Summary CIE AS Chemistry Note Unit 17 - Hydroxy compounds

Alevel Chemistry Revision OC 17
Revision Material
Duration: 9th – 14th March

Topic 17 Hydroxy compounds
This topic introduces the chemistry of a versatile class of organic compounds, hydroxy compounds, which contain an R–OH group.



Learning outcomes
Candidates should be able to:
17.1 Alcohols (a) recall the chemistry of alcohols, exemplified by ethanol, in the following reactions:
(i) combustion
(ii) substitution to halogenoalkanes
(iii) reaction with sodium
(iv) oxidation to carbonyl compounds and carboxylic acids
(v) dehydration to alkenes
(vi) formation of esters by esterification with carboxylic acids
(b)
(i) classify hydroxy compounds into primary, secondary and tertiary alcohols
(ii) suggest characteristic distinguishing reactions, e.g. mild oxidation
(c) deduce the presence of a CH3CH(OH)– group in an alcohol from its reaction with alkaline
aqueous iodine to form tri-iodomethane

, 17.1 Alcohols
1. Structure
R – OH (Oh alcohol group )
General molecular formula CnH2n+1OH


e.g. CH3CH2OH primary alcohol
CH3CHCH3 secondary alcohol
OH
CH3OH primary alcohol


2. Names of alcohols
CH3OH methanol CH3CH2OH ethanol


CH3CH2CH2OH CH3CHCH3
propan-1-ol OH propan-2-ol positional isomers
(1, the position of the “OH” group)


CH3
CH3CH2CHOH but-2-ol


3. Physical properties of alcohols
- soluble in water, the alcohol can form hydrogen bonds with water molecules
e.g. CH3CH2OH & H2O




- relatively high b.p
they are hydrogen bonds formed between alcohol molecules




- soluble in other organic solvents


4. making alcohols
(1) hydration of alkenes (electrophilic addition)




(conc. H3PO4, heating)
From crude oil
e.g. CH2=CH2 + H2O(g) → CH3CH2OH (conc. H3PO4, heating)