Carboxyl Flashcards

1
Q

Preparation

A

1.From alkenes: Vigorous oxidation
Oxidation of terminal alkenes attached to one H and one R
H2SO4 (aq) and KMnO4(aq) heat
2.From Aldehyde: Oxidation
H2SO4(aq) and KMnO4/K2Cr2O7 heat
3.From primary alcohol: Oxidation
H2SO4(aq) and KMnO4/K2Cr2O7 heat w reflux
4.From esters: Acidic hydrolysis also forms alcohol
HCl(aq), heat
5.From amides acidic hydrolysis also forms amine
HCl(aq), heat
6.From acyl chlorides: Hydrolysis
H2O(l), r.t.
7.From alkyl benzene side chain oxidation
H2SO4(aq), KMnO4 (aq), heat
8.Nitrile acidic hydrolysis
HCl(aq), heat

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2
Q

Why carboxylic acids are the most acidic compared to phenols and alkoxide?

A

Carboxylic acids have a double resonance structure due to the delocalisation of negative charge over two highly negative O atoms. This greatly stabilises the carboxylate anion. Hence acid dissociation is most favoured

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3
Q

Physical properties

A

Polar and soluble in water as it can form H bonds with water mol.
Solubility in water decreases as hydrocarbon chain lengthens
MP and BP depends on size of electron cloud, degree of branching and extensiveness of H bonding (2 per mol, usually)

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4
Q

Reactions

A
  1. Redox
    Na(s) to form carboxylate Na+
  2. Acid base w SB
    Carboxylate Na+ salt and water
    NaOH(aq)
  3. Acid base with WB
    NH3(g)
    Carboxylate salt which is the conjugate acid of the WB
  4. Acid base with Na2CO3
    Carboxylate Na+ salt and CO2 (effervescence) and water
  5. Condensation to form ester
    H2SO4 conc, R-OH, heat
  6. Substitution to form acyl chlorides
    PCl3 anhydrous
    PCl5 anhydrous
    SOCl2 anhydrous
    HX(g) dry
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5
Q

Acyl chlorides
Preparation

A
  1. Substitution of CA
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6
Q

Acyl chloride reaction

A
  1. Hydrolysis with water to form CA
    - H2O(l)
  2. Alkaline hydrolysis to form carboxylate salt
    - NaOH(aq)
  3. Condensation to form ester
    - ROH
  4. Condensation to form primary, tertiary and secondary amides
    - NH3(g) to form -CONH2R
    - RNH2 to form -CONHRR
    - RNHR to form -CONRRR
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7
Q

Esters
Reaction

A
  1. Acidic hydrolysis
    HCl(aq) heat to form COOH and OH

2.Alkaline hydrolysis
NaOH(aq) heat to form COO- and OH

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8
Q

Acyl chloride are have the most ease of hydrolysis followed by alkyl chloride then chloro benzene why?

A
  • Electronic factor: This is because C in acyl chlorides bonded to one highly electronegative O and Cl electron withdrawing groups inducing a greater partial positive charge on C which makes C much more electron deficient than in the other chlorides. Thus most susceptible to nucleophilic attack by an electron rich species
  • Steric hindrance is lesser due to lesser R groups being present making it easier for nucleophile to attack the electron deficient
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