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Chemistry > carboxylic acids > Flashcards

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
Q

what happens when tollens reagent is added to an aldehyde

A

silver ions ( acts as oxidising agent is presence of ammonia) is reduced to form silver mirror
aldehyde oxidised to carboxylic acid

26
Q

what functional group does carboxylic acid contain

A

carboxyl group

27
Q

what is carboxylic acid used for

A

medicine,painkillers,fruit juices,vinegar

28
Q

why are carboxylic acids soluble in water?

A

C=O and C-H bonds are polar allowing hydrogen bonds to form in water

29
Q

why are carboxylic acids with over 4 carbon atoms not soluble in water

A

as number of carbon atoms increase, solubility decreases as non-polar carbon chain has a greater effect on overall polarity

30
Q

what are properties of dicarboxylic acid

A

have 2 polar carboxyl groups to form hydrogen bonds. Solid at room temperature and dissolve readily in water

31
Q

what do carboxylic acids react with in redox

A

metals

32
Q

what do carboxylic acids react with in neutralisation

A

bases, alkalis , metal oxides , carbonates

33
Q

what is formed when carboxylic acids react in redox or neutralisation

A

carboxylate salts

Chemistry (18 decks)

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