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Chemistry Unit 4 > Benzenes > Flashcards

Benzenes Flashcards

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1
Q

Alcohol → Alkene
Reagents
Conditions
Type of reaction

A
  • Conc H2SO4
  • Reflux at 180°C
  • Dehydration
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2
Q

Alkene→Alcohol

A
  • H3PO4
  • steam, 60/70 atm & 300°C
  • Hydration
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3
Q

1° Alcohol→Aldehyde

A
  • Acidified potassium dichromate

* Distill off as it forms

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4
Q

2° Alcohol→Ketone

A

• Acidified Potassium Dichromate

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5
Q

Halogenoalkane → Alcohol

A
  • Aqueous NaOH
  • Reflux
  • Nucleophilic Substitution
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6
Q

Carboxylic Acid → Alcohol

A
  • LiAlH4

* Dry ether

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7
Q

Ketone → Secondary Alcohol

A
  • NaBH4
  • Dry ether
  • Secondary Alcohol
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8
Q

Carboxylic Acid → Alkane

A
  • NaOH
  • Heat
  • Na2CO3
  • Decarboxylation
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9
Q

Benzene → Nitrobenzene

A
  • Conc HNO3 and Conc H2SO4
  • reflux at 50°
  • Nitration
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10
Q

Ethanoyl Chloride → Carboxylic Acid

A
  • Water
  • Room temp
  • Steamy fumes of HCl
  • Hydrolysis
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11
Q

Ethanoyl Chloride → Ester

A
  • CH3OH

* Ester & HCl

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12
Q

Benzene → Methylbenzene
Reagents
Catalyst
Reaction type

A
  • CH3Cl
  • AlCl3
  • Electrophilic Substitution
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13
Q

Structure of Benzene

A

∙Formula C₆H₆
• Each C is bonded to 2C’s and 1H covalently
∙Trigonal planar with bond angle of 120°
• Sideways overlap of p orbitals
∙Delocalised structure of benzene has π cloud of electrons
∙All bond lengths are the same

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14
Q

Benzene → Bromobenzene
Reagents
Catalyst

A
  • Br2

* FeBr3

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15
Q

What type of reaction is Alcohol → Carboxylic Acid?

A

Oxidation

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16
Q

What type of reaction is Carboxylic Acid → Alcohol?

A

Reduction

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17
Q

What type of reaction is Halogenoalkane→Alcohol?

A

Nucleophilic substitution

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18
Q

What type of reaction is Alcohol→Ketone?

A

Oxidation

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19
Q

What type of reaction is Ketone→Alcohol?

A

Reduction

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20
Q

What type of reaction is Halogenoalkane→Alkene?

A

Elimination

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21
Q

What type of reaction is the Nitration of Benzene?

A

Electrophilic Substitution

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22
Q

What type of reaction is the Alkylation of Benzene? (Benzene→Methylbenzene)

A

Electrophilic Substitution

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23
Q

What test will show the presence of a CH₃C=O bond or a CH₃CH(OH) bond?

A

The Iodoform Tests

24
Q

What does 2,4-DNPH test positive for?

A

A carbonyl group

25
Q

What does Tollen’s reagant test for?

A

Aldehyde

26
Q

What colour change occurs when K₂Cr₂O₇/H⁺ acts as a oxidising agent?

A

Orange to Green

27
Q

In order of acidity from weakest to strongest, arrange these compounds- Ethanol, Phenol, Water, Ethanoic acid?

A

Ethanol, Water, Phenol, Ethanoic acid

28
Q

What does ‘heating under reflux’ mean?

A

Evaporation and Condensation of a material in which the condensed material returns to the flask

29
Q

Methylbenzene→Benzoic acid

A

KMnO₄ acidified with dil HCl

30
Q

1° Alcohol → Carboxylic Acid

Reagents

A

• Acidified Potassium Dichromate

31
Q

What is the positive test observation for Iodoform

A
  • Pale yellow precipitate

* CHI3

32
Q

What is the positive test observation for Tollen’s reagent

A

• Silver Mirror

33
Q

What does Fehling’s Solution test positive for?

A

An aliphatic aldehyde

34
Q

What is the positive test observation for Fehling’s Solution?

A

The blue solution forms a red precipitate

35
Q

Ester → Carboxylic Acid
Reagent
Condition
Product

A
  • dil HCl / Naoh
  • Room temp / Heated under reflux
  • Cooh acid & alcohol
36
Q

Carboxylic Acid → Ester
Reagents
Conditions
Product

A
  • Alcohol & Conc H2SO4
  • Heat
  • Ester and Water
37
Q 
Ester → Carboxylic Salt + Alcohol
Reagents
Conditions
Product
Reaction type
A
  • NaOH solution
  • Heated under reflux
  • Cooh Salt & alcohol
38
Q

Aldehyde → Carboxylic Acid
Reagents
Conditions

A
  • Acidified Potassium Dichromate

* Heat & reflux & excess of [o]

39
Q

Why does propan-1-ol have a greater solubility in water than pentan-1-ol?

A

The contribution of the OH group in pentan-1-ol is much less than in propan-1-ol because of the larger non-polar group in pentan-1-ol

40
Q

Phenol → Phenyl ethanoate
Reagents
Conditions
Products

A
  • Ethanoyl Chloride
  • Room temp
  • Phenyl ethanoate & HCl
41
Q 
Alcohol → Halogenoalkane
Formation of HBr
Reagents
Conditions
Products
A

• KBr & conc H2SO4

  • HBr
  • reflux
  • Halogenoalkane & water
42
Q

Ways to form an Alcohol

A
  • Nucleophilic Substitution of Halogenoalkane
  • Amine with Nitrous acid
  • Alkenes
  • Reduction of Carbonyls
  • Hydrolysis of Ester
43
Q

Carboxylic Acid → Alcohol

A

Reagents
Conditions
• LiAlH4
• Excess of reducing agent

44
Q

Halogenation of Benzene
Reagents
Conditions
Products

A
  • Cl/Br
  • Absence of light, room temp, anhydrous conditions & halogen carrier
  • C6H5Cl/Br & HCl
45
Q

Explain why it is difficult to react Chlorobenzene with sodium hydroxide

A

The chlorine line pairs interact with the ring electrons which strengthens the C-Cl bond by decreasing bond polarity. This makes chlorobenzene less susceptible to nucleophilic attack.

46
Q

Alkylation of Benzene
Reagents
Conditions

A
  • CH3Cl & AlCl3

* room temp & Dry inert solvent

47
Q

Alcohol → Aldehyde
Reagents
Conditions
Reaction type

A
  • Acidified Potassium Dichromate
  • Heat, excess alcohol & remove aldehyde as it forms
  • Oxidation
48
Q

Alcohol → Alkene
Reagents
Products

A
  • Al2O3 powder

* Ethene, water vapour

49
Q

Explain why phenol is more acidic than a primary alcohol.

A

The phenoxide ion is stabilised by charge delocalisation and the alkyl groups would not delocalise ion.

50
Q

The mechanism for the reaction between ethanal and hydrogen cyanide is shown below. Describe what is happening at each stage of this reaction mechanism and use your answer to explain why this reaction is described as nucleophilic addition.

A

Hydrogen cyanide dissociates giving a H+ and cyanide ion. The mechanism is described as nucleophilic addition because the cyanide ion acts as a nucleophile. Electron density increases and produces a negative charge on the oxygen atom. The oxygen acts as an electron pair donor, attacking a hydrogen ion. In effect, the HCN has added across the C=O.

51
Q

Explain what is meant by the delocalisation energy of benzene

A

The extra stability in the benzene molecule due to electron delocalisation.

52
Q

What does electrophilic addition involve

A

A C=C

53
Q

What does electrophilic substitution involve

A

A benzene ring

54
Q

What does nucleophilic substitution involve

A

A halogenoalkane and CN-, OH-, or NH3

55
Q

What does nucleophilic addition involve?

A

An aldehyde or a ketone

56
Q

Why is there such a low percentage yield when benzene is converted to benzoic acid?

A

There is a two step process which means losses can occur at both stages and oxidation may not be completed, forming some aldehydes.

Chemistry Unit 4 (4 decks)

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