CL 26- carbonyls and carboxylic acids Flashcards

1
Q

reduction of propanal

equation and reducing agent/ conditions

A

CH₃CH₂COH + 2[H] –> CH₃CH₂CH₂OH
forms a primary alcohol
NaBH₄ (warm, AQUEOUS)

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2
Q

reduction of propanone

equation and reducing agent/ conditions

A

CH₃COCH₃ + 2[H] –> CH₃CHOHCH₃
forms a secondary alcohol
NaBH₄ (warm, AQUEOUS)

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3
Q

ethanal with HCN

equation, conditions

A

CH₃CHO + HCN –> CH₃CH₂CHOHCN
H₂SO₄ + KCN (as HCN is very toxic, so produced ‘in situ’)

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4
Q

purpose of ethanal + HCN

A

makes the C chain longer

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5
Q

reagent to test for carbonyls

A

Brady’s reagent (2,4-DNP)
yellow/orange precipitate formed

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6
Q

how can you use the precipitate formed from 2,4-DNP to identify the exact carbonyl?

A
  • impure yellow/orange solid is filtered to separate the solid precipitate from the solution
  • solid is then recrystallised to produce a pure sample of crystals
  • find the melting point
  • compare to database
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7
Q

use of tollen’s reagent

equation to show what’s happening

A

silver mirror formed when reacted with aldehyde
Ag⁺₍ₐ₎ + e⁻ –> Ag₍ₛ₎

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8
Q

why are carboxylic acids water soluble?

A
  • C=O and O-H bonds are polar so can form hydrogen bonds with water molecules
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9
Q

trend of solubility of carboxylic acids

A
  • as the number of carbons increase (chain length increases), the solubility decreases
  • as the non-polar carbon chain has a greater effect on the overall polarity of the molecule
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10
Q

what is an acid anhydride?

A

formed by the removal of water from two carboxylic acid molecules

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11
Q

equation for forming ethanoic anhydride

A

2CH₃COOH –> CH₃COOCOCH₃ + H₂O

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12
Q

ethanoic anhydride with methanol

equation

A

CH₃COOCOCH₃ + CH₃OH –> CH₃COOCH₃ + CH₃COOH

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13
Q

advantages of using an acid anhydride over a carboxylic acid for esterification

A
  • provides better yields
  • requires less stringent conditions
  • acid anhydrides are easier to handle
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14
Q

advantage of alkaline hydrolysis over acid

A
  • irreversible reaction
  • products are easier to separate
  • lower production costs
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15
Q

formation of ethanoyl chloride from a carboxylic acid

A

CH₃COOH + SOCl₂ –> CH₃COCl + SO₂ + HCl

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16
Q

advantage of using ethanoyl chloride over ethanoic acid

A

ethanoyl chloride is more reactive

17
Q

why are acyl chlorides used in anhydrous conditions

A
  • they react violently with water, which diminishes the yield of the required product
18
Q

ethanoyl chloride with ammonia

equation

A

CH₃COCl + 2NH₃ –> CH₃CONH₂ (primary amide) + NH₄Cl

19
Q

acyl chloride + primary amine

A

secondary amide