4.2 Alcohols, Haloalkanes and Analysis (started)

Question 1

How do alcohols boiling points compare to similar sized alkanes?

Answer 1

Higher as alcohols have hydrogen bonds between molecules

Question 2

What internolecular forces are present in alcohols?

Answer 2

Hydrogen bonds between formula groups

Question 3

What is a primary, secondary and tertiary alcohol?

Answer 3

1° Primary - end of the carbon chain
2° Secondary - middle of the carbon chain
3° Tertiary - middle with another branch attached of the carbon chain

Question 4

What are the products of a combustion of an alcohol?

Answer 4

Carbon dioxide and water

Question 5

What is the general formula for an alcohol?

Answer 5

Cn H2n+1 OH

Question 6

What is the oxidising agent used to oxidise primary and secondary alcohols?

Answer 6

Acidified potassium dichromate

H+/Cr2O7 2-

Question 7

How are oxidising agents represented in chemical equations?

Answer 7

[O]

Question 8

How do you produce an aldehyde?

Answer 8

Oxidise a primary alcohol by distillation
Produces water as well
Colour change from orange to green

Question 9

How do you produce a carboxylic acid?

Answer 9

Further oxidise an aldehyde
Reflux a primary alcohol
Produces water as well (only from alcohol not from aldehyde)
Colour change from orange to green

Question 10

How do you produce a ketone?

Answer 10

Oxidise a secondary alcohol by reflux
Produces water as well
Colour change from orange to green

Question 11

What happens when you react tertiary alcohols with acidified potassium dichromate?

Answer 11

Nothing happens

Colour remains orange

Question 12

What is reflux?

Answer 12

Continual boiling and condensing of a reaction mixture to ensure the reaction goes to completion without the mixture boiling dry

Question 13

What is distillation?

Answer 13

The technique of heating a liquid to create vapour which is collected when cooled seperate from the original liquid

Question 14

What is an elimination reaction?

Answer 14

Dehydration an alcohol to form an alkene and water
Conc sulphuric acid
Heat
Reflux

Question 15

How do alcohols produce a haloalkane?

Answer 15

Substitution in the presence of an acid

Question 16

Why do you use infra red for spectrometry instead of ultra violet?

Answer 16

Ultra violet will break the bonds

Question 17

What happens if you shine the right amount of energy on a bond with infra red energy?

Answer 17

You can kick it into a higher state of vibration

The amount of energy needed will change and each bond will absorb a different frequency

Question 18

What are applications of infra red spectroscopy?

Answer 18

Breathalysers

Monitoring air pollution

Question 19

How do breathalysers work?

Answer 19

Identifying ethanol by absorbance in C-O O-H bonds

Identifying amount of ethanol by amount if IR absorption

Question 20

What bonds do the common greenhouse gases contain that can be found in IR sprectroscopy?

Answer 20

Carbon Dioxide C=O bonds
Water vapour O-H bonds
Methan C-H bonds

Question 21

What is the moleculer ion peak?

Answer 21

Furthest right peak which is the Mr of the molecuke

Question 22

Why could there be smaller peak just to the right of the molecular ion peak?

Answer 22

Due to a Carbon 13 isotope which will increase the Mr

Question 23

What does each peak show on a mass spectrometer?

Answer 23

Positive ions from fragments of molecule

e.g. CH3OCH3 can have fragments at 31for [CH3O]+ and 15 [CH3]+

Question 24

How does the rate of hydrolysis of a haloalkane depend on the halogen present?

Answer 24

The weaker the bond the faster the rate of reaction

C-I is the weakest and therefore fastest, rate decreases up the group