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chemistry > PL m: Ester, polyester, amide & nylon hydrolysis > Flashcards

PL m: Ester, polyester, amide & nylon hydrolysis Flashcards

1
Q

What is needed to break down an ester and what is the name of this process?

A
  • Water (+ acid catalyst) / alkali
  • Ester hydrolysis
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2
Q

How would you increase the rate and yield of an ester hydrolysis reaction?

A
  • Rate: acid catalyst
  • Yield: use excess water to move eq. position right
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3
Q

Write the general symbol and word equations for the __ hydrolysis of an ester.

  • Standard
  • Acid
  • Alkaline
A

Standard & acid

RCOOR’ + H2O ⇌ RCOOH + R’OH

Ester + water ⇌ carboxylic acid + alcohol

Alkaline

RCOOR’ + OH- → RCOO- + R’OH

Ester + alkali → carboxylate ion + alcohol

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4
Q

Write the symbol and word equation for the alkaline hydrolysis of ethyl ethanoate.

A

CH2COOC2H5 + OH- → CH3COO- + C2H5OH

Ethyl ethanoate + alkali → ethanoate ion + ethanol

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5
Q
  • Name the salt
  • What type of salt is it?

Ca(C2H5COO)2

A
  • Calcium propanoate
  • Carboxylate salt
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6
Q

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.

A
  1. C-O bond next to C=O
  2. C=O bond v polar. Hydrolysis by nucleophilic attack on δ+ C by 18O of water molecule. C-O bond breaks
  3. H+ attaches to (protonates) O in carbonyl group, making δ+ C more susceptible to attack
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7
Q

Explain why ester hydrolysis is not reversible when an alkaline catalyst is used.

A
  • Carboxylate salt formed: RCOO-
  • Draw: O- bad leaving group (unlikely to get O2- in solution)
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8
Q

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.

A

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
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9
Q
  • By what process is the C-N bond in amides broken?
  • How can the reaction be catalysed?
A
  • Hydrolysis
  • By an acid or alkali
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10
Q

What are the conditions needed to hydrolyse an amide?

A
  • Heat by reflux with H2SO4 / HCl, or:
  • Heat by reflux with NaOH
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11
Q

Write general symbol and word equations for the acid and alkaline hydrolysis of a primary and secondary amide.

A

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

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12
Q

Write the equation for the acid hydrolysis of ethanamide.

A

CH3CONH2 + H2O + H+ → CH3COOH + NH4+

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13
Q

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
A
  • +H3N-(CH2)6-NH3+ and HOOC-(CH2)8-COOH
  • H2N-(CH2)5-COO-
  • See image
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14
Q

Write the equation for the hydrolysis of N-methyl ethanamide using hydrochloric acid.

A

RCONHR’ + H2O + H+ → RCOOH + R’NH3+

CH3CONHCH3 + H2O + HCl → CH3COOH + CH3NH3Cl

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15
Q
  • Name CH3NH3Cl
  • What type of molecule is it?
A
  • Methylammonium chloride
  • An amine salt
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16
Q

Write a full structual equation showing the alkaline hydrolysis of CH3CONHR.

17
Q
A

CH3-CH(OH)-COOH, 2-hydroxypropanoic acid

CH2(OH)-COOH, hydroxyethanoic acid

  • Remember hydrolysis requires water.*
  • The extra OH groups are added to satisfy the valence issues on the CH and CH2 upon bond breakage.*
18
Q

Draw the structure of the reactant.

19
Q
  • Write the symbol equation for the hydrolysis of -(OCH2CH2OCOC6H4CO)- using NaOH
  • Name the products
A

-(OCH2CH2OCOC6H4CO)-n + 2nNaOH → nHOCH2CH2(OH) + n+Na-OOC-C6H4-COO-Na+

ethan-1,2-diol + sodium salt of benzene-1,4-dicarboxylic acid

20
Q

Give the products of the hydrolysis of the following esters and amides.

A

CH3COOH + CH3NH3+Cl-

C2H5COO-Na+ + C3H7NH2

CH3COOH + C2H5OH + 1/2Cl2

HCOO-Na+ + CH3OH

21
Q

Give the products of the hydrolysis of the following polyesters and polyamides.

A

Cl-H3N+(CH2)6NH3+Cl- + HOOC(CH2)4COOH

H2N(CH2)6NH2 + +Na-OOC(CH2)4COO-Na+

HOC2H4OH + HOOC-C6H4-COOH + Cl2

HOC2H4OH + +Na-OOC-C6H4-COO-Na+

chemistry (50 decks)

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