Alcohols
CnH2n+1OH
-can form hydrogen bonds, hence are usually miscible when small chain
Miscibility: Liquids mix in all forms, they form a single layer
Primary Alcohol: One carbon directly attached to the same carbon as the OH group
Preparation of alcohols
Heating halogenoalkanes under reflux with NaOH solution, hydrolysis and the liquid alcohol
can be distilled off and purified by fractional distillation
Reactions
Combustion:
Blue flame
Alcohols as alternative fuels
Alcohols burn readily, also burns more cleanly
Reaction with PCl5
-fume cupboard, solid disappears, misty fumes, mixture warms up
C2H5OH + PCl5 → C2H5Cl + POCl3 + HCl
With HBr
-Heat under reflux with HBr. HBr formed in situ from NaBr and H2S04
NaBr + H2S04 → NaHS04 + HBr
C2H5OH + HBr → C2H5Br + H20
With Sodium
Small piece of sodium metal added to alcohol, fizzing
2C2H50H + 2Na → 2C2H50Na + H2 (sodium ethoxide)
Mild Oxidation w. acidified potassium dichromate
Primary Alcohol
Heat w. acidified potassium dichromate, distil = aldehyde, reflux = c. acid
CH3CH20H → CH3CH0 → CH3C00H (Aldehyde (0) → Carboxylic Acid 2(0))
Changes from orange to green Tertiary Alcohols are resistant to mild oxidation
Secondary Alcohol Produces a ketone, orange to green + (0)
CnH2n+1OH
-can form hydrogen bonds, hence are usually miscible when small chain
Miscibility: Liquids mix in all forms, they form a single layer
Primary Alcohol: One carbon directly attached to the same carbon as the OH group
Preparation of alcohols
Heating halogenoalkanes under reflux with NaOH solution, hydrolysis and the liquid alcohol
can be distilled off and purified by fractional distillation
Reactions
Combustion:
Blue flame
Alcohols as alternative fuels
Alcohols burn readily, also burns more cleanly
Reaction with PCl5
-fume cupboard, solid disappears, misty fumes, mixture warms up
C2H5OH + PCl5 → C2H5Cl + POCl3 + HCl
With HBr
-Heat under reflux with HBr. HBr formed in situ from NaBr and H2S04
NaBr + H2S04 → NaHS04 + HBr
C2H5OH + HBr → C2H5Br + H20
With Sodium
Small piece of sodium metal added to alcohol, fizzing
2C2H50H + 2Na → 2C2H50Na + H2 (sodium ethoxide)
Mild Oxidation w. acidified potassium dichromate
Primary Alcohol
Heat w. acidified potassium dichromate, distil = aldehyde, reflux = c. acid
CH3CH20H → CH3CH0 → CH3C00H (Aldehyde (0) → Carboxylic Acid 2(0))
Changes from orange to green Tertiary Alcohols are resistant to mild oxidation
Secondary Alcohol Produces a ketone, orange to green + (0)
