5-Nitro-2-propoxyaniline

5-Nitro-2-propoxyaniline, also known as P-4000 and Ultrasüss, is one of the strongest sweet-tasting substances known, about 4,000 times the intensity of sucrose. It is an orange solid that is only slightly soluble in water. It is stable in boiling water and dilute acids. Because of its possible toxicity, it is banned in the United States, although it is used in some European countries as an artificial sweetener.

In the United States, food containing any added or detectable level of 5-nitro-2-propoxyaniline is deemed to be adulterated in violation of the act based upon an order published in the Federal Register of January 19, 1950 (15 FR 321).