4.3 Alcohols and phenols.

Question 1

How can we make alcohols from halogenoalkanes? and give an example.

Answer 1

Reflux from halogenoalkane with an aqueous solution of alkali (NaOH). (Nucleophilic substitution)

CH₃CH₂CH₂CH₂Br + NaOH –► CH₃CH₂CH₂OH + NaBr

Question 2

How can we make alcohols from carbonyl compounds?

Answer 2

This is a reduction reaction. Aldehydes and ketones are reduced using NaBH₄. This is represented as {H} in an equation.

However, NaBH₄ is not strong enough to reduced a carboxylic acids and instead has to use LiAlH₄

Question 3

What is the reaction of hydrogen halides with alcohols?

Answer 3

Slow and reversible reaction with poor yields.

Question 4

How do you produce a choroalkane?

Answer 4

Pass HCl gas through alcohol with dry ZnCl₂ as a catalyst. They can also be proudced using phosphorus pentachloride (PCl₅). Separation can be difficult if the halogenoalkane produced has a similar BP to POCl_3.

Question 5

How do you produce bromoalkene?

Answer 5

Carry out an “In situ” reaction. Heat a mixture of the alcohol, KBr and 50% H₂SO4

Question 6

How do you an produce iodoalkane?

Answer 6

Use warm damp red phosphorus and iodine which forms phosphorus (III) iodide, PCl₃

Question 7

What is the reaction of an alcohol when reacted with ethanoyl chloride?

Answer 7

An alcohol reacts with ethanoyl chloride (CH₃COCl) forming an ester and misty fumes of HCl are given off.

Question 8

What is the reaction of an alcohol with carboxylic acid?

Answer 8

The reactants are refluxed together with a concentrated H₂SO₄ catalyst. The products are then distilled and the ester is collected at its boiling point.

Question 9

Will phenols react with carboxylic acids?

Answer 9

No but they will react with ethanoyl chlorideto to form esters.

Question 10

How can you test for a phenol?

Answer 10

Iron (III) choride will turn from yellow to purple if a phenol group is present.