Nitrapyrin is an organic compound with the formula ClC5H3NCCl3, and is described as a white crystalline solid with a sweet odor.

[4] Nitrapyrin is an effective nitrification inhibitor to the bacteria Nitrosomonas and has been shown to drastically the reduce the amount of N2O emissions from the soil.

[3] Nitrapyrin is commonly produced by the photochlorination of 2-methylpyridine:[5] Nitrapyrin affects the ammonia monooxygenase (AMO) pathway,[6] which is important for NH3 oxidation in nitrification;[7] it also functions as an inhibitor of the urease enzyme in the nitrifying bacteria Nitrosomonas,[8] preventing hydrolytic action on urea.

The primary decomposition is the hydrolysis of the trichloromethyl functional group, resulting primarily in 6-chloro-picolinic acid[10][11] which is the only detected residue in plant metabolisms.

[13] Total N2O emissions reduced by 66-75% when compared to urea only experiments, suggesting that nitrapyrin affects the ability of ammonia-oxidizing bacteria to engage in nitrification and produce N2O gas.