Alcohols

Question 1

What are alcohols

Answer 1

Substituted alkanes in which one or more of the hydrogen atoms is replaced with a hydroxyl groups.

Question 2

Physical properties

Answer 2

• anomalously high boiling points compared to many other organic compounds of comparable relative formula mass and shape. This is due to the hydrogen bonds between its molecules.
• the shorter chain alcohols are miscible with water, but their solubility in water decreases as chain length increases. This is because the alkali chain is non-polar so as this increases the alcohol becomes less soluble in water.

Question 3

Why are alcohol groups present in a lot of drugs?

Answer 3

Since they are involved in hydrogen bonding they can interact with protein binding sites.

Question 4

Preparation reactions for alcohols?

Answer 4

• nucleophilic substitution from haloalkanes
• from alkenes by acid-catalysed hydration
• from carbonyls (reduction using LiAlH4)
• reduction of carboxylic acids using LiAlH4

Question 5

Reactions that alcohols take part in

Answer 5

• dehydration of alcohols to alkenes
• oxidation to alcohols
• formation of alkoxides by reaction with some reaction metals like Na and K
• formation of esters (with carboxylic acids, with acid chlorides)

Question 6

What catalysts are used in the dehydration of alcohols to alkenes?

Answer 6

• aluminium oxide
• concentrated sulphuric acid
• concentrated phosphoric acid

Question 7

Catalysts for oxidation of alcohols

Answer 7

• acidified potassium permanganate
• acidified dichromate
• hot copper(II) oxide

Question 8

Oxidation of primary alcohols

Answer 8

Primary alcohols oxidise to form aldehydes and then carboxylic acids

Question 9

Oxidation of secondary alcohols

Answer 9

Forms ketones

Question 10

Catalysts for formation of esters from carboxylic acids

Answer 10

Concentrated sulphuric/phosphoric acid

Question 11

Benefit of ester formation using acid chlorides

Answer 11

No catalyst is needed. This is still a condensation reaction.