Effect of temperature on the synthesis of 5-phenyl 1H-tetrazole^a.

Entry	Temp. (°C)	Yieldb (%)
1	Room temp.	19
2	40	22
3	55	43
4	70	55
5	85	79
6	100	92

^aReaction condition: benzaldehyde (1 mmol), hydroxylamine hydrochloride (1.2 mmol), sodium azide (1.5 mmol), H₂O (2 mL), humic acid (0.1 g) at different temperature for 4 h.

^bIsolated yield.