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OCR Chemistry > 6.1 AROMATIC COMPOUNDS,CARBONYLS & ACIDS > Flashcards

6.1 AROMATIC COMPOUNDS,CARBONYLS & ACIDS Flashcards

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1
Q

Define aliphatic

A
  • Straight or branched organic substance
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2
Q
A
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3
Q

State the two similarities of kekules benzene and delocalised benzene

A

1) Both have sideways overlap of p-orbitals
2) Both have π bonding above and below the carbon atoms

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4
Q

State the two differences of kekules benzene and delocalised benzene

A

1) Kekule has three alternating π bonds with localised π electrons
2) Delocalised has a π ring system where all p-orbitals overlap

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5
Q

State the three experimental evidence against kekules model

A

1) All six carbons have the same bond length
2) Benzene is resistant to addition reactions
3) ΔH hydrogenation is less exothermic that expected

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6
Q

Explain bond length evidence for delocalised benzene

A
  • The carbon bond lengths in delocalised benzene are a value between the C=C double bonds and C-C single bonds
  • So, all bond lengths are equal
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7
Q

Explain benzenes resistance to addition reaction evidence for delocalised benzene

A
  • Benzene doesnt readily undergo addition reactions like alkenes as benzene is less reactive than alkenes
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8
Q

Explain ΔH hydrogenation evidence for delocalised benzene

A
  • The ΔH hydrogenation of benzene is less exothermic than expected so is more stable than predicted
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9
Q

State the four reactions of benzene

A
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10
Q

Conditions/reaction/mechanism for the nitration of benzene

A
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11
Q

Conditions/reaction/mechanism for the halogenation of benzene

A
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12
Q

State why phenols are weak acids

A
  • The H in the OH group can only partially dissociate to release H+ in aqueous solution
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13
Q

State why phenols cant react with carbonates

A
  • Because phenols are weak acids so cannot react with a weak base like a carbonate
  • Only reacts with hydroxides
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14
Q

State the three reactions of phenols

A

1) Bromination of phenols to form 2,4,6-tribromophenol
2) Phenols with NaOH to form sodium phenoxide
3) Nitration of phenols to form a mixture of 2-nitrophenol and 4-nitrophenol (depending on HNO₃ concentration)

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15
Q

Conditions/reaction for the bromination of phenols

A
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16
Q

Conditions/reaction for phenols with NaOH

A
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17
Q

Conditions/reaction for the nitration of phenols

A
18
Q

State which atom groups on an aromatic ring cause a 2- and 4- directing affect

A
  • OH
  • NH2
  • (electron donating groups)
19
Q

State which atom group causes a 3- directing affect

A
  • NO2
  • (electron withdrawing groups)
20
Q

Explain why the relative ease of electrophilic substitution is easier for phenols compared to benzene

A
  • The phenols p-orbital electrons are donated to the π system of the aromatic ring
  • The π system of the aromatic ring now is more nucleophilic/electron dense
  • The ring becomes more susceptible to electrophilic attack as it can induce dipoles in nonpolar molecules better
21
Q

State the three reactions of carbonyl compounds

A

1) Oxidation of aldehydes to form carboxylic acids
2) NaBH₄ reduction of carbonyl compounds to form primary/secondary alcohols
3) HCN addition to carbonyl compounds to form hydroxynitriles

22
Q

Conditions/reaction for the oxidation of aldehydes

A
23
Q

Conditions/reaction/mechanism for carbonyl compounds with NaBH₄

A
24
Q

Conditions/reaction/mechanism for carbonyl compounds with HCN

A
25
Q

Describe the characteristic test for carbonyl compounds

A
  • 2,4-DNP reacts with both aldehydes and ketones to produce an orange percipitate
  • The melting point of the crystal orange percipitate can be compared to data to determine if its an aldehyde or ketone
26
Q

Describe the characteristic test for aldehydes

A
  • Tollens reagant
  • Produces a silver mirror percipitate coating when aldehyde is oxidised into a carboxylic acid
  • Does this by reducing silver ions to silver atoms
  • NO REACTION WITH KETONES
27
Q

Explain why carboxylic acids are weak acids

A
  • Because they partially dissociate in aqueous solution to release H⁺ from its hydroxyl OH⁻ group
  • Thus, is used in neutralistion reacts as an acid
28
Q

Explain the water solubility of carboxylic acids

A
  • They are water soluble because the carboxyl COOH can form hydrogen bonds with water molecules
  • Solubility decreases with nonpolar carbon chainlength as this part cannot form hydrogen bonds wih the water
29
Q

State the three ways of esterfication (forming esters)

A

1) Carboxylic acids with alcohol(conc H2SO4)
2) Acid anhydrase with alcohol
3) Acyl chloride with alcohol

30
Q

Conditions/reaction for esterification of carboxylic acids with alcohols

A
31
Q

Conditions/reaction for esterification of acid anhydrase with alcohols

A
32
Q

State the two ester hydrolysis reactions

A

1) Hydrolysis of esters in hot aqueous acids to form carboxylic acids and alcohols
2) Hydrolysis of esters in hot aqueous alkalis to form carboxylate salts and alcohols

33
Q

Conditions/reaction for hydrolysis of esters with hot aqueous acids

A
34
Q

Conditions/reaction for hydrolysis of esters with hot aqueous alkalis

A
35
Q

Conditions/reaction for how an acyl chloride is formed

A
36
Q

State the four reactions of acyl chlorides

A

1) Acyl chlorides with alcohols to form esters
2) Hydrolysis of acyl chlorides to form carboxylic acids
3) Acyl chlorides with ammonia to form primary amides
4) Acyl chlorides with primary amines to form secondary amides

37
Q

Conditions/reaction for acyl chlorides with alcohols

A
38
Q

Conditions/reaction for hydrolysis of acyl chlorides

A
39
Q

Conditions/reaction for acyl chlorides with ammonia

A
40
Q

Conditions/reaction for acyl chlorides with primary amines

A
41
Q

Explain why, during esterification, acyl chloride is used rather than carboxylic acid when using phenol (alcohol)

A
  • Because, carboxylic acids do NOT readily react with phenols as well as acyl chlorides do
42
Q

Conditions/reaction for acyl chlorides with phenols (as an alcohol)

A

OCR Chemistry (13 decks)

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