Alcohols, Haloalkanes and Analysis

Question 1

What is a primary alcohol?

Answer 1

An alcohol where is the functional group is attached to a carbon atom with no more than one alkyl group

Question 2

What is a secondary alcohol?

Answer 2

An alcohol where is the functional group is attached to a carbon atom with two alkyl groups

Question 3

What is a tertiary alcohol?

Answer 3

An alcohol where is the functional group is attached to a carbon atom with three alkyl groups

Question 4

What happens to the boiling point of alcohols as chain length increases? why?

Answer 4

BP increases as chain length increases because as the molecules get longer there are more surface area contacts and so stronger dipole-dipole inter-molecular forces therefore meaning more energy is needed to overcome these attractive forces

Question 5

Why are the boiling points of alcohols higher than their corresponding alkanes?

Answer 5

There are hydrogen bonds between alcohol molecules thus more energy is needed to break these stronger bonds.

Question 6

Are alcohols soluble in water? why?

Answer 6

Water molecules are polar and so is the OH group, meaning methanol, ethanol and propanol are soluble in water by creating hydrogen bonds.

Question 7

What is produced when an alcohol is completely combusted?

Answer 7

Carbon dioxide and water

Question 8

What are the reaction conditions required to turn a primary alcohol into an aldehyde and what observations would be made?

Answer 8

Gentle heating

colour change: orange -> green

Question 9

What are the reaction conditions required to turn a primary alcohol into a carboxylic acid and what observations would be made?

Answer 9

Stronger heating under reflux with excess potassium dichromate (oxidising agent)
colour change: orange -> green

Question 10

What are the reaction conditions required to turn a secondary alcohol into a ketone and what observations would be made?

Answer 10

Heat under reflux

Colour change: orange -> green

Question 11

Can you oxidise a tertiary alcohol?

Answer 11

No

Question 12

If you gently heat a primary alcohol, what is produced?

Answer 12

An aldehyde

Question 13

If you heat a primary alcohol under reflux with excess potassium dichromate, what is produced?

Answer 13

A carboxylic acid

Question 14

If you heat a secondary alcohol under reflux, what is produced?

Answer 14

A ketone

Question 15

How do you make an ester?

Answer 15

• A few cm3 of alcohol and carboxylic acid are added to a test tube
• Add a few drops of sulphuric acid as a catalyst
• Heat test tube to 80 degrees.
• Once you can smell the fruity ester smell, the ester has been formed.

Question 16

What is dehydration?

Answer 16

A chemical reaction in which water is lost from an organic compound.

Question 17

How do you dehydrate an alcohol?

Answer 17

Heat the alcohol under reflux with concentrated sulphuric acid for about 40 mins.

Question 18

What is elimination?

Answer 18

An organic reaction in which one reactant forms two products, usually releasing a small molecule like water.

Question 19

What is a primary haloalkane?

Answer 19

A chain of carbon atoms with a halogen atom at the end of the chain

Question 20

Are haloalkanes polar or non-polar?

Answer 20

Polar

Question 21

What are nucleophiles?

Answer 21

Electron pair donars

Question 22

How does the strength of the carbon-halogen bond increase down group 7? why?

Answer 22

Going down the group, atoms get larger so their bonding electrons are further away from the nuclei and feel stronger shielding. This results in lower mean bond enthalpies and the bonds are easier to break.

Question 23

What is nucleophilic substitution?

Answer 23

A chemical reaction in which an atom or group of atoms are exchanged for a nucleophile

Question 24

What is hydrolysis?

Answer 24

A chemical reaction in which water is a reactant

Question 25

How do you investigate the rate of hydrolysis for a primary haloalkane?

Answer 25

• Add 1 cm3 of haloalkane into test tube
• Put test tubes into 50 degree water bath
• Half fill a separate test tube with ethanol, water and silver nitrate ions and place them into the water bath
• When the liquids have reached the same temperature, add 1 cm3 of the mixture into the haloalkane and time how long it takes for the precipitate to appear.

Question 26

How does the rate of hydrolysis change as you go down the halide group?

Answer 26

The rate of hydrolysis increases due to a C-I bond being easier to break than a C-Br bond.

Question 27

What are Chloro-fluoro-carbons (CFCs)?

Answer 27

A class of inert organic compounds containing chlorine and fluorine atoms

Question 28

What is the ozone layer?

Answer 28

An area of high ozone (O3) concentration in the stratosphere

Question 29

What is a radical?

Answer 29

A highly reactive species with one or more unpaired electrons

Question 30

At what wavelength in infrared spectroscopy would the C=O bond peak at?

Answer 30

1640-1750

Question 31

At what wavelength in infrared spectroscopy would the O-H bond peak at for carboxylic acids?

Answer 31

2500-3300

Question 32

At what wavelength in infrared spectroscopy would the O-H bond peak at for alcohols?

Answer 32

3200-3550

Question 33

What is the molecular ion?

Answer 33

The positive ion formed in mass spectrometry when a molecule loses an electron