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Chemistry 6.1.2: Carbonyl Compounds > exam questions > Flashcards

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1
Q

describe suitable chemical tests with observations that would confirm the presence of a ketone, aldehyde and alkene (4)

A
  • ketone = orange ppt in 2,4 DNP
  • no result with tollens reagent
  • aldehyde = silver mirror with tollens reagent
  • alkene = decolourises bromine water
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2
Q

what is the name of the mechanism when an aldehyde reacts with NaCN and H+ ? (1)

A

nucleophilic addition

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3
Q

explain why nucleophilic addition involves heterolytic fission (2)

A
  • both electrons go to one atom
  • the covalent bond breaks
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4
Q

what is produced when a ketone reacts with NaBH4?

A

alcohol

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5
Q

what are the reagents for the reaction of an alcohol to haloalkane?

A
  • NaBr
  • H2SO4
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6
Q

what are the reagents for the reaction of a haloalkane to an amine?

A
  • NH3
  • ethanol
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7
Q

what is the reagent for a reaction of an amine to a salt?

A

HCl

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8
Q

what is produced when a nitrile reacts with excess H2/Ni?

A

amine

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9
Q

suggest a suitable chemical test to confirm that a compound contains an unsaturated carbon chain (1)

A

Br2 decolourises

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10
Q

describe a chemical test to confirm that a compound contains an aldehyde functional group (1)

A
  • tollens reagent
  • silver mirror
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11
Q

describe a chemical test to confirm the presence of a carbonyl group. how can 2 products be distinguished? (3)

A
  • 2,4 DNP
  • orange precipitate
  • measure melting points and compare to known data values
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12
Q

in a nucleophilic substitution reaction of haloalkane to nitrile, where do the dipoles and curly arrows go? (2)

A
  • from lone pair on CN to carbon in haloalkane
  • from carbon in haloalkane to the halide bond
  • pos on carbon, neg on halide
  • produces a nitrile and Cl-
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13
Q

what reacts with NaCN to produce an hydroxynitrile? (1)

A

ketone

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14
Q

what is the reagent for the reaction of hydroxynitrile to carboxylic acid? (1)

A

HCl

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15
Q

what are the reagents for the reactions of hydroxynitriles to amines? (1)

A
  • H2
  • Ni catalyst
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16
Q

explain why an amine can react with dilute HCl to form a salt (1)

A
  • it is a base
  • the lone pair accepts a proton
17
Q

suggest why a compound can be biodegradable (1)

A

polar bonds can be hydrolysed

18
Q

state the reagent, observations and equation for the test for carboxylic acids (2)

A
  • sodium carbonate
  • effervescence
  • RCOOH + Na2CO3–> RCOONa + CO2 + H2O
19
Q

state the reagent, observations and equation for the test for aldehydes (2)

A
  • tollens
  • silver mirror
  • RCHO + [O] –> RCOOH
20
Q

state the reagent and observations for the test of ketones (1)

A
  • 2,4 DNP
  • orange precipitate
21
Q

state the reagent and observations that can be used to identify the products of ester hydrolysis (1)

A
  • acidified K2Cr2O7
  • orange to green solution
  • is positive for the alcohol
22
Q

what is produced when a compound is oxidised with potassium dichromate, where the product has a positive test with tollens? (1)

A

primary alcohol

23
Q

suggest a reagent that could be used in the reaction of a hydroxynitrile to a carboxylic acid (1)

A

H2SO4 / HCl

24
Q

how does a hydroxide ion act as a nucleophile? (1)

A

donates a pair of electrons

25
Q

what is the product when an aldehyde reacts with tollens reagent under acidic conditions? (1)

A

carboxylic acid

26
Q

what is the product when an aldehyde reacts under alkaline conditions? (1)

A

salt

27
Q

explain what is happening to the electron pairs and bonds in a nucleophilic addition reaction of carbonyls (3)

A
  • nucleophile attracted to delta pos carbon, forming a dative covalent bond
  • the electron pair is broken
  • the electrons are now on the O
28
Q

what is the organic product formed when butanal reacts with tollens reagent? (1)

A

butanoic acid

29
Q

outline how mixtures containing orange precipitates from 2,4 DNP can be used to distinguish between butanal and butanone (3)

A
  • purify/crystallise ppt
  • measure melting points
  • compare to known data values
30
Q

why does the tollens reagent test give a different result with aldehydes than ketones? (1)

A

aldehydes are oxidised to carboxylic acids

31
Q

why do ketones not give the silver mirror product when reacting with tollens reagent?

A
  • tollens is a mild oxidising agent
  • ketones do not have H on C=O so are less easily oxidised than aldehydes
32
Q

explain what happens to the tollens reagent and aldehyde in a reaction (2)

A
  • silver ions reduced
  • aldehyde oxidised

Chemistry 6.1.2: Carbonyl Compounds (4 decks)

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