Alcohols

Question 1

What can a primary alcohol produce when oxidised

Answer 1

Aldehyde
If oxidised further it can produce a carboxylic acid

Question 2

What can a secondary alcohol produce

Answer 2

Ketone

Question 3

What is suitable to use in order to seperate an aldehyde from its oxidising agent

Answer 3

Distillation

Question 4

What is suitable to use if a carboxylic acid or ketone is being produced

Answer 4

Reflux

Question 5

Summary of oxidation of alcohols

Answer 5

Primary and secondary alcohols can be oxidised by an oxidising agent such has acidified potassium dichromate ( H+/ K2Cr2O7)

Question 6

What is the dehydration of an alcohol also known as

Answer 6

Elimination reaction, creating 2 molecules from 1

Question 7

What is the test for alkene

Answer 7

Excess reactant added to bromine water
Electrophilic addition will occur
Positive test will result in decolorisation from orange/yellow

Question 8

Test for alcohol

Answer 8

Acidified (HCl or H2SO4) potassium dichromate
Few drops of alcohol
If no reaction in cold, heat in water bath
Solution turns orange to green if positive, forming chromium (III) ions

Tertiary alcohols produce no colour change

Question 9

Tollen’s reagent

Answer 9

add reactant to 1drop of NaOH to silver (I) nitrate solution, brown silver oxide precipitate
Dissolve precipitate with dilute ammonia

Ketone - no colour change in colourless solution
Aldehyde - Colourless to grey precipitate of silver form mirror around test tube

Question 10

Fehlings solution

Answer 10

Contains copper (II) ions)
Few drops of aldehyde or ketone added to reagent
Warmed gently in hot water bath for few mins

Ketone - No change in solution
Aldehyde - Blue to dark red precipitate

Question 11

Test for carboxylic acid

Answer 11

React with carbonate solution
2cm^3 Na2CO3 or NaHCO3 added
Bubbles produced
Bubble gas through limewater
If limewater molly or cloudy, CO2 produced

Acid + carbonate —> carbon dioxide + water + salt

Question 12

Combustion of alcohol

Answer 12

CnH2n+1OH + O2 —> CO2 + H2O

Question 13

Why do alcohols have a high boiling point?

Answer 13

The OH allows hydrogen bonding to occur

Question 14

What is the solubility of alcohols like?

Answer 14

Short chain alcohols are soluble in water

However long chains are not as the non polar long hydrocarbon chain dominates, chain is not polar enough.

Question 15

Equation for production of ethanol from crude oil + conditions

Answer 15

C2H4 + H2O –> C2H5OH

Phosphoric acid catalyst

Question 16

What is ethanol used for?

Answer 16

Solvent in cosmetics - aftershave
Drug manufacture
Detergents
Inks
Coatings

Question 17

How is ethanol made in plants? + equation

Answer 17

Fermentation via anaerobic respiration

C6H12O6 –> 2C2H5OH + 2CO2

Question 18

WHat are the conditions required for the dehydration of an alcohol?

Answer 18

Phosphoric acid catalyst or Al2O3 or conc sulfuric acid

600K