Process for the preparation of very pure ureas of the formula phenyl--(NH--CO--NR.sub.1 R.sub.2).sub.n in which phenyl represents an unsubstituted or substituted phenyl or phenylene group and R.sub.1 and R.sub.2 are either identical and each represent an alkyl group, or are different, in which case R.sub.1 represents a hydrogen atom and R.sub.2 represents an alkyl or phenyl group, or R.sub.1 and R.sub.2, together with the nitrogen atom, represent an aliphatic heterocyclic ring and n is the number 1 or 2, by reacting a phenylurea of the formula phenyl--(NH--CO--NH.sub.2).sub.n with an amine of the formula NR.sub.1 R.sub.2 H at temperatures from 100 to 200.degree. C. in a diluent which is inert under the reaction conditions, the reaction being interrupted before by-products are formed, and the urea which is formed being removed from the starting compounds, and the unreacted starting compounds being returned to the process if appropriate.
制备纯度极高的苯基-(NH-CO-NR1R2)n式
尿素的方法,其中苯基代表未取代或取代的苯基或苯基亚甲基基团,R1和R2要么相同且各代表一个烷基基团,要么不同,在这种情况下,R1代表氢原子,R2代表烷基或苯基基团,或者R1和R2与氮原子一起代表脂环杂环,n为数字1或2。方法是在惰性反应条件下的稀释剂中,将式为苯基-(NH-CO-NH2)n的苯基
脲与式为NR1R2H的胺在100至200℃的温度下反应,反应在产生副产物之前中断,从起始化合物中除去生成的
尿素,如果需要,将未反应的起始化合物返回到过程中。