Alcohols

Question 1

what functional group do alcohols contain?

Answer 1

the hydroxyl functional group

Question 2

what is meant by the term functional group?

Answer 2

Atom/group of atoms that give molecules their characteristic for reactions

Question 3

What is the general formula for aliphatic alcohols with one OH group only?

Answer 3

CnH(2n+2)O

Question 4

what are phenols?

Answer 4

Aromatic alcohols

Question 5

Where is the OH group attached to on phenol?

Answer 5

alcohol group directly attached directly to the benzene ring

Question 6

why can alcohols make hydrogen bonds with water molecules and with each other?

Answer 6

because they have H bonded to electronegative O

Question 7

What does hydrogen bond between alcohol molecules do?

Answer 7

reduces their volatility (the ease of conversion from liquid to gas)

Question 8

what the more OH groups that alcohol has result in?

Answer 8

The more hydrogen bonds it can form and the lower of volatility

Question 9

why do alcohols have a tendency to be water soluble?

Answer 9

Because they can form hydrogen bonds

Question 10

what does solubility decrease with?

Answer 10

Solubility decreases as the hydrocarbon chain increases

Question 11

what causes solubility to decrease as the hydrocarbon chain increases is size?

Answer 11

The OH group has less influence and the solubility (lack of) of the longer hydrocarbon chain beccomes more dominant

Question 12

What is a primary alcohol?

Answer 12

The -OH group is attached to a C with at least two H atoms on it and one alkyl group

Question 13

What are secondary alcohols?

Answer 13

The -OH group is attached to a carbon atom with only one H atom on it and two alkyl groups.

Question 14

what are tertiary alcohols?

Answer 14

The -OH group is attached to a carbon atom with no H atoms on it and three alkyl groups.

Question 15

what are the four types of chemical reactions of the alcohols?

Answer 15

-Combustion
-Dehydration
-Substitution
-Oxidation

Question 16

What is combustion of alcohol?

Answer 16

like organic materials, alcohols burn in excess oxygen to produce carbon dioxide and water

Question 17

What does the term dehydration mean?

Answer 17

to remove water from one molecule

Question 18

what is a good dehydrating agent?

Answer 18

Concentrated sulphuric acid or concentrated phosphoric acid

Question 19

what are the conditions for dehydration of alcohol?

Answer 19

Heat under reflux

Question 20

What does dehydration make?

Answer 20

An Alkene

Question 21

Why is dehydration described as elimination?

Answer 21

because H and OH are being taken out from two adjacent c atoms to make water

Question 22

what is substitution reactions of alcohol?

Answer 22

-Alcohols can form when you react with hydrogen halide
-The hydrogen halide is generated in place

Question 23

what is an example of substitution reactions of alcohol?

Answer 23

An alcohol is heated, under reflux, in the presence of sodium chlorine and dilute sulphuric , hydrogen chloride forms in situ (in place)

Question 24

Why do chemical reactions usually need to be heated?

Answer 24

in order to overcome activation energy and increase the rate of reaction

Question 25

what is reflux commonly used to do?

Answer 25

to prepare organic liquids without boiling off the solvent, reactants or products.

Question 26

In the reflux, why is the condenser in an upright position and never a stopper/thermometer at the top?

Answer 26

This would create a closed system

Question 27

why is distillation a commonly used part of the purification of organic liquid?

Answer 27

it separates a pure liquid from its impurities by collecting at the boiling point of the pure liquid

Question 28

What is another use of distillation?

Answer 28

to produce an aldehyde, rather than a carboxylic acid when oxidising a primary alcohol

Question 29

how can primary and secondary alcohols oxidised?

Answer 29

using oxidising agents potassium dichromate, in dilute sulphuric acid

Question 30

What are primary alcohols oxidised to? (loss of H)

Answer 30

Aldehydes

Question 31

What does [O] represent in the oxidation of alcohols?

Answer 31

Oxidising agent

Question 32

Why would you heat alcohol under distillation conditions in oxidation?

Answer 32

So the lower boiling point aldehyde (no H bonds) distils out of the reaction mixture as it forms

Question 33

what would happen if acidified potassium dichromate was used as the oxidising reagent in oxidation?

Answer 33

A quick change from Orange to Green will occur in this reaction (because dichromate is being reduced to chromium (III)

Question 34

What can occur if the oxidising agent is used in excess (oxidation)?

Answer 34

further oxidation can occur to give a carboxylic acid

Question 35

why would you heat oxidation of alcohols under reflux?

Answer 35

so that any alcohol in the initially made goes back into the flask to be further oxidised

Question 36

how can secondary alcohols be oxidised?

Answer 36

they can be oxidised in a similar way to primary alcohols to form ketones

Question 37

why does further oxidation not occur in secondary alcohols?

Answer 37

Ketones cannot be oxidised

Question 38

Can tertiary alcohols be oxidised?

Answer 38

No