Contain three and more than three hydroxyl group.
Alkanes having tertiary carbon on oxidation with cold alkaline KMnO4 give tertiary alcohol.
Alkenes can be converted into alcohol by the following reactions:
Alkyl halides give alcohol with KOH/NaOH or with moist Ag2O.
(a) Reduction by reducing agents
(i) Aldehyde gives primary alcohol
(ii) Ketone gives secondary alcohol
(i) LiAlH4 (ii) NaBH4
(iii) Na/C2H5OH (iv) Metal (Zn, Fe or Sn)/Acid (HCl, dil H2SO4 or CH3COOH)
(v) (a) Aluminium isopropoxide/isoproppylalcohol (b) H2O
NaBH4 and aluminium isopropoxide reduces only carbonyl group and has no effect on any other group.
Reducing with aluminium isopropoxides is known as Meerwein – Ponndorf Verley (MPV) reduction.
LiAlH4 has no effect on double and triple bonds but if compound is β - aryl, α, β - unsaturated carbonyl compound then double bond also undergoes reduction.
Addition followed by hydrolysis
Methanol can not be prepared by this method.
(a) Reduction by LiAlH4
G = OH (acid)
G = Cl (acid chloride)
G = OR′ (ester)
(b) Reduction by BH3
Carboxylic acids and esters are reduced in to primary alcohol by BH3.
It react with nitrous acid to give alcohol.
Nature of alcohol depends on the nature of carbon having ⎯NH2 group.
Reaction proceeds through carbocation hence rearranged alcohol is obtained.
Oxiranes react with Grignard reagent to give mono hydric alcohol. Nature of G.R is basic hence it attack on less hindered carbon of oxirane ring.