bromide Methanal Phenyl methanol CH CH MgBr + CH CHO CH CH - C - OMgBr H O CH CH CHCH Ethyl magnesium bromide Acetaldehyde Ethanal Butan- -ol + CH COCH OMgBr CH H O -methylhexan- -ol n-butyl magnesium bromide Propanone (Acetone) 2CH MgBr + H - C - O - CH - CH CH i) ether solvent ii) H O + + Mg Br OCH - CH CH (CH ) MgBr CH (CH ) CH (CH ) Formate ester is used to prepare a secondary alcohol with identical alkyl groups Example ethylmethanoate propan - - ol ( (Formaldehyde) Ether Ether Ether H + H + H + XII U11-Hydroxy XII U11-Hydroxy - - - - . Hydroboration: Diborane reacts with an alkene to form trialkyl borane which on treatment with H O in presence of NaOH gives an alcohol. (Refer reactions of diborane) The overall reaction is hydration of an alkene. This reaction yields an anti-Markownikoff's product.
6CH CH = CH + B H (CH CH CH ) B Tripropylborane (CH CH ) B + 3H O OH - 3CH propan- -ol + B (OH) . Reduction of carbonyl compounds: Reduction of aldehydes/ketones with LiAlH in the presence of solvents like THF (Tetrahydrofuran) followed by hydrolysis gives alcohols. Unlike other reducing agents such as Raney Ni, Na-Hg/H O, the lithium aluminium hydride does not reduce the carbon – carbon double bond present in unsaturated carbonyl compound and hence it is a best reagent to prepare unsaturated alcohols. Examples CH - C = O i) LiAlH ii) H O CH - C - H acetone propan- -ol C H -COOH C H CH OH Benzoic acid (i)LiAlH (ii)H O Phenyl methanol(Benzyl alcohol) CH COOCH CH (i)LiAlH (ii)H O (ii)H O 2CH CH OH Ethyl ethanoate Ethanol (ethyl