12 Alcohols and haloalkanes

Question 1

How can the rate of hydrolysis of haloalkanes be followed?

Answer 1

with the speed of the formation of a silver precipitate

Question 2

What does CFC stand for?

Answer 2

chlorofluorocarbons

Question 3

What is the definition of a nucleophile?

Answer 3

atom with a negative charge or an atom that has a δ− charge/ a species that can donate a lone pair of electrons

Question 4

Is 2-chloropropane a primary, secondary, or tertiary haloalkane?

Answer 4

secondary

Question 5

What colour precipitate will a bromoalkane form upon addition of silver nitrate?

Answer 5

Pale cream

Question 6

What is the chemical formula for ozone?

Answer 6

O3

Question 7

What type of reaction happens when a haloalkane reacts with aqueous sodium hydroxide or potassium hydroxide?

Answer 7

nucleophilic substitution

Question 8

Why do haloalkanes contain polar bonds?

Answer 8

due to the difference in electronegativity between the halogens and carbon

Question 9

Which Halogen–carbon bond is the most reactive?

Answer 9

C—I

Question 10

Why do alcohols have a higher boiling point than comparable alkanes?

Answer 10

due to their stronger intermolecular bonds or hydrogen bonds

Question 11

Are alcohols more volatile than alkanes?

Answer 11

alcohols are less volatile

Question 12

How many OH group are there in a -triol molecule?

Answer 12

Three

Question 13

Why are alcohols polar?

Answer 13

due to the difference in electronegativity between oxygen and hydrogen

Question 14

What do primary alcohols partially oxidise to?

Answer 14

aldehydes

Question 15

What do primary alcohols fully oxidise to?

Answer 15

carboxylic acids

Question 16

What type of intermolecular bonding is found in alcohols but not in alkanes?

Answer 16

hydrogen bonding

Question 17

What do secondary alcohols oxidise to?

Answer 17

Ketones

Question 18

What do tertiary alcohols oxidise to?

Answer 18

they do not oxidise

Question 19

What colour change can be seen in the oxidation of alcohols by potassium dichromate(VII)?

Answer 19

orange acidified potassium dichromate(VII) (Cr2O72−) will reduce to green chromium ions (Cr3+) in the reaction

Question 20

How can you partially oxidise alcohols to aldehydes?

Answer 20

You get an aldehyde if you use an excess of the alcohol, and distil off the aldehyde as soon as it forms.

Question 21

How do you fully oxidise alcohols to crboxylic acids?

Answer 21

The alcohol is heated under reflux with an excess of the oxidising agent. Make sure that the aldehyde formed as the half-way product stays in the mixture using a reflux condenser. When the reaction is complete, the carboxylic acid is distilled off.

Question 22

What can secondary alcohols be oxidised to?

Answer 22

Secondary alcohols are oxidised to ketones - and that’s it.

Question 23

How can you distinguish between the primary and secondary alcohols?

Answer 23

There are various things which aldehydes do which ketones don’t. These include the reactions with Tollens’ reagent, Fehling’s solution and Benedict’s solution.

A much simpler but fairly reliable test is to use cold Schiff’s reagent. In the presence of even small amounts of an aldehyde, it turns bright magenta.

Question 24

How can gaseous alcohols be dehydrated to give an alkene.

Answer 24

If ethanol vapour is passed over heated aluminium oxide powder, the ethanol is essentially cracked to give ethene and water vapour.