Alcohols Flashcards
(23 cards)
What is the alcohols functional group
CnH2n+1OH
What does the polar OH allow?
Hydrogen bonding in water therefore they are miscible
What is a primary, secondary and tertiary alcohol?
Primary - One carbon directly bonded to the carbon atom that is bonded to the OH group
Secondary - two
Tertiary - Three
What are the main methods of preparing alcohols?
1) From the corresponding halogenoalkane by heating the halogenoalkane under reflux with sodium bromide solution, which is hydrolysis and occurs by nucleophilic substitution
2) A liquid alcohol can be distilled off by fractional distillation
What is the colour of the flame when alcohols are burnt?
Blue
Why is ethanol considered a carbon neutral fuel?
It can be formed from fermentation of plant sugars made during photosynthesis. Photosynthesis uses up CO2 in the atmosphere. Less soot given off while burnt as it burns with a clean blue flame
What are the conditions for an alcohol reacting with phosphorus pentachloride PCl5
In a fume cupboard, add phosphorus pentachloride to the alcohol
Products?
halogenoalkane, POCl3 (phosphorus oxychloride) and HCl
Observations?
Misty fumes, solid disappears, exothermic
What are the conditions for an alcohol to react with hydrogen bromide
Heat under reflux with HBr - HBr generated in situ from NaBr and H2SO4
Products
Halogenoalkane and water
What are the conditions for an alcohol to react with sodium
A small piece of sodium metal added to the alcohol
What are the products
Sodium alkoxide (H drops off OH and it becomes ONa) and hydrogen
Observations
Fizzing
What is acidified potassium dichromate (VI) solution used for
The mild oxidation of organic compounds
What is used to acidify the compounds?
Sulfuric acid as it is already in its highest oxidation state
What happens when a primary alcohol is mildly oxidised?
Undergoes oxidation
Alcohol → Aldehyde → Carboxylic acid
What are the conditions necessary for the mild oxidation of a primary alcohol
Heat with acidified potassium dichromate (VI) solution
How do you obtain the carboxylic acid / aldehyde
Heat under reflux - Carboxylic acid
Heat and distill - Aldehyde
What are the observations?
Orange solution → Green solution
What happens when you heat a secondary alcohol with acidified potassium dichromate (VI) solution?
2º alcohol → Ketone
Orange solution → Green solution
Are tertiary alcohols able to be oxidised?
No, they are resistant to mild oxidation
Write the mild oxidation of butan-2-ol to butanone using [O] to represent the oxidising agent
KC 14
