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Chemistry > aldehydes and ketones > Flashcards

aldehydes and ketones Flashcards

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1
Q

general formula aldehydes and ketones

A

CnH2nO

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2
Q

fuctional group

A

aldehydes and ketones both contain the carbonile bond (=O)

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3
Q

where is the functional carbonie bond on an aldehyde

A

end of chain

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4
Q

where is the functional carbonile bond on ketones

A

middle of chain

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5
Q

what are aldehydes and ketones with the same number of carbon atoms, in relation to eachother

A

functional group isomers

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6
Q

how can aldehydes and ketones be prepared

A

oxidation of alcohols

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7
Q

what are aldehydes readily oxidised to

A

carboxylic acids

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8
Q

what 3 reagents can be used to oxidise an aldehyde to a carboxylic acid

A
  • acidified potassium dichromate and warm
  • fehlings solution and warm
  • tollens reagent and warm
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9
Q

what observations with acidified potassium dichromate and warm and aldehyde

A

orange>green

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10
Q

what observations with fehlings solutions and warm and aldehyde

A

blue solution>brick red ppt

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11
Q

what observations with tollens reagent and warm and adlehyde

A

silver mirror

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12
Q

what are tollens reagent and fehings solutions used as

A

chemical tests to distinguish between aldehydes and ketones

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13
Q

how are tollens and fehlings used to distinguish between aldehydes and ketones

A

ketones cannot be further oxidised and will not react with either tollens reagent/fehlings solution

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14
Q

what complex ion does tollens reagent contain

A

Ag(NH3)2+

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15
Q

why is a silver mirror seen when an aldehyde is warmed with tollens

A

the aldehyde is oxidised to a carboxylic acid and the silver ions are reduced to silver metal

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16
Q

equation for reaction of aldehyde with tollens

A

RCOH+(O)>RCOOH

Ag+aq>Ags

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17
Q

what does (O) represent in equation for aldehyde and tollens

A

oxidising agent- tollens

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18
Q

which ions does fehlings solution contain

A

cu2+

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19
Q

why is a brick red ppt seen when an aldehyde is warmed with fehlings

A

aldehyde is oxidised to a carboxylic acid and the copper ions are reduced to copper 1 oxide (cu2o)

20
Q

what does the presence of the delta+ c atom in aldehydes and ketones mean

A

theyre susceptible to attack by nucleophiles

21
Q

why do aldehydes and ketones have a delta+ c atom

A

polar C=O bond

22
Q

what is a nucleophile

A

an electron pair donor

23
Q

how can the nucleophile attach the delta+ carbon

A

forming a new covalent bond, an addition reaction then occurs across the double bond

24
Q

what can aldehydes and ketones be reduced to

A

alcohols

25
Q

how does the reduction of aldehydes and ketones occur

A

via a nucleophilic addition mechanism

26
Q

reagent for reduction of aldehydes and ketones

A

NaBH4

27
Q

conditions for reduction of aldehydes and ketones

A

aqueous solution

28
Q

GENERAL EQUATION FOR REDUCTION OF ALDEHYDES

A

RCOH + 2[H] > RH2COH

29
Q

what are aldehydes reduced to form

A

primary alcohols

30
Q

what is the reducing agent often simplified as in balanced equations

A

[H]

31
Q

general equation for reduction of ketones

A

RCOR + 2[H] > RCHOHR

32
Q

name of mechanism for reduction of aldehydes/ketones

A

nucleophilic addition

33
Q

nucleophile for reduction of aldehydes/ketones

A

hydride ion H-

34
Q

how can aldehydes and ketones be converted into hydroxynitriles

A

addition of HCN

35
Q

mechanism for addition of HCN to aldehyde/ketone

A

nucleophilic addition

36
Q

reagents for addition of HCN

A

KCN followed by dilute acid

37
Q

general equation for addition of HCN to aldehydes

A

RCOH + HCN > RCHOHCN

38
Q

general equation for addition of HCN to ketones

A

RCOR + HCN > RCOHRCN

39
Q

what will reacting an aldehyde/ketone with cyanide increase

A

the length of the carbon chain

40
Q

nucleophile in addition of HCN to aldehyde/ketone

A

cyanide ion CN-

41
Q

why is KCN used as opposed to HCN

A

HCN TOXIC GAS

KCN ALSO TOXIC BUT IS AN IONIC SOLID- READILY DISSOLVES TO FORM SOLUTION

42
Q

what forms when aldehydes and unsymmetrical ketones undergo reaction with KCN followed by dilute acid

A

a racemic mixture of 2 enantiomers

43
Q

racemic mix

A

a mixture of equal amounts of the two enantiomers

44
Q

what are enantiomers

A

optical isomers

45
Q

optical isomers

A

non superimposable mirror imahes

46
Q

how does the shape of the aldehyde/unsymmetrical ketone lead to a mixture with equal amounts of the two enantiomers being formed

A

trig planar- attack from each side equally likely

Chemistry (42 decks)

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