Chapter 14 - Alcohols Flashcards
General Formula, Functional group
CnH2n+1OH
-OH
name ends in -ol
How are alcohols classified
As primary, secondary and tertiary
Primary Alcohols
-OH grp is attached to C which is attached to 2 H and one alkyl group
Secondary Alcohols
-OH grp is attached to C which is attached to 1 H and two alkyl group
Tertiary Alcohols
-OH grp is attached to C which is attached to no H and three alkyl group
What is Methanol classified as
Primary Alcohol although technically none
Physical properties of alcohols
compared to alkanes they are:
- less volatile
- higher m.p.
- more solubility
how can properties of alcohols be explained
Alcohols have polar O-H bond so molecule is polar leading to hydrogen bonding
- stronger bonds so more energy needed so higher b.p. and so less volatile
- polar can dissolve in water (also polar)
as the chain length increases the differences between alkanes and alcohols…
….decreases
- the chain length increases so london forces do, therefore the effects of the hydrogen bonds are less significant
reactions of alcohols
- combustion
- oxidation
- dehydration
- substitution
Dehydration
- is any reaction where a H2O molecule is removed from the starting material
- needs acid catalyst like conc. sulphuric/phosphoric acid & reflux
- makes alkene
- elimination reaction
what is heating under reflux
when you repeatedly heat a substance then condense it allowing the reaction to take place
substitution
- substitution with halide ions is when alcohols react with hydrogen halides
- forms haloalkanes
- reflux with sodium halide, sulfuric acid to make hydrogen halide in situ
why do you make the hydrogen halide in situ?
as it’s solid and not toxic
substitution equations
CH3CHOHCH3 + NaBr + H2SO4 –> CH3CHBrCH3 + NaHSO4 + H2O
NaBr + H2SO4 <–> NaHSO4 + HBr
