relationship between the rate of the acylation reaction and the stability of the leaving group?
the more stable the Z (leaving group), the quicker the reaction
what is the relationship between the rate of the acylation reaction and the strength of the nucleophile?
the easier the lone pair is donated, the quicker the reaction.
what have the fastest acylation reactions?
acyl chlorides
why do acyl chlorides have the fastest acylation reactions?
carbon is delta positive
leaving group is stable
nucleophile is strong (lone pair donated easily)
what makes a better nucleophile?
how easily the e- pair is donated
(how basic the nucleophile is)
what are the drawbacks to using ethanoic (acid) anhydrides?
lower atom economy
slower reaction
what is the reason we don’t use acyl chlorides over acid anhydrides?
toxic by-product of HCl gas
what type of molecules are formed when we react a primary amine with an acyl chloride?
amide
TOXIC HCl (hydrogen chloride) gas
what type of molecules are formed when we react ammonia with an acyl chloride?
amide
toxic HCl gas
what type of molecules are formed when we react an alcohol with an acyl chloride?
ester
toxic HCl gas
what type of molecules are formed when we react an acyl chloride with water?
carboxylic acid
toxic HCl gas
what type of molecules are formed when we react a primary amine with an acid anhydride?
amide
carboxylic acid
what type of molecules are formed when we react ammonia with an acid anhydride?
amide
acid anhydride
what type of molecules are formed when we react an alcohol with an acid anhydride?
ester
carboxylic acid
what type of molecules are formed when we react water with an acid anhydride?
carboxylic acid
carboxylic acid
what are the positives with reacting acyl chlorides?
reaction is extremely quick
high atom economy
what are the positives with reacting acid anhydrides?
by-product is NON TOXIC
what is the negative when using acyl chlorides in reaction?
TOXIC BY-PRODUCT of hydrogen chloride gas
what are the negatives of using acid anhydrides in reaction?
reaction is slower
atom economy is lower
