The catalyst used for the reaction is sodium methoxide. For standardizing the concentration of methanol and sodium hydrox- ide, several trials were done using a range of 5–25% methanol and 0.5–1.5% NaOH. The methanol–alkali mixture was blended by continuous gentle agitation at 700 rpm for 20 min. The alco- hol–alkaline solution was prepared freshly in order to maintain the catalytic activity and to prevent the moisture absorbance.