What's In A Medicine

Question 1

Why do alcohols have a higher boiling point than their corresponding alkanes?

Answer 1

The -OH group on the alcohol is able to form hydrogen bonds which require more energy to break

Question 2

What is the difference between a primary, secondary, and tertiary alcohol?

Answer 2

Primary: -OH group bonded to a carbon bonded to one other carbon

Secondary: -OH group bonded to a carbon bonded to two other carbons

Tertiary: -OH group bonded to a carbon bonded to three other carbons

Question 3

Oxidation of primary alcohols

Answer 3

Products: Aldehyde made first, if there is excess oxidsing agent then a carboxylic acid is formed

Oxidsing agent: Acidified potassium dichromate (VI)

Final Colour of reaction mixture: Green

Question 4

Oxidation of secondary alcohols

Answer 4

Products: Ketone

Oxidsing agent: Acidified potassium dichromate (VI)

Final colour of reaction mixture: Green

Question 5

Oxidation of tertiary alcohols

Answer 5

Products: Does not oxidise

Final colour of reaction mixture: Orange

Question 6

How does reflux work

Answer 6

Liquid is boiled in a vertically mounted condenser so the vapour condenses and returns back into the reaction mixture

Used for heating volatile and flammable liquids

Question 7

Dehydration of alcohols

Answer 7

Alcohols can loose a molecule of water to form an alkene

Conditions: Alumina (Al2O3) catalyst at 300°C OR reflux with concentrated sulphuric acid

Dehydration is an example of a elimination reaction

Question 8

Substitution reactions will alcohols

Answer 8

Nucleophilic substitution with halide ions in the presence of a strong acid

Question 9

Esterification with carboxylic acids and acid anhydrides

Answer 9

Carboxylic acid:
Alcohol + Acid –> Ester + Water
Small amount of concentrated acid as catalyst
Named by alcohol then acid

Acid anhydride:
Alcohol + Acid anhydride –> Ester + Acid
Higher yelid of ester
Named by alcohol then anhydride

Question 10

Ethers

Answer 10

General formula of R-O-R

Structural isomers of alcohols

Question 11

Which molecules contain a hydroxyl group

Answer 11

Alcohols, phenols, and carboxylic acid

Question 12

The order of acidic strength; water, carboxylic acids, phenol, alcohol

Answer 12

Alcohol < Water < Phenol < Carboxylic Acids

Question 13

Reactions with carbonates

Answer 13

Only carboxylic acids have a high enough concentrations of H+ ions to produce carbon dioxide on reactions with carbonates

Alcohols and phenols will not react

Question 14

How to test for phenols

Answer 14

Reaction with iron (III) chloride

If phenol present, the mixture turns purple

Question 15

Ester formation with phenols

Answer 15

Phenol + Acid anhydride –> Ester + Acids
Under alkaline conditions

Phenols do not reaction with carboxylic acids to produce esters

Question 16

Equation linking speed of light, wavelength, and frequency

Answer 16

Speed of light = Wavelength x Frequency

Question 17

What does quantise mean

Answer 17

Molecules must take a small number of definite energy values rather than any energy values

Question 18

Different types of bond deformation

Answer 18

• Symmetric stretch
• Asymmetric stretch
• Symmetric bend

Question 19

Two most important regions on IR spectra

Answer 19

-OH group, around 3000

C double bond O, around 1600

Question 20

Fingerprint region

Answer 20

The region below 1500 which is characteristic of the particular molecule

Question 21

What can be told from mass spectrometry

Answer 21

• The molecular ion, M+
• The fragment pattern
• The relative abundance of fragment ions

Question 22

Recrystallisation

Answer 22

1) Seleft a solvent in which the desired substance is very soluble at high temperatures and and insoluble at low temperatures
2) Dissolve the mixture in the minimum quantity of hot solvent to better the yield
3) Filter to remove any insoluble impurities
4) Leave to cool until crystals form
5) Collect crystals by vacuum filtration
6) Leave the crystals to dry

Question 23

Thin Layer Chromatography

Answer 23

Used to test the purity of a substance

Question 24

Melting point determination

Answer 24

Used to test the purity of substances. A pure compound should melt within 0.5°C of it’s true melting point