carboxylic acids Flashcards

1
Q

where is the carbonyl group ( c=o) in aldehydes

A

at the end of the carbon chain , CHO

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2
Q

where is the carbonyl group in ketones?

A

joined to 2 carbon atoms

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3
Q

what is octanal in nature

A

CH3(CH2)7CHO , a colourless fragrant liquid found in oranges
used to attract mates for birds during breeding season

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4
Q

what happens in oxidation of aldehydes

A

oxidised to carboxylic acid when refluxed with acidified potassium dichromate ion, K2CR2O7^, and dilute sulfuric acid

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5
Q

what are the conditions for oxidation of aldehydes

A

refluxed with acidified potassium dichromate ion, K2CR2O7^, and dilute sulfuric acid

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6
Q

why dont ketones undergo oxidation reactions

A

lack of reactivty

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7
Q

why is reactivity of alkenes and carbonyl groups different?

A

double bond ( c=o) in carbonyls are polar as oxygen is more electronegative
double bond ( c=c) in alkenes are non-polar

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8
Q

what type of reaction does carbonyls undergo

A

nucleophilic addition , nucleophiles are attracted to positive carbon atom

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9
Q

what type of reactions does alkenes undergo

A

electrophilic addition

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10
Q

what is used to reduce aldehydes and ketones to alcohols?

A

NaBH4

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11
Q

what are aldehydes reduced to

A

primary alcohols

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12
Q

what are ketones reduced to

A

secondary alcohols

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13
Q

why is hydrogen cyanide used to react to aldehydes and ketones

A

to increase length of carbon chain

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14
Q

why is hydrogen cyanide (HCN) dangerous

A

colourless and poisonous liquid that boils slightly above room temperature

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15
Q

how is hydrogen cyanide formed

A

sodium cyanide and sulfuric acid are reacted together

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16
Q

what is the nucleophile for reduction of aldehydes and ketones

A

the hydride ion , H-, from NaBH4

17
Q

what is the mechanism for reaction of aldehydes and ketones with NaB4

A

lone pair of electrons from hydride ion is attracted to and donated to slightly positive carbon atom. A dative covalent bond is formed between hydride ion and aldehyde/ketone. The pi bond in the c=o breaks by heterolytic fission forming a negatively charged intermediate ( oxygen) which donates a lone pair of electrons to a hydrogen atom in a water molecule to form an alcohol.

18
Q

what is the nucleophile in NaCN/H+

A

cyanide ion , CN-

19
Q

what is the mechanism for reaction of aldehydes/ketone with NaCN/H+

A

lone pair of electrons from cyanide ion is attracted to slightly positive carbon atom forming dative covalent bond. The pi bond in c=o breaks by heterolytic fission forming a negatively charged intermediate ( oxygen) which donates a lone pair of electrons to a hydrogen ion to form the product ( hydroxynitrile)

20
Q

what is brady reagent

A

2,4 DNP with sulfuric acid

21
Q

what is brady reagent used for

A

detect presence of carbonyl group in aldehydes and ketones forming orange precipitate

22
Q

what is DNPH used for

A

reacts with carbonyl group in a nucleophilic addition-elimination reaction called condensation. NH2 adds across double bond and water is removed

23
Q

what is used to distinguish an aldehyde and a ketone

A

tollens reagent

24
Q

what does tollens reagent contain

A

solution of silver nitrate in aqueous ammonia

25
what happens when tollens reagent is added to an aldehyde
silver ions ( acts as oxidising agent is presence of ammonia) is reduced to form silver mirror aldehyde oxidised to carboxylic acid
26
what functional group does carboxylic acid contain
carboxyl group
27
what is carboxylic acid used for
medicine,painkillers,fruit juices,vinegar
28
why are carboxylic acids soluble in water?
C=O and C-H bonds are polar allowing hydrogen bonds to form in water
29
why are carboxylic acids with over 4 carbon atoms not soluble in water
as number of carbon atoms increase, solubility decreases as non-polar carbon chain has a greater effect on overall polarity
30
what are properties of dicarboxylic acid
have 2 polar carboxyl groups to form hydrogen bonds. Solid at room temperature and dissolve readily in water
31
what do carboxylic acids react with in redox
metals
32
what do carboxylic acids react with in neutralisation
bases, alkalis , metal oxides , carbonates
33
what is formed when carboxylic acids react in redox or neutralisation
carboxylate salts