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Module 4- Core organic > 14 Alcohols > Flashcards

14 Alcohols Flashcards

1
Q

What is an alcohol?
(1 mark)

A

A compound that contains hydroxyl (OH) group(s).

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2
Q

Why are alcohols polar and what does this cause?
(4 marks)

A

Difference in electronegativity between delta negative O and delta positive H.
This means hydrogen bonds can be formed
and melting and boiling points are higher,
due to stronger intermolecular forces.

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3
Q

Describe the trend in solubility in alcohols.
(3 marks)

A

As the hydrocarbon chain length of the alcohol increases, solubility decreases
because the influence of the hydroxyl group becomes relatively smaller,
decreasing the interactions with water molecules.

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4
Q

What is a primary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to one other carbon atom.

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5
Q

What is a secondary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to two other carbon atoms.

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6
Q

What is a tertiary alcohol?
(1 mark)

A

When the carbon bonded to the hydroxyl group is attracted to three other carbon atoms.

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7
Q

Describe the trend in boiling point of alcohols.
(3 marks)

A

Boiling point increases as the length of the carbon chain in the alcohol increases.
This is because the induced dipole-dipole interactions become stronger,
therefore more energy is required to overcome the intermolecular forces,
so the boiling point is higher.

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8
Q

Why is propane-1,2,3-triol more soluble in water than propan-1-ol?
(4 marks)

A

Propane-1,2,3-triol has three hydroxyl groups.
Propan-1-ol has one hydroxyl group.
Propane-1,2,3-triol has more hydroxyl groups to form hydrogen bonds with water molecules.
The more hydrogen bonds formed between a molecule and water, the greater the solubility.

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9
Q

What is the suffix for alcohols?
(1 mark)

A

-ol

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10
Q

What shapes do alcohols form?
(2 marks)

A

Pyramid-like
Bent

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11
Q

What should be included in a diagram showing hydrogen bonds?
(4 marks)

A

The HOH should be in a straight line
Partial charges
Line pair of electrons (on the oxygen)
Hydrogen bond should be labelled

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12
Q

Do lone pairs or bonding pairs repel more?
(1 mark)

A

Lone pairs

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13
Q

State and explain the HCH and COH angles in ethanol- might need paper.
(6 marks)

A

HCH:
4 areas of electron density
4 bonding pairs
Repel equally
109.5 degree bond angle

COH:
4 areas of electron density
2 bonding pairs, 2 line pairs of electrons
Lone pairs repel more
104.5 degree bond angle (109.5 - (2.5 x 2))

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14
Q

Describe the combustion of alcohols. (4 marks)

A

Burn completely
In a plentiful supply of oxygen
To produce H2O and CO2
Exothermic reaction

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15
Q

How are primary and secondary alcohols oxidised? (3 marks)

A

Using oxidising agents
Potassium dichromate
And dilute sulphuric acid

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16
Q

If an alcohol os oxidised, what colour change is expected and why? (3 marks)

A

Orange to green
Redox reaction takes place
To produce water and chromium ions

17
Q

Describe how aldehydes are prepared. (3 marks)

A

Gently heating primary alcohol
With potassium dichromate and dilute sulphuric acid
The aldehyde is distilled out of the mixture as it forms

18
Q

Why is the aldehyde distilled out of the mixture as it is formed? (2 marks)

A

To prevent any further reaction with the oxidising agent
To ensure the aldehyde is formed rather than the carboxylic acid

19
Q

Describe how carboxylic acids are prepared. (2 marks)

A

Primary alcohol is heated strongly under reflux (with excess potassium dichromate and dilute sulphuric acid).

20
Q

When producing carboxylic acids, why is heating under reflux used? (1 mark)

A

It ensures that any aldehyde formed initially in the reaction also undergoes oxidation to produce the carboxylic acid.

21
Q

What is produced when a primary alcohol is partially oxidised? (1mark)

A

Aldehyde

22
Q

What is produced when a primary alcohol is fully oxidised? (1 mark)

A

Carboxylic acid

23
Q

What is produced when a secondary alcohol is oxidised? (1 mark)

A

Ketone

24
Q

How are ketones produced? (2 marks)

A

Heating secondary alcohols
Under reflux (with potassium dichromate and dilute sulphuric acid).

25
Q

How are tertiary alcohols oxidised? (1 mark)

A

THEY DO NOT UNDERGO OXIDATION REACTIONS

26
Q

What type of reaction is a dehydration reaction? (1 mark)

A

Elimination reaction

27
Q

What is removed during a dehydration reaction? (1 mark)

A

Water

28
Q

What is produced in a dehydration of alcohol reaction?

A

Alkene

29
Q

Describe how dehydration of alcohols is done?

A

Heated under reflux
In the presence of an acid catalyst

30
Q

What is produced from an alcohol and a hydrogen halide? (1 mark)

A

Haloalkane

31
Q

Describe the conditions of a substitution reaction of an alcohol.

A

Heated under reflux
With sulphuric acid and a sodium halide.

Module 4- Core organic (7 decks)

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