Alcohols

Question 1

What type of bonding occurs between alcohols?

Answer 1

Hydrogen bonding between the polar OH groups due to O and H having different electronegativity.

Question 2

Do alcohols have a higher or lower volatility than alkanes and why?

Answer 2

Lower- like alkanes alcohols have weak London forces yet they also have strong hydrogen bonds so more energy is required to overcome the attractions therefore compared to alkanes they have high boiling points and lower volatility.

Question 3

Do alcohols have high or low water solubility and why?

Answer 3

High- both alcohol and water molecules can form hydrogen bonds between each other

Question 4

What effects the water solubility of alcohols?

Answer 4

Chain length- longer the hydrocarbon chain= more non-polar and OH influence decreases so less soluble
Number of OH groups- more OH groups= more soluble

Question 5

How do you classify primary, secondary and tertiary alcohols?

Answer 5

Primary- The C with the OH group attached only has 1 R group
Secondary- 2 R groups
Tertiary- 3 R groups

Question 6

What is the oxidising agent for oxidising alcohols?

Answer 6

K2Cr207/ H2SO4 (aq)

Question 7

How many ways can a primary alcohol oxidise and why?

Answer 7

2 due to the 2 H’s on the C with the OH group

Question 8

What is the reaction equation for the oxidation of a primary alcohol under distillation, what is formed and what are the conditions?

Answer 8

RCH2OH + [O] -> RCHO + H2O
An aldehyde is formed
Conditions- [O]= K2Cr2O7/H2SO4(aq)
Heat under distillation

Question 9

What is the reaction equation for the oxidation of a primary alcohol under reflux, what is formed and what are the conditions?

Answer 9

RCH2OH+ 2[O] -> RCOOH+ H2O
A carboxylic acid is formed
Conditions- K2Cr2O7/H2SO4(aq)
Heat under reflux

Question 10

What is the reaction equation of the oxidation of an aldehyde to a carboxylic acid and what are the conditions?

Answer 10

RCHO + [O] -> RCOOH

Conditions: K2Cr2O7/ H2SO4 (aq)
Heat under reflux

Question 11

How many times can a secondary alcohol be oxidised?

Answer 11

1 as it has 1 Hydrogen on the C with the OH group

Question 12

What is the reaction of the oxidation of a secondary alcohol, what is formed and what are the conditions?

Answer 12

R2CHOH+ [O] -> R2C=O + H2O
A ketone is formed
Conditions: Conditions: K2Cr2O7/ H2SO4 (aq)
Heat under reflux (for best yield)

Question 13

How many times can a tertiary alcohol be oxidised and why?

Answer 13

No times as there are no H’s on the carbon with the OH group (the C-C bond = too strong)

Question 14

Uses of alcohols:

Answer 14

Fuel
Chemical feedstock
Solvent

(NOT A SOLUTION)

Question 15

How are alcohols formed?

Answer 15

Hydration of an alkane with steam and a conc H3PO4/ H2SO4 (aq)

Question 16

What colour will the solution turn if it has been oxidised?

Answer 16

From orange (K2Cr2O7/ H2SO4 (aq) ) to green

Question 17

What are the products of dehydration of an alcohol?

Answer 17

An alkene and water

Reverse of hydration of alkenes

Question 18

How many alkenes are produced in the dehydration of a primary alcohol and give the equation and conditions:

Answer 18

Only 1 alkene produced

RCH2CH2OH -> RCH=CH2 + H2O

Conditions: H2SO4/ H3PO4 (aq) catalyst
Heat under reflux

Question 19

How many alkenes can be produced by secondary and tertiary alcohols and what does this depend on?

Answer 19

More than 1
Asymmetric alcohols= 2 or 3 alkenes
Symmetric alcohols= only 1 alkene

Question 20

What is the overall reaction for a substitution reaction of an alcohol and what are the conditions? And what is formed?

Answer 20

ROH + HX(aq) ->RX +H2O

Conditions prepared in situ:
NaX (s) + H2SO4 -> NaHSO4 + HX
Heat under reflux

A haloalkane is formed!