Dehydrating alcohols

Question 1

What do you eliminate from alcohols?

Answer 1

Water

Question 2

What is formed when you dehydrated an alcohol?

Answer 2

Alkene

Question 3

What is the general formula for the dehydration of an alcohol?

Answer 3

CnH2n+1OH -> CnH2n + H2O

Question 4

Why is a dehydration reaction beneficial?

Answer 4

Produce alkenes from renewable sources eg. make ethanol from glucose from plants
Make polymers without needing oil

Question 5

What catalyst is used in a dehydration reaction?

Answer 5

Concentrated sulfuric acid

or phosphoric acid

Question 6

What does the dehydration of longer, unsymmetrical alcohols result in?

Answer 6

More than one product

Double bond can go to either side of the carbon that has the OH group on

Question 7

What is the issue with the products of organic reactions?

Answer 7

They are often impure

Question 8

What does the end mixture of a dehydration reaction contain?

Answer 8

The product
The reactant 
Acid
Water 
Other impurities

Question 9

What technique is used to separate the chemicals?

Answer 9

Distillation

Question 10

Outline the process of distillation.

Answer 10

1) Add concentrated sulphuric acid and phosphoric acid to a round bottomed flask containing the alcohol. Swirl to mix and add boiling chips
2) Connect to distillation apparatus (Thermometer, condenser, cooled collection flask)
3) Gently heat to the boiling point of the alcohol in a water bath or electric heater
4) Chemicals with that boiling point will evaporate. The warm gas will rise out of the flask and into the condenser
5) The condenser has cold running water through the outside so cooler temperatures turn the gas to a liquid and product is collected.

Question 11

Outline the process of separation.

Answer 11

1) Product collected will still contain impurities
2) Transfer to a separating funnel and add water to dissolve water soluble impurities and create an aqueous solution
3) Allow mixture to settle into laters. Drain off aqueous later at the bottom, leaving impure alkene.

Question 12

Outline the process of purification.

Answer 12

1) Drain off the impure alkene into a round bottomed flash
2) Add anhydrous CaCl2 (drying agent) and stopper to the flash
3) let mixture dry with occasional swirling
4) The alkene may still have small amounts of impurities so distill the mixture one last time