M4 Chapter 14 - Alcohols

Question 1

What is the functional group of an alcohol?

Answer 1

-OH / Hydroxyl Group

Question 2

What is the general formula of an alcohol?

Answer 2

CnH2n+1OH

Question 3

How do you name alcohols? (prefix/suffix)

Answer 3

Hydroxyl- or -ol

Question 4

What kind of intermolecular forces do alcohols have? Why?

Answer 4

Hydrogen bonding due to the difference in electronegativity in the O-H bond.

Question 5

How do alcohols’ melting point and boiling point compare to other hydrocarbons’ of similar C chain lengths? Why?

Answer 5

The points are higher due to Hydrogen Bonding (This is the strongest type of intermolecular force, stronger than London Forces)

Question 6

Are alcohols soluble in water? Why does solubility depend on chain length?

Answer 6

Soluble when short chain due to the OH hydrogen bonds to hydrogen bond in water.
Insoluble when longer as the non-polarity of C-H takes precedence meaning the alcohol represents an alkane more.

Question 7

What makes an alcohol primary?

Answer 7

When the C bonded to the OH is only bonded to one other C atom.

Question 8

What makes an alcohol secondary?

Answer 8

C bonded to OH is bonded to two other C atoms.

Question 9

What makes an alcohol tertiary?

Answer 9

C bonded to OH is bonded to three other C atoms.

Question 10

What reactions can alcohols undergo?

Answer 10

Combustion
Oxidation
Dehydration
Substitution

Question 11

Write the equation for the combustion of ethanol.

Answer 11

C2H5OH(l) + 3O2(g) –> 2CO2(g) + 3H2O(l)

Question 12

What forms if you partially oxidise a primary alcohol?

Answer 12

An aldehyde

Question 13

What conditions are needed to partially oxidise a primary alcohol?

Answer 13

Acidified Potassium Dichromate
Distill (gentle heating)

Question 14

Write the equation for the partial oxidation of ethanol.

Answer 14

C2H5OH(l) + [O] –> CH3CHO(g) + H2O(l)

Question 15

Why do we use distillation here rather than reflux?

Answer 15

Because we need to remove the aldehyde from the reaction mixture as it can still be oxidised further.

Question 16

What forms if you fully oxidise a primary alcohol?

Answer 16

Carboxylic Acid

Question 17

What conditions are needed to fully oxidise a primary alcohol?

Answer 17

Acidified Potassium Dichromate
Reflux (Strong Heating)

Question 18

Write an equation for the full oxidation of ethanol.

Answer 18

CH3CH2OH(l) + 2[O] –> CH3COOH(g) + H2O(l)

Question 19

What forms if you oxidise a secondary alcohol?

Answer 19

Ketone

Question 20

What conditions are needed for the oxidation of a secondary alcohol?

Answer 20

Acidified Potassium Dichromate
Reflux (Strong Heating)

Question 21

Write an equation for the oxidation of propan-2-ol.

Answer 21

CH3CH(OH)CH3(l) + [O] –> CH3COCH3(g) + H2O(l)

Question 22

Is it possible to oxidise a tertiary alcohol?

Answer 22

No

Question 23

What is a dehydration reaction?

Answer 23

A reaction where water is lost to form an organic compound.

Question 24

What are the reactants, conditions, products of a dehydration reaction with an alcohol?

Answer 24

Reactants = Alcohol
Conditions = Reflux, Acid Catalyst (Eg: H3PO4), 170C
Products = Alkene + Water

Question 25

What are the reactants, conditions, products of a halide substitution reaction with an alcohol?

Answer 25

Reactants = Alcohol Conditions = Reflux, Sulfuric Acid, Sodium Halide Products = Haloalkane (primary/secondary dependant on alcohol) and Water

Question 26

What form is the halide used in halide substitution reaction for alcohols?

Answer 26

In the form of a Hydrogen Halide

Question 27

How is hydrogen halide made in situ(then and there during the reaction)? Give examples.

Answer 27

A salt is reacted with acid to form the hydrogen halide. Eg: NaBr reacts with Sulfuric Acid to form HBr (reaction below) --> NaBr + H2SO4 --> NaHSO4 + HBr (this is all during the halide substitution reaction too)

Question 28

During the halide substitution reaction of iodine, why do we use phosphoric acid rather than sulfuric acid?

Answer 28

Because if we used the sulfuric acid, it would oxidise a lot of the iodide ions and not form a lot of HI (the product needed to be made in situ)