14.2 Reactions of alcohols Flashcards

1
Q

What do alcohols burn completely to produce in a plentiful supply of oxygen

A

Carbon dioxide and water

Reaction is exothermic, releasing large quantity of energy in form of heat

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2
Q

How does the quantity of heat released per mole change as the number of atoms in the alcohol chain increases

A

The quantity of heat released per mole also increases

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3
Q

How can primary and secondary alcohols be oxidised

A

By an oxidising agent

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4
Q

What is the usual oxidising mixture of primary and secondary alcohols

A

Solution of potassium divhromate, acidified with dilute sulfuric acid
If alcohol is oxidised, orange solution containing dichromate ions reduced to green solution containing chromium

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5
Q

What can primary alcohols be oxidised to

A

Either aldehydes or carboxylic acids

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6
Q

What is formed when primary alcohols and acidified potassium dichromate are gently heated

A

An aldehyde is formed

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7
Q

How can we ensure that an aldehyde is formed rather than a carboxylic acid

A

The aldehyde is distilled out of the reaction mixture as it forms
Prevents any further reaction with oxidising agent
Dichromate ions colour changes from orange to green

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8
Q

What is formed if a primary alcohol is heated strongly under reflux with an excess of acidified potassium dichromate

A

A carboxylic acid is formed
Use of excess of acidified potassium dichromate ensures that all of alcohol is oxidised
Heating under reflux ensures any aldehyde formed undergoes oxidation

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9
Q

When preparing the aldehyde, use ______ to remove the aldehyde from the reaction mixture. When preparing the carboxylic acid, ______ the alcohol under ______.

A

Distillation
Heat
Reflux

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10
Q

What are secondary alcohols oxidised to

A

Ketones
Not possible to further oxidise ketones using acidified dichromate (VI) ions
Ensure reaction to completion, heated under reflux with oxidising mixture

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11
Q

Oxidation reactions of tertiary alcohols

A

NONONO
THEY DO NOT UNDERGO
The acidified dichromate (VI) remains orange

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12
Q

On oxidation:

A

Primary alcohol - aldehyde, carboxylic acid
Secondary alcohol - ketone
Tertiary alcohol - no reaction

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13
Q

What symbol is used to show that an oxidising agent is being used in an equation

A

[O]

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14
Q

What is dehydration

A

In any reaction, this is where a water molecule is removed from the starting material

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15
Q

What is the dehydration of an alcohol an example of

A

An elimination reaction

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16
Q

What do alcohols react with hydrogen halides to form

A

Haloalkanes

Alcohol is heated under reflux with sulfuric acid and sodium halide, hydrogen bromide formed in situ (in place)

17
Q

What is the product of the reaction of an acid under reflux in the presence of an acid catalyst such as sulfuric acid (while heated)

A

An alkene