Chapter 14 - Alcohols Flashcards

Properties of alcohols, Reaction of alcohols.

1
Q

What is the functional group of alcohols?

A

-OH

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2
Q

Why do alcohols with few carbon atoms have much higher boiling points than alkanes with the same number of carbon atoms?

A

Alcohols have the polar O-H bond, which forms the strong hydrogen bonds between bonds so require more energy to break.

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3
Q

How do alcohols and alkanes compare in volatility?

A

Alcohols with the same number of carbon atoms as an alkane will be less volatile.

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4
Q

Why are alcohols soluble in water?

A

The polar OH bond forms hydrogen bonds with the water molecules.

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5
Q

As hydrocarbon chain increases, how does solubility of alcohols change?

A

It decreases as the OH group’s influence becomes relatively small and solubility shifts to that of alkanes.

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6
Q

What is a primary alcohol?

A

The OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group.

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7
Q

What kind of alcohol is methanol?

A

Although misleading it is a primary alcohol.

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8
Q

Therefore, what are secondary and tertiary alcohols?

A

Secondary: OH attached to carbon attached to two alkyl groups
Tertiary: OH attached to carbon attached to three alkyl groups

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9
Q

The combustion of alcohols has what products?

A

Carbon dioxide and water

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10
Q

What is used to oxidise alcohols?

A

(acidified) Potassium dichromate

K2Cr2O7/H+

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11
Q

What are the two forms of chromium in oxidation reactions?

A

Dichromate(VI) ions that are orange

Chromium(III) ions that are green

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12
Q

Which two products can be formed from the oxidation of primary alcohols?

A

Aldehydes or carboxylic acids

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13
Q

How are aldehydes prepared from the oxidation of primary alcohols?

A

Gentle heating of primary alcohols with acidified potassium dichromate.
Distillation

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14
Q

What measure is taken to ensure no carboxylic acid is made?

A

Aldehyde is distilled out of the mixture as it forms to prevent any further reaction.

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15
Q

How are carboxylic acids prepared from the oxidation of primary alcohols?

A

Primary alcohol is heated strongly under reflux with an excess of acidified potassium dichromate.

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16
Q

Why is it under reflux for carboxylic acid preparation?

A

To ensure any aldehyde initially formed also undegoes oxidation to the carboxylic acid.

17
Q

What product is formed from the oxidation of secondary alcohols?

A

Ketones

18
Q

How are ketones prepared from the oxidation of secondary alcohols?

A

Heated under reflux with acidified potassium dichromate.

19
Q

What product is formed from the oxidation of tertiary alcohols?

A

Tertiary alcohols do not undergo oxidation reactions.

20
Q

What is dehydration?

A

Any reaction in which a water molecule is removed from the starting material.

21
Q

What are the conditions of a dehydration reaction?

A

Alcohol is heated under reflux in the presence of concentrated sulfuric acid or phosphoric acid.

22
Q

What are the products of a dehydration reaction?

A

An alkene and water

23
Q

Alcohols react with hydrogen halides to form what?

A

Haloalkanes and water

24
Q

What are the conditions of a halogen substitution reaction of an alcohol?

A

Alcohol is heated under reflux with sulfuric acid and a sodium halide, the hydrogen halide is formed in situ.