Isobutylidenediurea (abbreviated IBDU) is an organic compound with the formula (CH3)2CHCH{NHC(O)NH2}2. It is a derivative of urea (OC(NH2)2), which itself is highly soluble in water, but IBDU is not. It functions as a controlled-release fertiliser owing to its low solubility, which limits the rate of its hydrolysis to urea, which is a fast-acting fertiliser. It is produced by the condensation reaction of isobutyraldehyde and two equivalents of urea: (CH3)2CHCHO + 2 OC(NH2)2 → (CH3)2CHCH{NHC(O)NH2}2 + H2O The controlled-release process is the reverse of the above reaction, which only occurs after the IBDU dissolves. Related materials A number of CRF's have been developed based on urea. Related to IBDU is crotonylidene diurea (Crotodur). Simpler are various urea-formaldehyde materials such as ureaform, which consists of methylene diurea and dimethylene triurea. References Ureas Soil improvers Fertilizers