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Alevel chemistry year2 > aromatic compounds, carbonyl and amines > Flashcards

aromatic compounds, carbonyl and amines Flashcards

1
Q

What is the molecular formula of benzene

A

C6H6

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2
Q

What are aromatic, aliphatic and alicyclic compounds

A

Aromatic- containing benzene
aliphatic- ogranaic compound with open chain structure, can be cyclic but not benzene
alicyclic- cyclical but not benzene

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3
Q

What was kekule model for benzene

A

6 member ring of carbon with alternating single and double bonds, snake eating tail

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4
Q

Why did chemists disapprove with the kekule model

A

The model contain explain the physical and chemical properties of benzene

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5
Q

What are the factors that disprove the kekule model

A

1- benzene contains double bonds and therefore should decolourise bromine what but instead it doesn’t undergo any electrophillic addition reaction(therefore cannot have C=C) bonds
2- The bond length measure using X-ray diffraction showed that the bond length of each C bond was the same meaning that there were no double bonds
3- due to the double bonds the enthalpy of hydrogenation was expected to be *3 that of cyclohexene but it is actually much lower -208 so benzene is more stable

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6
Q

Delocalised model of benzene

A
  • Each carbon atom has an electron in a p-orbital at right angles to the plain of bonded H atoms causing adjacent P orbitals to overlap causing a ring with high electron density
    -Pi bond system spreads over all the carbon atoms, they are said to be delocalised
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7
Q

What are the groups that are prefixes to benzene

A

short alkyl chains, halogens and nitro groups

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8
Q

What happens when the carbon chain is longer than 7

A

the benzene is considered substituent and becomes the prefix eg phenyl ethanone

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9
Q

What are the 3 expections to this

A

Benzoic acid, phenylamine, benzaldehyde

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10
Q

What kind of reaction does benzene undergo

A

Electrophillic substitution, electrophile attracted to high electron density(strong electrophiles)

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11
Q

How do substitution reactions work on benzene

A

Hydrogen atom on benzene is replaced by atom atom/ group

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12
Q

conditions for nitration of benzene

A

catalysed by sulfuric acid and heated at 50 degrees

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13
Q

Conditions of acylation of benzene

A

60 degrees with halogen carrier

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14
Q

conditions for halogenation of benzene

A

Room temperature with halogen catalyst

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15
Q

Condition for alkylation of benzene

A

Room temperature with halogen carrier

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16
Q

catalyst for the Nitration of benzene

A

HNO3
creation:
HNO3 + H2SO4 -> HSO4 + H2NO3
H2NO3 -> NO3- + H2O
restoring catalyst
HSO4- + H+ -> H2S04

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17
Q

Halogen carrier for alkylation of benzene

A

Creation
CH3Cl + AlCl3 -> CH3+ + AlCl4-

AlCl4- + H+ -> AlCl3 + HCLl

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18
Q

Halogen carrier for acylation of benzene

A

Ch3COCl + AlCal3 -> Ch3CO+ + AlCl4-

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19
Q

All the hydrogen carriers

A

AlCl3, AlBr3, FeCl3

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20
Q

Why does benzene require halogen carriers

A

Too stable to react with non-polar or weak electrophiles to electrophiles produced from halogen carrier catalysts are much stronger

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21
Q

What is an electrophile/ nucleophile

A

electrophile- Chemical species that forms bonds by accepting a pair of electrons
nucleophile- Chemical species that form bonds by donating a pair of electrons

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22
Q

Comparing alkene to reactivity of alkenes

A
  1. Pi bond in alkenes are localised above and below the 2 carbons in a double bond for an area of high electron density
  2. These electrons induce a dipole in the non polar bromine making one of them slightly positive
  3. slightly positive bromine enables bromine to act as an electrophile
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23
Q

Comparing alkenes and benzene

A
  • Benzene doesn’t react with bromine unless it has a halogen carrier, due to delocalised pi electrons above and below the Carbon ring
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24
Q

What is phenol

A

Benzene ring with an OH group(c6h5OH)

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25
Q

What are the exceptions in naming phenol

A

carboxylic group added, longer alkyl chain than the phenol 6 ring

26
Q

Properties of phenol

A
  • Weak acid due to OH group which dissociates to release H+ ion and phenoxide ion
    -less soluble than alcohols due to non polar benzene ring
    -solid at room temp due to H bonding
27
Q

phenol + NaOH
Acid + Alkali

A

Phenoxide ion + Na+ + H20
(Salt + water)neutralisation reaction

28
Q

Phenol + 2k
(Acid + metal)

A

Potassium phenoxide + H2(g)
(Salt + Hydrogen)

29
Q

Does phenol react with benzene

A

Yes decolourises bromine water

30
Q

What does OH do to the electron ring

A

OH- has a lone pair of electrons which adds to the electron density of the carbon ring at positions 2,4 and 6 also allows it to polarise bromine on its own

31
Q

What are the first 3 positions on benzene called

A

Ortho, meta and para

32
Q

What are electron adding/ withdrawing groups

A

Groups with lone pairs of electrons add to the electron ring and then direct groups to positions 2,4 and 6
Electron withdrawing groups remove electron density from the electron ring and 3,5 directs

33
Q

conditions for the oxidation of aldehydes

A

cr2o72-/ H+(H2SO4)

34
Q

What makes carbonyls more susceptible to attack

A

C=O is polar so C becomes delta positive while attracts nucleophiles

35
Q

Conditions for the reduction of aldehydes/ketones

A

NaBH4 as reducing agent which provides [H] toms lightly warmed with water

36
Q

What ions are used in reduction of aldehydes/ketones

A

H-, then reacts with H on water to make OH group

37
Q

Conditions for reaction of carbonyls with HCN

A

NaCN(provides CN)/H2So4(provides H atoms) HCN

38
Q

What does the reaction of carbonyls + HCN produce

A

Hydroxy nitriles

39
Q

What ions are used in HCN mechanism

A

CN- is nucleophile and H+ for OH group

40
Q

What is used to test for the presence of carbonyls and what is the positive test

A

2,4 DNP yellow/ orange

41
Q

How is the exact compound found from 2,4 DNP

A

ppt is filtered, recrystalised and melted the melting point is an indicator of the actual compound

42
Q

What is the test for aldehydes, postive test?

A

Tollens reagent, which is a solution of silver nitrate in aq ammonia which produces a silver mirror as the aq silver ions are oxidised to form solid ones

43
Q

Why are carboxylic acids soluable in water

A

OH/CO bonds dissolve in water

44
Q

How does COOH dissociate

A

carboxylate ion and H+

45
Q

What kind of reactions do COOH undergo

A

redox reactions with metals and neutralisation reaction with bases
COOH + Metal -> Salt + Hydrogen
COOH + Metal Oxide -> Salt + Water
COOH + Carbonate -> Salt + CO2 + Water

46
Q

How can carboxylic acids be identified

A

Reaction wtih carbonates as they are the only organic molecule that can react with carbonates

47
Q

What are carboxylic acid derivates

A

Compounds that can be hydrolysed to form carboxylic acids
acyl chlorides, esters and acid anhyrides

48
Q

How are acids anhydrides made

A

reaction of two carboxylic acids together

49
Q

How are esters made & conditions

A

The reaction of alcohols with COOH, conditions(conc H2SO4 and warmed slightly)

50
Q

How are esters hydrolysed

A

By aq acid/alkali in the presence of water

51
Q

How are acyl chlorides made

A

Reaction of esters with SOCl2 which makes an acyl chloride + SO2 +HCl

52
Q

How do acyl chlorides react

A

Have polar C=Cl bond which allows for nucleophilic attack

53
Q

Reactions of acyl chlorides

A

acyl chloride + phenol -> phenyl ester + HCL
acyl chloride +H2O -> COOH + HCL
Acyl chloride + Ammonia -> primary amide and again for secondary

54
Q

How do acid anhydrides react

A

similarly to phenols, water, h3 and amines

55
Q

What are the prefix and suffixes for amines

A

Amine- suffix
amino- prefix

56
Q

secondary / tertiary amines

A

Must directly be bond to 2/3 carbons

57
Q

How do amines react

A

Lone pair on the nitrogen acts as a nucleophile

58
Q

Production of amine

A

Haloalkane + NH3 -> ammonium salt
ammonium salt +NaOH -> primary amine + NaCl + H2O

59
Q

Production of secondary amine

A

Amine + haloalkane -> secondary amide

60
Q

How are aromatic amines made

A

Reduction of nitrobenzene, heated under reful with tin and HCl for reuducing agent to produce an ammonium salt which then reacts with NaOh to produce an aromatic compound

Alevel chemistry year2 (4 decks)

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