The invention discloses a method for synthesizing n-
butyl isocyanate. The method comprises the following steps: weighing n-
valeric acid and
thionyl chloride according to the
mole ratio of 1: 1, putting n-
valeric acid and
thionyl chloride in a round-bottomed flask, enabling an opening of the round-bottomed flask to be connected to a
reflux condensing tube, of which an upper opening is provided with a
calcium chloride drying tube, carrying out magnetic stirring, heating the round-bottomed flask to the temperature of 60-70 DEG C in
oil bath, and carrying out reaction for 4-5 hours, so as to obtain a n-valeryl chloride crude product; and dissolving the crude product and a catalyst in an
anhydrous toluene solvent, heating the solution to the temperature of 60-80 DEG C in a three-necked flask, enabling the three-necked flask to be connected to a
thermometer, a
reflux condensing tube, of which an upper opening is provided with a
calcium chloride
drying tube, and a flask
cork respectively, carrying out magnetic stirring for 5-8 minutes, then, slowly adding
drying sodium azide, of which the mole is equal to that of n-
valeric acid, carrying out reaction until no gas is produced, keeping the reaction for 10-15 minutes, then, filtering out insolubles, and carrying out rotary
evaporation to remove
toluene, thereby obtaining n-
butyl isocyanate. The method has the advantages of high yield, mild
reaction conditions, simplicity in operation, short reaction time and little environmental
pollution.