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A Level Chemistry > Aromatic compounds & Carbonyls > Flashcards

Aromatic compounds & Carbonyls Flashcards

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1
Q

how do you make an ester ?

A

react an alcohol with a carboxylic acid or a carboxylic acid derivative

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2
Q

what is a carboxylic acid derivative ?

A

substance made from carboxylic acid (like an acyl chloride)

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3
Q

how do you name an ester ?

A

first part of name - alkyl group

second part - carboxylic acid group, but ‘oate’ replaces ‘oic acid’

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4
Q

what is an esterification reaction ?

A

reversible reaction between alcohol and carboxylic acid to make an ester

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5
Q

what is needed for an esterification reaction ?

A

heated / concentrated sulfuric acid catalyst

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6
Q

as an esterification reaction is reversible, what must you do…

A

separate the product as its formed

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7
Q

describe esterification reaction for small esters

A

warm (product) mixture to distil off the ester as is more volatile than other compounds

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8
Q

define volatile

A

easily evaporated

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9
Q

what else is produced in esterification reaction

A

water

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10
Q

what type of reaction is an esterification reaction

A

condensation reaction

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11
Q

describe esterification reaction for large esters

A

heat under reflux and use fractional distillation to separate ester from other compounds

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12
Q

what is an acid anhydride ?

A

two carboxylic molecules - H20 (from condensation reaction)

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13
Q

how can ester be formed from acid anhydride and alcohol ?

A

react together with heat (no catalyst)

produces ester and carboxylic acid - separate with fractional distillation

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14
Q

what is the 3rd way to make an ester ?

A

alcohol + acyl chlorides, which forms and ester and HCl gas

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15
Q

what are the two ways to hydorlyse esters?

A

acid hydrolysis and base hydrolysis

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16
Q

what happens when you hydrolyse an ester ?

A

forms an alcohol

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17
Q

Describe acid hydrolysis of an ester

A
  • splits ester into carboxylic acid and an alcohol
  • heat under reflux with dilute acid (HCl)
  • reversible reaction so lots of water needed
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18
Q

Describe base hydrolysis of an ester

A
  • splits ester into carboxylate salt and alcohol

- heat under reflux with dilute alkali (NaOH)

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19
Q

why is kekule’s model no longer used?

A

the model suggested that there were C=C and C-C bonds with diff. lengths, when really they are all the same length

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20
Q

what 3D shape is benzene ?

A

planar (flat)

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21
Q

what are compounds containing a benzene ring called ?

A

arenes / aromatic compounds

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22
Q

electrons in benzene ring are …

A

delocalised

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23
Q

what evidence is there for benzene being more stable than kekule’s ?

A

hydrogenation is less exothermic than expected, so more energy needed to break bonds

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24
Q

what is thought to cause the stability of benzene ?

A

delocalised ring of electrons

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25
Q

what does a catalyst do to a species to allow it to act as an electrophile for benzene ?

A

polarises it

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26
Q

what type of reaction does benzene undergo ?

A

electrophillic substitution

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27
Q

what catalyst for chlorination of benzene ?

A

anhydrous AlCl3

28
Q

what catalyst for bromination of benzene ?

A

anhydrous FeBr3

29
Q

what catalyst / reagent for nitration of benzene ?

A

conc sulfuric acid, nitric acid

30
Q

what conditions / reagents for alkylation of benzene ?

A

reflux, AlCl3 catalyst and haloalkane

31
Q

what is the non organic product of nitration of benzene ?

A

water

32
Q

what conditions / reagents for acylation of benzene ?

A

acyl chloride, reflux, AlCl3 catalyst

33
Q

why keep temp lower than 55 for nitration of benzene ?

A

to get only one substitution

34
Q

why is phenol more reactive than benzene ?

A
  • lone pair on oxygen partially delocalises into electron ring
  • increases electron density
  • more likely to be attacked by electrophiles
35
Q

what are some electron donating groups ?

A

OH-, NH2-

36
Q

what positions for electron donating groups ?

A

2, 4, 6

37
Q

what are some electron withdrawing groups ?

A

NO2+

38
Q

what are the positions for electron withdrawing groups ?

A

3, 5

39
Q

what is formed from reaction between bromine water and phenol ?

A

2,4,6-tribromophenol and hydrogen bromide

40
Q

what is formed from the nitration of phenol ?

A

2 isomers of nitrophenol (at position 2 / 4)

water

41
Q

what is needed for the nitration of phenol ?

A

just dilute nitric acid

42
Q

what about phenol means it can undergo typical acid-base reactions ?

A

it is weakly acidic

43
Q

what is the formula for acidified potassium dichromate ?

A

K2Cr2O7 / H2SO4

44
Q

state the test for carboxylic acids

A

add sodium carbonate

effervescence shows positive test

45
Q

what is the product formed from carboxylic acid test ?

A

carboxylate salt

46
Q

what type of reaction is carboxylic acid test ?

A

acid - base

47
Q

state the test for alkenes

A

add bromine water

orange colour decolourises

48
Q

state the test for phenols

A

add bromine water

orange decolourises and white ppt forms

49
Q

what type of reaction is test for phenol?

A

electrophillic substitution

50
Q

state the test for aldehydes

A

add ammonical silver nitrate solution (tollens)

silver mirror will form

51
Q

what product is formed in tollens ?

A

carboxylic acid

52
Q

what type of reaction is tollens ?

A

oxidation

53
Q

state the test for aldehydes and ketones

A

2,4-DNPH (Brady’s)

orange ppt will form from orange solution

54
Q

what type of reaction is Brady’s ?

A

condensation

55
Q

what reagent is used in the reduction of carbonyls ?

A

NaBH4

56
Q

what type of mechanism is reduction of carbonyls ?

A

nucleophillic addition

57
Q

what to remember with reduction of carbonyls ?

A

2 [H]

58
Q

describe how hydrogen cyanide (HCN) reacts w/ carbonyls

A

dissociates to H+ and CN-
nucleophillic addition occurs w/ CN- as nucleophile
hydroxynitirle formed

59
Q

what makes carboxylic acids so soluble ?

A

form H bonds with water

60
Q

how do you name an acyl chloride ?

A

-oyl chloride

61
Q

how are acyl chlorides formed ? (give products too)

A

carboxylic acid + SOCl2 — acyl chloride + SO2 + HCl

62
Q

what substances do acyl chlorides react w/ and lose their chlorine ?

A

cold water / alcohol / ammonia / amine / phenol

63
Q

when acyl chloride reacts and loses chlorine, what is ALWAYS formed ?

A

HCl gas

64
Q

why are electron donating groups 2,4,6 directing ?

A
  • electrons delocalise into ring, increasing electron density
  • greater electron density at 2,4,6 carbons so more attracted to electrophiles
65
Q

why are electron withdrawing groups 3,5 directing ?

A
  • withdraws electrons from ring, decreasing electron density
  • withdraws electron density from 2,4,6 so unlikely to react w/ these positions

A Level Chemistry (21 decks)

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