Chemistry 4.3 by Holly Jones

Alcohols and carboxylic acids

hol_cjones — 2019-01-30 12:12:20 UTC

Alcohol + Carboxylic acid ⇌ Ester + Water
----> esterification
<----- hydrolosis

Alcohols with ethanoyl chloride

hol_cjones — 2019-01-30 12:12:20 UTC

Esters can be made by alcohol with carboxylic acids or alcohols with ethanoyl chloride.

Alcohols with hydrogen halides

hol_cjones — 2019-01-30 12:12:20 UTC

Chlorination

Pass hydrogen chloride gas into the alcohol (boiled under reflux) using a zinc chloride catalyst

HCl

Example: CH₃CH₂CH₂CH₂OH --------> CH₃CH₂CH₂CH₂Cl

ZnCl₂Bromination

Make hydrogen bromide by reacting potassium bromide with concentrated sulfuric acid. The hydrogen bromide then reacts with the alcohol (also in the mixture)
KBr + H₂SO₄ ----> KHSO₄ + HBr
Example: CH₃CH₂CH₂OH + HBr ----> CH₃CH₂CH₂Br + H₂0

(propan-1-ol) (1-bromopropane)
Iodination

Reflux iodine with red phosphorus and the alcohol
2P + 3I₂ ----> 2PI₃
Example: 3CH₃CH₂OH + PI₃----> 3CH₃CH₂I + H₃PO₃

(ethanol) (iodoethane)

Can halogenoalkanes make phenol?

hol_cjones — 2019-01-30 12:12:20 UTC

Requires drastic conditions because of π bonds around Cl
Most industries would make phenol in a different way

Alcohols from halogenoalkanes

hol_cjones — 2019-01-30 12:12:20 UTC

R-X + OH^- ---> R-OH + X^-Halogenoalkane + OH^- (from NaOH) ---> Alcohol + Halide

Example
CH₃CH₂CH₂Br + OH^- ---> CH₃CH₂CH₂OH + Br^-Mechanism: Nucleophilic Substitution

Alcohols from carbonyl compounds

hol_cjones — 2019-01-30 12:12:20 UTC

We can make primary or secondary alcohols by reducing carbonyl compounds (aldehydes, ketones and carboxylic acids, all of which contain a C=O group)
Aldehyde ---> Primary Alcohol
Ketone ---> Secondary Alcohol
Reducing Agents:

Lithium tetrahydridoaluminate (III) (Anhydrous conditions) LiAlH₄
Sodium tetrahydridoborate (III) (aqueous conditions) NaBH₄

Good reducing agents because they have a lot of hydrogens

Alcohol Oxidation

hol_cjones — 2019-01-30 12:12:20 UTC

To a test tube:

5 drops of propan-1-ol
4 drops of K₂Cr₂O₇
10 drops of H₂SO₄ (1 mol dm^-3)
Heat in a water bath

Example of alcohol with ethanoyl chloride

hol_cjones — 2019-01-30 12:12:20 UTC

Ethanoyl chloride + propan-1-ol —> propylethanoate + hydrochloric acid

hol_cjones — 2019-01-30 12:12:20 UTC

Esters can be made by alcohol with carboxylic acids or alcohols with ethanoyl chlorides.

hol_cjones — 2019-01-30 12:12:20 UTC

Any benzene derivative with a phenolic group will react with iron (III) chloride to form a brightly coloured complex that appears purple, blue or green.

Test for phenols

hol_cjones — 2019-01-30 12:12:20 UTC

Reactant: bromine water
Observation: White PPT

Reactant: Iron (III) chloride (FeCl_3(aq))
Observation: Purple solution (NOT A PPT!)

NOTE

hol_cjones — 2019-01-30 12:12:20 UTC

ALCOHOLS DO NOT GIVE SUCH A COLOUR WITH AQUEOUS IRON (III) CHLORIDE.

I HAD THIS WRITTEN IN MY BOOKS BUT IT DOESN'T MAKE A LOT OF SENSE

Why is the C-OH bond harder to break in phenols than in regular alcohols?

hol_cjones — 2019-01-30 12:12:20 UTC

In phenol, the oxygen atom contains a p-orbital that can enter into the delocalised system if the electrons in the benzene ring, called the π orbital. This extends the π orbital. So it is hard to remove the -OH group but the H atom itself is more vulnerable.
A H⁺ ion may be lost from phenol to leave a phenoxide ion. This is stable as its negative charge can be spread around the ring system. So phenol is a H⁺ ion donor (an acid!)