Six magnesium alcoholates from bifunctional alcohols HO-(CH2)(n)-OH, n = 2...6, 8 were prepared and characterized. The thermal decomposition leads to magnesium oxide with a distinct particle size as a function of the alcohol chain length n. The final decomposition temperature to MgO is much lower as compared to inorganic precursors, for example, magnesium carbonate. It was shown for these diolates that the thermal decomposition under air most likely includes the formation of Mg-OH groups; the thermal intermediates can be described as alkoxy/hydroxy species.