Alcohols

Question 1

Physical properties

Answer 1

High boiling temperature - can form London forces and hydrogen bonding with itself
Soluble - OH group can form hydrogen bonds with water with the

Question 2

How does increasing carbon chain affect the solubility

Answer 2

More carbon chains makes the molecules less soluble as the large insoluble hydrocarbon portion outweighs the influence of the polar OH group - London forces between the molecules become more influential than the hydrogen bonding

Question 3

primary/secondary alcohol –> chloroalkane

Answer 3

Substitution
PCl5
Room temperature
Misty fumes of HCl produced
Damp blue litmus paper –> red
PCl5 + CH3CH2OH –> POCL3 + CH3CH2Cl + HCl

Question 4

tertiary alcohol –> chloroalkane

Answer 4

Substitution
Shake with conc. HCl
Room temperature
CH3CH2OH + HCl –> CH3CH2Cl + H2O

Question 5

alcohol –> bromoalkane

Answer 5

Substitution
Add KBr (s)
Heat under reflux
50% conc. H2SO4
KBr(S) + H2SO4 –> KHSO4 + HBr(g)
2KBr + H2SO4 –> K2SO4 + HBr(g)
HBr + CH3CH2OH –> CH3CH2Br + H20

Question 6

alcohol –> iodoalkane

Answer 6

Substitution
Add damp red phosphorus
Add iodine
Heat under reflux
2P + 3I2 –> 2PI3 phosphorus triiodide
PI3 + 3CH3CH2OH –> 3CH3CH2I + H3PO3
Forms phosphonic acid

Question 7

Why can’t KI be used for iodination as in bromination

Answer 7

KI + H2SO4 –> HI
HI is oxidised by H2SO4 –> I2 + SO2 + H20
rather than reacting with the alcohol