PL m: Ester, polyester, amide & nylon hydrolysis Flashcards
What is needed to break down an ester and what is the name of this process?
- Water (+ acid catalyst) / alkali
- Ester hydrolysis
How would you increase the rate and yield of an ester hydrolysis reaction?
- Rate: acid catalyst
- Yield: use excess water to move eq. position right
Write the general symbol and word equations for the __ hydrolysis of an ester.
- Standard
- Acid
- Alkaline
Standard & acid
RCOOR’ + H2O ⇌ RCOOH + R’OH
Ester + water ⇌ carboxylic acid + alcohol
Alkaline
RCOOR’ + OH- → RCOO- + R’OH
Ester + alkali → carboxylate ion + alcohol
Write the symbol and word equation for the alkaline hydrolysis of ethyl ethanoate.
CH2COOC2H5 + OH- → CH3COO- + C2H5OH
Ethyl ethanoate + alkali → ethanoate ion + ethanol
- Name the salt
- What type of salt is it?
Ca(C2H5COO)2
- Calcium propanoate
- Carboxylate salt
You could prove which ester bond was broken by seeing which of the acid and alcohol was heavier than expected and thus received the 18O.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/331/318/657/q_image_thumb.png?1602508188)
- C-O bond next to C=O
- C=O bond v polar. Hydrolysis by nucleophilic attack on δ+ C by 18O of water molecule. C-O bond breaks
- H+ attaches to (protonates) O in carbonyl group, making δ+ C more susceptible to attack
Explain why ester hydrolysis is not reversible when an alkaline catalyst is used.
- Carboxylate salt formed: RCOO-
- Draw: O- bad leaving group (unlikely to get O2- in solution)
Draw mechanisms showing the hydrolysis of an ester bond in standard, acidic and alkaline conditions. Explain how the use of the catalysts makes the bond easier to break.
Acid:
- Carbonyl O protonated (mechanism below wrong)
- New bond with H means one of its Os is further away from it
- So attracts C’s e- more strongly
- C=O bond v polar; this makes C even more δ+ + susceptible to nucleophilic attack
Alkaline
- Water deprotonated
- O negative so more e- available to use
- Better nucleophile
- By what process is the C-N bond in amides broken?
- How can the reaction be catalysed?
- Hydrolysis
- By an acid or alkali
What are the conditions needed to hydrolyse an amide?
- Heat by reflux with H2SO4 / HCl, or:
- Heat by reflux with NaOH
Write general symbol and word equations for the acid and alkaline hydrolysis of a primary and secondary amide.
Acid
RCONH2 + H2O + H+ → RCOOH + NH4+
RCONHR’ + H2O + H+ → RCOOH + R’NH3+
Primary / secondary amide + water + acid → carb acid + ammonium / amine salt
Alkali
RCONH2 + OH- → RCOO- + NH3
RCONHR’ + OH- → RCOO- + R’NH2
Primary / secondary amide + alkali → carboxylate ion + ammonia / amine
Write the equation for the acid hydrolysis of ethanamide.
CH3CONH2 + H2O + H+ → CH3COOH + NH4+
![](https://s3.amazonaws.com/brainscape-prod/system/cm/331/318/663/a_image_thumb.png?1593165695)
Write/draw the formulae of the products of the:
- acid hydrolysis of nylon 6,10
- alkaline hydrolysis of nylon-6
- acid hydrolysis of Kevlar, shown below
![](https://s3.amazonaws.com/brainscape-prod/system/cm/331/318/664/q_image_thumb.png?1593279905)
- +H3N-(CH2)6-NH3+ and HOOC-(CH2)8-COOH
- H2N-(CH2)5-COO-
- See image
![](https://s3.amazonaws.com/brainscape-prod/system/cm/331/318/664/a_image_thumb.png?1593280241)
Write the equation for the hydrolysis of N-methyl ethanamide using hydrochloric acid.
RCONHR’ + H2O + H+ → RCOOH + R’NH3+
CH3CONHCH3 + H2O + HCl → CH3COOH + CH3NH3Cl
- Name CH3NH3Cl
- What type of molecule is it?
- Methylammonium chloride
- An amine salt