The kinetics of Zerewkinoff reaction between ethyl magnesium bromide and amines, alcohols and 1- alkynes, which are very weak Bronsted acids, was investigated in detail by gas evolution method in diethyl ether at 25 °C. The reaction was found tobe second order overall and first order with respect to each reactant. SEi mechanism (int- ramolecular electrophilicsubstitution), which the transition State was believed to involve both electrophilic attack by active hydrogen at the a carbon of ethyl magnesium bromide and nucleophilic attack by the conjugate base of very weak acid at the magnesium atom, was proposed.