Topic B3 - Alcohols

Question 1

Why do alcohols have a higher boiling point than alkanes?

Answer 1

-alcohols have a polar O-H bonds (due to difference in electronegativity of oxygen and hydrogen atoms)
-hence, alcohol molecules are polar
-IMFs will be weak London forces but their will also ne much stronger hydrogen bonds between the polar O-H groups

Question 2

Alcohols have a lower volatility when compared to…

Answer 2

alkanes with the same number of carbon atoms

Question 3

What are alcohols solubility in water?

Answer 3

completely soluble in water as hydrogen bonds form between polar -OH group of alcohol and water

Question 4

Solubility of alcohols decreases as…

Answer 4

hydrocarbon chain increases in size

Question 5

What is a primary alcohol?

Answer 5

-OH group is attached to a carbon atoms that is attached to:
-2 hydrogen atoms
-1 alkyl group

Question 6

What is a secondary alcohol?

Answer 6

-OH group is attached to a carbon atom that is attached to:
-1 hydrogen atom
-2 alkyl groups

Question 7

Complete combustion of alcohols

Answer 7

-produces carbon dioxide and water
-exothermic reaction
-as number of carbons in the chain increases, quantity of heat released per mole increases

Question 8

Partial oxidation of primary alcohols —>

Answer 8

aldehyde

Question 9

Complete oxidation of primary alcohols —>

Answer 9

carboxylic acid

Question 10

Forming an aldehyde via partial oxidation

Answer 10

-gently heat primary alcohol with potassium dichromate
-distil aldehyde out of reaction mixture immediately as it forms

Question 11

Colour change of alcohol oxidation

Answer 11

orange —> green

Question 12

Forming a carboxylic acid via full oxidation

Answer 12

-heat strongly under reflux
-with an excess of potassium dichromate

Question 13

Oxidation of secondary alcohols —>

Answer 13

ketones

Question 14

Forming a ketone via oxidation

Answer 14

-heated under reflux
-potassium dichromate

Question 15

Tertiary alcohols oxidation

Answer 15

cannot undergo oxidation reactions - potassium dichromate remains orange

Question 16

Dehydration of an alcohol

Answer 16

-heated under reflux
-concentrated sulfuric acid catalyst
-produces an alkene

Question 17

Dehydration of an alcohol is an example of what type of reaction?

Answer 17

elimination

Question 18

Alcohol + hydrogen halide —>

Answer 18

haloalkane

Question 19

Forming a halolalkane from an alcohol + hydrogen halide

Answer 19

-heated under reflux
-sulfuric acid
-sodium halide