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

6.1 AROMATIC COMPOUNDS,CARBONYLS & ACIDS Flashcards

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

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

23
Q

Conditions/reaction/mechanism for carbonyl compounds with NaBH₄

24
Q

Conditions/reaction/mechanism for carbonyl compounds with HCN

25
Describe the **characteristic test** for **carbonyl compounds**
- **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
Describe the **characteristic test** for **aldehydes**
- **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
Explain why **carboxylic acids** are **weak acids**
- 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
Explain the **water solubility** of **carboxylic acids**
- 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
State the **three** ways of **esterfication** (forming esters)
1) **Carboxylic acids** with **alcohol**(conc H2SO4) 2) **Acid anhydrase** with **alcohol** 3) **Acyl chloride** with **alcohol**
30
Conditions/reaction for **esterification** of **carboxylic acids** with **alcohols**
31
Conditions/reaction for **esterification** of **acid anhydrase** with **alcohols**
32
State the **two ester hydrolysis** reactions
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
Conditions/reaction for **hydrolysis** of **esters** with **hot aqueous acids**
34
Conditions/reaction for **hydrolysis** of **esters** with **hot aqueous alkalis**
35
Conditions/reaction for how an **acyl chloride** is formed
36
State the **four** reactions of **acyl chlorides**
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
Conditions/reaction for **acyl chlorides** with **alcohols**
38
Conditions/reaction for **hydrolysis** of **acyl chlorides**
39
Conditions/reaction for **acyl chlorides** with **ammonia**
40
Conditions/reaction for **acyl chlorides** with **primary amines**
41
Explain why, during **esterification**, **acyl chloride** is used rather than **carboxylic acid** when using **phenol** (**alcohol**)
- Because, **carboxylic acids** do **NOT** readily **react** with **phenols** as well as **acyl chlorides** do
42
Conditions/reaction for **acyl chlorides** with **phenols** (as an alcohol)

OCR Chemistry (13 decks)

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